Skywatching Archives

August 13, 2014December 23, 2015 by David Dickinson

A Spectacular Dawn Conjunction of Venus and Jupiter Set For August 18th

The last dawn pairing of Venus, Jupiter and the crescent Moon in the dawn sky in 2012... this month's will be much tighter! Credit: Tavi Greiner.

“What are those two bright stars in the morning sky?”

About once a year we can be assured that we’ll start fielding inquires to this effect, as the third and fourth brightest natural objects in the sky once again meet up.

We’re talking about a conjunction of the planets Jupiter and Venus. Venus has been dominating the dawn sky for 2014, and Jupiter is fresh off of solar conjunction on the far side of the Sun on July 24th and is currently racing up to greet it.

We just caught sight of Jupiter for the first time for this apparition yesterday from our campsite on F.E. Warren Air Force Base in Cheyenne, Wyoming. We’d just wrapped up an early vigil for Perseid meteors and scrambled to shoot a quick sequence of the supermoon setting behind a distant wind farm. Jupiter was an easy catch, first with binoculars, and then the naked eye, using brilliant Venus as a guide post.

The view looking eastward at dawn on August 18th, including a five degree telrad (red circles) and a one degree telescopic field of view (inset). Created using Stellarium.

And Jupiter will become more prominent as the week progresses, climaxing with a fine conjunction of the pair on Monday, August 18^th. This will be the closest planet versus planet conjunction for 2014. At their closest — around 4:00 Universal Time or midnight Eastern Daylight Saving Time — Venus and Jupiter will stand only 11.9’ apart, less than half the diameter of a Full Moon. This will make the pair an “easy squeeze” into the same telescopic field of view at low power. Venus will shine at magnitude -3.9, while Jupiter is currently about 2 magnitudes or 6.3 times fainter at magnitude -1.8. In fact, Jupiter shines about as bright as another famous star just emerging into the dawn sky, Sirius. Such a dawn sighting is known as a heliacal rising, and the first recovery of Sirius in the dawn heralded the flooding of the Nile for the ancient Egyptians and the start what we now term the Dog Days of Summer.

To the naked eye, enormous Jupiter will appear to be the “moon” that Venus never had next weekend. The spurious and legendary Neith reported by astronomers of yore lives! You can imagine the view of the Earth and our large Moon as a would-be Venusian astronomer stares back at us (you’d have to get up above those sulfuric acid clouds, of course!)

Said conjunction is only a product of our Earthly vantage point. Venus currently exhibits a waxing gibbous disk 10” across — three times smaller than Jupiter — but Venus is also four times closer to Earth at 1.61 astronomical units distant. And from Jupiter’s vantage point, you’d see a splendid conjunction of Venus and the Earth, albeit only three degrees from the Sun:

How often do the two brightest planets in the sky meet up? Well, Jupiter reaches the same solar longitude (say, returns back to opposition again) about once every 13 months. Venus, however, never strays more than 47.1 degrees elongation from the Sun and can thus always be found in either the dawn or dusk sky. This means that Jupiter pairs up with Venus roughly about once a year:

A list of Venus and Jupiter conjunctions, including angular separation and elongations (west=dawn, east=dusk) from now until 2020. Created by author.

Note that next year and 2019 offer up two pairings of Jupiter and Venus, while 2018 lacks even one. And the conjunction on August 27^th, 2016 is only 4’ apart! And yes, Venus can indeed occult Jupiter, although that hasn’t happened since 1818 and won’t be seen again from Earth until – mark your calendars – November 22^nd, 2065, though only a scant eight degrees from the Sun. Hey, maybe SOHO’s solar observing successor will be on duty by then…

Venus has been the culprit in many UFO sightings, as pilots have been known to chase after it and air traffic controllers have made furtive attempts to hail it over the years. And astronomy can indeed save lives when it comes to conjunctions: in fact, last year’s close pairing of Jupiter and Venus in the dusk sky nearly sparked an international incident, when Indian Army sentries along the Himalayan border with China mistook the pair for Chinese spy drones. Luckily, Indian astronomers identified the conjunction before shots were exchanged!

Earth strikes back... — Earth strikes back… firing a 5mw green laser at the 2013 conjunction of Jupiter and Venus. Photo by author.

Next week’s conjunction also occurs against the backdrop of Messier 44/Praesepe, also known as the “Beehive cluster”. It’ll be difficult to catch sight of M44, however, because the entire “tri-conjunction” sits only 18 degrees from the Sun in the dawn sky. Binocs or a low power field of view might tease out the distant cluster from behind the planetary pair.

And to top it off, the waning crescent Moon joins the group on the mornings of August 23^rd and 24^th, passing about five degrees distant. Photo op! Can you follow Venus up into the daytime sky, using the Moon as a guide? How about Jupiter? Be sure to block that blinding Sun behind a hill or building while making this attempt.

