Skywatching Archives

August 27, 2012April 26, 2016 by Tammy Plotner

Blue Moon This Week

When you hear someone say “Once in a Blue Moon” you know what they mean. They’re usually talking about something rare, silly, and even absurd. After all, when was the last time you saw the Moon turn blue? Well, rare or not, we’re having one this week, and according to astronomer David Reneke writer and publicist for Australasian Science magazine, a Blue Moon is slated for the last day of this month, Friday, August 31.

It’s not at all clear where the term ‘Blue Moon’ comes from. According to modern folklore it dates back at least 400 years. A Blue Moon is the second Full Moon in a calendar month. “Usually months have only one Full Moon, but occasionally a second one sneaks in, David said. “Ancient cultures around the world considered the second Full Moon to be spiritually significant.”

Full Moons are separated by 29 days, while most months are 30 or 31 days long, so it is possible to fit two Full Moons in a single month. This happens every two and a half years, on average. By the way, February is the only month that can never have a Blue Moon by this definition. We had one Full Moon on August 2 this year and the second will be Friday night.

Does the Blue Moon actually turn blue? No. Physically colored Blue Moons are rare, and that’s where the phrase comes from, “Once in a Blue Moon”. There are occasions though when pollution in the Earth’s atmosphere can make the Moon appear to look blue in color. The extra dust scatters blue light. For example, the Moon appeared bluish green across the entire Earth for about 2 years after the eruption of Krakatoa in 1883.

There were also reports of a blue-green coloured Moon caused by Mt. St. Helens in 1980 and Mount Pinatubo in 1991. “So in a sneaky sort of way, it could be true,” Dave said with a grin. Look up at the night sky on August 31 and see for yourself. Everywhere in the world the full Moon rises in the east just as the Sun is setting in the west.

“Blue Moons don’t have any real significance scientifically but they’re fun to look at,” David said. “Anytime you can get people out to look at the real sky to me is a great plus, enjoy it while you can this Friday night and while you’re looking moonward, think of Neil Armstrong, OK?”

Story Contributed by Dave Reneke. Image Credit: John Chumack.

August 26, 2012December 23, 2015 by Tammy Plotner

Weekly SkyWatcher’s Forecast: August 27-September 2, 2012

Greetings, fellow SkyWatchers! If you only get your telescope or binoculars out once in a Blue Moon, then get them out this week when a Blue Moon actually happens! However, if you can’t wait, then let’s explore some great lunar features, bright star clusters and great double stars. When you’re ready to learn some history, mystery and more, then just step on inside…

Monday, August 27 – Tonight the waxing Moon’s most notable features will be the vast area of craters dominating the south-central portion near and along the terminator. Now emerging is Ptolemaeus – just north-northeast of Albategnius. This large round crater is a mountain walled plain filled with lava flow. With the exception of interior crater Ptolemaeus A, binoculars will see it as very smooth. Telescopes, however, can reveal faint mottling in the surface of the crater’s interior, along with a single elongated craterlet to the northeast. Despite its apparent uniformity, close inspection has revealed as many as 195 interior craterlets within Ptolemaeus! Look for a variety of interior ridges and shallow depressions.

With the Moon low to the southwest, we have a chance to go northeast to Cepheus for a new study – NGC 7160 (Right Ascension: 21 : 53.7 (hours : minutes) Declination: +62 : 36). At magnitude 6.1, this small open cluster is easily identified in scopes and may be seen as a faint starfield in binoculars. You’ll find it about a finger-width north of Nu Cephei.

Tuesday, August 28 – In 1789 on this day, Sir William Herschel discovered Saturn’s moon Enceladus.

On the lunar surface tonight, we’ll start by following the southward descent of large crater rings Ptolemaeus, Alphonsus, and Arzachel to a smaller, bright one southwest named Thebit. We’re going to have a look at Hell…

Just west of Thebit and its prominent A crater to the northwest, you see the Straight Wall – Rupes Recta – appearing as a thin, white line. Continue south until you see large, eroded crater Deslandres. On its western shore, is a bright ring that marks the boundary of Hell. While this might seem like an unusual name for a crater, it was named for an astronomer – and clergyman!

Once you’ve been to Hell, let’s go to the heavens for NGC 7235 (Right Ascension: 22 : 12.6 – Declination: +57 : 17). Locate the star crowded area of Epsilon Cephei which will also include this 7.7 magnitude open cluster in the same low power field. Give it a try. Look for a small, rectangular assortment of 10th magnitude and fainter stars, including a beautiful ruby red, west-northwest of Epsilon.

Wednesday, August 29 – Due south of mighty Copernicus on the eastern edge of Mare Cognitum, you will see a ruined pair of flattened craters. They are Bonpland and Parry – with Frau Mauro just above them. The smallest and brightest of these ancient twins is the eastern Parry. Have a look at its south wall where a huge section is entirely lost. It was near this location that Ranger 7 ended its successful flight in 1964. Just south of Parry is another example of a well-worn Class V crater. See if you can distinguish the ruins of Guericke. Not much is left save for a slight U-shape to its battered walls. These are some of the oldest visible features on the Moon!

If you’d like to head for something very young, have a look at 6.8 magnitude open cluster NGC 6811 (Right Ascension: 19 : 37.3 – Declination: +46 : 23) in Cygnus. This mid-sized, unusually dense open cluster is found less than finger-width north-northwest of Delta – the westernmost star of the Northern Cross. Like most open clusters, the age of NGC 6811 is measured in millions, rather than billions, of years. Visible in binoculars on most nights, telescopes should show a half dozen or so broadly-spaced resolvable stars overlaying a fainter field. Be sure to return again on a moonless night, and have another look a disparate double Delta!

Thursday, August 30 – Today celebrates the Yohkoh Mission, launched in 1991. It was a joint effort of both Japan and the United States to monitor solar flares and the corona. While its initial mission was quite successful, on December 14, 2001 the signal was lost during a total eclipse. Unable to reposition the satellite back towards the Sun, the batteries discharged and Yohkoh became inoperable.

While the graceful Gassendi will try to steal the lunar show tonight, let’s have a go at Foucault instead. To find it, head north to Sinus Iridum and locate Bianchini in the Juras Mountains. Just northeast, and near the shore of south-eastern Mare Frigoris, look for a bright little ring.

Physicist Jean Foucault played an instrumental role in the creation of today’s parabolic mirrors. His “Foucault knife edge test” made it possible for opticians to test mirror curves for optical excellence during the final phases of shaping before metallization. Thanks to Foucault’s insight, we can turn our telescopes on such difficult double stars as Beta Delphini and resolve its 0.6 arc-second distant 5.0 magnitude companion. A challenge for smaller scopes is MU Cygni. This 4.5 and 6.0 magnitude pair should be resolvable in any scope that passed Foucault’s test!

Tonight let’s view a double star, Eta Lyra. Just on the edge of unaided visibility, you will find it around three finger-widths due east of Vega. This wide, disparate pair of 4.5 and 8.0 magnitude stars should be resolvable in just about any scope, but is beyond the reach of binoculars.

Friday, August 31 – Tonight we will begin entering the stream of the Andromedid meteor shower, which peaks off and on for the next couple of months. For those of you in the northern hemisphere, look for the lazy “W” of Cassiopeia to the northeast. This is the radiant – or relative point of origin – for this meteor stream. At times, this shower has been known to be spectacular, but let’s stick with an accepted fall rate of around 20 per hour. These are the offspring of Beila’s Comet, one that split apart leaving radically different streams – much like 73/P Schwassman-Wachmann did last year. These meteors have a reputation for red fireballs with spectacular trains, so watch for them in the weeks ahead.

It’s Blue Moon! That doesn’t mean the Moon is going to be colored any differently – it just means it’s the second full Moon within a month.

Think having all this Moon around is the pits? Then let’s venture to Zeta Sagittarii and have a look at Ascella – “The Armpit of the Centaur.” While you’ll find Zeta easily as the southern star in the handle of the teapot formation, what you won’t find is an easy double. With almost identical magnitudes, Ascella is one of the most difficult of all binaries. Discovered by W. C. Winlock in 1867, the components of this pair orbit each other very quickly – in just a little more than 21 years. While they are about 140 light-years away, this gravitationally bound pair waltz no further apart than our own Sun and Uranus!

Too difficult? Then have a look at Nu Sagittarii – Ain al Rami, or the “Eye of the Archer.” It’s one of the earliest known double stars and was recorded by Ptolemy. While Nu 1 and Nu 2 are actually not physically related to one another, they are an easy split in binoculars. Eastern Nu 2 is a K type spectral giant that is around 270 light-years from our solar system. But take a very close look at the western Nu 1 – while it appears almost as bright, this one is 1850 light-years away! As a bonus, power up in the telescope, because this is one very tight triple star system!

Saturday, September 1 – On this day 1859, solar physicist Richard Carrington (who originally assigned sunspot rotation numbers) observed the first solar flare ever recorded. Naturally enough, an intense aurora followed the next day. 120 years later in 1979, Pioneer 11 made history as it flew by Saturn.

While the Moon essentially appears to be full throughout the night, take the time to compare the western and eastern limbs. To the west, you will see the smooth arc no longer displays high contrast features. To the east you should see a broken edge now in sunset. Watch in the days ahead as many of your favorite craters begin to reveal themselves in a “different light.”

Tonight let’s visit Alya. One of the fainter stars to receive a proper name, Theta Serpens Caput is located around a hand span due east of Beta Ophiuchi. Thankfully, resolving this wide, matched magnitude pair is easier than finding it. If you have high power, self-stabilizing binoculars, this one could be real fun!

Sunday, September 2 – It won’t be long until the Moon lights the skies, so let’s have a look at disparate double Kappa Pegasi. It’s the westernmost star of northern Pegasus and is around a hand span due south of Sadr – the central star of the Northern Cross. At magnitude 4.3, look for a faint companion leading the orange-yellow primary across the sky. This one could be tough for small scopes – so make a challenge of it!

Now let’s have a look at Beta and Gamma Lyrae – the lower two stars in the “Harp.” Beta is actually a quick change variable dropping to less than half the brightness of Gamma every 12 days, but for a few days the two stars appear to be of near equal brightness. Beta is a very unusual eclipsing spectroscopic binary. Its unseen companion may be a “collapsar.”
Before you call it a night, head a finger-width north of Omicron Andromedae for 15 Lacertae. Just on the edge of unaided visibility, this carbon star is also a disparate double. The 5.2 magnitude variable primary will appear more red at its faintest, but its 11.0 magnitude companion is the faintest of all!

But don’t put the telescope away just yet. If you can locate the Moon, you can locate Uranus! Just take a look about 3 degrees away to lunar south to catch the slightly greenish orb of the outer planet.

Until next week, ask for the Moon… But keep on reaching for the stars!

