A Twist on the “Trunk” – IC1396 and Van den Berg 142 by Takayuki Yoshida

IC1396 and Van den Berg 142 by Takayuki Yoshida

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Out in the reaches of the constellation of Cepheus some 2400 light years from Earth, a cloud of hydrogen gas and dust harbors young star cluster IC 1396. These newborn stars emit their light upon the scene… shedding infrared radiation through a 20 light year wide corridor known as the “Elephant’s Trunk”…

Cataloged by Dreyer as far back as 1888, galactic cluster IC 1396 has long been known to have an air of nebulosity around it and perhaps a shroud of mystery as well. As telescopes improved, so did the view and observers began to notice dark patches and a bright, sinuous rim. The dark interstellar clouds took a very special observer in the late 1800s to discover them – E.E. Barnard – and he labeled his discovery B163. Nothing more than a cold area in space – obscuring dust waiting to gel into stars. Just another dark hole obscuring a mystery inside IC 1396… and tiny patch of nebula that would one day be known as Van den Berg 142.

In 1975 Robert B. Loren (et al) was the first to report on the molecular cloud structure in IC 1396. His observations were made using the Kitt Peak scope, doing their best to confirm the hypothesis that cometary like structure was the result of an ionization front as it progressed into neutral hydrogen territory. High density gases, a dark rimmed nebula… But, they still didn’t quite grasp what lay inside – a concentration of interstellar gas and dust that is being illuminated and ionized by a very bright, massive star.

And the tiny dense globules hiding from the intense ultraviolet rays…

In 1996, G. H. Moriarty Schieven was the first to announce H I “Tails” from cometary globules in IC 1396. In his reports he writes: “IC 1396 is a relatively nearby, large, H ii region ionized by a single O6.5 V star and containing bright rimmed cometary globules. We have made the first arcminute resolution images of atomic hydrogen toward IC 1396, and have found remarkable “tail” like structures associated with some of the globules and extending up to 6.5 pc radially away from the central ionizing star. These H i “tails” may be material which has been ablated from the globule through ionization and/or photodissociation and then accelerated away from the globule by the stellar wind, but which has since drifted into the “shadow” of the globules.” This report was the first results of the Galactic Plane Survey Project began by the Dominion Radio Astrophysical Observatory and opened the gateway into the twisted tale of the “Trunk”.

The Elephant’s Trunk nebula is an intense concentration of interstellar gas which contains embedded globule IC 1396A and is now believed to be the site of star formation. Located inside the opening where the stellar winds have cleared a cavity are two very young stars – their pressure driving the material outwards and revealing the presence of protostars.

In 2003, Alaina Henry picked up the ball once again. “Since emission line stars are
relatively rare, the discovery of a cluster of emission line stars is adequate proof that star formation is taking place in a cluster. In addition, young stars often display variable luminosity. It is thought that non-constant mass accretion rates cause variations in the luminosity of young stellar objects. BRC 37 is a small globule in the extended, HII region, IC 1396. It is about I’ wide and 5′ long in the optical, and has a bright rim of Ho emission in the north, due to recombination of ionized hydrogen. The source of the ionization is thought to be the 06 star, HO 206267, which lies several degrees away on the sky. The infrared source, IRAS 21388+5622 is located at the head of the globule and showed another signature of star formation in BRC 37 by discovering a bipolar molecular outflow associated with the IRAS source. We identify eight likely young stellar objects in BRC 37, based on the presence of an infrared excess. We also identify four of our observed sources with Ho emission line stars. Of these 11 sources, five are sub-stellar objects, below the hydrogen burning limit. While the eleven objects in table 1 are apparently young stellar objects, it is likely that there are many more young stellar objects in BRC 37… ”

As recently as mid-2005 even more discovery was made by Astrofisico di Arcetri at the end of a 16 year study. “In spite of the relatively high far-infrared luminosities of the embedded sources H2O maser emission was detected towards three globules only. Since the occurrence of water masers is higher towards bright IRAS sources, the lack of frequent H2O maser emission is somewhat surprising if the suggestion of induced intermediate- and high-mass star formation within these globules is correct. The maser properties of two BRCs are characteristic of exciting sources of low-mass, while the last one (BRC 38) is consistent with an intermediate-mass object.”

Around 18 months later at the beginning of 2007, Konstantin V. Getman (et al) used the Chandra X-Ray Observatory to draw conclusions on this same strange area as well: “The IC 1396N cometary globule (CG) within the large nearby H II region IC 1396 has been observed with the ACIS detector on board the Chandra X-Ray Observatory. We detect 117 X-ray sources, of which ~50-60 are likely members of the young open cluster Trumpler 37 dispersed throughout the H II region, and 25 are associated with young stars formed within the globule…. We find that the Chandra source associated with the luminous Class 0/I protostar IRAS 21391+5802 is one of the youngest stars ever detected in the X-ray band.”

Is there even more things yet to be discovered inside the twisted “Trunk”? Astronomers haven’t stopped looking. Just as recently as November 2008 yet another study was released Zoltan Bolag (et al) searching for protoplanetary discs. “Overall, our observations support theoretical predictions in which photoevaporation removes the gas relatively quickly (<=105 yr) from the outer region of a protoplanetary disk, but leaves an inner, more robust, and possibly gas-rich disk component of radius 5-10 AU. With the gas gone, larger solid bodies in the outer disk can experience a high rate of collisions and produce elevated amounts of dust. This dust is being stripped from the system by the photon pressure of the O star to form a gas-free dusty tail." What will the future hold? My many thanks to Takayuki Yoshida of Northern Galactic for turning me on to this incredible image which sparked my desire to learn and share what I’d learned about this region. Arigato!

Telescopium

Telescopium

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The small constellation of Telescopium is located just south of the ecliptic plane and was originally charted by Abbe Nicolas Louis de Lacaille who named it. It was later adopted by the IAU as one of the modern 88 constellations. Telescopium spans 252 square degrees of sky – ranking 57th in size. It has 2 primary stars in its asterism and 13 Bayer Flamsteed designated stars within its confines. Telescopium is bordered by the constellations of Ara, Corona Australis, Indus, Microscopium, Pavo and Sagittarius. It is visible to observers located at latitudes between +40° and -90° and its primary stars are best seen at culmination during the month of August.

Since Telescopium is considered a “new” constellation, there is no mythology associated with it – only Abbe Nicolas Louis de Lacaille’s love of all things science and what Telescopium is meant to represent – the telescope of Sir William Herschel. In Lacaille’s time, it was called “Beta Telescopii” and when represented on Johann Bode’s charts, it pointed northwards, towards Sagittarius and Corona Australis. Since Bode actually depicted it clear up into Ophichus, he also changed the name to “Tubus Astronomicus” as well. Later, both the name – and the constellation – became more abbreviated as it was adopted by the International Astronomical Union.

Let’s begin our binocular tour of Telescopium with its brightest star – Alpha – the “a” symbol on our chart. While Alpha is far from bright to our vision, this class B (B3) blue subgiant star shines more than 900 times brighter than our own Sun from a distance of 250 light years away. It is a young star, just beginning to evolve away from a core-hydrogen-fusing dwarf. While it is rotating very slowing, Alpha is also chemically peculiar, because it is a helium rich star with very strong stellar magnetic fields. It is believed that it may someday evolve into a massive white dwarf like Sirius-B.

Now aim your binoculars towards Delta – the “8” symbol. It won’t take long to discover this designation is shared by two stars! That’s right, we’re looking at an optical double star. Delta 1 and Delta 2 are both blue-white B-type subgiant stars, but Delta 1 (slightly brighter) is approximately 800 light years from Earth, while Delta 2 is closer to 1,100 light years distant!

Are you ready for Kappa? That’s the “k” symbol on our chart. Kappa Telescopii is also a visual double star. It is a yellow G-type giant star located 293 light years from our solar system.

