Posted on by Tammy Plotner

The Moon Meets The Pleiades On September 19-20, 2008

Be sure to mark your calendar for tomorrow night. For lucky observers in northeastern North America, eastern Canada, and western Europe, the evening of September 19-20, 2008 is your opportunity to watch the face of the peaceful gibbous Moon glide across the ancient blue beauty of the Plieades…

On Friday night, September 19, 2008, observers in northeastern North America, eastern Canada need to be outdoors and ready when the Moon begins to rise low in the east-northeast. If you live in Western Europe, the event takes place high in the sky just before dawn on the morning of September 20th. Don’t come alone, bring binoculars or a telescope with you, because this is your chance to see the stars first disappear behind the Moon’s bright limb and then reappear on the dark side.

Although we rarely call the Pleiades by name, let’s try them on for size. The brightest is Alcyone at magnitude 2.86, followed by Atlas at 3.62, Electra at 3.7, Maia at 3.86, Merope at 4.17 and Taygeta at magnitude 4.29. While it may be a bit difficult for a novice to read the occultation information, please check this occultation information at IOTA where you can get precise times for your location for the disappearance and reappearance of each individual star.

To help you understand a bit further, let’s choose Alycone. Click on the September 20th category for the US and let’s choose Cleveland, Ohio. Alycone would disappear behind the bright limb of the Moon at 02:14:09 UT (which would be 10:14:09 pm, September 19th). Alycone will re-emerge from behind the dark edge of the Moon at 02:45:47 UT (or 10:45:47 pm). See? It’s not that hard! The most difficult part is simply figuring out the universal time difference is all it takes, and there’s even a website for that!

While you can watch the event without any optical aid, the Moon will overpower the stars. Use a card or something held at arm’s length to help diminish the glare. However, if you’re serious? A telescope is the key to really enjoying this event. It is great fun to keep tabs on each star as it slowly approaches the lunar limb and then just winks out! Timing of these events is critical, because it helps astronomers to further understand lunar features. How? By assessing times, astronomers are able to determine if there are peaks and valleys that we simply do not know about. For example, a bright star may wink off and on several times before it finally disappears behind a hidden lunar mountain… and the same holds true when it reappears.

Although the Moon frequently encounters the Pleiades on each monthly journey across the ecliptic plane, it’s infrequent that we have such a great opportunity to watch several occultation events in a well-placed area of the sky during a comfortable time of the year. Enjoy this great event…

Images accompanying this article are the Pleiades Occultation by John Cudworth and the annotated image of the Plieades by David Malin, courtesy of the Anglo-Australian Observatory/University of Edinburgh.

Posted on by Tammy Plotner

Just Another Harvest Moon…

September 26, 2007 APOD - Saguaro Moon by Stefan Seip

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Actually, the official time was September 15 at 5:13 a.m. EDT, but missing the exact time isn’t going to stop a little beauty from happening tonight. What else can I say except “Come a little bit closer.. Hear what I have to say. Just like children sleepin’… We could dream this night away. But there’s a full moon risin’… Let’s go dancin’ in the light. We know where the music’s playin’… Let’s go out and feel the night…”

I love Harvest Moon time – mainly because there’s so much folklore and legend attached to it. Here in the heartland, we associate it with tractors in the field, working late into the night gathering the harvest by the light of our nearest astronomical neighbor. It’s a romantic and fanciful thought – especially since modern tractors just combine the stuff down with headlights approximately bright enough to land a Boeing 747. However, it’s still a lot of fun to think about old cultures like the Norse folks who believed the Moon granted them Loki’s blessing for plenty. I’ve heard it called the Singing Moon, too… A time for rest after harvest, sit around, sing some songs, smoke a peace pipe. Or, you can celebrate with the Celtics. They called it the Wine Moon, eh? No matter what your choice may be, the whole object is to be mellow.

But, hey! What’s mellow without a little science behind it? What constitutes the Harvest Moon most of all is that it’s closest to Equinox. Just this little tidbit and the change of seasons ought to give you a clue of what’s going on. Most of time during the year, the Moon comes along about 50 minutes later each night, but as the tilt of our Earth is gradually changing, that time is a bit shorter – by around 20 minutes for several evenings in a row. Why? The answer is easy enough. The ecliptic – or plane of Earth’s orbit around the sun – makes a narrow angle with respect to the horizon in the evening in autumn.