Ptolemaeus Crater Image Credit: Damian Peach

August 20, 2012December 23, 2015 by Tammy Plotner

Weekly SkyWatcher’s Forecast: August 20-26, 2012

Greetings, fellow SkyWatchers! It’s going to be a great week to catch up on your lunar studies, but be sure to mark your calendar for Tuesday’s splendid conjunction! There will be bright stars and clusters to study, so enjoy these temperate nights while they last! Whenever you’re ready to learn more about the history, mystery and majesty of what’s out there, meet me in the back yard…

Monday, August 20 – Tonight the Moon sets by skydark, but if you’re looking for a lunar challenge, return to crater Petavius about one-third the way up from the southern cusp just after sunset. This ancient crater is a wonderland of detail when lying on the terminator. Look for its rugged walls interrupted by crater Wrottesley to the northwest and elongated Palitzsch southeast. If conditions are stable, power up to look for a massive, multi-peaked central mountain region, along with a deep scar – Rima Petavius – cutting diagonally across the wavelike floor.

When the Moon has set, look for the southern Crown – Corona Australis. Its hidden jewel is 7.3 magnitude, 28,000 light-year distant globular cluster NGC 6723 (Right Ascension: 18 : 59.6 – Declination: -36 : 38). Discovered on June 3, 1826 by James Dunlop of New South Wales, Australia, NGC 6723 can be best found by heading less than 7 degrees due south of Zeta Sagittarii. This mid-sized cluster gives a surprising view, but if you’re more north, best catch it at its highest.

Now, relax! Tonight is the peak of the Kappa Cygnid meteor shower. Although the Moon will interfere early in the evening, wait until it has set and watch the area near Deneb. Discovered in the late 1800?s, the Kappa Cygnids are often overlooked because the grander, more prolific Perseids tend to get more attention. Although the stream has been verified, peak dates and fall rates vary from year to year. The average fall rate is usually no more than 5 per hour, but it is not uncommon to see 12 or more per hour with many fireballs. The stream’s duration is around 15 days. Clear skies!

Tuesday, August 21 – Deep Blue Celestial Scenery Alert! Don’t goof around tonight. Find yourself an open western horizon and be outside at sky dark for the awe inspiring combination of the Moon, Spica, Mars and Saturn. The powerful blue/white star will be located just northeast of the lunar edge while Mars resides to the east/southeast and Saturn reigns above them all. This will be a very photographic opportunity, so be sure to take advantage of this splendid conjunction. Tell your family and friends!

Although we have traveled this road before, let’s go further south than last night’s lunar study and have another look at Furnerius. Shallower and less impressive than Petavius, Furnerius will fade to obscurity as the Moon waxes. This flooded old crater has no central peak, but a much younger crater has punched a hole in its lava-filled floor. Look for the long “crack” extending from Furnerius’ north shore to crater rim. Perhaps it was caused by the impact? Sharp-eyed observers with good conditions and high power will also spot a multitude of small craters within and along Furnerius’ walls. For binocular viewers, try spotting crater Stevinus to the north and Fraunhofer to the south.

Now let’s go have a look at a star buried in one of the spiral arms of our own galaxy – W Sagittarii…

Located less than a fingerwidth north of Gamma, the tip of the “teapot spout,” W is a Cepheid variable that’s worth keeping an eye on. While its brightness only varies by less than a magnitude, it does so in less than 8 days! Normally holding close to a magnitude 4, nearby field stars will help you correctly assess when minimum and maximum occur. While it’s difficult for a beginner to see such changes, watch it over a period of time. At maximum, it will be only slightly fainter than Gamma to the south. At minimum, it will be only slightly brighter than the stars to its northeast and southwest.

While you watch W go through its changes – think on this: not only is W a Cepheid variable (a standard for distance measurements), but it is also one that periodically changes its shape. Not enough? Then think twice… Because W is also a Cepheid binary. Still not enough? Then you might like to know that recent research points toward W having a third companion as well!

Wednesday, August 22 – On the lunar surface tonight, head to the eastern shore of Mare Nectaris to catch an easily noticed broken black line. This is the western flank of the Pyrenees Mountains which stretch close to 350 kilometers north to south. The black line you see is a good example of a lunar scarp, a feature more like a cliff than a true mountain range. This scarp ends to the north in crater Guttenberg. Just south of Guttenberg, you will find high contrast Santbech.

Although it will be tough to locate with the unaided eye thanks to the Moon, let’s take a closer look at one of the most unsung stars in this region of sky – Eta Sagittarii. This M-class giant star will show a wonderful color contrast to binoculars or scopes, being slightly more orange than the surrounding field. Located 149 light-years away, this irregular variable star is a source of infrared radiation and is a little larger than our own Sun – yet 585 times brighter. At around 3 billion years old, Eta has either expended its helium core or just begun to use it to fuse carbon and oxygen – creating an unstable star capable of changing its luminosity by about 4%. But have a closer look… For Eta is also a binary system with an 8th magnitude companion!

Thursday, August 23 – Do you remember a few days ago in history when Lunar Orbiter 1 was launched? Well, on this day in history it made headlines as it sent back the very first photo of Earth seen from space!

On the lunar surface tonight, we’ll return to identify Metius, Fabricus and Janssen to the south. Southwest of this trio you will see a sharply defined small crater known as Vlacq. Power up to resolve its small central mountain peak. Angling off to the west and extending westward is multiple crater Hommel. Look especially for Hommel A and Hommel C which fit nicely and precisely within the borders of the older crater. Note how many individual craters make up its borders. Just north of Hommel is Pitiscus and to its south is Nearch.

Now let’s have a look at the brightest star in the “Archer” – Epsilon Sagittarii. Known as Kaus Australis, or the “Southern Bow,” Epsilon holds a respectable magnitude 1.8 and is located around 120 light-years from Earth. This sparkling blue/white star is 250 times brighter than our own Sun. While a major challenge would be to spot Epsilon’s 14th magnitude companion star located about 32? away, even the smallest of telescopes and most binoculars can try for the 7th magnitude visual companion widely spaced to the north-northwest.

Friday, August 24 – Today in 1966 from an Earth-orbiting platform, the Luna 11 mission was launched on a three day trip. After successfully achieving orbit, the mission went on to study many things, including lunar composition and nearby meteoroid streams.

Tonight’s prominent lunar features are also Astronomical League challenges. Look southwest of previous study Theophilus for the huge form of Maurolycus. Its cratered floor may be either partially lit or fully disclosed depending on your observing time. Note especially Maurolycus’ multiple central mountains. North of Maurolycus you will see the well-eroded remains of Gemma Frisius. Its broken walls will show well under current illumination. Finally look carefully for crater Goodacre which has destroyed Gemma Frisius’ northern wall.

The Moon is now becoming the “highlight” of the night sky. Try using “higher power” to diminish some of its glare. While southwestern Sagittarius is also high, why not observe some of its other globular clusters?

Center the scope on Epsilon and sweep less than 3 degrees north-northeast to find small 7.7 magnitude globular M69 (Right Ascension: 18 : 31.4 – Declination: -32 : 21). M69 gives an appearance similar to that of other compact clusters – such as M28 and M80. Small and moderately bright, it appears coarsely textured through smaller instruments and requires larger scopes to bring out its brightest 14th magnitude members. This cluster sits near a blue 7th magnitude star which complicates seeing M69 through binoculars and finderscopes.

Now head a little more than a degree southeast, then north of a pair of 6th magnitude stars to locate NGC 6652 (Right Ascension: 18 : 35.8 – Declination: -32 : 59) – a very small 9th magnitude globular. Go less than 2 degrees northeast to find brighter (8.1 magnitude), larger M70 (Right Ascension: 18 : 43.2 – Declination: -32 : 18). Notice how more of M70?s light is concentrated in its core than M69. Continuing a little more than 3 degrees in the direction of Zeta we encounter M54 (Right Ascension: 18 : 55.1 – Declination: -30 : 29). Through a modest scope, this 7.7 magnitude globular is small, very blue, and intensely concentrated at the core. Larger amateur instruments will only bring out a few 15th magnitude members out of this globular’s faintly glowing form.

Charles Messier discovered M69 and M70 on August 31, 1780 from Paris while trying to confirm a discovery made by Lacaille using a half-inch spyglass in South Africa. These two globulars lie within 2,000 light-years of each other and less than 30,000 light-years from Earth. Due to unusual richness in metal content – for astronomers, “metals” are any elements other than hydrogen and helium – M69 may be a relatively young cluster. At some 90,000 light-years, M54 is the most distant Messier globular cluster – and may not be a globular at all – but the core of a dwarf galaxy beyond the bounds of the Milky Way! In fact M54 is intrinsically larger (300 light-years in diameter) and brighter (magnitude 10.1) than any other globular within the Milky Way itself.

Saturday, August 25 – Tonight the waxing Moon’s most notable features will be the vast area of craters dominating the south-central portion near and along the terminator. Now emerging is Ptolemaeus – just north-northeast of Albategnius. This large round crater is a mountain walled plain filled with lava flow. With the exception of interior crater Ptolemaeus A, binoculars will see it as very smooth. Telescopes however can reveal faint mottling in the surface of the crater’s interior, along with a single elongated craterlet to the northeast. Despite its apparent uniformity, close inspection has revealed as many as 195 interior craterlets within Ptolemaeus! Look for a variety of interior ridges and shallow depressions.

With the moonlight causing studies to be mildly hampered, our main feature for tonight will definitely improve once the Moon sets – so while we’re waiting, let’s drop by open cluster M29 (Right Ascension: 20 : 23.9 – Declination: +38 : 32) less than 2 degrees south-southeast of Gamma Cygni. At lower power, or through small scopes, its handful of brightest members makes this 6.6 magnitude open cluster look more like an asterism than a real group. Lacking any sense of a core, higher power and larger scopes will bring out another dozen or so stars. Those with binoculars will enjoy seeing a few of M29?s brightest stars against a vague nebulosity.

Now let’s see what the “I” can “C”… Less than 2 degrees southwest of M29 (just south of 5th magnitude P Cygni) lies another open cluster of similar brightness and size to M29 – IC 4996 (Right Ascension: 20 – : 16.5 – Declination: +37 : 38). How do these two compare? The less conspicuous IC 4996 lies in a richer Milky Way field and consists of fewer and more compact bright stars. Smaller scopes see this one as a patch of nebulosity.

Now for M55 (Right Ascension: 19 : 40.0 – Declination: -30 : 58). Found in the far reaches of eastern Sagittarius, and west-southwest of Zeta, M55 is one of the coarsest globulars known. At magnitude 7.0, M55 can be seen as a large pale ghost of luminosity in binoculars or finderscopes. This is one very open globular cluster! A multitude of fine, easily resolved stars spread oblately over the mid-power field. Long exposure photos show this to be a true globular glowing with the combined light of almost 100,000 suns.

Tonight is also the peak of the Northern Iota Aquarid meteor shower. While the Moon will totally interfere most of the evening, you still might catch a bright streak!

Sunday, August 26 – The most outstanding feature tonight on the Moon will be a southern crater near the terminator – Maurolycus. Depending on your viewing time, the terminator may be running through it. These shadows will multiply its contrast many times over and display its vivid formations. As true lunar challenge, Maurolycus will definitely catch your eye with its black interior and western crest stretched over the terminator’s darkness. Too many southern craters to be sure? Don’t worry. Maurolycus dominates them all tonight. Look for its double southern wall and multiple crater strikes along its edges. Maurolycus is found about two Crisium lengths southwest of Theophilus and in tonight’s light will appear especially fine. But look just north of Maurolycus to pick out the battered remains of Class III crater Gemma Frisius, another lunar challenge. Spanning 56 miles and descending 17,100 feet below the Moon’s surface, you’ll find its walls broken, yet enough of its northern boundary remains to clearly reveal the impact that created Goodacre. Look for the shadows which blend Goodacre and Gemma Frisius together.