Get out large binoculars or a small telescope for a look at a very rare type of variable star – RR Telescopii (RA 20 04 18.54 Dec -55 43 33.2). Here we have an example of what is called a Symbiotic Nova. According to the work of F.L. Crawford: “The optical spectrum of RR Tel is very rich in emission. By comparing the results of this study with previous publications on the subject, it is found that the RR Tel system is advancing towards higher degrees of excitation. It is also shown that several nebular lines (for example, [OIII] 4363 Angstroms and NeIV 4714 Angstroms) demonstrate component structure, perhaps caused by the different densities of the emitting plasmas.” Also, infrared and optical photometric and spectroscopic observations of the symbiotic nova RR Telecopii are used to study the effects and properties of dust in symbiotic binaries containing a cool Mira component, as well as showing “obscuration events” of increased absorption, which are typical for such Mira-type variable stars. RR Telescopii erupted in 1944 and took nearly 1600 days to reach maximum. At its lowest, RR can be as dim as magnitude 11 – or as bright as magnitude 7!

Keep a telescope handy to have a look at globular cluster NGC 6584 (RA 18 : 18.6 Dec -52 : 13). At around magnitude 9, this 8 arc minute sized globular will delight you. Discovered by James Dunlop on June 5, 1826 and cataloged originally as Dunlop 376, you will pull a lot of nice resolution out of the core region with larger aperture. A lot of photometry work has been done on this particular star cluster – looking for calcium abundances, blue straggler stars and hot stars located in the galactic halo region.

Now aim your large telescope towards challenging planetary nebula IC 4699 (RA 18 : 18.5 Dec -45 : 59) At magnitude 12 and nearly stellar in size, this particular planetary nebula will be difficult to distinguish from the field without the aid of a nebula filter which will aid in revealing the small disc.

Sources:
SEDS
Wikipedia
Chart Courtesy of Your Sky.

Taurus

Taurus

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The ancient zodiacal constellation of Taurus was one of Ptolemy’s original 48 constellations and remains today as part of the official 88 modern constellations recognized by the IAU. It is perhaps one of the oldest constellations of all and may have even been recognized prehistorically. Taurus spreads over 797 square degrees of sky and contains 7 main stars in its asterism with 130 Bayer Flamsteed designated stars located within its confines. It is bordered by the constellations of Auriga, Perseus, Aries, Cetus, Eridanus, Orion and Gemini. Taurus is visible to all observers located at latitudes between +90° and ?65° and is best seen at culmination during the month of January.

There is one major annual meteor shower associated with the constellation of Taurus, the annual Taurids, which peak on or about November 5 of each year and have a duration period of about 45 days. The maximum fall rate for this meteor shower is about 10 meteors per hour average, with many bright fireballs often occuring when the parent comet – Encke – has passed near perihelion. Look for the radiant, or point of origin, to be near the Pleiades.

Taurus is considered by some to be one of the oldest recognized constellations known, and may have even been depicted with the Pleiades in cave paints dating back to 13,000 BC. According to Greek myth, Taurus was the god Zeus, transformed into a bull in order to woo princess Europa, and perhaps could represent one of the Cretean Bull of Herculean fame. The ancient Egyptians also worshiped a bull-god for which this constellation might represent, just as the Arabs also considered it to be bovine by nature. The Hyades cluster was meant to represent the sisters of Hyas, a great hunter, placed in the sky to honor their mourning for the loss of their brother – just as the Pleiades represent the seven sisters of Greek mythology – as well as many other things in many other cultural beliefs. The Persians called this group of stars “Taura”, just as the Arabs referred to it as “Al Thaur”. No matter what way you want to look at it, this handsome collection of stars contains many fine deep sky objects to pique your interest!

Let’s begin our binocular and telescope tour of Taurus with its brightest star- Alpha – the “a” symbol on our map. Known to the Arabs as Al Dabaran, or “the Follower,” Alpha Tauri got its name because it appears to follow the Pleiades across the sky. In Latin it was called Stella Dominatrix, yet the Olde English knew it as Oculus Tauri, or very literally the “eye of Taurus.” No matter which source of ancient astronomical lore we explore, there are references to Aldebaran.

As the 13th brightest star in the sky, it almost appears from Earth to be a member of the V-shaped Hyades star cluster, but this association is merely coincidental, since it is about twice as close to us as the cluster is. In reality, Aldebaran is on the small end as far as K5 stars go, and like many other orange giants, it could possibly be a variable. Aldebaran is also known to have five close companions, but they are faint and very difficult to observe with backyard equipment. At a distance of approximately 68 light-years, Alpha is “only” about 40 times larger than our own Sun and approximately 125 times brighter. To try to grasp such a size, think of it as being about the same size as Earth’s orbit! Because of its position along the ecliptic, Aldebaran is one of the very few stars of first magnitude that can be occulted by the Moon.

Now, head off to Beta Tauri – the “B” symbol on our chart. Located 131 light years from our solar system, El Nath, or Gamma Aurigae, is a main sequence star about to evolve into a peculiar giant star – one high in manganese content, but low in calcium and magnesium. While you won’t find anything else spectacular about El Nath, there is a good reason to remember its position – it, too, get frequently occulted by the Moon. Such occultations occur when the moon’s ascending node is near the vernal equinox. Most occultations are visible only in parts of the Southern Hemisphere, because the star lies at the northern edge of the lunar occultation zone and occasionally it may be occulted as far north as southern California.

Now, turn your binoculars or small telescopes towards Omicron – the “o”. Omicron is sometimes called Atirsagne, meaning the “Verdant One”, but there’s nothing green about this 212 light year distant yellow G-type giant star, only that it has a great optical companion! Be sure to take a look at Kappa Tau, too… the “k”. Kappa is also a visual double star – but a whole lot more. Located 153 light years from Earth, this Hyades cluster member is dominated by white A-type subgiant star K1 and white A-type main sequence dwarf star, K2. They are 5.8 arcminutes, or at least a quarter light year apart. Between the two bright stars is a binary star made up of two 9th magnitude stars, Kappa Tauri C and Kappa Tauri D, which are 5.3 arcseconds from each other and 183 arcseconds from K1 Tau. Two more 12th magnitude companions fill out the star system, Kappa Tauri E, which is 136 arcseconds from K1 Tau, and Kappa Tauri F, 340 arcseconds away from K2 Tau. Still more? Then have a look at 37 Tauri, an orange giant star with a faint optical companion star… or 10 Tauri! 10 Tauri is only 45 light years away, and while it just slightly larger and brighter than our Sun, its almost the same age. It is believed to be a spectroscopic binary star, but you’ll easily see it’s optical companion. What’s more, thanks to noticing a huge amount of infrared radiation being produced by 10, we know it also has a dusty debris disk surrounding it!

Now, let’s have a go at variable stars – starting with Lambda, the upside down “Y” on our map. Al Thaur is in reality a binary star system as well as being an eclipsing variable star. The primary is a blue-white B-type main sequence dwarf star located about 370 light years away. However, located at a distance of 0.1 AU away from it is a white A-type subgiant star, too… and a third player even further away. Watch over a period of 3.95 days as first one, then the other passes in front of the primary star, dimming it by almost a full stellar magnitude! Don’t forget to check out HU Tauri, too. It is also an eclipsing binary star that drops by a magnitude every 2.6 days!

Ready to take a look at Messier 45? Visible to the unaided eye, small binoculars and every telescope, the Pleiades bright components will resolve easily to any instrument and is simply stunning. The recognition of the Pleiades dates back to antiquity and they’re known by many names in many cultures. The Greeks and Romans referred to them as the “Starry Seven,” the “Net of Stars,” “The Seven Virgins,” “The Daughters of Pleione” and even “The Children of Atlas.” The Egyptians referred to them as “The Stars of Athyr,” the Germans as “Siebengestiren” (the Seven Stars), the Russians as “Baba” after Baba Yaga, the witch who flew through the skies on her fiery broom. The Japanese call them “Subaru,” Norsemen saw them as packs of dogs and the Tongans as “Matarii” (the Little Eyes). American Indians viewed the Pleiades as seven maidens placed high upon a tower to protect them from the claws of giant bears, and even Tolkien immortalized the stargroup in The Hobbit as “Remmirath.” The Pleiades have even been mentioned in the Bible! So, you see, no matter where we look in our “starry” history, this cluster of seven bright stars has been part of it.