The addition of the Moon will provide the opportunity to catch a skewed “emoticon” conjunction. A rare smiley face “:)” conjunction occurred in 2009, and another tight skewed tri-conjunction is in the offering for 2056. While many national flags incorporate examples of close pairings of Venus and the crescent Moon, we feel at least one should include a “smiley face” conjunction, if for no other reason than to highlight the irony of the cosmos.

A challenge: can you catch a time exposure of the International Space Station passing Venus and Jupiter? You might at least pull off a “:/” emoticon image!

Don’t miss the astronomical action unfolding in a dawn sky near you over the coming weeks. And be sure to spread the word: astronomical knowledge may just well avert a global catastrophe. The fate of the free world lies in the hands of amateur astronomers!

August 10, 2014December 23, 2015 by Bob King

Fear Not the Moon, Perseids Always a Great Show

The annual Perseid meteor shower radiates from a point in the constellation Perseus just below the W of Cassiopeia. Rates are usually about 100-120 meteors per hour from a dark, moonless sky at peak but will be cut in half due to moonlight this time around. This map shows the sky facing east around midnight Aug. 12-13. Source: Stellarium

Get ready for the darling of meteor showers this week — the Perseids. Who can deny their appeal? Not only is the shower rich with fiery flashes of meteoric light, but the meteors come in August when the weather’s couldn’t be more ideal. Peak activity is expected Tuesday night, Aug. 12-13, when up to 100 meteors an hour might be seen.

Ah, but there’s a rub. This year the moon will be only two days past full and radiant enough to drown out the fainter shower members. We’re more likely to see something like 30 meteors an hour, maybe fewer. But all it takes is one bright meteoric flash to make it all worthwhile. Nothing gets the heart pumping like a bright Perseid and the anticipation of the next.

While more meteors are surely more exciting, it’s not a number thing, but the experience of the raw event that makes all the difference. Sure beats sitting in front of a computer screen or watching the latest rerun of The Big Bang Theory, right?

A fine Perseid flashes straight out of the radiant on August 12, 2013. The fuzzy-starry clump near the start of the trail is the Double Cluster. Credit: Bob King — A fine Perseid flashes straight out of the radiant on August 12 last year. The two bright dots above the start of the trail form the well-known Perseus Double Cluster. Credit: Bob King

Find a place away from glaring lights to allow your eyes to adapt to the darkness. That way you’ll see more meteors. While the Perseids spit out the occasional fireball, most shower members are going to be closer in brightness to the stars of the Big Dipper. Some leave “smoke” trails called meteor trains. They’re actually tubes of glowing air molecules created as the meteoroid particles speed through the atmosphere at 130,000 mph. Though ‘shooting stars’ can look surprisingly close by, they typically burn up 60-70 miles overhead.

Perseid meteors radiate from the constellation Perseus (hence the name) located a short distance below the “W” of Cassiopeia in the northeastern sky. To know for sure if you’ve seen the genuine item and not a random meteor, follow the trail backward — if it points toward the northeast, you’ve got a ringer!

Perseid meteor ISS Ron Garan Aug13_2011 — A remarkable orbital view of a Perseid (right, center) burning up in Earth’s atmosphere photographed by astronaut Ron Garan on Aug. 13, 2011. The star Arcturus is directly above the bright trail. Credit: Ron Garan / ISS Expedition 28 crew / NASA

You can watch for Perseids all week long, but peak activity begins Tuesday evening and continues through dawn Wednesday. The later you stay up, the more meteors you’ll spot because the radiant or point in the sky from which the meteors appear to radiate rises higher with every hour. The higher the radiant, the fewer meteors that get cut off by the horizon.

Composite of bright Perseid meteors recorded by NASA all-sky cameras in 2011. Each is a grain of rock shed from the tail of comet 109P/ Swift-Tuttle. Every year in mid-August, Earth passes through the comet’s debris trail as it orbits around the sun. Any particles we smack into burn up as meteors about 60-70 miles overhead. Credit: NASA — Composite of bright Perseid meteors recorded by NASA all-sky cameras in 2011. Each is a grain of rock shed from the tail of comet 109P/Swift-Tuttle. Every year in mid-August, Earth passes through the comet’s debris trail as it orbits around the sun. Credit: NASA

The observing equipment you were born with and a comfortable chair are all you need to make the most of the event. OK, it’s nice to have a friend along, too, to share the ‘wow’ moments and keep from falling asleep. Sometimes I’m too lazy to haul out a chair and instead sprawl out on the deck or grass. Others prefer their Perseids from a steaming hot tub.

A 2010 Perseid meteor streaks over the European Southern Observatory's Very Large Telescope (VLT). Credit: ESO — A 2010 Perseid meteor streaks over the European Southern Observatory’s Very Large Telescope (VLT). Credit: ESO

Left-behind sand, seed and pebble-sized particles from comet 109P/Swift-Tuttle are responsible for all the fun. Discovered in 1862, the comet circles the sun every 120 years. Over millennia, 109P has left a stream of debris along its orbit, which the Earth passes through every year in mid-August. Comet grit hits our atmosphere like bugs smacking a car windshield and vaporize in a flashes of light or meteors.