On this date in 1981, Voyager 2 made a fly-by of Saturn. Eight years later in 1989, Voyager 2 flew by Neptune on this date. Why don’t we make a “date” tonight to have a look at this distant blue world? You’ll find it on the ecliptic plane. While large binoculars can pick up Neptune’s very tiny blue orb, you’ll need a telescope tonight to spot it through the lunar glare.

Until next week? Wishing you clear skies!

August 12, 2012December 23, 2015 by Tammy Plotner

Weekly SkyWatcher’s Forecast: August 13-19, 2012

Greetings, fellow SkyWatchers! Even if you missed the peak of the Perseid meteor shower, there will still be plenty of “strays” to sparkle this week’s dark nights. For astronomy without a telescope, be sure to check out all the planetary alignments – and tell your friends! When you’re ready to learn more about what to view and when this week, then meet me in the back yard…

Monday, August 13 – Celestial scenery alert! If you’re out before dawn this morning, look for the very close pairing of Venus and the slender crescent Moon. For viewers in the north-eastern Asia area, this is an occultation event, so be sure to check resources for times and locations in your area! How about some more eye candy? Then check out the splendid alignment of Saturn, Mars and Spica just after sky dark. Look for the blue/white star to the west, accompanied by red Mars to the east and yellow Saturn even higher to the east. The trio will be roughly separated by the same distance from each other and the colors will be a welcome sight. Be sure to alert your family and friends to all the celestial action that doesn’t require a telescope today!

Tonight, begin with just your eyes as you gaze about four fingerwidths above the top of the Sagittarius “teapot dome” for an open window on the stars and mighty M24 (Right Ascension: 18 : 18.4 – Declination: -18 : 25)…

This huge, hazy patch of stars is in reality an area of space known as “Baade’s Window” – an area free of obscuring gas and dust. Cataloged by Messier in 1764 as object 24, even small binoculars will reveal the incredible vista of the “Sagittarius Star Cloud.” Although it’s actually not a cluster, but rather a clean view of an area of our own galaxy’s spiral arm, that will not lessen the impact when viewed through a telescope. Spanning a degree and a half of sky, it is one of the few areas in which even a novice can easily perceive areas of dark dust.

For larger telescopes, look for the dim, open cluster NGC 6603 (Right Ascension: 18 : 18.4 – Declination: -18 : 25) in the northeastern position of the Window. There are two very notable dark nebulae, B92 and B93, located in the northern segment as well. Near teardrop shaped B92 and its single central star, you should spot open cluster Collinder 469 and also Markarian 38 south of B93. You’ll find B86 near Gamma Sagittarii . At the southern edge of the star cloud, look for emission nebula IC 1283-1284, along with the reflection nebulae NGC 6589 (Right Ascension: 18 : 16.9 – Declination: -19 : 46) and NGC 6590 (Right Ascension: 18 : 17.0 – Declination: -19 : 53) and open cluster NGC 6595 (Right Ascension: 18 : 17.0 – Declination: -19 : 53). Still up for more? Then head west to see if you can find 12th-magnitude planetary nebula NGC 6567 (Right Ascension: 18 : 13.7 – Declination: -19 : 05).

Even if you don’t accept these challenges, you can still enjoy looking at a 560 light-year swatch of stars from one of the Milky Way’s loving arms! (If you’re out late, look for Mira… It was discovered by Fabricius on this date in 1596.)

Tuesday, August 14 – Celestial scenery alert! Be out just after sunset to catch a splendid stellar and planetary conjunction. To the west you’ll see bright Spica. Just above it, Mars. And just above that? Saturn! The trio are all separated by just a few degrees, so be sure to stop and enjoy!
Your first challenge for tonight will be to venture about three fingerwidths northeast of Lambda Sagittarii to visit a well-known but little visited galactic cluster – M25 (Right Ascension: 18 : 31.6 – Declination: -19 : 15).

First discovered by Cheseaux and then cataloged by Messier, it was observed and recorded by William Herschel, Johann Elert Bode, Admiral Smythe and T. W. Webb…but never added to the NGC catalog of John Herschel! Thanks to J.L.E. Dreyer, it did make the second Index Catalog as IC 4725.

Seen with even the slightest optical aid, this 5th magnitude cluster contains two G-type giants as well as a Delta Cephei-type variable with the designation of U, which changes about one magnitude in a period of less than a week. It’s very old for an open cluster, perhaps near 90 million years, and the light you see tonight left the cluster over 2000 years ago. While binoculars will see around a double handful of bright stars overlaying fainter members, telescopes will reveal more and more as aperture increases. At one time it was believed to have only about 30 members, but this was later revised to 86. But recent studies by Archinal and Hynes indicate it may have as many as 601 member stars!

Wednesday, August 15 – Celestial scenery alert! Get up before dawn to spot Mercury low on the eastern horizon, a very tiny crescent Moon to its west/southwest and brilliant Venus ruling above it all! To add to the mix, you’ll see the pairing of the Gemini Twins – Castor and Pollux – just about a handspan above Mercury and luminous Procyon about the same distance due south. If you missed your opportunity to view Spica, Mars and Saturn on Monday, don’t worry. The colorful trio is still around tonight just after sky dark to the west, but now you can see that Mars has moved slightly to the south. Ain’t celestial mechanics grand?!

Tonight we’ll head back to Scorpius to have a look at three pristine open clusters. Begin your starhop at the colorful southern Zeta pair and head north less than one degree for NGC 6231 (Right Ascension: 16 : 54.0 – Declination: -41 : 48).

Wonderfully bright in binoculars and well resolved to the telescope, this tight open cluster was first discovered by Hodierna before 1654. De Cheseaux cataloged it as object 9, Lacaille as II.13, Dunlop as 499, Melotte as 153, and Collinder as 315. No matter what catalog number you chose to put in your notes, you’ll find the 3.2 million year young cluster shining as the “Northern Jewelbox!” For high power fans, look for the brightest star in this group – it’s van den Bos 1833, a splendid binary.

About another degree north is loose open cluster Collinder 316, with its stars scattered widely across the sky. Caught on its eastern edge is another cluster known as Trumpler 24, a site where new variables might be found. This entire region is encased in a 90 arc minute faint emission nebula called IC 4628 (Right Ascension: 16 : 57.0 – Declination: -40 : 20) – making this low power journey through southern Scorpius a red hot summer treat!

Thursday, August 16 – If you did not get a chance to look at the Northern Jewelbox region in Scorpius, return again and sweep the area tonight. For those with larger telescopes, we’re going to hop about a degree and a half south of twin Nu for NGC 6242 (Right Ascension: 16 : 55.6 – Declination: -39 : 30).

Discovered by Lacaille and cataloged as I.4, it is also known as Dunlop 520, Melotte 155 and Collinder 317. At roughly magnitude 6, this open cluster is within binocular range, but truly needs a telescope to appreciate its fainter stars. While NGC 6242 might seem like nothing more than a pretty little cluster with a bright double star, it contains an x-ray binary which is a “runaway” black hole. It is surmised that it formed near the galactic center and was vaulted into an eccentric orbit when the progenitor star exploded. Its kinetic energy is much like a neutron star or a millisecond pulsar, and it was the first black hole confirmed to be in motion.

Now head a little more than a degree east-southeast for NGC 6268 (Right Ascension: 17 : 02.4 – Declination: -39 : 44). At a rough magnitude of 9, this small open cluster can be easily observed in smaller scopes and resolved in larger ones. The cluster itself is somewhat lopsided, with more of its members concentrated on the western half of its borders. While it, too, might not seem particularly interesting, this young cluster is highly evolved and contains some magnetic, chemically peculiar stars and Be class, or metal-weak, members.

Friday, August 17 – Today in 1966 Pioneer 7 was launched. It was the second in a series of satellites sent to monitor the solar wind, and study cosmic rays, interplanetary space, and magnetic fields. If you’re out early, be sure to take a look for the close pairing of Mars and Saturn and Spica. If you’ve had the opportunity to view them over the last few days, you can see how quickly Mars has moved! Instead of being in a line, the trio now… well… triangulates!

Tonight it’s New Moon! Let’s return to previous study star Lambda Scorpii and hop three fingerwidths northeast… We’re re-hunting the “Butterfly!”

Easily seen in binoculars and tremendous in the telescope, this brilliant magnitude 4 open cluster was first discovered by Hodierna before 1654 and independently discovered by de Cheseaux as his object 1, before being cataloged by Messier as M6 (Right Ascension: 17 : 40.1 – Declination: -32 : 13). Containing around 80 stars, the light you see tonight left its home in space around the year 473 A.D. It is believed to be around 95 million years old and contains a single yellow supergiant – the variable BM Scorpii. While most of M6?s stars are hot, blue main sequence, the unique shape of this cluster gives it not only visual appeal, but wonderful color contrast as well!

Now let’s head towards more unusual open clusters – this time in Cygnus. Starting with Gamma Cygni, locate a loose cluster involving Gamma, Do (Dolidze) 43. Now shift two degrees southwest to pick up Do 42 as well. Don’t confuse Do 42 with nearby M29 though, for the two look very similar. For fans of the “Double Cluster” in Perseus, you’ll like the next pairing! Shift another half degree southwest along the body of Cygnus to pick out Do 40 and Do 41. This pretty pair can be placed in the same low power field. By moving another half degree due west, you’ll find highly populated Do 39 and that, too, is a double treat. The brighter clump of stars in the same low power field is IC 4996 (Right Ascension: 20 : 16.5 – Declination: +37 : 38).

Now for two bright open clusters. The first, Ruprecht 173 is about a degree northwest of Epsilon Cygni. You’ll truly appreciate this heavily populated star cluster! The next is as easy as identifying the constellation of Lyra. Just southeast of bright Vega is a wonderful double for binoculars, Delta 1 and 2 – the easternmost most two stars in the lyre. This bright pair is part of an open cluster known as Stephenson 1.

Saturday, August 18 – On this day in 1868, Norman Lockyer was very busy as he was the first to see helium absorption lines in the Sun’s spectrum. Tonight we’ll take a walk from helium rich Lambda Scorpii about three fingerwidths east-northeast to an even more prominent area of stars that was known to Ptolemy as far back as 130 AD.

Astronomers throughout the ages have spent time with this cluster: Hodierna as Ha II.2; Halley in 1678 as number 29, Derham in 1733 as number 16, De Cheseaux as number 10, Lacaille as II.14; Bode as 41; once for William Herschel and again for John as h 3710; Dreyer as NGC 6475… But we know it best as Messier Object 7 (Right Ascension: 17 : 53.9 – Declination: -34 : 49).

Set against the backdrop of the Milky Way, even the smallest of binoculars will enjoy this bright open cluster while telescopes can resolve its 80 members. Roughly 800 light-years away, it contains many different spectral types in various stages of evolution, giving the cluster an apparent age of about 260 million years. Full of binaries and close doubles, an extreme test of tonight’s lighting conditions would be to see if you can spot the 11th magnitude globular cluster NGC 6453 (Right Ascension: 17 : 50.9 – Declination: -34 : 36) to the northwest!