The date of the Pleiades culmination (its highest point in the sky) has been celebrated through its rich history by being marked with various festivals and ancient rites — but there is one particular rite that really fits this occasion! What could be spookier on this date than to imagine a bunch of Druids celebrating the Pleiades’ midnight “high” with Black Sabbath? This night of “unholy revelry” is still observed in the modern world as “All Hallows Eve” or more commonly as “Halloween.” Although the actual date of the Pleiades’ midnight culmination is now on November 21 instead of October 31. Thanks to its nebulous regions M45 looks wonderfully like a “ghost” haunting the starry skies. Binoculars give an incredible view of the entire region, revealing far more stars than are visible with the naked eye. Small telescopes at lowest power will enjoy M45’s rich, icy-blue stars and fog-like nebulae. Larger telescopes and higher power reveal many pairs of double stars buried within its silver folds. No matter what you chose, the Pleiades definitely rocks!

Our next most famous Messier catalog object in Taurus is M1 – the “Crab Nebula”. Although M1 was discovered by John Bevis in 1731, it became the first object on Charles Messier’s astronomical list. He rediscovered M1 while searching for the expected return of Halley’s Comet in late August 1758 and these “comet confusions” prompted Messier to start cataloging. It wasn’t until Lord Rosse gathered enough light from M1 in the mid-1840’s that the faint filamentary structure was noted (although he may not have given the Crab Nebula its name). To have a look for yourself, locate Zeta Tauri and look about a finger-width northwest. You won’t see the “Crab legs” in small scopes – but there’s much more to learn about this famous “supernova remnant”.

Factually, we know the “Crab Nebula” to be the remains of an exploded star recorded by the Chinese in 1054. We know it to be a rapid expanding cloud of gas moving outward at a rate of 1,000 km per second, just as we understand there is a pulsar in the center. We also know it as first recorded by John Bevis in 1758, and then later cataloged as the beginning Messier object – penned by Charles himself some 27 years later to avoid confusion while searching for comets. We see it revealed beautifully in timed exposure photographs, its glory captured forever through the eye of the camera — but have you ever really taken the time to truly study the M1? Then you just may surprise yourself… In a small telescope, the “Crab Nebula” might seem to be a disappointment – but do not just glance at it and move on. There is a very strange quality to the light which reaches your eye, even though at first it may just appear as a vague, misty patch. To small aperture and well-adjusted eyes, the M1 will appear to have “living” qualities – a sense of movement in something that should be motionless. This aroused my curiosity to study and by using a 12.5″ scope, the reasons become very clear to me as the full dimensions of the M1 “came to light”.

The “Crab” Nebula holds true to so many other spectroscopic studies I have enjoyed over the years. The concept of differing light waves crossing over one another and canceling each other out – with each trough and crest revealing differing details to the eye – is never more apparent than during study. To truly watch the M1 is to at one moment see a “cloud” of nebulosity, the next a broad ribbon or filament, and at another a dark patch. When skies are perfectly stable you may see an embedded star, and it is possible to see six such stars. It is sometimes difficult to “see” what others understand through experience, but it can be explained. It is more than just the pulsar at its center teasing the eye, it is the “living” quality of which I speak -TRUE astronomy in action. There is so much information being fed into the brain by the eye!

I believe we are all born with the ability to see spectral qualities, but they just go undeveloped. From ionization to polarization – our eye and brain are capable of seeing to the edge of infra-red and ultra-violet. How about magnetism? We can interpret magnetism visually – one only has to view the “Wilson Effect” in solar studies to understand. What of the spinning neutron star at its heart? We’ve known since 1969 the M1 produces a “visual” pulsar effect! We are now aware that about once every five minutes, changes occurring in the neutron star’s pulsation effect the amount of polarization, causing the light waves to sweep around like a giant “cosmic lighthouse” and flash across our eyes. For now, l’ll get down of my “physics” soapbox and just let it suffice to say that the M1 is much, much more than just another Messier. Capture it tonight!!

Since we’ve studied the “death” of a star, why not take the time tonight to discover the “birth” of one? Get out your telescope! Our journey will start by identifying Aldeberan (Alpha Tauri) and moving northwest to bright Epsilon. Hop 1.8 degrees west and slightly to the north for an incredibly unusual variable star – T Tauri. Discovered by J.R. Hind in October 1852, T Tauri and its accompanying nebula, NGC 1554/55 set the stage for discovery with a pre-main sequence variable star. Hind reported the nebula, but also noted that no catalog listed such an object in that position. His observance also included a 10th magnitude uncharted star and he surmised that the star in question was a variable. On either account, Hind was right and both were followed by astronomers for several years until they began to fade in 1861. By 1868, neither could be seen and it wasn’t until 1890 that the pair was re-discovered by E.E. Barnard and S.W. Burnham. Five years later? They vanished again.

T Tauri is the prototype of this particular class of variable stars and is itself totally unpredictable. In a period as short as a few weeks, it might move from magnitude 9 to 13 and other times remain constant for months on end. It is about average to our own Sun in temperature and mass – and its spectral signature is very similar to Sol’s chromosphere – but the resemblance ends there. T Tauri is a star in the initial stages of birth! So what exactly are T Tauri stars? They may be very similar in ways to our own Sun but they are far more luminous and rotate much faster. For the most part, they are located near molecular clouds and produce massive outflows of this material in accretion as evidenced by the variable nebula, NGC 1554/55. Like Sol, they produce X-ray emissions, but a thousand times more strong! We know they are young because of the spectra – high in lithium – which is not present at low core temperatures. T Tauri has not reached the point yet where proton to proton fusion is possible! Perhaps in a few million years T Tauri will ignite in nuclear fusion and the accretion disk become a solar system. And just think! We’re lucky enough to see them both…

For a large telescope challenge, let’s try NGC 1514 (RA 4 : 09.2 +30 : 47). This magnitude 10 planetary nebula is fairly small and dim… and it was discovered by William Herschel on November 13, 1790. If he could do it over 300 years ago, so can you! Chances are this particular nebula is a gaseous envelope which surrounds a tight double star, but revealing it was what startled Herschel the most. In his reports he writes: “A most singular phenomena… surrounded with a faintly luminous atmosphere… judgement I may venture to say, will be, that the nebulosity about the star is not of a starry nature”.

Planetary nebulae were first described as “planetary” by William Herschel in 1785. Before then, all were simply considered “nebulae.” It was once thought they were made of stars, but today we know planetaries are created from material given off by a single star. Many show well-defined rings of one type or another. Others – like M1 – are irregularly shaped supernova remnants. NGC 1514’s material is slowly boiled off over time, rather than caused by a violent explosion. It would be very hard to find the neutron central star in M1, but almost any scope can make out NGC 1514’s 10th magnitude fueling star as it quietly cooks away gases to feed its nebulous shroud. Because it is so bright, it can easily overwhelm the eye. This makes NGC 1514 similar to the famous “Blinking Planetary” – NGC 6826 – in Cygnus.

Are you ready for some galactic star clusters? Then let’s head for NGC 1647 (RA 4 : 46.0 Dec +19 : 04). At nearly unaided eye visibility and large enough to be easily seen in small binoculars and telescope, this widely scattered star cluster contains several dozen well resolved members and lots of double stars. The brighter stars are A or B-type main sequence stars, however there are also a few colorful orange giants to delight the eye, and the two brightest are located on the southern edge of the cluster.