Normally I’d recommend facing east or southeast to watch the shower, but with the moon dominating that direction, look off to the northeast, north or southwest to keep from getting zapped by that old devil moonlight. Even a little dark adaption will help boost your Perseid count. Once situated, sit back, look up and enjoy each and every sparkler that drops from the sky.

And don’t forget to take in the big picture show rolling by. The sky’s a giant calendar that begins with the mid-summer constellations at nightfall and advances through the fall stars to the onset of winter with the rising of Orion at dawn. Let the months fall away as the Earth turns you toward the sun.

August 4, 2014December 23, 2015 by David Dickinson

Get Set For Super (Duper?) Moon 2 of 3 For 2014

The July 2014 Supermoon rising over the University of Texas at Austin Tower. Credit: Mark Ezell, used with permission.

You could be forgiven for thinking this summer that the “supermoon” is now a monthly occurrence. But this coming weekend’s Full Moon is indeed (we swear) the closest to Earth for 2014.

What’s going on here? Well, as we wrote one synodic month ago — the time it takes for the Moon to return to the same phase at 29.5 days — we’re currently in a cycle of supermoons this summer. That is, a supermoon as reckoned as when the Full Moon falls within 24 hours of perigee, a much handier definition than the nebulous “falls within 90% of its orbit” proposed and popularized by astrologers.

A super-sized shot of the July 2014 supermoon. Credit: Russell Bateman.

The supermoons for 2014 fall on July 13th, August 10th and September 8th respectively. You could say that this weekend’s supermoon is act two in a three act movement, a sort of Empire Strikes Back to last month’s A New Hope.

Now for the specifics: Full Moon this weekend occurs on August 10^th at 18:10 Universal Time (UT) or 2:10 PM EDT. The Moon will reach perigee or its closest point to the Earth at 17:44 UT/1:44 PM EDT just 26 minutes prior to Full, at 55.96 Earth radii distant or 356,896 kilometres away. This is just under 500 kilometres shy of the closest perigee that can occur at 356,400 kilometres distant. Perigee was closer to Full phase time-wise last year on June 23^rd, 2013, but this value won’t be topped or tied again until November 25^th, 2034. The Moon will be at the zenith and closest to the surface of the Earth at the moment it passes Full over the mid-Indian Ocean on Sunday evening nearing local midnight.

Now for a reality check: The August lunar perigee only beats out the January 1^st approach of the Moon for the closest of 2014 by a scant 25 kilometres. Perigees routinely happen whether the Moon is Full or not, and they occur once every anomalistic month, which is the average span from perigee-to-perigee at 27.6 days. This difference between the anomalistic and synodic period causes the coincidence that is the supermoon to precess forward about a month a year. You can see our list of supermoon seasons out until 2020 here.

And don’t forget, the Moon actually approaches you to the tune of about half of the radius of the Earth while it rises to the zenith, only to recede again as it sinks back down to the horizon. The rising Full Moon on the horizon only appears larger mainly due to an illusion known as the Ponzo Effect.

The apparent size of the Moon varies about 14% in angular diameter from 29.3′ (known as an apogee “mini-Moon”) to 34.1′ at its most perigee “super-size” as seen from the Earth.

Astronomers prefer the use of the term Perigee Full Moon, but the supermoon meme has taken on a cyber-life of its own. Of course, we’ve gone on record before and stated that we prefer the more archaic term Proxigean Moon, but the supermoon seems here to stay.

And as with many Full Moon myths, this week’s supermoon will be implicated in everything from earthquakes to lost car keys to other terrestrial woes, though of course no such links exist. Coworkers/family members/strangers on Twitter will once again insist it was “the biggest ever,” and claim it took up “half the sky” as they unwittingly take part in an impromptu psychological perception test.

Fun fact: you could ring local the horizon with 633 supermoons!

And of course, many a website will recycle their supermoon posts, though of course not here at Universe Today, as we bake our science fresh daily.

So what can you expect? Well, a perigee Full Moon can make for higher than usual tides. New York City residents had the bad fortune of a Full Moon tidal surge in 2012 when Hurricane Sandy made landfall. Though there doesn’t seem to be a chance for a repeat of such an occurrence in 2014 in the Atlantic, super-typhoon Halong is churning towards the Japanese coastline for landfall this weekend…

The rising Waxing Gibbous Moon on the evening of August 9th. Credit: Stellarium.

Observationally, Full Moon is actually a lousy time for astronomical observations, causing many a deep sky astrophotographer to instead stay home and visit the family, while lurking astrophotography forums and debunking YouTube UFO videos.