And for last, the densely populated open cluster M11 (Right Ascension: 18 : 51.1 – Declination: -06 : 16). The “Wild Duck” cluster soars about a fist’s width northeast of M16. Dominated by a single 8th magnitude star, this conically-shaped 3,000 member assembly of stardust easily resolves into innumerable stars with any significant amount of magnification. Through intermediate aperture, this 6000 light-year distant, 250 million year old cluster takes on a new form as several hundred 13th and 14th magnitude members begin to spill outside its V-shaped bounds! Discovered by Gottfried Kirch of Berlin observatory in 1681, the cluster was first noted as stellar by William Derham in the first third of the 18th century. Charles Messier added it to his catalog May 30, 1764.

Sunday, August 19 – Born today in 1646, let’s have a look at John Flamsteed. He was an English astronomer with a passion for what he did. Despite a rather difficult childhood and no formal education, he went on to become the First Observer at the Royal Observatory and his catalog of 3000 stars was perhaps the most accurate yet published. Flamsteed star numbers are still in use. Also born on this day was Orville Wright, in 1871, and in 1891, Milton Humason, a colleague of Edwin Hubble at Mts. Wilson and Palomar. The latter was instrumental in measuring the faint spectra of galaxies, which in turn provided evidence for the expansion of the Universe.

This would be a great time for us to have a look at one of the summer’s most curious galaxies – NGC 6822 (Right Ascension: 19 : 44.9 – Declination: -14 : 48). This study is a telescopic challenge even for skilled observers. Set your sights roughly 2 degrees northeast of easy double 54 Sagittarii, and have a look at this distant dwarf galaxy bound to our own Milky Way by invisible gravitational attraction…

Named after its discoverer (E. E. Barnard – 1884), “Barnard’s Galaxy” is a not-so-nearby member of our local galaxy group. Discovered with a 6? refractor, this 1.7 million light-year distant galaxy is not easily found, but can be seen with very dark sky conditions and at the lowest possible power. Due to large apparent size, and overall faintness (magnitude 9), low power is essential in larger telescopes to give a better sense of the galaxy’s frontier. Observers using large scopes will see faint regions of glowing gas (HII regions) and unresolved concentrations of bright stars. To distinguish them, try a nebula filter to enhance the HII and downplay the star fields. Barnard’s Galaxy appears like a very faint open cluster overlaid with a sheen of nebulosity, but the practiced eye using the above technique will clearly see that the “shine” behind the stars is extragalactic in nature.

Now look less than a degree north-northwest to turn up pale blue-green NGC 6818 (Right Ascension: 19 : 44.0 – Declination: -14 : 09) – the “Little Gem” planetary. Easily found in any size scope, this bright and condensed nebula reveals its annular nature in larger scopes but hints at it in scopes as small as 6?. Use a super wide field long-focus eyepiece to frame them both!

Until next week? Wishing you clear skies!

August 8, 2012December 23, 2015 by Nancy Atkinson

See the “Martian Triangle” in the Sky Tonight!

If — like me — you’ve been focusing on all the great images and news coming from the Mars Science Laboratory, perhaps you’ve missed the great view of the “Martian Triangle,” now visible in the night sky at twilight! Astrophotographer John Chumack hasn’t missed the view. This image is from August 6, 2012 from his observatory in Yellow Springs, Ohio.

The Martian Triangle show starts at twilight, and you can find it by looking low in the southwestern sky. The star at the top is actually the planet Saturn, the star on the bottom left is Spica, and the bright spot on bottom right is the planet Mars. And remember, somewhere in your field of view, there’s a few spacecraft on and around Mars and another orbiting Saturn.

John took this image with a modified Canon Rebel Xsi DSLR and a 47mm Lens, at F5.6, ISO 800, 10 second exposure. See more of John’s wonderful astrophotos at his Flickr page or at his website, Galactic Images.

Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.

July 31, 2012December 23, 2015 by Tammy Plotner

Weekly SkyWatcher’s Forecast: July 30 – August 5, 2012

Greetings, fellow SkyWatchers! It’s big. It’s bright. There’s no escaping it. This week the Moon will be our major point of study, but don’t rule out some bright globular clusters and interesting stars! There’s plenty of history and science to explore, too. Whenever you’re ready, just meet me in the back yard…

Monday, July 30 – Today’s history celebrates the 2001 flyby of the Moon by the Wilkinson Microwave Anisotropy Probe (WMAP) on its way to Lagrange Point 2 to study the cosmic microwave background radiation.

Now that we’re back at Sinus Iridum on the lunar surface, we’ll hop across Mare Frigoris and northeast of the punctuation of Harpalus for a grand old crater – J. Herschel. Although it looks small because it is seen on the curve, this wonderful old walled plain named for John Herschel contains some very tiny details. Its southeastern rim forms the edge of Mare Frigoris and the small (24 km) Horrebow dots its southwest edge. The crater walls are so eroded with time that not much remains of the original structure. Look for many very small telescopic impact craters which dot J. Herschel’s uneven basin and exterior edges. Power up! If you can spot the small central crater C, you are resolving a feature only 12 kilometers wide from some 385,000 kilometers away! Formed in the Pre-Nectarian period, this walled plain could be as much as 4 billion years old…

Now, relax and enjoy the peak of the Capricornid meteor shower. Although it is hard for the casual observer to distinguish these meteors from the Delta Aquarids, no one minds. Again, face southeast and enjoy! The fall rate for this shower is around 10 to 35 per hour, but unlike the Aquarids, this stream produces those great “fireballs” known as bolides. Enjoy…

Tuesday, July 31 – Tonight on the Moon, look south of Mare Humorum is darker Paulus Epidemiarum eastward and paler Lacus Excellentiae westward. To their south you will see a complex cojoined series of craters we’ll take a closer look at – Hainzel and Mee. Hainzel was named for Tycho Brahe’s assistant and measures about 70 kilometers in length and sports several various interior wall structures. Power up and look. Hainzel’s once high walls were obliterated on the north-east by the strike that caused Hainzel C and to the north by impact which caused the formation of Hainzel A. To its basic south is eroded Mee – named for a Scottish astronomer. While Crater Mee doesn’t appear to be much more than simple scenery, it spans 172 kilometers and is far older than Hainzel. While you can spot it easily in binoculars, close telescope inspection shows how the crater is completely deformed by Hainzel. Its once high walls have collapsed to the northwest and its floor is destroyed. Can you spot small impact crater Mee E on the northern edge?

Now, let’s take the opportunity to look at two multiple star systems – Nu and Xi Scorpii.

Starting with Nu about a fingerwidth east and slightly north of bright Beta, we find a handsome duo of stars in a field of nebulosity that will challenge telescopic observers much the way that Epsilon Lyrae does. With any small telescope, the observer will easily see the widely separated A and C stars. Add just a little power and take your time… The C star has a D companion to the southwest! For larger telescopes, take a very close look at the primary star. Can you separate the B companion to the south?

Now let’s hop to Xi about four fingerwidths north of Beta.

Discovered by Sir William Herschel in 1782, this 80 light-year distant system poses a nice challenge for mid-sized scopes. The yellow-hued A and B pair share a very eccentric orbit about the same distance as Uranus is from our Sun. During the 2007 observing year they should be fairly well spaced, and the slightly fainter secondary should appear to the north. Look a good distance away for the 7th magnitude orange C component and south for yet another closely-matched double of 7th and 8th magnitude – the D and E stars.

For the larger scope, this multiple star system does display a little bit of color. Most will see the A and B components as yellow/white, the C star as slightly orange, and the D/E pair as slightly tinged with blue. Be sure to mark your observations for this is one of the finest!

Wednesday, August 1 – Today is the birthdate of Maria Mitchell. Born in 1818, Mitchell became the first woman to be elected as an astronomer to the American Academy of Arts and Sciences. She later rocketed to worldwide fame when she discovered a bright comet in 1847.

For larger telescopes, let’s try a challenging lunar study worthy of your observing skills. Due west of Hansteen you will find a small crater known as Sirsalis near the terminator. It will appear as a small, dark ellipse with a bright west wall along with its twin, Sirsalis B. The feature you will be looking for is the Sirsalis Rille – the longest lunar “wrinkle” presently known. Stretching northeast of Sirsalis and ex-tending 459 kilometers south to the bright rays of Byrgius, this major “crack” in the lunar surface shows several branchings – like a long dry river bed. Geologically forming in the Imbrian period, chances are the Sirsalis Rille is lunar graben. Thanks to Lunar Orbiter images, the evidence points to shifting tectonic plates as the source of this incredible feature.

Tonight, let’s continue our exploration of globular clusters. These gravitationally bound concentrations of stars contain anywhere from ten thousand to one million members and attain sizes of up to 200 light-years in diameter. At one time, these fantastic members of our galactic halo were believed to be round nebulae. Perhaps the very first to be discovered was M22 in by Abraham Ihle in 1665. This particular globular is easily seen in even small binoculars and can be located just slightly more than two degrees northeast of the “teapot’s lid,” Lambda Sagittarii.

Ranking third amongst the 151 known globular clusters in total light, M22 (Right Ascension: 18 : 36.4 – Declination: -23 : 54) is probably the nearest of these incredible systems to our Earth with an approximate distance of 9600 light-years, and it is also one of the nearest globulars to the galactic plane. Since it resides less than a degree from the ecliptic, it often shares the same eyepiece field with a planet. At magnitude 6, the class VII M22 will begin to show individual stars to even modest instruments and will burst into stunning resolution for larger aperture. About a degree west-northwest, mid-sized telescopes and larger binoculars will capture smaller 8th magnitude NGC 6642. At class V, this particular globular will show more concentration toward the core region than M22. Enjoy them both!

Thursday, August 2 – Tonight we’ll fly right by the Full Buck Moon as we continue our studies to have a look at Mu 1 and Mu 2 Scorpii about two fingerwidths north of Zeta.

Very close to the same magnitude and spectral type, the twin Mu stars are easy to separate visually and most definitely worth a look in telescopes or binoculars. They are considered an actual physical pair because they share the exact same distance and proper motion, but they are separated by less than one light-year.

Hanging out in space some 520 light-years away, western Mu 1 is a spectroscopic binary – the very first discovered to have double lines. This Beta Lyrae-type star has an orbiting companion that eclipses it around every day and a half, yet causes no significant visual drop in magnitude – even though the orbiting companion is only 10 million kilometers away from it! While that sounds like plenty of distance, when the two pass, their surfaces would nearly touch each other!

Friday, August 3 – Tonight let’s race ahead of the rising Moon as we continue our studies with one of the globulars nearest to the galactic center – M14 (Right Ascension: 17 : 37.6 – Declination: -03 : 15). Located about sixteen degrees (less than a handspan) south of Alpha Ophiuchi, this ninth magnitude, class VIII cluster can be spotted with larger binoculars, but will only be fully appreciated with the telescope.