Another bright, big and beautiful open star cluster for all optics is NGC 1746 (RA 5 : 03.6 Dec +23 : 49). It contains about two dozen members and although its not very compressed to the telescope, makes a very nice showing in binoculars or a rich field telescope. What’s clever about this particular cluster, is there is also two other open clusters which are superimposed on top! Look for NGC 1750 and NGC 1758 as part of this region as well. While it was debated for many years that Sir William Herschel was crazy when he designated three separate clusters for this region, later science proved him right!

How about another pair of open star clusters? Then have a look at NGC 1817 (RA 5 : 12.1 Dec +16 : 42) and NGC 1807 (RA 5 : 10.7 Dec +16 : 32). Both can be squeezed in the same field in binoculars and resolved very well to the telescope. Found a little less than a hand span northwest of Betelguese, NGC 1807 and NGC 1817 aren’t exactly twins. Both clusters are of similar magnitude and can be seen as faint patches in binoculars. Through a telescope, NGC 1817 appears far more populated with stars than its neighbor. Studies based on stellar motion reveal that NGC 1817 has far more stars than the brighter NGC 1807. Although the two are quite distant from one another in space, we get to see them both as close friends…

Sources:
Chandra Observatory
SEDS
Wikipedia
Chart Courtesy of Your Sky.

Sextans

Sextans

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Located just south of the ecliptic plane, the small, dim constellation of Sextans was originally introduced in the 17th century by astronomer Johannes Hevelius. It covers 314 square degrees of sky and ranks 47th in constellation size. Sextans has 3 primary stars in its asterism and 28 Bayer Flamsteed designated stars within its confines. It is bordered by the constellations of Leo, Hydra and Crater. Sextans is visible to all observers located at latitudes between +80° and ?80° and is best seen at culmination during the month of April.

There is one annual meteor shower associated with Sextans which occurs during the daytime. The Sextantids begin their activity on or about September 9 and last through October 9 of each year with the peak date occurring on or about September 27. This daytime radio meteor stream can produce up to three or four per hour at maximum rate.

Since Sextans is considered a relatively “new” constellation, it has no mythology associated with it – only the object which it represents. Its original name – Sextans Uranae – is Latin for the astronomical sextant, an instrument which Johannes Hevelius made frequent use of in his stellar observations. Although the constellation is very faint, its angles do resemble this particular tool with which the ancient astronomer measured and charted star positions and it was adopted as the constellation Sextans by the International Astronomical Union as one of the 88 modern constellations.

Let’s begin our binocular tour with its brightest star – Alpha – the “a” symbol on our map. Just barely visible to the unaided eye and standing right on the celestial equator, Alpha Sextantis shines 122 times brighter than our Sun and is about 3 times larger. Little wonder it appears so dim, considering that its about 285 light years from Earth! At an estimated 300 million years old, Alpha is nearing the end of its hydrogen fusing lifetime and is about to become an orange giant star – one with its pole pointed right at us. Take note of Alpha’s position in the sky… Because thanks to Earth’s nutation, it was 7 arc seconds more to the north a century ago!

Now, shift your attention towards Beta – the “B” symbol. Beta is a a blue-white B-type main sequence dwarf star located about 345 light years from our solar system. While it looks very ordinary… It isn’t. Beta is a Alpha 2 Canum Venaticorum variable star – one that varies its magnitude ever so slightly just about every 15 days or so.

Ready to go to the telescope? Then aim it at Gamma – the “Y” symbol on our chart. Gamma Sextantis is a triple star system approximately 262 light years from Earth. Its two primary components, A and B, are approximately 0.38 arcseconds apart or approximately 30 Astronomical Units With apparent magnitudes of +5.8 and +6.2 this close proximity means you better have a big telescope and some super resolution to pull this pair apart! However, orbiting the binary star pair at a distance of 36 arcseconds, or roughly a hundred times farther out, is Gamma Sextantis C, a 12th magnitude companion that is also gravitationally bound to the system. Faint… But far enough away to be seen!

Before you give up on Sextans, be sure to turn your telescope or big binoculars towards NGC 3115 (RA 10 : 05.2 Dec -07 : 43). With a magnitude of 9 and more than 8 arc minutes of size, the “Spindle Galaxy” is sure to please everyone! This lenticular galaxy was discovered by William Herschel on February 22, 1787. At about 32 million light-years away from us, it might not look large in the eyepiece, but in reality it is several times bigger than our own Milky Way Galaxy. In 1992, a supermassive black hole was observed in NGC 3115 – the largest found to that date. With an estimated mass of 2 billion times the mass of the Sun, astronomers have kept a close eye on activity since its discovery. The galaxy itself appears to be comprised of mostly old stars and the growth of the black hole hasn’t increased in size since it was first observed.

The Chandra X-Ray Telescope has maintained its vigil and according to its press releases: “This is the best black hole candidate that is massive enough to have powered a quasar.”

These findings strengthen the popular view that quasars – the brightest objects in the Universe – are powered by accretion onto massive black holes. Quasars can be seen farther away than any other object. In many cases, their light has been traveling toward us for most of the age of the Universe. Therefore we see quasars as they were long ago. As a result, astronomers can infer how the quasar population evolved with time. They find that quasars were numerous when the Universe was 1/4 of its present age. Now they have mostly died out. So dead quasars should be hiding in many nearby galaxies. Quasar energies imply that the dead remnants should have masses of a billion Suns. The discovery of a supermassive black hole is a crucial confirmation of the black hole accretion theory of quasars.

Ironically, NGC 3115 is otherwise undistinguished. It’s name comes from its listing as object number 3115 in J. Dreyer’s “New General Catalog” of nebulae and star clusters, published in 1888. The galaxy is visible in moderate-sized amateur telescopes as a faint fuzzy patch in the constellation Sextans, The Sextant. But at a distance of 30 million light years, NGC 3115 is more than ten times farther from us than Andromeda or M32. In reality, it is several times bigger than our own Milky Way. But its stars are mostly old, it contains virtually no gas, and little is going on now apart from the stately orbits of its stars. In particular, its nucleus is extremely inactive. The growth of the black hole and the nuclear activity that it feeds are over, unless additional stars wander too close to the center. Whenever that happens, the nucleus is expected to experience a brief but energetic rebirth.

Although these findings support our general picture of quasars, they also highlight a number of unresolved issues. “We have only a very speculative idea of how supermassive black holes form,” Richstone said. “The processes that control their feeding, make them shine, and later turn them off are also poorly understood.” Finding nearby black holes is crucial to further progress. NGC 3115 provides a billion-solar-mass example.”

Sources:
Wikipedia
University of Illinois
Chart Courtesy of Your Sky.

Weekend SkyWatcher’s Forecast – January 16-18, 2009

Greetings, fellow SkyWatchers! Are you ready for another weekend under the stars? Then get out your telescopes and let’s go globular as we hunt down Messier Object 79. Polar weather got you down? Then let’s take a look at the pole stars both north and south and check into what Sir William Herschel was doing at this time of year. Then learn your history and I’ll meet you outside in the dark….

Friday, January 16, 2009 – In 1978 on this date, NASA named 35 candidates for space shuttle missions, including Sally Ride as the first female U.S. astronaut and Guion Bluford, Jr., as the first black. In 1973, the Lunokhod 2 mission was beginning its robotic lunar expedition, and in 1969 Soyuz 4 and 5 became the first vehicles to dock in space and exchange cosmonauts. The year 1730 saw the birth of Jean Bochart – publisher of LaPlace’s planet/ecliptic theory. Although eventually beheaded for his politics, Bochart put together Europe’s largest collection of astronomical instruments and was renowned for his calculations of cometary orbits, made jointly with long-time friend and co-observer Charles Messier.