Pro-tip: want your supermoon photo/video to go viral? Shoot the rising Moon just the evening prior when it’s waxing gibbous but nearly Full. Not only will it be more likely to be picked up while everyone is focused on supermoon lunacy, but you’ll also have the added bonus of catching the Moon silhouetted against a low-contrast dusk sky. We have a pre-supermoon rising video from a few years back that still trends with each synodic period!

Well, that’s it ‘til September, when it’ll be The Return (Revenge?) of the Supermoon. Be sure to send those pics in to Universe Today’s Flickr forum, you just might make the supermoon roundup!

July 31, 2014December 30, 2015 by Elizabeth Howell

Stargazing Timelapse Plus Apollo 14 Launch Soundtrack Is Pure Magic

It feels like a real stargazing session watching this video. You head out at dusk, waiting for the first few stars to emerge. Then there’s a moment when — if you’re in the right spot — whammo. The Milky Way pops out. The sky turns into a three-dimensional playground.

Combine that feeling with the Apollo 14 launch audio from 1971, and this timelapse is a lot of fun.

Continue reading “Stargazing Timelapse Plus Apollo 14 Launch Soundtrack Is Pure Magic”

July 28, 2014December 23, 2015 by Bob King

Observing Alert – Delta Aquarid Meteor Shower Peaks This Week

A bright meteor from September 21, 1994. Credit: John Chumack.

With the southern Delta Aquarid meteor shower peaking tomorrow morning, the summer meteor-watching season officially begins. While not a rich shower from mid-northern latitudes, pleasant weather and a chance to see the flaming remains of a comet seem motivation enough to go out for a look. With a rate 10-15 per meteors an hour you’re bound to catch a few.

The farther south you live, the better it gets. Observers in the southern hemisphere can expect double that number because the shower’s radiant will be much higher in the sky. Any meteors flashing south of the radiant won’t get cut off by the southern horizon like they do further north.

The annual shower gets its name from Delta Aquarii, a dim star in the dim zodiac constellation Aquarius. You don’t need to know the constellations to enjoy the show, but if you know the general direction of the radiant you’ll be able to tell shower members from the nightly sprinkle of random meteors called sporadics. If you can trace the path of a meteor backward toward Aquarius, chances are it’s an Aquarid.

Delta Aquarid Meteors (2) on 07-30-2013 — A Southern Delta Aquarid meteor captured on July 30, 2013. Credit: John Chumack

There are actually two meteor showers in Aquarius active this time of year – the northern and southern Delta Aquarids. The northern version sprinkles fewer meteors and peaks in mid-August.

The Southern Deltas peak over the next two mornings – July 29 and 30 – but will be out all week. Both serve as a warm-up for the upcoming Perseid meteor shower that climaxes on August 12.

Tonight’s shower will suffer no interference from moonlight, making for ideal meteor watching. Unfortunately, Perseid rates will be reduced by a bright waning gibbous moon.

Don’t be surprised if you see a few Perseids anyway. The shower’s just becoming active. If you can draw a meteor’s trail back to the northeastern sky, it just might be a member. Read more about Perseid prospects from our own David Dickinson.

Meteors from Delta Aquarid meteor shower radiate from near the star Delta Aquarii not far from the bright star Fomalhaut in the Southern Fish low in the south before dawn. Stellarium

Nearly all meteor showers originate from clouds of sand to seed-sized bits of debris spewed by vaporizing comet ice as they swing near the sun. The Delta Aquarids may trace its origin to dust boiled off Comet 96P/Machholz.

The best time to watch the shower is in the early morning hours before dawn when the radiant rises in the south-southeastern sky above the bright star Fomalhaut. Try to get away from city lights. Point your lawn chair south and spend some time in heavenly contemplation as you wait for Aquarius to toss a few javelins of light your way.

July 28, 2014December 23, 2015 by David Dickinson

When Good Meteor Showers Go Bad: Prospects for the 2014 Perseids

It’s that time of year again, when the most famous of all meteor showers puts on its best display.

Why are the Perseids such an all ‘round favorite of sky watchers? Well, while it’s true that other annual meteor showers such as the Quadrantids and Geminids can exceed the Perseids in maximum output, the Perseids do have a few key things going for them. First, the shower happens in mid-August, which finds many northern hemisphere residents camping out under warm, dark skies prior to the start of the new school year. And second, unlike showers such as the elusive Quads which peak over just a few hours, the Perseids enjoy a broad span of enhanced activity, often covering a week or more.

The orientation of the orbital path of Comet 109P/Swift-Tuttle and the position of the Earth on August 12th. Credit: JPL-Horizons.

These are all good reasons to start watching for Perseids now. Here’s the low down on the Perseid meteors for 2014:

The History: The Perseids are sometimes referred to as “The Tears of Saint Lawrence,” who was martyred right around the same date on August 10^th, 258 A.D. The source of the shower is comet 109P Swift-Tuttle, which was first identified as such by Schiaparelli in 1866. The comet itself visited the inner solar system again recently in 1992 on its 120 year orbit about the Sun, and rates were enhanced throughout the 1990s.