Is it really more orange or yellow than normal? How about larger? Oh, yes. You want those science facts, don’t you? Sure! Why not… Oftentimes we perceive the Harvest Moon as being more orange than at any other time of the year. The reason is not only scientific enough – but true. Coloration is caused by the scattering of the light by particles in our atmosphere. When the Moon is low, as it is now, we get more scattering effect and it truly is a deeper orange. The very act of harvesting itself also produces dust and oftentimes that color will last through the whole night. As for larger? Well, that’s just an illusion. Everyone knows the Moon looks larger on the horizon, but did you know this is a psychological phenomenon and not a physical one? Prove it to yourself by looking at the rising Moon upright…it looks larger, doesn’t it? Now stand on your head, or find a comfortable way to view it upside down…now how big is it?

Go on out tonight and enjoy the Harvest Moon… “Harvest moon… I see the days grow shorter. I feel the nights grow cold. Harvest moon… Young people feeling restless. Old people feeling old. Harvest moon… I sense the darkness clearer. I feel the presence here. Harvest moon… A change in the weather. I love this time of year. Harvest Moon….”

Posted on by Tammy Plotner

The Wall – NGC 7000 Region by Kent Wood

NGC 7000 Wall Region by Kent Wood

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Known as Caldwell 20 to some, NGC 7000 to others and the North America Nebula to most, this diffuse emission/reflection nebula near Deneb can frequently be seen by the unaided eye from a dark location, but the sheer size of this 1600 light year distant gas cloud often confuses people as to the reality of what they are seeing. Let’s take a look at just a few of the bricks in the “Wall”..

Hey you, out there beyond the wall… Is there anybody out there?

In this image taken by Kent Wood, we are looking a just a close-up of the region shaped like the Gulf of Mexico and often referred to as the “Cygnus Wall”. It is here that light from young, energetic stars is taking the surrounding cold gas fields and warming them, causing an ionization front to form – filled with dense and delightfully delicate filaments. This highly energized “shock front” stands out in bold relief against the complex dark gases and streaking dark dustlanes.

What shall we use… To fill the empty spaces? What shall we use… To complete the wall?

Let’s try star formation, eruptive variables, flare stars and T-Tauri types. According to G.W. Marcy: “A slitless spectrographic search for H..cap alpha.. emission stars in NGC 7000 has revealed 18 new examples, most of which are presumably T Tau stars. An examination of all known T Tau stars in these fields has uncovered no events of the FU Ori type, except for that of V1057 Cygni.” All of these make themselves at home in the warm ionized gas in the local interstellar medium. However, it is the properties of this ionized gas that are so curious to study. In this case, in the faint optical emission lines of hydrogen alpha.

Hey you, don’t help them to bury the light…

Along the bright rim of the wall is where the action is at. According to the work of Koji (et al), it is here where most of the star forming action is going on. “We have found small clusters of near-infrared sources having young stellar object (YSO) colors in some of these objects; most of the cluster members are considered to be older than the IRAS point sources and to be pre–main-sequence stars such as T Tauri stars. In at least six bright-rimmed clouds, the clusters are elongated toward the bright-rim tip or the exciting star(s) of the bright rim with the IRAS sources situated near the other end. There is a tendency for bluer (i.e., older) stars to be located closer to the exciting star(s) and for redder (i.e., younger) stars to be closer to the IRAS sources. This asymmetric distribution of the cluster members strongly suggests small-scale sequential star formation or propagation of star formation from the side of the exciting star(s) to the IRAS position in a few times 105 yr, as a result of the advance of the shock caused by the UV radiation from the exciting star(s).”

And all in all it was just a brick in the wall…

But some of the true beauty is the dust and soot laced clouds filled with PAHs. We learned about those Polycyclic Aromatic Hydrocarbons, not long ago and just what they mean. And, we know the Cygnus X region is one of the richest star formation sites in the Galaxy. But what about this structure? This Wall?

The Wall- NGC 7000 (Panorama) by Kent Wood
The Wall- NGC 7000 (Panorama) by Kent Wood

A distant ship, smoke on the horizon…. You are only coming through in waves.

Believe it or not, NGC 7000 was imaged from the lunar surface during the 1972 Apollo 16 mission and continues to be studied for its polarization properties and scattering in h-alpha wavelengths. It has even had its electron temperature taken to prove that interstellar dust is masking the light we see. However, what we do see may be an illusion. From the studies of R.J. Reynolds; “According to photoionization models of the warm ionized medium, these [O i]/Ha ratios suggest that most of the Ha originates from density-bounded, nearly fully ionized regions along the lines of sight rather than from partially ionized H i clouds or layers of H ii on the surfaces of H i clouds.”