When studied spectroscopically, globular clusters are found to be much lower in heavy element abundance than stars such as own Sun. These earlier generation stars (Population II) began their formation during the birth of our galaxy, making globular clusters the oldest of formations that we can study. In comparison, the disk stars have evolved many times, going through cycles of starbirth and supernovae, which in turn enrich the heavy element concentration in star forming clouds and may cause their collapse. Of course, as you may have guessed, M14 breaks the rules. It contains an unusually high number of variable stars – in excess of 70 – with many of them known to be the W Virginis type. In 1938, a nova appeared in M14, but it was undiscovered until 1964 when Amelia Wehlau of the University of Ontario was surveying the photographic plates taken by Helen Sawyer Hogg. The nova was revealed on eight of these plates taken on consecutive nights, and showed itself as a 16th magnitude star – and was believed to be at one time almost 5 times brighter than the cluster members. Unlike 80 years earlier with T Scorpii in M80, actual photographic evidence of the event existed. In 1991, the eyes of the Hubble were turned its way, but neither the suspect star nor traces of a nebulous remnant were discovered. Then six years later, a carbon star was discovered in M14.

To a small telescope, M14 will offer little to no resolution and will appear almost like an elliptical galaxy, lacking in any central condensation. Larger scopes will show hints of resolution, with a gradual fading towards the cluster’s slightly oblate edges. A true beauty!

Saturday, August 4 – As we explore globular clusters, we simply assume them all to be part of the Milky Way galaxy, but that might not always be the case. We know they are basically concentrated around the galactic center, but there may be four of them that actually belong to another galaxy. Tonight we’ll look at one such cluster being drawn into the Milky Way’s halo. Set your sights just about one and a half degrees west-southwest of Zeta Sagittarii for M54 (Right Ascension: 18 : 55.1 – Declination: -30 : 29).

At around magnitude 7.6, M54 is definitely bright enough to be spotted in binoculars, but its rich class III concentration is more notable in a telescope. Despite its brightness and deeply concentrated core, M54 isn’t exactly easy to resolve. At one time we thought it to be around 65,000 light-years distant, and rich in variables – with 82 known RR Lyrae types. We knew it was receding, but when the Sagittarius Dwarf Elliptical Galaxy was discovered in 1994, it was noted that M54 was receding at almost precisely the same speed! When more accurate distances were measured, we found M54 to coincide with the SagDEG distance of 80-90,000 light-years, and M54?s distance is now calculated to be 87,400 light-years. No wonder it’s hard to resolve – it’s outside our galaxy!

As we know, most globular clusters congregate around the galactic center in the Ophiuchus/Sagittarius region. Tonight let’s explore what creates a globular cluster’s form… We’ll start with the “head of the class,” M75 (Right Ascension: 20 : 06.1 – Declination: -21 : 55).

Orbiting the galactic center for billions of years, globular clusters endured a wide variety of disturbances. Their component stars escape when accelerated by mutual encounters and the tidal force of our own Milky Way pulls them apart when they are near periapsis, that is, closest to the galactic center. Even close encounters with other masses, such as other clusters and nebulae, can affect them! At the same time, their stellar members are also evolving and this loss of gas can contribute to mass loss and deflation of these magnificent clusters. Although this happens far less quickly than in open clusters, our observable globular friends may only be the survivors of a once larger population, whose stars have been spread throughout the halo. This destruction process is never-ending, and it is believed that globular clusters will cease to exist in about 10 billion years.

Although it will be later evening when M75 appears on the Sagittarius/Capricornus border, you will find the journey of about 8 degrees southwest of Beta Capricorni worth the wait. At magnitude 8, it can be glimpsed as a small round patch in binoculars, but a telescope is needed to see its true glory. Residing around 67,500 light-years from our solar system, M75 is one of the more remote of Messier’s globular clusters. Since it is so far from the galactic center – possibly 100,000 light-years distant – M75 has survived almost intact for billions of years to remain one of the few Class I globular clusters. Although resolution is possible in very large scopes, note that this globular cluster is one of the most concentrated in the sky, with only the outlying stars resolvable to most instruments.

Sunday, August 5 – Today we celebrate the birthday of Neil Armstrong, the first human to walk on the Moon. Congratulations! Also on this date in 1864, Giovanni Donati made the very first spectroscopic observations of a comet (Tempel, 1864 II). His observations of three absorption lines led to what we now know as the Swan bands, from a form of the carbon radical C2.

Our study continues tonight as we move away from the galactic center in search of a remote globular cluster that can be viewed by most telescopes. As we have learned, radial velocity measurements show us the majority of globulars are involved in highly eccentric elliptical orbits, which take them far outside the plane of the Milky Way. These orbits form a sort of spherical “halo” which tends to be more concentrated toward our galactic center. Reaching out several thousands of light-years, this halo is actually larger than the disk of our own galaxy. Since globular clusters aren’t involved in our galaxy’s disk rotation, they may possess very high relative velocities. Tonight let’s head toward the constellation of Aquila and look at one such globular – NGC 7006 (Right Ascension: 21 : 01.5 – Declination: +16 : 11).

Located about half a fist’s width east of Gamma Aquilae, NGC 7006 is speeding towards us at a velocity of around 345 kilometers per second. At 150,000 light-years from the center of our galaxy, this particular globular could very well be an extra-galactic object. At magnitude 11.5, it’s not for the faint of heart, but can be spotted in scopes as small as 150mm, and requires larger aperture to look like anything more than a suggestion. Given its tremendous distance from the galactic center, it’s not hard to realize this is a class I – although it is quite faint. Even the largest of amateur scopes will find it unresolvable!

Until next week? May all your skies by clear and steady…

Lead image caption: Crater J. Herschel – Credit: Damian Peach

July 22, 2012December 23, 2015 by Tammy Plotner

Weekly SkyWatcher’s Forecast: July 23-29, 2012

IC 4665 - Credit: Palomar Observatory, courtesy of Caltech

Greetings, fellow SkyWatchers! Are you ready for a week filled with alternative astronomical observing studies? If so, you’ll enjoy looking at some unusual stars and star clusters. If you want to keep things cool, then come along as we mine for lunar ice. Feeling a bit more lazy? Then kick back and enjoy the Delta Aquarid meteor shower or just step out after sunset and enjoy a splendid conjunction! It’s all here… Just head outside!

Monday, July 23 – Tonight we’ll launch our imaginations as we view the area around Mare Crisium and have a look at this month’s lunar challenge – Macrobius. You’ll find it just northwest of the Crisium shore. Spanning 64 kilometers in diameter, this Class I impact crater drops to a depth of nearly 3600 meters – about the same as many of our earthly mines. Its central peak rises up 1100 meters, and may be visible as a small speck inside the crater’s interior. Be sure to mark your lunar challenges and look for other features you may have missed before!

Now, relax and let’s talk until the Moon sets…

As we know most stars begin life in stellar nurseries and end life either alone or in very small groups as doubles or multiple stars. Tonight we can have a look at a group of young stars beginning their stellar evolution and end with an old solitary elder preparing to move on to an even “higher realm.” Open cluster IC 4665 (Right Ascension: 17 : 46.3 – Declination: +05 : 43) is easily detected with just about any optical aid about a finger-width north-northeast of Beta Ophiuchi. Discovered by Philippe Loys de Cheseaux in the mid-1700s, this 1400 light-year distant cluster consists of about 30 mixed magnitude stars all less than 40 million years of age. Despite its early discovery, the cluster did not achieve broad enough recognition for Dreyer to include it in the late 19th century New General Catalog and it was later added as a supplement to the NGC in the Index Catalog of 1908. Be sure to use low power to so see all of this large group.

About three finger-widths north-northeast of IC 4665 is a study that did make Dreyer’s catalogue – NGC 6572 (Right Ascension: 18 : 12.1 – Declination: +06 : 51). This 9th magnitude planetary is very small – but intense. Like the “Cat’s Eye” in Draco, and NGC 6210 in Hercules, this planetary can take a lot of magnification. Those with large scopes should look for a small, round, blue inner core encased is a faint shell. A challenge to find? You bet. Worth the work? Sometimes working for something makes it all the more fun!

Tuesday, July 24 – As our observing evening begins, be sure to look for one of the finest conjunctions of the year! Hovering around the waxing crescent Moon like bees drawn to a hive, you’ll find Mars to the upper right and Spica to the upper left (northwest and northeast respectively). To Spica’s upper right, you’ll find Saturn joining the show, too! This is a very “photogenic” opportunity…

With plenty of Moon to explore tonight, why don’t we try locating an area where many lunar exploration missions made their mark? Binoculars will easily reveal the fully disclosed areas of Mare Serenitatis and Mare Tranquillitatis, and it is where these two vast lava plains converge that we will set our sights. Telescopically, you will see a bright “peninsula” westward of where the two conjoin which extends toward the east. Just off that look for bright and small crater Pliny. It is near this rather inconspicuous feature that the remains Ranger 6 lie forever preserved where it crashed on February 2, 1964.

Unfortunately, technical errors occurred and it was never able to transmit lunar pictures. Not so Ranger 8! On a very successful mission to the same relative area, this time we received 7137 “postcards from the Moon” in the last 23 minutes before hard landing. On the “softer” side, Surveyor 5 also touched down near this area safely after two days of malfunctions on September 10, 1967. Incredibly enough, the tiny Surveyor 5 endured temperatures of up to 283 degrees F, but was able to spectrographically analyze the area’s soil… And by the way, it also managed to televise an incredible 18,006 frames of “home movies” from its distant lunar locale.

Wednesday, July 25 – Today in 1971, Apollo 15 was launched on its way towards the Moon, and we’ll continue our celebration of space exploration and walk on the Moon where the first man set foot. For SkyWatchers, the dark round area you see on the northeastern limb is Mare Crisium and the dark area below that is Mare Fecunditatis. Now look mid-way on the terminator for the dark area that is Mare Tranquillitatis. At its southwest edge, history was made.

In binoculars, trace along the terminator where the Caucasus Mountains stand – and then south for the Apennines and the Haemus Mountains. As you continue towards the center of the Moon, you will see where the shore of Mare Serenitatis curves east, and also the bright ring of Pliny. Continue south along the terminator until you spot the small, bright ring of Dionysius along the edge of Mare Tranquillitatis. Just to the southwest, you may be able to see the soft rings of Sabine and Ritter. It is near here where the base section of the Apollo 11 landing module – Eagle – lies forever enshrined in “magnificent desolation.”

For telescope users, the time is now to power up! See if you can spot small craters Armstrong, Aldrin and Collins just east. Even if you cannot, the Apollo 11 landing area is about the same distance as Sabine and Ritter are wide to the east-southeast. Even if you don’t have the opportunity to see it tonight, take the time during the next couple of days to point it out to your children, grandchildren, or even just a friend… The Moon is a spectacular world and we’ve been there!
Tonight let’s have a look with our eyes first at Delta Ophiuchi. Known as Yed Prior (“The Hand”), look for its optical double Epsilon to the southeast: Yed Posterior. Now have a look in binoculars or a telescope at absolute minimum power for another undiscovered gem…

Delta Ophiuchi is 170 light-years from us, while Epsilon is 108 – but look at the magnificent field they share. Stars of every spectral type are in an area of sky which could easily be covered by a small coin held at arm’s length. Enjoy this fantastic field – from the hot, blue youngsters to the old red giants!