A 2013 Perseid pierces the plane of the Milky Way. Credit: Stephen Rahn.

Unlike most showers, the Perseids have a very broad peak, and observers and automated networks such as UKMON and NASA’s All Sky Camera sites have already begun to catch activity starting in late July.

A pair of early 2014 Perseids recently captured by UKMON’s Wilcot station. Credit: The UK-MON network.

In recent years, the rates for the Perseids have been lowering a bit but are still enhanced, with ZHRs at 91(2010), 58(2011), 122(2012), and 109(2013). It’s also worth noting that the Perseids typically exhibit a twin peak maximum within a 24 hour span. The International Meteor Organization maintains an excellent page for quick look data to check out what observers worldwide are currently seeing. The IMO also encourages observers worldwide to submit meteor counts by location. Note that the phase of the Moon was near Full in 2011, with observing circumstances very similar to 2014.

The Prospects for 2014: Unfortunately, the 2014 Perseid meteors have a major strike going against them this year: the Moon will be at waning gibbous during its peak and just two days past Full illumination. This will make for short exposure times and light polluted skies. There are, however, some observational strategies that you can use to combat this: one is to place a large building or hill between yourself and the Moon while you observe — another is to start your morning vigil a few days early, before the Moon reaches Full. The expected Zenithal Hourly Rate for 2014 is predicted to hover around 90 and arrive around 00:15 to 2:00 UT on August 13^th favoring Europe, Africa and the Middle East.

The orientation of Earth’s shadow during the projected peak of the Perseids on August 13th at 00:15 Universal Time. The positions where the Sun, Moon, and radiant of the Perseids are directly overhead are also noted. Created by Author.

The Radiant: It’s strange but true: meteor shower radiants wander slightly across the sky during weeks surrounding peak activity, due mostly to the motion of the Earth around the Sun. Because of this, the radiant of the Perseids is not actually in the constellation Perseus on the date that it peaks! At its maximum, the radiant actually sits juuusst north of the constellation that it’s named for on the border of Camelopardalis and Cassiopeia. This is a great pedantic point to bring up with your friends on your August meteor vigil… they’ll sure be glad that you pointed this out to ’em and hopefully, invite you back for next year’s Perseid watch.

The actual position of the radiant sits at 3 Hours 04’ Right Ascension and +58 degrees north declination.

The movement of the radiant of the Perseids. The sky is simulated for latitude 30 degrees north at 2:00 AM local on August 13th. Credit: Starry Night Education software.

Meteor-speak: Don’t know your antihelion from a zenithal hourly rate? We wrote a whole glossary that’ll have you talking meteors like a pro for Adrian West’s outstanding Meteorwatch site a few years back. Just remember, the crucial “ZHR” of a shower that is often quoted is an ideal extrapolated rate… light pollution, the true position of the radiant, observer fatigue and limited field of view all conspire to cause you to see less than this predicted maximum. The universe and its meteor showers are indeed a harsh mistress!

Observing: But don’t let this put you off. As Wayne Gretsky said, “You miss 100% of the shots that you don’t take,” and the same is true with meteor observing: you’re sure to see exactly zero if you don’t observe at all. Some of my most memorable fireball sightings over the years have been Perseids. And remember, the best time to watch for meteors is after local midnight, as the Earth is turned forward into the meteor stream. Remember, the car windshield (Earth) gets the bugs (meteors) moving down the summer highway…

Good luck, and let us know of those tales of Perseid hunting and send those meteor pics in to Universe Today!

July 26, 2014December 23, 2015 by Bob King

Comet Jacques Makes a ‘Questionable’ Appearance

Comet Jacques and IC 405, better known as the Flaming Star Nebula, align to create a temporary question mark in the sky this morning July 26. Credit: Rolando Ligustri

What an awesome photo! Italian amateur astronomer Rolando Ligustri nailed it earlier today using a remote telescope in New Mexico and wide-field 4-inch (106 mm) refractor. Currently the brightest comet in the sky at magnitude 6.5, C/2014 E2 Jacques has been slowly climbing out of morning twilight into a darker sky over the last two weeks. This morning it passed the Flaming Star Nebula in the constellation Auriga. Together, nebula and pigtailed visitor conspired to ask a question of the sky in a rare display of celestial punctuation. IC 405 is a combination emission-reflection nebula. Some of its light stems from starlight reflecting off grains of cosmic dust, but the deep red results from hydrogen excited to fluorescence by powerful ultraviolet light from those same stars. The depth of field hidden within the image is enormous: the nebula lies 1,500 light years away, the comet a mere 112 million miles or 75 million times closer. Coincidentally, the comet also glows in similar fashion. The short dust tail to the left of the coma is sunlight reflecting off minute grains of dust boiled from the nucleus. The long, straight tail is primarily composed of carbon monoxide gas fluorescing in ultraviolet light from the sun.