Tonight, venture into Lepus for a faint, round, fuzzy object that might easily be mistaken for a comet in a small telescope or binoculars—Messier Object 79 (RA 05 24 10 Dec +24 31 27). The true beauty of this object is revealed in large telescopes. Behold a globular cluster, one of many densely packed balls of stars that mainly congregate near our galactic center. Discovered by Pierre Mechain and cataloged by Messier in 1780, M79 is on the opposite side of our galaxy, and about 4,200 light-years away. Spanning 118 light-years, this starry sphere may not be an original member of our galaxy at all but an import. Although we can’t see it happening, the Canis Major Dwarf galaxy is slowly being incorporated into our own system, and M79 might very well be a product of this union!

Thanks to Mechain and Messier’s careful notes, William Herschel later recovered M79 and resolved its stars. Although the practice of maintaining an astronomy diary isn’t for everyone, keeping simple records is very rewarding. Make note of the object’s appearance, equipment used, and sky conditions. Observing diaries just like those of Messier and Mechain have led countless astronomers along the road of discovery to all the deep-sky objects we know today!

Saturday, January 17, 2009 – Celebrate the 1723 birthday of Johann Tobias Mayer, the German astronomer who created the first lunar tables for determining longitudes at sea. His calculations were accurate to within a half degree! If you’re up before sunrise, look at the Moon now nearing third quarter. How many lunar seas can you still identify? Can you navigate to Spica nearby?

Turning Still- Joe Orman
Turning Still - Joe Orman
Tonight let’s go from one navigational extreme to another as viewers in the Northern Hemisphere try their hand (and eye) at 390 light-year distant Polaris . Its fame as a ‘‘fixed star’’ is a bit undeserved, because it is approaching us at 25 kilometers per second. Only its sky position closest to the north celestial pole makes Polaris appear to ‘‘stand still’’ while the other stars revolve around it.

Ranked the 49th brightest star, Alpha Ursa Minoris may look ordinary but is not. Polaris is a Cepheid variable, a star that expands and contracts on a regular basis, changing its brightness slightly. Modern
interferometry has revealed it as slightly irregular—an ‘‘overtone pulsator’’—and a multiple one at that. Polaris’ triple system took the resolving power of the Hubble Space Telescope to reveal its spectroscopic component, but even a small telescope can spot its gravitationally bound blue companion!

The Southern Hemisphere also has a near-pole star—Sigma Octanis—but at magnitude 5 (300 times fainter than Polaris), it doesn’t make a good guide star. Ancient navigators found better success with the constellation Crux, better known as the Southern Cross. Its two brightest stars, Gacrux and acrux, are oriented north–south and point across the pole to brilliant Archenar. Splitting the distance between Gacrux and Archenar lands you within 2 degrees of the south celestial pole. A southern double star comparable to Polaris in appearance is Lambda Centauri. The difference in magnitude between components and separation are about the same!

Sunday, January 18, 2009 – ‘‘I have looked farther into space than ever a human being did before me,’’ writes Sir William Herschel, discoverer of thousands of deep-sky objects. While 400 of these make up a popular observing list, many more deserve attention. This night in 1784, Herschel aimed his telescope toward Orion’s stars, and he found two new sky gems! Starting with binoculars, aim about 2 degrees northwest of the northernmost star in Orion’s ‘‘bow’’ (Pi1 Orionis) to view NGC 1662 (RA 04 48 24 Dec +10 56 00).

With a combined magnitude of 6, this small galactic cluster will show as a slight compression of the starfield, a challenging binocular deep-sky object. A small telescope at modest magnification will resolve NGC 1662 into a jewel-like chain of blue and gold stars. Astronomers have studied it extensively to refine its members’ proper motions, and it may have once contained more stars during its 300-million-year evolution!

Now return to M42 and go slightly north (RA 05 35 15 Dec -04 53 12) to examine NGC 1977). Also discovered on this night by Herschel, seasoned sky veterans know this area by its nickname ‘‘the Running Man’’. Consisting of three separate areas of emission and reflection nebulae that seem to be visually connected, 1,500-light-year-distant NGC 1977/1975/1973 complex would be spectacular on its own if weren’t so close to M42! The conjoining nebula is whispery soft, its dark lanes created by interstellar dust and fine needle-like shards of carbon. Illuminating the gases is its fueling source, the multiple star 42 Orionis—a prized double on many lists. Through a telescope, this lovely triangle of bright nebulae and its several enshrouded stars make a wonderful region for exploration. Can you see the Running Man within?

Until next week? Dreams really do come true… When you keep on reaching for the stars!

This week’s awesome images are: M79: Credit—Palomar Observatory, courtesy of Caltech, Sally Ride: Credit—NASA, ‘‘Turning Still’’: Credit—Joe Orman, Tobias Mayer (historical image), NGC 1662 and NGC 1977: Credit—Palomar Observatory, courtesy of Caltech. Thank you so much!

Serpens Cauda

Serpens Cauda

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The constellation of Serpens is unique – being the only one to be divided into two parts. Serpens Cauda represents the eastern half. Serpens was one of the 48 constellations listed by the 1st century astronomer Ptolemy and it remains one of the 88 modern constellations. The entire constellation spans 637 square degrees of sky and contains 9 main stars within its asterism and 57 Bayer Flamsteed designated stars within its confines. Serpens Caput is bordered by the constellations of Aquila, Sagittarius, Scutum and separated from its counterpart by Ophiuchus. Serpens Cauda can be seen by all observers located at latitudes between +80° and -80° and is best seen at culmination during the month of July.

In mythology, Serpens represents a huge snake held by the constellation Ophiuchus. It can either be referred to as simply “Serpens” or by its western half (Caput – the “Snake’s Head”) or its eastern half (Cauda – the “Snake’s Tail”). Ophiuchus was believed to have been the son of Apollo and a healer. According to legend, the snake is also meant to represent healing as it sheds its skin in rebirth.

Let’s begin our binocular tour of Serpens Cauda with its brightest star – Eta Serpentis – the “n” symbol on our map. Eta Serpentis is approximately 61 light years from Earth and it is an orange K-type giant star about 15 times more luminous than our Sun. Don’t forget Xi, the squiggle at the southern border, either… while it’s strictly a visual double star, this 105 light year distant group is very attractive in binoculars!

Are you ready for more? Then let’s head to M16 (RA 18 : 18.8 Dec -13 : 47). While the attendant open cluster NGC 6611 was discovered by Cheseaux in 1745-6, it was Charles Messier who cataloged the object as Messier 16. And he was the first to note the nearby nebula IC 4703, now commonly known as the Eagle. At 7000 light-years distant, this roughly 7th magnitude cluster and nebula can be spotted in binoculars, but at best it is only a hint. As part of the same giant cloud of gas and dust as neighboring M17, the Eagle is also a place of starbirth illuminated by these hot, high energy stellar youngsters which are only about five and a half million years old.

In small to mid-sized telescopes, the cluster of around 20 brighter stars comes alive with a faint nebulosity that tends to be brighter in three areas. For larger telescopes, low power is essential for Messier 16. With good conditions, it is very possible to see areas of dark obscuration and the wonderful notch where the “Pillars of Creation” are located. Immortalized by the Hubble Space Telescope, they won’t be nearly as grand or as colorful as the HST saw them, but what a thrill to know they are there!

For binoculars and all telescopes, let’s take a look a IC 4756 (RA 18 : 39.0 Dec +05 : 27). This huge, 5th magnitude open star cluster is sometimes referred to as “Graff’s Cluster”. Located about about 13,000 light years away from our solar system, you will see far more stars than you can count in this terrific field!

Sources:
Wikipedia
Chandra Observatory
SEDS
Chart Courtesy of Your Sky.

Serpens Caput

Serpens Caput

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The constellation of Serpens is unique – being the only one to be divided into two parts. Serpens Caput represents the western half. Serpens was one of the 48 constellations listed by the 1st century astronomer Ptolemy and it remains one of the 88 modern constellations. The entire constellation spans 637 square degrees of sky and contains 9 main stars within its asterism and 57 Bayer Flamsteed designated stars within its confines. Serpens Caput is bordered by the constellations of Hercules, Corona Borealis, Virgo, Libra, Bootes and separated from its counterpart by Ophiuchus. Serpens Caput can be seen by all observers located at latitudes between +80° and ?80° and is best seen at culmination during the month of July.