Thursday, July 26 – Long before the Sun sets, look for the Moon to appear in the still-blue sky. As it darkens, watch for shadows on the surface. Have you ever wondered if there was any place on the lunar surface that hasn’t seen the sunlight? Then let’s go searching for one tonight…

Our first order of business will be to identify crater Albategnius. Directly in the center of the Moon is a dark floored area known as Sinus Medii. South of it will be two conspicuously large craters – Hipparchus to the north and ancient Albategnius to the south. Trace along the terminator toward the south until you have almost reached its point (cusp) and you will see a black oval. This normal looking crater with the brilliant west wall is equally ancient crater Curtius. Because of its high southern latitude, we shall never see the interior of this crater – and neither has the Sun! It is believed that the inner walls are quite steep and that Curtius’ interior has never been illuminated since its formation billions of years ago. Because it has remained dark, we can speculate that there may be “lunar ice” pocketed inside its many cracks and rilles that date back to the Moon’s formation!

Because our Moon has no atmosphere, the entire surface is exposed to the vacuum of space. When sunlit, the surface reaches up to 385 K, so any exposed “ice” would vaporize and be lost because the Moon’s gravity cannot hold it. The only way for “ice” to exist would be in a permanently shadowed area. Near Curtius is the Moon’s south pole, and the Clementine spacecraft’s imaging showed around 15,000 square kilometers in which such conditions could exist. So where did this “ice” come from? The lunar surface never ceases to be pelted by meteorites – most of which contain water ice. As we know, many craters were formed by just such impacts. Once hidden from the sunlight, this “ice” could remain for millions of years!

Friday, July 27 – Tonight let’s skip the Moon and take a look at an astounding system called 36 Ophiuchi, located about a thumb’s width southeast of Theta. Situated in space less than 20 light-years from Earth, even small telescopes can split this pair of 5th magnitude K type giants very similar to our own Sun, and larger telescopes can also pick up the C component as well. 36 Ophiuchi B is also known as system 544…because it has what could very likely be a planet in a habitable zone!

Now we’ll have a look at a beautifully contrasting pair of stars – Zeta 1 and 2 Scorpii. You’ll find them a little less than a handspan south-southeast of Antares and at the western corner of the J of the constellation’s shape.

Although the two Zetas aren’t a true physical pair, they are nonetheless interesting. The easternmost, orange sub-giant Zeta 2 appears far brighter for a reason… It’s much closer at only 155 light-years away. But, focus your attention on western Zeta 1. It’s a blue supergiant that’s around 5700 light-years away and shines with the light of 100,000 suns and exceeds even Rigel in sheer power! The colorful pair is easily visible as two separate stars to the unaided eye, but a real delight in binoculars or a low power telescope field. Check them out tonight!

Saturday, July 28 – Tonight let’s continue our studies of the lunar poles by returning to previous study crater Plato. North of Plato you will see a long horizontal area with a gray floor – Mare Frigoris. North of it you will note a double crater. This elongated diamond-shape is Goldschmidt and the crater which cuts across its western border is Anaxagoras. The lunar north pole isn’t far from Goldschmidt, and since Anaxagoras is just about one degree outside of the Moon’s theoretical “arctic circle” the lunar sun will never go high enough to clear the southernmost rim.

On March 5, 1998, NASA announced that Lunar Prospector’s neutron spectrometer data showed that water ice had been discovered at both lunar poles. The first results showed the ice was mixed in with lunar regolith (soil, rocks and dust), but long term data confirmed near pure pockets hidden beneath about 40 cm of surface material – with the results being strongest in the northern polar region. It is estimated there may be as much as 6 trillion kg (6.6 billion tons) of this valuable resource! If this still doesn’t get your motor running, then realize that without it, we could never establish a manned lunar base because of the tremendous expense involved in transporting our most basic human need – water.

The presence of lunar water could also mean a source of oxygen, another vital material we need to survive! And for returning home or voyaging further, these same deposits could provide hydrogen which could be used as rocket fuel. So as you view Anaxagoras tonight, realize that you may be viewing one of mankind’s future “homes” on a distant world!

Now grab a comfortable seat because the Delta Aquarid meteor shower reaches its peak tonight. It is not considered a prolific shower, and the average fall rate is about 25 per hour – but who wouldn’t want to take a chance on observing a meteor about every 4 to 5 minutes? These travelers are considered to be quite slow, with speeds around 24 kilometers per second and are known to leave yellow trails. One of the most endearing qualities of this annual shower is its broad stream of around 20 days before and 20 days after peak. This will allow it to continue for at least another week and overlap the beginning stages of the famous Perseids.

The Delta Aquarid stream is a complicated one, and a mystery not quite yet solved. It is possible that gravity split the stream from a single comet into two parts, and each may very well be a separate stream. One thing we know for certain is they will seem to emanate from the area around Capricornus and Aquarius, so you will have best luck facing southeast and getting away from city lights. Although the Moon will interfere, just relax and enjoy a warm summer night. It’s time to catch a “falling star!”

Sunday, July 29 – Tonight let’s take an entirely different view of the Moon as we do a little “mountain climbing!” The most outstanding feature on the Moon will be the emerging Copernicus, but since we’ve delved into the deepest areas of the lunar surface, why not climb to some of its peaks?

Using Copernicus as our guide, to the north and northwest of this ancient crater lie the Carpathian Mountains, ringing the southern edge of Mare Imbrium. As you can see, they begin well east of the terminator, but look into the shadow! Extending some 40 kilometers beyond the line of daylight, you will continue to see bright peaks – some of which reach 2072 meters high! When the area is fully revealed tomorrow, you will see the Carpathian Mountains eventually disappear into the lava flow that once formed them. Continuing onward to Plato, which sits on the northern shore of Imbrium, we will look for the singular peak of Pico. It is between Plato and Mons Pico that you will find the scattered peaks of the Teneriffe Mountains. It is possible that these are the remnants of much taller summits of a once stronger range, but only around 1890 meters still survives above the surface.

Time to power up! Lather, rinse and repeat until you know these by heart… To the west of the Teneriffes, and very near the terminator, you will see a narrow series of hills cutting through the region west-southwest of Plato. This is known as the Straight Range – Montes Recti – and some of its peaks reach up to 2072 meters. Although this doesn’t sound particularly impressive, that’s over twice as tall as the Vosges Mountains in central Europe and on the average very comparable to the Appalachian Mountains in the eastern United States. Not bad!

Now head about a palm’s width east of our previous study star – Zeta Scorpii – for lovely Theta. Named Sargas, this 1.8 magnitude star resides around 650 light-years distant in a very impressive field of stars for binoculars or a small telescope. While all of these are only optical companions, the field itself is worth a look – and worth remembering for the future.

About three fingerwidths north is true double Lambda Scorpii, also known as Shaula (The Sting). As the brightest known star in its class, 1.6 magnitude Lambda is a spectroscopic binary which is also a variable of the Beta Canis Majoris type, changing ever so slightly in little more than 5 hours. Although we can’t see the companion star, nearby is yet another that will make learning this starhop “marker” worth your time.

Until next week? Ask for the Moon, but keep on reaching for the stars!

July 16, 2012December 23, 2015 by Nancy Atkinson

Spectacular Views: The Moon Occults Jupiter

Caption: July 15 2012 occultation, taken with Canon 550D on Newton 200/1200 mounted on NEQ6Pro. Credit: Andrei Juravle

Astrophotographers in Northern Africa, Europe and the Middle East were treated to a beautiful sight in the early morning hours of July 15, 2012. A lunar occultation of Jupiter took place just before dawn, as the waning crescent Moon slid in front of the planet Jupiter. Venus was hanging around nearby, too. Several astrophotographers were able to capture the event, and some got a bonus look at Jupiter’s Galilean moons, as well! Above is a lovely image by Andrei Juravle.

More below!

Caption: The Moon, Venus and Jupiter. Credit Thierry Legault.

Astrophotographer extraordinaire Thierry Legault took this great shot of Venus, Jupiter and the Moon from Saint-Cloud, France with a Canon 5D mark II and 135mm lens. But look closely: the satellites of Jupiter are visible:

Caption: A closer look reveals Jupiter’s moons! Credit: Thierry Legault.

And as always, you should check out Thierry’s website for more incredible images.

Caption: Jupiter and the Moon hover over Dolmabahce Mosque in Istanbul, Turkey. Credit: Rasid Tugral.

Caption: Clouds nearly covered the view in Mombaroccio, Marche, Italy. Credit: Niki Giada.

Caption: A series of images of the Moon’s occultation of Jupiter as seen in Saida, Lebanon. Credit: astroZ1 on Flickr.

Caption: Occultation of Jupiter by the Moon as seen from Smolyan, Bulgaria. Credit: Zlatan Merakov.

More images are still coming in, and you can see more on Universe Today’s Flickr page. Thanks to everyone who submitted their gorgeous images!

July 15, 2012December 23, 2015 by Tammy Plotner

Weekly SkyWatcher’s Forecast: July 16-22, 2012

Messier 19 - Credit: Doug Williams, REU Program/NOAO/AURA/NSF

Greetings, fellow SkyWatchers! My satellite dish and internet connection has now returned from the land of Oz. While it was great to have a span of days where no electric meant no annoying lights, it also meant creative cooking excursions on the gas grill in 100 degree weather. Ah, well… the things we do for dark skies! This is New Moon week, so get out there and enjoy the Milky Way! Whenever you’re ready, meet me in the back yard…

Monday, July 16 – Today in 1850 at Harvard University, the first photograph of a star (other than the Sun) was made. The honors went to Vega! In 1994, an impact event was about to happen as nearly two dozen fragments of Comet Shoemaker-Levy 9 were speeding their way to the surface of Jupiter. The result was spectacular, and the visible features left behind on the planet’s atmosphere were the finest ever recorded.

Now let’s return again to the oblate and beautiful M19 and drop two fingerwidths south for another misshapen globular – M62 (Right Ascension: 17 : 01.2 – Declination: -30 : 07).

At magnitude 6, this 22,500 light-year distant Class IV cluster can be spotted in binoculars, but comes to wonderful life in the telescope. First discovered by Messier in 1771, Herschel was the first to resolve it and report on its deformation. Because it is so near to the galactic center, tidal forces have “crushed” it – much like M19. You will note when studying in the telescope that its core is very off center. Unlike M19, M62 has at least 89 known variable stars – 85 more than its neighbor – and the dense core may have undergone collapse. A large number of X-ray binaries have also been discovered within its structure, perhaps caused by the close proximity of stellar members. Enjoy it tonight!

Tuesday, July 17 – If you’re up to another challenge tonight, let’s go hunting Herschel I.44, also known as NGC 6401. You’ll find this 9.5 magnitude globular cluster around two fingerwidths northeast of Theta Ophiuchi and a little more than a degree due east of star 51 (Right Ascension: 17 : 38.6 – Declination: -23 : 55).

Discovered by William Herschel in 1784 and often classed as “uncertain,” today’s powerful telescopes have placed this halo object as a Class VIII and given it a rough distance from the galactic center of 8,800 light-years. Although neither William nor John could resolve this globular, and they listed it originally as a bright nebula, studies in 1977 revealed a nearby suspected planetary nebula named Peterson 1. Thirteen years later, further study revealed this to be a symbiotic star.

Symbiotic stars are a true rarity – not a singular star at all, but a binary system. A red giant dumps mass towards a white dwarf in the form of an accretion disc. When this reaches critical mass, it then causes a thermonuclear explosion resulting in a planetary nebula. While no evidence exists that this phenomenon is physically located within metal-rich NGC 6401, just being able to see it in the same field makes this journey both unique and exciting!