Follow Jacques in a small telescope or binoculars in its travels across Auriga into Perseus in the next two weeks before the moon interferes again. Comet positions are shown for 4 a.m. CDT every 5 days. Stars to magnitude +8.0. Click to enlarge. Source: Chris Marriott's SkyMap — Follow Jacques in a small telescope or binoculars in its travels across Auriga into Perseus during the next two weeks before the moonlight interferes. Comet positions are shown for 4 a.m. CDT every 5 days. Stars to magnitude +8.0. Click to enlarge. Source: Chris Marriott’s SkyMap

As Jacques swings toward its closest approach to Earth in late August, it’s gradually picking up speed from our perspective and pushing higher into the morning sky. A week ago, twilight had the upper hand. Now the comet’s some 20º high (two ‘fists’) above the northeastern horizon around 4 a.m. This morning I had no difficulty seeing it as a small, ‘fuzzy star’ in 10×50 binoculars. In my dusty but trusty 10-inch (25 cm) telescope at 76x, Comet Jacques was a dead ringer for one of those fuzzy dingle-balls hanging from a sombrero. I caught a hint of the very short dust tail but couldn’t make out the gas tail that shows so clearly in the photo. That will have to await darker skies.

A different perspective on Comet Jacques. This negative image, which accentuates detail in the comet's tails, was shot July 26, 2014 with an 8-inch (20 cm) telescope. Credit: Michael Jaeger — A different perspective on Comet Jacques. This negative image, which emphasizes details in the comet’s tails, was shot July 26, 2014 with an 8-inch (20 cm) telescope. Credit: Michael Jaeger

Maybe you’d like to try your own eyes on Jacques. Start with a pair of 40mm or larger binoculars or small telescope and use the map above to help you spot it. Oh, and don’t forget to keep an exclamation mark handy when you get that first look.

July 25, 2014December 23, 2015 by David Dickinson

Having Fun with the Equation of Time

An analemma of the Sun, taken from Budapest, Hungary over a one year span. (Courtesy of György Soponyai, used with permission).

If you’re like us, you might’ve looked at a globe of the Earth in elementary school long before the days of Google Earth and wondered just what that strange looking figure eight thing on its side was.

Chances are, your teacher had no idea either, and you got an answer such as “it’s a calendar, kid” based on the months of the year marking its border.

In a vague sense, this answer is correct… sort of. That funky figure eight is what’s known as an analemma, and it traces out the course of the Sun in the sky through the year as measured from a daily point fixed in apparent solar time.

Analemma (Wikimedia Commons image). — Ye ole analemma… perpetually lost in the South Pacific? (Wikimedia Commons image).

But try explaining that one to your 3^rd grade teacher. Turns out, measuring the passage of time isn’t as straight forward as you’d think. Our modern day clock and calendar is a sort of compromise, a method of marking the passage of time in a continuing battle to stay in sync with the heavens.

For most of history, the daily passage of time was denoted by the Sun. Solar Noon occurs when the Sun stands at its highest elevation (also known as its altitude) above the local horizon when it transits the north-south meridian. The trouble is, the passage apparent solar time doesn’t exactly match what we call solar mean time, or the 24 hour rotation of the Earth. In fact, this discrepancy can add up to as much as more than 16 minutes ahead of solar noon in late October and November and over 12 minutes behind it in February. This is worth bringing up this week because this factor, known as “The Equation of Time” — think “equation” in the sense that sundial owners must factor it in to make solar mean and apparent time “equal” — reaches its shallow minimum for 2014 this Saturday at 7:00 UT/3:00 AM EDT with a value of -6.54 minutes.

The solar analemma as plotted from the latitude of the Greenwich Observatory in England. (Wikimedia Commons/PAR/JPL Horizons).

So, what gives? Why won’t the pesky universe stay in sync?

Well, the discrepancy arises from two factors: the eccentricity of the Earth’s orbit, or how much it deviates from circular and the obliquity of the ecliptic to the celestial equator, think the tilt of Earth’s axis. Of the two, obliquity is the major factor, with eccentricity playing a minor but measurable role. And remember, we move slightly faster in our orbit in January near perihelion as per Kepler’s Laws of planetary motion than at aphelion, which occurred earlier this month , though be careful not to confuse the term “faster” with “sun fast.”

This means that were the Earth to orbit the Sun in a perfect circle with its poles perpendicular to its orbit, apparent and mean time would essentially stay in sync. Of course, no known planet has such a perfect alignment scenario, and other worlds do indeed host alien analemmas (analemmae?) of their own.