In mythology, Serpens represents a huge snake held by the constellation Ophiuchus. It can either be referred to as simply “Serpens” or by its western half (Caput – the “Snake’s Head”) or its eastern half (Cauda – the “Snake’s Tail”). Ophiuchus was believed to have been the son of Apollo and a healer. According to legend, the snake is also meant to represent healing as it sheds its skin in rebirth.

Let’s begin our binocular tour of Serpen Caput with its brightest star – Alpha Serpentis – the “a” symbol on our map. Alpha Serpentis goes by the proper name Unukalhai, meaning loosely the “heart of the serpent”. Alpha Serpentis is approximately 73.2 light years from Earth and it is a great binary star for a small telescope. The primary, Alpha Serpentis A is an orange K-type giant star about 15 times larger than our Sun and its 11th magnitude B star is about 58 arcseconds from the primary. But don’t stop there! If skies are steady, power up and keep looking for the 13th magnitude C star located 2.3 arcminutes from A.

Now, aim your telescope towards Theta – the “8” symbol on our chart. Theta Serpentis is located 132 light years from our solar system and goes by the name of Alya, which means “fat tail”. Guess what? It’s also a great multiple star system! Both Theta-1 Serpentis and Theta-2 Serpentis are white A-type main sequence dwarf stars, very close in magnitude and separated by 22 arcseconds, but Theta Serpentis C is a yellow G-type star that is widely separated from this par by about 7 arc minutes.

For binoculars and all telescopes, let’s take a look a Messier 5 (RA 15 : 18.6 Dec +02 : 05). At nearly unaided eye visible, you’ll like this one! This fifth brightest globular cluster in the sky is considered one of the most ancient at 13 billion years old. Located further away from the dusty galactic center, resolution explodes as we move up in aperture. Easily seen as a round ball of unresolved stars in binoculars, small scopes begin to pick up individual stellar points at higher magnifications. Careful attention shows that M5 is not perfectly round. Its brightest 11th and 12th magnitude stars actually are randomly distributed but seem to array themselves in great arcs.

For a big telescope challenge, try NGC 6118 (RA 16 : 21.8 Dec -02 : 17). It is a very low surface brightness, 13th magnitude spiral galaxy, and although its fairly large, it’s pretty hard to see in small telescopes. This quality has given rise to the nickname the “Blinking Galaxy”, since it only seems to appear during averted vision – only to disappear if the angle isn’t right. About 80 million light-years away, NGC 6118 is a grand-design spiral seen at an angle, with a very small central bar and tightly wound spiral arms. Thank to imagining by the VLA, we know more about this galaxy than ever. In 2004 a supernova event was caught near the galaxy’s center – believed to be the collision of two binary stars!

Sources:
SEDS
Chandra Observatory
Wikipedia
Chart Courtesy of Your Sky.

Scutum

Scutum

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The small constellation of Scutum was originally created by Johannes Hevelius in 1683 and was later adopted as a permanent constellation by the IAU. It resides just north of the ecliptic plane or about 10 degrees south of the celestial equator and spans 109 square degrees of sky, ranking 84th in constellation size. There are 2 main stars in Scutum’s asterism and it contains 7 Bayer Flamsteed designated stars within its confines. It is bordered by the Aquila constellation, Sagittarius and Serpens Cauda. Scutum is visible to all observers located at latitudes between +80° and ?90° and is best seen at culmination during the month of August.

There is one annual meteor shower associated with the constellation of Scutum – the June Scutiids. Beginning on or about June 2 and ending about July 29th, we pass into the meteoroid stream which brings on the activity. The peak date for this meteor shower is on or about June 27 and the maximum fall rate is 2-4 meteors per hour.

The constellation of Scutum wasn’t named for a mythological figure – but rather for an object to honor a classical one. In, 1683, Johannes Hevelius, who originally named it Scutum Sobiescianum (the shield of Sobieski), did to commemorate the victory of the Polish forces led by King John III Sobieski in the Battle of Vienna, and thus the name refers to Sobieski’s Janina Coat of Arms. Rather fitting, since this particular king helped Hevelius rebuild his observatory after it was destroyed by fire! It’s Latin name means “shield” and the name was later shortened to Scutum when it was adopted as a permanent constellation by the International Astronomical Union.

Let’s begin our binocular tour of Scutum with its brightest star – Alpha – the “a” symbol on our map. Alpha Scuti is an orange class K giant star located about 175 light years from Earth. While it is not uncommon for this type of star to be over 130 times brighter than our Sun and more than 20 times larger – what’s unusual is the way it has evolved. According to its mass, Alpha should be about 2 billion years old and beginning to fuse helium to carbon… However, it has been discovered that Alpha is slightly variable – meaning it could be shedding its outer layer and on the way to becoming a white dwarf star!

Now, have a look at Delta – the “8” symbol on our chart. Here’s a peculiar star if there ever was one… A star so strange that it’s the prototype of its class. Delta is a giant star – but it is also a variable star. Located 187 light years from our solar system, this metal-rich oddity shines 33 times brighter than our Sun, but it’s only about twice as big. Deep inside, it has stopped fusing hydrogen and it is on its way to becoming a red giant star. But, it’s pulsing like a heartbeat… Changing its magnitude by about 20% every 5 to 65 hours. Added to this are periods of 2.79 hours, 2.28 hours, 2.89 hours, and 20.11 hours. All of this adds up to a very complex rhythm which makes Delta unique! Now, take a look in a telescope, too… Because Delta isn’t alone – it is also a binary star. Look for a 12th magnitude companion 15.2 seconds of arc away from the primary and a 9th component 52.2 seconds away.

For binoculars and small telescopes, head off to Messier 11 (RA 18 : 51.1 Dec -06 : 16)! This incredible galactic star cluster was discovered in 1681 by German astronomer Gottfried Kirch at the Berlin Observatory, M11 was later cataloged by Charles Messier in 1764 and first dubbed the “Wild Duck” by Admiral Smyth. To our modern telescopes and binoculars, there is little doubt as to how this rich galactic cluster earned its name – for it has a distinctive wedge-shaped pattern that closely resembles a flight of ducks. This fantastic open cluster of several thousand stars (about 500 of them are magnitude 14 or brighter) is approximately 250 million years old. M11 is easily located by identifying Altair, the brightest star in Aquila. By counting two stars down the “body” of Aquila and stopping on Lambda, you will find your starhop guide. Near Lambda you will see three stars, the centermost is Eta Scuti. Now just aim! Even small binoculars will have no problem finding M11, but a telescope is required to start resolving individual stars. The larger the telescope’s aperture the more stars will be revealed in this most concentrated of all open clusters!

Keep binoculars and rich field telescopes handy as you shift over to Alpha Scutum and check east-northeast for neighboring 7.8 magnitude open cluster NGC 6664 (RA 18 : 36.7 Dec -08 : 13) . Compare the view to Scutum’s other Messier open cluster – similar sized M26 (RA 18 : 45.2 Dec -09 : 24). As one of the faintest Messier clusters, it’s surprising his scope was able to reveal it at all! To locate Messier 26 shift a little less than 3 degrees south-southeast of Alpha. Those with larger scopes should look for a strange void in the middle of the cluster.

Now, let’s go with a large telescope and have a look at globular cluster NGC 6712 (RA 18 : 53.1 Dec -08 : 42). At magnitude 8, it can be captured with smaller aperture, but requires some muscle to resolve! NGC 6712 was probably discovered by Le Gentil on July 9, 1749 when investigating the Milky Way star cloud in Aquila, but we know it was independently discovered by William Herschel on June 16, 1784. As for its nature? That took John Herschel, who was the first to described it as a “globular star cluster” during his observations in the 1830s!