Hey you, out there beyond the wall… Is there anybody out there?

Venture into the dark cloud and find out. According to Laugalys (et al) “Magnitudes and color indices of 430 stars down to V Ëœ 17.5 mag in the eight-color Vilnius + I photometric system were obtained in four areas of diameter 20′ within the dark cloud L935 separating the North America and Pelican nebulae. Spectral types, interstellar color excesses, extinctions and distances of stars were determined from the photometric data. The plot of extinction vs. distance shows that the dark cloud begins at a distance of 520±50 pc. About 40 stars in the cloud, mostly K and M dwarfs, are suspected to have Hα emission; these stars also exhibit infrared excesses. Four of them are known pre-main-sequence stars. Our star set contains J205551.3+435225 (V = 13.24) which, according to Camerón and Pasquali (2005), is the O5 V type star ionizing the North America and Pelican nebulae. If this spectral type is confirmed, the star would have an extinction AV between 9 and 10 magnitudes (depending on the accepted extinction law) and a distance which is not very different from the dust cloud distance.”.

How shall I fill the final places? How should I complete the wall?

I guess the last words would be the illuminating source. In a study done by Comerón and Pasquali; “We present the results of a search for the ionizing star of the North America (NGC 7000) and the Pelican (IC 5070) nebulae complex. The application of adequate selection criteria to the 2MASS JH KS broad-band photometry allows us to narrow the search down to 19 preliminary candidates in a circle of 0o 5 radius containing most of the L935 dark cloud that separates both nebulae. Follow-up near-infrared spectroscopy shows that most of these objects are carbon stars and mid-to-late-type giants, including some AGB stars. Two of the three remaining objects turn out to be later than spectral type B and thus cannot account for the ionization of the nebula, but a third object, 2MASS J205551.25+435224.6, has infrared properties consistent with it being a mid O-type star at the distance of the nebulae complex and reddened by AV ≃ 9.6. We confirm its O5V spectral type by means of visible spectroscopy in the blue. This star has the spectral type required by the ionization conditions of the nebulae and photometric properties consistent with the most recent estimates of their distance. Moreover, it lies close to the geometric center of the complex that other studies have proposed as the most likely location for the ionizing star, and is also very close to the position inferred from the morphology of cloud rims detected in radio continuum. Given the fulfillment of all the conditions and the existence of only one star in the whole search area that satisfies them, we thus propose 2MASS J205551.25+435224.6 as the ionizing star of the North America/Pelican complex.”

All in all… It’s just another brick in the wall.

We would like to thank AORAIA member, Kent Wood for the splendid image and the great research challenge!

Posted on by Tammy Plotner

William Optics Binoviewers – A Class Act

I like using binoculars… and I like using a telescope. So what happens when you combine both? For savvy telescope users, the result is called a binoviewer – but using one can sometimes introduce problems. Dark images, fast focal ratio telescopes, problems with focusing and outright expense… But can these problems be overcome in a binoviewer that’s easy to afford, works with all telescopes, doesn’t cost an arm and a leg and is high quality? The answer is yes…

Say hello to the William Optics Binoviewer.

At first I really wasn’t very interested in working with a binoviewer because the 3D effect definitely throws my mind a curve when studying at the telescope. Oh, yes. I had all kinds of excuses. More difficulty focusing with one eye than another, my favorite scope has a fast focal ratio, I use reflectors… You name it. But William Optics changed my mind.

When I opened the well-made little carton with it’s pretty embossed logo, I was stunned at the craftsmanship. Pictures do not do it justice. The William Optics Binoviewers are very precision in appearance with sterile white powder coat paint, heavy – but not too heavy, big, easy-to-grip thumbscrews and brass compression ring fittings for the eyepieces. Instead of needing to purchase two additional eyepieces, it comes already equipped with twin William Optics Wide Angle (66º) 20mm occulars. Just to state a case in point here, I know for a fact these two eyepieces alone are worth more than half of what the binoviewers cost! But, back to the task in hand…

The William Optics Binoviewers spread easily to accommodate interpupillary distance and each eyepiece holder has its own separate helical focuser. What’s more – and this is a feature that sets them apart – they come already equipped with a 1.6X barlow nosepiece. What’s inside? According to the manufacturer specs, we’re talking about a true BaK4 prism with a genuine 20.2mm of clear aperture. So what does terms like that mean to just the average Joe? It means we aren’t talking about a pair of binoviewers that are going to lay around in your eyepiece case because they deliver cruddy images… We’re talking about a class act.