It’s also interesting to note that the two each major and minor minima of the Equation of Time roughly coincide with the four cross quarter tie in days of the year (marked by Groundhog’s Day, May Day, Lammas Day and Halloween, respectively) while the zero value points fall within a few weeks of the equinoxes and solstices.

A graph showing the flucuation of the value of the Equation of Time throughout the callendar year. (Created by the author). — A graph showing the fluctuation of the value of the Equation of Time (with minutes on the vertical axis) throughout the calendar year. (Created by the author).

In the current epoch, the deep minimum falls on February 21^st, while the highest maximum falls on November 3^rd on non-leap years. The four zero value dates are April 15^th, June 13^th, September 1^st and December 25^th respectively. The exact timing of these also slip to the tune of about a second a year, but of course, most sundials lack this sort of precision.

A "globe sundial" on the University of North Dakota at grand Forks campus. (Photo by author). — A “globe sundial” on the University of North Dakota at Grand Forks campus. (Photo by author).

So, why should we care about the Equation of Time in the modern atomic clock age? It is true that there have been calls over the past few years to “abolish the leap second” and go off of the astronomical time standard entirely… if this ever does come to pass, some future Pope Gregory will have to institute a “leap hour” circa 10,000 A.D. or so to stop the Sun from rising at 2 AM. But some modern day Sun tracking devices (think heliostats or solar panels) do in fact use mechanical timers and must take the equation of time into account to maximize effectiveness.

Impatient? You can plot your very own simulated analemma using a desktop planetarium program. (Credit: Starry Night Education software).

Want to see the Equation of Time in action? You can make your own analemma simply by photographing the position of the Sun at the same time each day. Just remember to account for the shift on and off of Daylight Saving if you live in an area that observes the archaic practice, residents of Arizona need not to take heed. Otherwise, you’ll end up with a “split analemma…” Wintertime near the December Solstice is the best time to start this project, as the Sun is at its lowest noonday culmination and this will assure that your very own personal analemma won’t fall below the local horizon.

Farther afield, the effects of the Precession of the Equinoxes will also tweak the dates of the Equation of Time values a bit. Live out a full 72 year life span, and the equinoctial points will have drifted along the ecliptic by about one degree, twice the diameter of the Full Moon. Incidentally, the failure to take Precession into account is yet another spectacular fail of modern astrology: most “houses” or “signs” have drifted in the past millennia to the point where most “Leos” are in fact “Cancers!”

Such is the challenges and vagaries of modern day astronomical time-keeping. Let us know of your tales of tragedy and triumph as you hunt down the elusive analemma.

July 23, 2014December 23, 2015 by Elizabeth Howell

‘Weak’ New Meteor Shower Due To Fragile Comet Dust

A Camelopardalid seen frame-by-frame in a recording taken May 24, 2014 at 1:58:08 a.m. UT (9:58:08 p.m. ET). Credit: Original recording by Peter C. Slansky; compilation by Jim Albers and Peter Jenniskens.

While the Camelopardalid shower only produced a few meteors, the lack of flashy disintegrations showed astronomers something new, a new study reveals: the dust from its parent comet (Comet 209P/Linear) was much more fragile than the usual. The reasons are still being investigated, but one theory is that after a century in space, there wasn’t much left to run into.

“Some mechanism was at work that efficiently fragmented the larger meteoroids,” stated Peter Jenniskens, a meteor astronomer with the SETI Institute who, along with colleague Esko Lyytinen, first predicted the existence of the shower a decade ago.

“Our best meteor was no more luminous than the star Vega,” added Jenniskens, “but it gave us a clue as to why there were few bright ones: It was so fragile that the meteoroid suddenly dispersed into a cloud of dust at the end of its trajectory.”

This ‘weak” shower stands in contrast to two meteor showers that took place out of interactions with comet 21P/Giacobinni-Zinner. This produced meteor “storms” in 1933 and 1946 during the Draconids. That comet was more active and the dust grains that left it likely had a lot of ice in them. Comet 209P/Linear did not have that type of ejection, nor was it very active.

You can read more Universe Today observations of the new shower in this past story.

Source: SETI Institute

July 18, 2014December 23, 2015 by David Dickinson

Observing Challenge: 6 White Dwarf Stars to See in Your Backyard Telescope

Dazzlimg Sirius, with its white dwarf companion to the lower left. Credit: NASA, ESA, H. Bond (STScI) and M. Barstow (University of Leicester).

Looking for something off beat to observe? Some examples of curious astronomical objects lie within the reach of the dedicated amateur armed with a moderate-sized backyard telescope. With a little skill and persistence, you just might be able to track down a white dwarf star. Unlike splashy nebulae or globular clusters, a white dwarf star will just appear as a speck, a tiny dot in the field of view of your telescope’s eyepiece. But just as in the case of observing other exotic objects such as red giants and quasars, part of the thrill of tracking down these astrophysical beasties is in knowing just what it is that you’re seeing. Heck, many amateur astronomers fail to realize that any white dwarf stars are within range of their instruments and have never tracked one down.