Last, but not least, let’s do something that you don’t even need a telescope for – R Scuti. This terrific red variable star ranges from 4th to 8th magnitude in 142 days. Chances are, R is probably a red supergiant star, surrounded by a shell of material thousands of times bigger than the interior star itself. One day, it will drop its envelope – turning into a planetary nebula and the star into a white dwarf… But until then? We can simply enjoy this beautiful mystery star!

Sources:
Wikipedia
SEDS
Chandra Observatory
Chart Courtesy of Your Sky.

Sculptor

Sculptor

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The small constellation of Sculptor is located south of the ecliptic plane. It was originally charted by Abbe Nicolas Louis de Lacaille who named it “Apparatus Sculptoris” – the Sculptor’s Studio. It was later adopted by the International Astronomical Union as one of the 88 modern constellations and its name shortened to Sculptor. It covers 475 square degrees of sky and ranks 36th in constellation size. Sculptor has 4 main stars in its asterism and contains 18 Bayer Flamsteed designated stars within its boundaries. It is bordered by the constellations of Cetus, Aquarius, Piscis Austrinus, Grus, Phoenix and Fornax. Sculptor is visible to all observers located at latitudes between +50° and ?90° and is best seen at culmination during the month of November.

Since Sculptor is considered a “new” constellation, there is no mythology associated with it – only the story of how its name came to be. French astronomer Nicolas Louis de Lacaille charted the southern hemisphere skies from the Cape of Good Hope during the time period of 1751-1752 and his love of all objects in art and science were portrayed in the names he assigned to his newly created constellations. Depicted on his chart as a fanciful tripod with a carved bust and the artist’s tools, ” l’Atelier du Sculpteur” was later shortened to the simpler term – Sculptor – and adopted by the International Astronomical Union as a permanent constellation.

Let’s begin our binocular tour of Sculptor with its brightest star – Alpha – the “a” symbol on our map. Located approximately 680 light years from Earth, Alpha Sculptoris is a blue-white B-type giant classified as an SX Arietis type variable star and its magnitude varies by 0.01. While changes in brightness and spectral composition that small would never be detectable to the human eye, at one time it was believed to be caused by orbiting black hole – but were later identified to chemical variations in its atmosphere. While Alpha doesn’t appear to be much, take a closer look… It still shines over 1700 times brighter than our own Sun – yet is only 7 times larger! It is one of the weirdest stars you will ever see – a helium weak star that rotates ever-so-slowly. Thanks to this creeping motion, Alpha can generate a huge stellar magnetic field which allows it to concentrate its chemicals in certain areas – and even flip its magnetic poles!

For other binocular attractions, take a look at Beta Sculptoris – the “B” symbol. It’s a a blue-white B-type subgiant star positioned approximately 178 light years from our solar system. Or Gamma – the “Y” symbol – it’s an an orange K-type giant that is 179 light years away… or even Delta – the “8” symbol. Delta is is a triple star system that’s 139 light years distant and the primary component, Delta Sculptoris A, is a white A-type main sequence dwarf star! Take out the telescope and look for a faint, 11th magnitude companion, Delta Sculptoris B, 4 arcseconds, or more than 175 AU, away from it. Orbiting this pair at the much greater separation of 74 arcseconds, is the third player in this drama, the yellow G-type Delta Sculptoris C, which has an apparent stellar magnitude of 9.4.

For telescope observers, one of the greatest challenges you will ever encounter is the Sculptor Dwarf Galaxy (RA 01 : 00.0 Dec -33 : 42). Discovered by Harlow Shapley on photographic plates in 1937, this extreme low surface brightness elliptical galaxy is a member of our own local galaxy group and is about 290,000 light-years away. Use at least a 150mm telescope and an absolute minimum of magnification to spot just a compression in the starfield at this location!

Now, let’s take a look at the Sculptor Group – a a loose group of galaxies near the south galactic pole and one of the closest groups of galaxies to the Milky Way Local Group. At the head of this class is the Sculptor Galaxy – NGC 253 – is an intermediate spiral galaxy (RA 0 : 47.6 Dec -25 : 17). Discovered by Caroline Herschel, this brilliant magnitude 7 beauty is a starburst galaxy, undergoing periods of intense star formation, and can easily be seen with a small telescope or binoculars. However, companion galaxies NGC 247, PGC 2881, PGC 2933, Sculptor-dE1, and UGCA 15 will need much more aperture! This association forms a gravitationally bound core near the center of the group and most other galaxies associated with the Sculptor Group are only weakly gravitationally bound to this core.

While there, drop south and take a look at NGC 288 (RA 00:52:47.5 Dec -26:35:24). This 8th magnitude globular cluster was discovered by Sir William Herschel and can often be spotted in the same binocular field as NGC 253. While this small globular doesn’t appear to be worthy of much attention, think again… In the late 1980’s it was discovered that it is about 3 billion years older than other globular clusters!

Need to take a look at the home of a supernova? The stop by NGC 150 (RA 0 : 34.3 Dec -27 : 48). Home to an event in 1990, this spiral galaxy is also a great radio emitter, too. Even though it will require a larger telescope to catch anything at magnitude 11, it will still give a nice oblong presentation with a bright core region.

For another binocular and small telescope galaxy, take a look at NGC 55 (RA 0 : 14.9 Dec -39 : 11). This huge, magnitude 8 irregular galaxy gives a great, near edge-on presentation and is believed to be very similar to the Large Magellanic Cloud (LMC). Spanning about 50,000 light-years, large telescopes will be able to resolve out brighter regions of emission nebulae – large star forming regions producing new stars.

For an unusual mid-size telescope challenge, take a look at NGC 7793 (RA 23 : 57.8 Dec -32 : 35). At magnitude 9 and about 9 arc minutes in size, you’ll find 10 million light year distant Bennett 130 to be a beautiful spiral with a sharp nucleus and round, hazy spiral galaxy structure. It was discovered by James Dunlop and it is also part of the Sculptor Group. In 2005, the Spitzer Space Telescope was able to pierce through its clouds and take a closer look at star formation driving the evolution of the galaxy.

Don’t forget while you’re in Sculptor to take on large telescope challenges like NGC 7713 (RA 23 : 36.5 Dec -37 : 56) – a 12th magnitude spiral galaxy, NGC 7755 (RA 23 : 47.9 Dec -30 : 31), also 12th magnitude, but a much smaller elliptical galaxy. How about small and faint NGC 24 (RA 0 : 09.9 Dec -24 : 58) or far easier NGC 134 (RA 0 : 30.4 Dec -33 : 15). There’s galaxies galore just waiting to be carved out of Sculptor and enjoyed!

Sources:
SEDS
Chandra Observatory
Wikipedia
Chart Courtesy of Your Sky.

Scorpius

Scorpius

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The zodiacal constellation of Scorpius resides on the ecliptic plane and was one of the original 48 constellations charted by Ptolemy to be later adopted as a modern constellation by the IAU. It covers 497 square degrees of sky and ranks 33rd in size. Scorpius has 15 main stars in its asterism and 47 Bayer Flamsteed designated stars within its confines. It is bordered by the constellations of Sagittarius, Ophiuchus, Libra, Lupus, Norma, Ara and Corona Australis. Scorpius is visible to all observers located at latitudes between +40° and ?90° and is best seen at culmination during the month of July.

There are two annual meteor showers associated with the constellation of Scorpius. The first is the Alpha Scorpiids – which begin on or about April 16 and end around May 9. The peak date of most activity is on or about May 3 and the radiant is near the brilliant red star, Antares. The second meteor shower, the June Scorpiids peaks on or about June 5 of each year. The radiant for this particular meteor shower is closer to the Ophiuchus border and the activity rate on the peak date is high – with about 20 meteors (average) per hour and many reported fireballs.