Wednesday, July 18 – On this day 27 years ago, India launched its first satellite (Rohini 1), and 31 years ago in the United States Gemini 10 launched carrying John Young and Michael Collins to space.

Now, let’s carry ourselves into space as we take a very unusual and beautiful journey to a bright and very colorful pair of stars known as Omicron 1 Cygni. Easily located about halfway between Alpha (Deneb) and Delta on the western side, this is a pure delight in binoculars or any size telescope. The striking gold color of 3.7 magnitude 31 Cygni (Omicron 1) is easily highlighted against the blue of same field companion, 5th magnitude 30 Cygni. Although this wide pairing is only an optical one, the K-type giant is a double star – an eclipsing variable around 150 times larger than or own Sun – and is surrounded by a gaseous corona more than double the size as the star itself. If you are using a scope, you can easy spot the blue tinted, 7th magnitude B star about one third the distance as between the two giants. Although our true pair are some 1.2 billion miles apart, they are oriented nearly edge-on from our point of view – allowing the smaller star to be totally eclipsed during each revolution. This total eclipse lasts for 63 days and happens about every 10.4 years, but don’t stay up too late… We’ve still got 7 years to wait!

Thursday, July 19 – Today in 1846, Edward Pickering was born. Although his name is not well known, he became a pioneer in the field of spectroscopy. Pickering was the Harvard College Observatory Director from 1876 to 1919, and it was during his time there that photography and astronomy began to merge. Known as the Harvard Plate Collection, these archived beginnings still remain a valuable source of data.

It’s New Moon, so why not have a look at something that would make Edward Pickering proud? He enthusiastically encouraged amateur astronomers, and founded the American Association of Variable Star Observers – so set your sights on RR Scorpius about two fingerwidths northeast of Eta and less than a fingerwidth southwest M62 (RA 16 56 37.84 Dec -30 34 48.2). This very red Mira type can reach as high as magnitude 5 and drop as low as 12 in about 280 days!

Tonight let’s just enjoy a little stargazing and revel in the beauty of our own galaxy’s spiral arm – the Milky Way. For those living in the city, you owe it to yourself to get away to a dark location to enjoy this veritable “river of stars” which spans out of the galactic center south and runs overhead. Almost directly behind you from the galactic anti-center stretches the Perseus arm, and the sight is a beautiful one. If skies are fine, you can easily see the dark dust rift where the arm separates and the billows of light of unresolved stars. It’s the most glorious sight of summer! While we have many days yet before the Aquarid meteor shower officially reaches its peak, you will be pleasantly surprised at this year’s high activity. They’ve been flying out of the night sky for almost two weeks now, and it would not surprise me if you saw ten or more per hour of these quick, bright visitors.

Friday, July 20 – Today was a busy day in astronomy history! In 1969, the world held its breath as the Apollo 11 lander touched down and Neil Armstrong and Edwin Aldrin became the first humans to touch the lunar surface. We celebrate our very humanity because even Armstrong was so moved that he messed up his lines! The famous words were meant to be “A small step for a man. A giant leap for mankind.” That’s nothing more than one small error for a man, and mankind’s success continued on July 20, 1976 when Viking 1 landed on Mars – sending back the first images ever taken from that planet’s surface.

If you’re out at sunset, be sure to look for the slimmest crescent Moon you can imagine… It will point your way to nearby Mercury! For lucky viewers “down under” this is an occultation event and will only be observable after sunset from southernmost regions of central Australia. Be sure to check the resources for websites like IOTA for specific times and locations.

The first assignment of the evening is a pair of interacting galaxies. 40 degrees northwest of Beta Canum Venaticorum is NGC 4490 (Right Ascension: 12 : 30.6 – Declination: +41 : 38) and smaller, fainter companion NGC 4485 (Right Ascension: 12 : 30.5 – Declination: +41 : 42). This pair, also known as Arp 269, are quite unusual in appearance to the larger scope. NGC 4490 is around magnitude 10 and shows a bright, irregular core region and a rather strange profile. Known as the “Cocoon” galaxy, it appears to almost reach toward its companion 3 degrees to the north. Progressively larger scopes under ideal conditions will be able to make out some faint mottling in the NGC 4490’s structure.

Now let’s honor southern skies by exploring the fantastic, NGC 3372 (Right Ascension: 10 : 43.8 – Declination: -59 : 52) – the Eta Carinae Nebula. As a giant, diffuse nebula with a visual brightness of magnitude 1, (wow!) it contains the most massive and luminous star in our Milky Way galaxy, Eta Carinae. It’s also home to a small cluster, Collinder 228, which is only one of 8 cataloged open clusters within the area of this huge star-forming region; the others are Bochum (Bo) 10, Trumpler (Tr) 14 (also cataloged as Cr 230), Tr 15 (= Cr 231), Cr 232, Tr 16 (= Cr 233), Cr 234, and Bo 11. Star Eta Carinae is involved in open cluster Trumpler 16. This fantastic nebula contains details which northerners can only dream about, such as the dark “Keyhole” and the “Homunkulus” around the giant star itself. A fantastic region for exploration with both telescopes and binoculars!

Saturday, July 21 – Today in 1961, Mercury 4 was launched, sending Gus Grissom into suborbital space on the second manned flight, and he returned safely in Liberty Bell 7.

Since the moonlight will now begin to interfere with our early evening globular cluster studies, let’s waive them for a while as we take a look at some of the region’s most beautiful stars. Tonight your goal is to locate Omicron Ophiuchi, about a fingerwidth northeast of Theta. At a distance of 360 light-years, this system is easily split by even small telescopes. The primary star is slightly dimmer than magnitude 5 and appears yellow to the eye. The secondary is near 7th magnitude and tends to be more orange in color. This wonderful star is part of many double star observing lists, so be sure to note it!

Tonight would be an ideal time to look at a brilliant open cluster about a fist width east of Epsilon Scorpii – M6 (Right Ascension: 17 : 40.1 – Declination: -32 : 13). On a moonless night, the 50 or so members of this 2000 light year distant, 100 million year old cluster can usually be seen unaided as a small fuzzy patch just above the Scorpion’s tail. Tonight we visit because the brighter skies will aid you in seeing the primary stars distinctive asterism. Using binoculars or telescope at lowest power, the outline of stars does truly resemble its namesake – the “Butterfly Cluster”. The M6 is much more than “just a pretty face” and we’ll be back to study under darker skies.

Sunday, July 22 – Tonight instead of lunar exploration, we will note the work of Friedrich Bessel, who was born on this day in 1784. Bessel was a German astronomer and mathematician whose functions, used in many areas of mathematical physics, still carry his name. But, you may put away your calculator, because Bessel was also the very first person to measure a star’s parallax. In 1837, he chose 61 Cygni and the result was no more than a third of an arc second. His work ended a debate that had stretched back two millennia to Aristotle’s time and the Greek’s theories about the distances to the stars.

Although you’ll need to use your finderscope with tonight’s brighter skies, you’ll easily locate 61 between Deneb (Alpha) and Zeta on the eastern side. Look for a small trio of stars and choose the westernmost. Not only is it famous because of Bessel’s work, but it is one of the most noteworthy of double stars for a small telescope. 61 Cygni is the fourth nearest star to Earth, with only Alpha Centauri, Sirius, and Epsilon Eridani closer. Just how close is it? Try right around 11 light-years.

Visually, the two components have a slightly orange tint, are less than a magnitude apart in brightness and have a nice separation of around 30 degrees to the south-southeast. Back in 1792, Piazzi first noticed 61’s abnormally large proper motion and dubbed it “The Flying Star.” At that time, it was only separated by around 10 degrees and the B star was to the northeast. It takes nearly 7 centuries for the pair to orbit each other, but there is another curiosity here. Orbiting the A star around every 4.8 years is an unseen body that is believed to be about 8 times larger than Jupiter. A star – or a planet? With a mass considerably smaller than any known star, chances are good that when you view 61 Cygni, you’re looking toward a distant world!

Until next week, dreams really do come true when you keep on reaching for the stars!

June 25, 2012December 23, 2015 by Tammy Plotner

Weekly SkyWatcher’s Forecast: June 25 – July 1, 2012

Crater Julius Caesar - Credit: Wes Higgins

Greetings, fellow SkyWatchers! What a great week to enjoy lunar features! We’ll celebrate many famous birthdays – including Charles Messier – and take on challenging double stars. If you’re in the mood to just kick back in a lawn chair and enjoy, then check out the June Draconid meteor shower. (sssssh… it may have been responsible for the Tunguska Blast!) Still more? Then keep an eye on the western horizon, because Mercury is about to become a “guest star” in the Beehive Cluster! When ever you’re ready, just meet me in the back yard…

Monday, June 25 – Today celebrates the birth of Hermann Oberth – who has often been considered the father of modern rocketry. Born in Transylvania in 1894, Oberth was a visionary who was convinced space travel would one day be possible. Inspired by the works of Jules Verne, Oberth studied rockets and wrote many books devoted to the possibility of achieving spaceflight. He was the first to conceive of rocket “stages” – allowing vehicles to expend their fuel and lose dead weight. But tonight you won’t need one of Oberth’s rockets to travel to the Moon, as take on another challenge as we look mid-way along the terminator at the west shore of Mare Tranquillitatis for crater Julius Caesar.

This is also a ruined crater, but it met its demise not through lava flow – but from a cataclysmic event. The crater is 88 kilometers long and 73 kilometers wide. Although its west wall still stands over 1200 meters high, look carefully at the east and south walls. At one time, something plowed its way across the lunar surface, breaking down Julius Caesar’s walls and leaving them to stand no higher than 600 meters at the tallest. While visiting the “Tranquil Sea”, look for the unusually shaped crater Hypatia. Can you spot its rima on the southern shore of Tranquillitatis? Perhaps the bright pockmark of Moltke on its north edge will help. Hypatia sits on the northern shore of a rugged area known as Sinus Asperitatis. Do you see Alfraganus on the terminator? Follow the terrain to Theophilus and look west for Ibyn-Rushd with crater Kant to the northwest and the beautiful peak of Mons Penck to its east.

Tuesday, June 26 – On this day in 1949, asteroid Icarus was discovered on a 48-inch Schmidt plate made nine months after that telescope went into operation, and just prior to the beginning of the multi-year National Geographic-Palomar Sky Survey. The asteroid was found to have a highly eccentric orbit and a perihelion distance of just 27 million kilometers, closer to the Sun than Mercury, giving it its unusual name. It was just 6.4 million kilometers from Earth at the time of discovery, and variations in its orbital parameters have been used to determine Mercury’s mass and test Einstein’s theory of general relativity.

But, today is even more special because it is the birthday of none other than Charles Messier, the famed French comet hunter. Born in 1730, Messier is best known for cataloging the 100 or so bright nebulae and star clusters that we now refer to as the Messier objects. The catalog was intended to keep both Messier and others from confusing these stationary objects with possible new comets.