The astrophysical nature of white dwarf stars was first uncovered in the early 20^th century. Most of the early white dwarf stars discovered were companions in binary star systems and this allowed astronomers to gauge their mass by following the orbital motion of such pairs over time. Soon, astronomers realized that they were looking at something peculiar, a new type of compact but massive stellar object that stubbornly refused to be pigeon-holed along the main sequence of the freshly conceived Hertzsprung-Russell diagram.

Today, we know that white dwarf stars are the remnants of stars which have long since passed the Red Giant stage. We say that a white dwarf is a degenerate star, and no, this not a commentary on its moral state. The Chandrasekhar limit gives us an upper limit in size for a white dwarf at about 1.4 solar masses, beyond which electron degeneracy pressure can no longer act against the inward pull of gravity. Our Sun will one day become a white dwarf, over 6 billion years from now. Think of cramming the mass of our star into the volume of the Earth and you have some idea just how dense a white dwarf is: a cubic centimetre of white dwarf weighs 250 about tons, and two cup fulls of white dwarf would weigh more than a Nimitz-class aircraft carrier.

Think of a white dwarf as a cooling ember of a star long past its hydrogen fusing prime. And white dwarfs will cool down to infrared radiating black dwarfs over trillions of years, far longer than the present 13.7 billion year age of the universe. In fact, the age of white dwarfs currently observed is one on the underpinning tenets of modern Big Bang cosmology.

All amazing stuff. In any event, here is a baker’s half dozen of white dwarf stars that you can find with a telescope tonight. A more extensive list of the nearest white dwarfs to the Earth can be found on Sol Station.

The orbit of Sirius B. Wikimedia Commons image in the Public Domain.

Sirius B: This is the nearest white dwarf to the Earth at 8.6 light years distant. Shining at magnitude +8.5, Sirius B would be a cinch to see, if only dazzling Sirius A — the brightest star in our sky at magnitude -1.5 — were not nearby. Sirius B orbits its primary once every 50 years and will reach a maximum separation of 11.5” from its primary in 2025, a prime time to cross it off of your life list in the coming decade. Blocking the primary just out of the field of view, or using an occulting bar eyepiece is key to finding Sirius B.

Sirius B was discovered by American telescope maker Alvan Graham Clark in 1862. The Dogon people of Mali also have some curious myths surrounding the star Sirius.

Constellation: Canis Major

Right Ascension: 6 Hours 45’

Declination: -16° 43’

The apparent orbit of Procyon B through 2039. Graphic created by the author.

Procyon B: Located 11.5 light years distant, Procyon B was discovered in 1896 by John Martin Schaeberle from the Lick observatory. Shining at magnitude +10.7, the chief difficultly with spotting this white dwarf, as with Sirius B, is that it has a companion about 10 magnitudes – that’s 10,000 times brighter – nearby just 4.3” away.

Constellation: Canis Minor

Right Ascension: 7 hours 39’

Declination: +5 13’

-LP145-141: Also known as GJ 440, LP145-141 is one of the best southern hemisphere white dwarf stars on the list. LP145-141 is a solitary white dwarf shining at magnitude +11.5. Located 15 light years distant, LP145-141 is thought to be a member of the nearby Wolf 219 Moving Group of stars.

Constellation: Musca

Right Ascension: 11 Hours 46’

Declination: -64° 50’

The location of Van Maanen’s Star in the constellation Pisces. Credit: Stellarium

-Van Maanen’s Star: Shining at magnitude +12.4 and located 14.1 light years distant, Van Maanen’s star is the closest solitary white dwarf to Earth and the best example of a white dwarf for small telescopes. Discovered by Ariaan van Maanen in 1917, Van Maanen’s Star also has a very high proper motion of 3” per year.

Constellation: Pisces

Right Ascension: 00 Hours 49’

Declination: 05° 23’

The 40 Omicron Eridani system. Image by Author

-40 Omicron Eridani B: This is a great one to track down. The triple system of 40 Omicron Eridani b contains a fine example of a red and white dwarf orbiting a main sequence star. Located 16.5 light years distant and shining at magnitude +9.5, Omicron Eridani was the first white dwarf star discovered in 1783 by Sir William Herschel, although its true nature wasn’t deduced until 1910. Omicron Eridani B is currently 82” from its primary, an easy split.

Constellation: Eridanus

Right Ascension: 4 Hours 15’

Declination: 7° 39’

-Stein 2051: Rounding off the list and located just over 18 light years distant, Stein 2051 is another example of a red dwarf/white dwarf pair. Stein 2051 b shines at a similar brightest to Van Maanen’s star at magnitude +12.4.

Constellation: Camelopardalis

Right Ascension: 04 Hours 31’

Declination: +58° 59’

Let us know about your trials and triumphs in hunting down these fascinating objects!