Because Scorpius was easy visible to ancient civilizations and its patterns do resemble the Scorpion which it represents, there is a great deal of mythology associated with this constellation. To the Greeks it represented the creature sent by Hera to eliminate Orion the Hunter – forever kept apart in the sky to continue their heavenly feud. Perhaps it was Apollo who sent the Scorpion and Orion flees it? Scorpius was also said to appear to Phaethon, who wrecked the sun-chariot when the horses balked at the mighty monster’s appearance. The Oriental culture recognized this pattern of stars as part of the Dragon, while the Polynesians saw it as a fishhook. No matter what legend you choose to place on this pattern of stars, its curving asterism is very distinctive and easy to recognize!

Let’s begin our binocular tour of Scorpius with its brightest star – Alpha – the “a” symbol on our chart. Antares is part of of the Upper Scorpius Association of Stars and is no doubt also a star poised on the edge of extinction. At a safe distance of 500 light-years, you’ll find this pulsating red variable equally fascinating to the eye as well as to the telescope. Unlike other stars, Alpha Scorpii also has a companion which can be revealed to small telescopes under steady conditions. Discovered on April 13, 1819 during a lunar occultation, this 6.5 magnitude green companion isn’t the easiest to split from such a bright primary – but it’s certainly fun to try to spot its 5.4 magnitude green companion. Like winter’s Sirius, the Antares pair needs especially still – but not necessarily dark – skies. It also requires a well-chosen magnification – one high enough to separate the two close stars (2.9 arc seconds), but low enough to concentrate the fainter star’s (magnitude 5.4) light. Did you know that Antares’ true rival is brighter Betelgeuse? Photometric measurements show that more massive Betelgeuse is slightly redder than Antares. Fortunately, the “Rival” does reside along the ecliptic plane allowing us many opportunities to see it accompany other solar system objects and be occulted by the Moon!

Keep your binoculars handy because all you have to know is Antares and go west…

Just slightly more than a degree away you’ll find a major globular cluster perfectly suited for every size telescope and binoculars – M4 (RA 16 23 35 Dec 26 31 31). This 5th magnitude Class IX cluster can even be spotted unaided from a dark location! In 1746 Philippe Loys de Cheseaux happened upon this 7200 light-year distant beauty – one of the nearest to us. It was also included in Lacaille’s catalog as object I.9 and noted by Messier in 1764. Much to Charles’ credit, he was the first to resolve it!

As one of the loosest globular clusters, M4 would be tremendous if we were not looking at it through a heavy cloud of interstellar dust. To binoculars, it is easy to pick out a very round, diffuse patch – yet it will begin resolution with even a small telescope. Large telescopes will also easily see a central “bar” of stellar concentration across M4’s core region, which was first noted by William Herschel. As an object of scientific study, the first millisecond pulsar was discovered within M4 in 1987 – one which spins 10 times faster than the Crab Nebula pulsar. Photographed by the Hubble Space Telescope in 1995, M4 was found to contain white dwarf stars – the oldest in our galaxy – with a planet orbiting one of them! A little more than twice the size of Jupiter, this planet is believed to be as old as the cluster itself. At 13 billion years, it would be three times the age of the Sol system!

Keep your binoculars or a small telescope handy as well go off to explore a single small globular cluster – Messier 80. Located about 4 degrees northwest of Antares (half a fist), this little globular cluster is a powerpunch. Located in a region heavily obscured by dark dust, the M80 will shine like an unresolvable star to small binoculars and reveal itself to be one of the most heavily concentrated globulars to the telescope. Discovered within days of each other by Messier and Mechain respectively in 1781, this intense cluster is around 36,000 light years distant.

In 1860, the M80 became the first globular cluster to contain a nova. As stunned scientists watched, a centrally located star brightened to magnitude 7 over a period of days and became known as T Scorpii. The event then dimmed more rapidly than expected, making observers wonder exactly what they had seen. Since most globular clusters contain stars all of relatively the same age, the hypothesis was put forward that perhaps they had witnessed an actual collision of stellar members. Given the cluster contains more than a million stars, the probability remains that some 2700 collisions of this type may have occurred during the M80’s lifetime.

Now head for Lambda Scorpii and hop three fingerwidths northeast to NGC 6406 (RA 17 40 18 Dec -32 12 00)… We’re hunting the “Butterfly!” Easily seen in binoculars and tremendous in the telescope, this brilliant 4th magnitude open cluster was discovered by Hodierna before 1654 and independently found by de Cheseaux as his Object 1 before being cataloged by Messier as M6. Containing about 80 stars, the light you see tonight left its home in space around the year 473 AD. Messier 6 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, and belong to the main sequence, the unique shape of this cluster gives it not only visual appeal, but wonderful color contrast as well.

Less than 3 arc minutes east of 3.3 magnitude G Scorpii (the tail star of the Scorpion) is 7.4 magnitude globular cluster NGC 6441. No challenge here. This 38,000 light-year distant compact cluster is around 13 thousand light-years from the galactic core. It was first noted by James Dunlop from southeastern Australia in 1826.

Around two and a half degrees northeast of G Scorpii (and NGC 6441) is another interesting deep sky twosome – bright open cluster M7 and faint globular NGC 6453. M7 was first recorded as a glowing region of faint stars by Ptolemy circa 130 CE. Located 800 light-years away, the cluster includes more than half a dozen 6th magnitude stars easily resolved with the least amount of optical aid. Through telescopes, as many as 80 various stars can be seen and it rocks in binoculars!

Now head northeast and the faint haze of 31,000 light-year distant globular cluster NGC 6453 will reveal itself to mid- and large-sized scopes. Like NGC 6441, this globular cluster was discovered from the southern hemisphere, in this case by John Herschel on June 8, 1837 while observing from the Cape of Good Hope, South Africa.

It’s time to aim your telescope at NGC 6302, a very curious planetary nebula located around three fingerwidths west of Lambda Scorpii: it is better known as the “Bug” nebula (RA 17 13 44 Dec -37 06 16). With a rough visual magnitude of 9.5, the Bug belongs to the telescope – but it’s history as a very extreme planetary nebula belongs to us all. At its center is a 10th magnitude star, one of the hottest known. Appearing in the telescope as a small bowtie, or figure 8 shape, huge amounts of dust lie within it – very special dust. Early studies showed it to be composed of hydrocarbons, carbonates and iron. At one time, carbonates were believed associated with liquid water, and NGC 6302 is one of only two regions known to contain carbonates – perhaps in a crystalline form.

Ejected at a high speed in a bi-polar outflow, further research on the dust has shown the presence of calcite and dolomite, making scientists reconsider the kind of places where carbonates might form. The processes that formed the Bug may have begun 10,000 years ago – meaning it may now have stopped losing material. Hanging out about 4000 light-years from our own solar system, we’ll never see NGC 6302 as well as the Hubble Telescope presents its beauty, but that won’t stop you from enjoying one of the most fascinating of planetary nebulae!

Now begin your starhop at the colorful southern Zeta pair and head north less than one degree for NGC 6231 (RA 16 : 54.0 Dec -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 faint emission nebula called IC 4628 – making this low power journey through southern Scorpius a red hot summer treat!

When you are done, hop west (RA 16 25 18 Dec 40 39 00) to encounter the fine open cluster NGC 6124. Discovered by Lacaille and known to him as object I.8, this 5th magnitude open cluster is also known as Dunlop 514, as well as Melotte 145 and Collinder 301. Situated about 19 light-years away, it will show as a fine, round, faint spray of stars to binoculars and be resolved into about 100 stellar members to larger telescopes. While NGC 6124 is on the low side for northern observers, it’s worth the wait for it to hit its best position. Be sure to mark your notes, because this delightful galactic cluster is a Caldwell object and a southern skies binocular reward!

There are many, many more splendid object to be discovered in the constellation of Scorpius, so be sure to get a detailed star chart and enjoy!

Sources:
Wikipedia
Chandra Observatory
Chart Courtesy of Your Sky.