] If you missed your chance last night to see the incredible Alpine Valley, it’s now fully disclosed in the sunlight. Viewable through binoculars as a thin, dark line, telescopic observers at highest powers will enjoy a wealth of details in this area, such as a crack running inside its boundaries. It’s a wonderful lunar observing challenge and a guide to our next lunar feature – Cassini and Cassini A. Where the valley joins the lunar Alps, follow the range south into Mare Imbrium. Along the way you will see the protruding bright peaks of Mons Blanc, Promontorium DeVille, and at the very end, Promontorium Agassiz ending in the smooth sands. Southeast of Agassiz you will spot Cassini. The major crater spans 57 kilometers and reaches a floor depth of 1240 meters. The challenge is to also spot the central crater A, which is only 17 kilometers wide, yet drops down another 2830 meters below the surface. This shallow crater holds another challenge within – Cassini A. But look carefully, can you spot the B crater on Cassini’s inner southwestern rim? Or the very small M crater just outside the northern edge?

For more advanced lunar observers, head a bit further south to the Haemus Mountains to look for the bright punctuation of a small crater on the southwest shore of Mare Serenitatis. Increase your magnification and look for a curious feature with an even more curious name… Rima Sulpicius Gallus. It is nothing more than a lunar wrinkle which accompanies the crater of the same name – a long-gone Roman counselor. Can you trace its 90 kilometer length?

Now see how many Messier objects that you can capture and wish Charles a happy birthday!

Wednesday, June 27 – Let’s begin our lunar studies tonight with a little “mountain climbing!” Using Copernicus as our guide, to the north and northwest of this ancient crater lie the Carpathian Mountains ringing the southern edge of Mare Imbrium. As you can see, they begin well east of the terminator, but look into the shadow! Extending some 40 kilometers beyond the line of daylight, you will continue to see bright peaks – some of which reach a height of 2072 meters. When the area is fully revealed tomorrow, you will see the Carpathian Mountains disappear into the lava flow that once formed them.

Let’s try looking just south of Sinus Medii and identifying these features: (1) Flammarion, (2) Herschel, (3) Ptolemaeus, (4) Alphonsus, (5) Davy, (6) Alpetragius, (7) Arzachel, (8) Thebit, (9) Purbach, (10) Lacaille, (11) Blanchinus, (12) Delaunay, (13) Faye, (14) Donati, (15) Airy, (16) Argelander, (17) Vogel, (18) Parrot, (19) Klein, (20) Albategnius, (21) Muller, (22) Halley, (23) Horrocks, (24) Hipparchus, (25) Sinus Medii

When skies are dark, it’s time to have a look at the 250 light-year distant silicon star Iota Librae. This is a real challenge for binoculars – but not because the components are so close. In Iota’s case, the near 5th magnitude primary simply overshadows its 9th magnitude companion! In 1782, Sir William Herschel measured them and determined them to be a true physical pair. Yet, in 1940 Librae A was determined to have an equal magnitude companion only .2 arc seconds away…. And the secondary was proved to have a companion of its own that echoes the primary. A four star system!

While you’re out, keep watch for a handful of meteors originating near the constellation of Corvus. The Corvid meteor shower is not well documented, but you might spot as many as ten per hour.

Thursday, June 28 – Tonight on the lunar surface, use crater Copernicus as a guide and look north-northwest to survey the Carpathian Mountains. The Carpathians ring the southern edge of Mare Imbrium beginning well east of the terminator. But let’s look on the dark side. Extending some 40 km beyond into the Moon’s own shadow, you can continue to see bright peaks – some reaching 2000 meters high! Tomorrow, when this area is fully revealed, you will see the Carpathians begin to disappear into the lava flow forming them. Continuing northward to Plato – on the northern shore of Mare Imbrium – re-identify the singular peak of Pico. Between Plato and Mons Pico you will find the many scattered peaks of the Teneriffe Mountains. It is possible that these are the remnants of much taller summits of a once precipitous range. Now the peaks rise less than 2000 meters above the surface.

Time to power up! West of the Teneriffes, and very near the terminator, you will see a narrow line of mountains, very similar in size to the Alpine Valley. This is known as the Straight Range or the Montes Recti. To binoculars or small scopes at low power, this isolated strip of mountains will appear as a white line drawn across the grey mare. It is believed this feature may be all that is left of a crater wall from the Imbrium impact. It runs for a distance of around 90 kilometers, and is approximately 15 kilometers wide. Some of its peaks reach as high as 2072 meters! Although this doesn’t sound particularly impressive, that’s over twice as tall as the Vosges Mountains in west-central Europe, and on the average very comparable to the Appalachian Mountains in the eastern United States.

When you’re finished with your lunar observations, tonight let’s try a challenging double star – Upsilon Librae. This beautiful red star is right at the limit for a small telescope, but quite worthy as the pair is a widely disparate double. Look for the 11.5 magnitude companion to the south in a very nice field of stars!

Friday, June 29 – Today we celebrate the birthday of George Ellery Hale, who was born in 1868. Hale was the founding father of the Mt. Wilson Observatory. Although he had no education beyond his baccalaureate in physics, he became the leading astronomer of his day. He invented the spectroheliograph, coined the word astrophysics, and founded the Astrophysical Journal and Yerkes Observatory. At the time, Mt. Wilson dominated the world of astronomy, confirming what galaxies were and verifying the expanding universe cosmology, making Mt. Wilson one of the most productive facilities ever built. When Hale went on to found Palomar Observatory, the 5-meter (200?) telescope was named for him and dedicated on June 3, 1948. It continues to be the largest telescope in the continental United States.

It’s time to head deeper toward the lunar south as we take a close look at the dark, heart-shaped region Palus Epidemiarum. Caught on its southern edge is the largely eroded Campanus with well defined Cichus to the east and Ramsden to the west. Power up in your telescope and look carefully at its smooth floors. If conditions are favorable, you will catch Rima Hesiodus cutting across its northern boundary and the crisscross pattern of Rima Ramsden in the western lobe. Can you make out a small, deep puncture mark to the northeast? It might be small, but it has a name – Marth.
Now let’s go deep south and have look at an area which once held something almost half a bright as tonight’s Moon and over four times brighter than Venus. Only one thing could light up the skies like that – a supernova. According to historical records from Europe, China, Egypt, Arabia and Japan, 1001 years ago the very first supernova event was noted. Appearing in the constellation of Lupus, it was at first believed to be a comet by the Egyptians, yet the Arabs saw it as an illuminating “star.”

Located less than a fingerwidth northeast of Beta Lupus (RA 15 02 48.40 Dec -41 54 42.0) and a half degree east of Kappa Centaurus, no visible trace is left of a once grand event that spanned five months of observation beginning in May, and lasting until it dropped below the horizon in September, 1006. It is believed all the force created from the event was converted to energy and very little mass remains. In the area, a 17th magnitude star shows a tiny gas ring and radio source 1459-41 remains our best candidate for pinpointing this incredible event.

Saturday, June 30 – We start our observing evening with the beautiful Moon as we return first to the ancient and graceful landmark crater Gassendi standing at the north edge of Mare Humorum. The mare itself is around the size of the state of Arkansas and is one of the oldest of the circular maria on the visible surface. As you view the bright ring of Gassendi, look for evidence of the massive impact which may have formed Humorum. It is believed the original crater may have been in excess of 462 kilometers in diameter, indenting the lunar surface almost twice over. Over time, similar smaller strikes formed the many craters around its edges and lava flow gradually gave the area the ridge- and rille-covered floor we see tonight. Its name is the “Sea of Moisture,” but look for its frozen waves in the long dry landscape.

Caught on the north-western rim of Mare Humorum, look for crater Mersenius. It is a typical Nectarian geological formation, spanning approximately 51 miles in diameter in all directions. Power up in a telescope to look for fine features such as steep slopes supporting newer impact crater Mersenius P and tiny interior craterlet chains. Can you spot white formations and crevices along its terraced walls? How about Rimae Mersenius? Further south you’ll spy tiny Liebig helping to support Mersenius D’s older structure, along with its own small set of mountains known as the Rupes Liebig. Continue to follow the edge of Mare Humorum around the wall known as Rimae Doppelmayer until you reach the shallow old crater Doppelmayer. As you can see, the whole floor fractured crater has been filled with lava flow from Mare Humorum’s formation, pointing to an age older than Humorum itself. Look for a shallow mountain peak in its center – there’s a very good chance this peak is actually higher than the crater walls. Did this crater begin to upwell as it filled? Or did it experience some volcanic activity of its own? Take a closer look at the floor if the lighting is right to spy a small lava dome and evidence of dark pyroclastic deposits – it’s a testament to what once was!

Still got the moonlight blues? Then try your hand at a super challenging double – Mu Librae. This pair is only a magnitude apart in brightness and right at the limit for a small telescope. Up the power slowly and look for the companion just to the southwest of the primary. Good luck and mark your observation because Mu’s blues are on many observing lists!

And out of the blue comes a meteor shower! Keep watch tonight for the June Draconids. The radiant for this shower will be near handle of Big Dipper – Ursa Major. The fall rate varies from 10 to 100 per hour, but tonight’s bright skies will toast most of the offspring of comet Pons-Winnecke. On a curious note, today in 1908 was when the great Tunguska impact happened in Siberia. A fragment of a comet, perhaps?

Sunday, July 1 – Today In 1917, the astronomers at Mt. Wilson were celebrating as the 100? primary mirror arrived. Up until that time, the 60? Hale telescope (donated by George Hale’s father) was the premier creation of St. Gobrain Glassworks – which was later commissioned to create the blank for the Hooker telescope. Thanks to the funds provided by John D. Hooker (and Carnegie), the dream was realized after years of hard work and ingenuity to create not only a building to properly house it – but the telescope workings as well. It saw “first light” five months later on November 1.
As anxious astronomers waited for this groundbreaking moment, the scope was aimed at Jupiter but the image was horrible – to their dismay, workmen had left the dome open and the Sun had heated the massive mirror! Try as they might to rest until it had cooled – no astronomer slept. Fearful of the worst, sometime around three in the morning they returned again long after Jupiter had set. Pointing the massive scope towards a star, they achieved a perfect image!

If you’re looking for a perfect image, then look no further than the western horizon tonight at twilight. Why? Because Mercury is going to be a “guest star” in the Beehive Cluster! Be sure to at least get out your binoculars and look at the speedy little inner planet as it cruises about a degree or so to the western edge of M44.

Tonight we’ll return again to our landmark lunar feature – crater Grimaldi – and begin our journey north…

As you move north of Grimaldi on a crater hop, the next feature you will en-counter is the walled plain of Hevelius. With a diameter of about 64 miles, this round area doesn’t have a height we can really measure because of its lunar position, but we can see that it does have some relatively steep walls around its edges. Hevelius was formed in the Nectarian geological period and if you look closely you’ll see that it has a small central peak, a fine rimae and many craterlet chains, too. Can you spot large interior Crater Hevelius A with just binoculars? How about companion crater Cavalerius which is part of its northern border?

While you’re out, take the time to look at lowly Theta Lupi about a fistwidth south-southwest of the mighty Antares. While this rather ordinary looking 4th magnitude star appears to be nothing special – there’s a lesson to be learned here. So often in our quest to look at the bright and incredible – the distant and the impressive – we often forget about the beauty of a single star. When you take the time to seek the path less traveled, you just might find more than you expected. Hiding behind a veil of the “ordinary” lies a trio of three spectral types and three magnitudes in a diamond-dust field. An undiscovered gem…

Until next week? Ask for the Moon, but keep on reaching for the stars!