I’m not exactly sure what makes the William Optics Binoviewers work so well, maybe it’s the 4″ optical path, but whatever it is, they are unlike any inexpensive binoviewers I’ve ever used. Combine it with a h-alpha solar telescope and once you’re in tune you’ll get an image that will blow your mind. Put it in a refractor telescope and go for Jupiter… the effect of sheer dimensionality and being able to tell distance in the galiean moons will make you a planetary observer. Use it in your workhorse reflector and study the Moon. You’ll feel like you’re there, dude. Drop the binoviewer into a big dob and check out something familiar – like the M27. Holy guacamole… It looks like something you’d see in an IMAX theatre! Put it in a little rich field telescope and look at a star cluster… You can see the light years between the stars. Put it in an observatory telescope and look at a galaxy?

And you’ll become a believer.

How do I feel about the William Optics Binoviewer now? While it may never surpass the Denkmeier or Bino Vue in some folks opinion, it’s not going to take part of your life savings to afford and you won’t regret the purchase. As far as compatibility goes, it worked with every telescope I happen to own and provided sharp clarity, bright images and an absolutely stunning three-dimensional effect on every object I chose. For $199 you get the complete package and no surprises. You won’t need to buy eyepieces, adapters or a special nosepiece – it works with any 1.25″ focuser and probably any telescope you choose to put it in. Small wonder I’ve never heard anyone say anything bad about William Optics Binoviewers…

They’re a real class act.

We would like to thank Oceanside Photo and Telescope for providing the William Optics Binoviewers for this product review. If you’re interested in purchasing a pair of William Optics Binoviewers from OPT, please remember to put “Universe Today Astronomers” in the club affiliation box when you check out to receive your special UT discount on your final bill!

Posted on by Tammy Plotner

Weekend SkyWatcher’s Forecast – September 12 -14, 2008

Greetings, fellow SkyWatchers! It’s big… It’s bright. It’s undeniably the Moon. So what are we going to do this weekend? Why, study of course! We’ll take a look at some history, some mystery and even some cool variability that can be studied without any special equipment. Are you ready to journey into the night?

Friday, September 12, 2008 – Arthur Auwers was born today in 1838. His life’s work included unifying the world’s observational catalogs. He specialized in astrometry, making very precise measurements of stellar positions and motions and he also calculated the orbits of Sirius and Procyon long before their companions were discovered. Auwers also directed expeditions to measure the transits of Venus and began a project to unify the all available sky charts, an interest that began with his catalog of nebulae which he published in 1862. There’s even a lunar crater named for him!

Also today, in 1959, the USSR’s Luna 2 became the first manmade object to hit the moon. It was the first spacecraft to reach the surface of the Moon, and it impacted the lunar surface west of Mare Serenitatis near the craters Aristides, Archimedes, and Autolycus. Scientifically, Luna 2 is most famous for confirming the earlier detection of the solar wind by Luna 1. However, it’s most famous for what it did after it launched! When it separated from its third stage, the spacecraft released a bright orange cloud of sodium gas, which aided in spacecraft tracking and acted as an experiment on the behavior of gas in space. Can you imagine the sight? Today also celebrates the 1966 Gemini 11 launch – the highest Earth orbit ever reached by an American manned spacecraft (1374 kilometer altitude).

Tonight our primary lunar study is crater Kepler. Look for it as a bright point, slightly north of lunar center near the terminator. Its home is the Oceanus Procellarum – a sprawling dark mare composed primarily of minerals of low reflectivity (low albedo), such as iron and magnesium. Bright, young Kepler will display a wonderfully developed ray system. The crater rim is very bright, consisting mostly of a pale rock called anorthosite. The “lines” extending from Kepler are fragments that were splashed out and flung across the lunar surface when the impact occurred. The region is also home to features known as “domes” – seen between the crater and the Carpathian Mountains. So unique are Kepler’s geological formations that it became the first crater mapped by U.S. Geological Survey in 1962.

Saturday, September 13, 2008 – Today in 1922, the highest air temperature ever recorded on the surface of the Earth occurred. The measurement, taken in Libya, burned in at a blistering 136° F (58° C) – but did you know that the temperatures in the sunlight on the Moon double that? If you think the surface of the Moon is a bit too warm for comfort, then know that surface temperatures on the closest planet to the Sun can reach up to 800° F (430° C) at the equator during the day! As odd as it may sound, and even as close to the Sun as Mercury is, it could very well have ice deposits hidden below the surface at its poles.

Get out your telescope, because tonight we’re going to have a look at a lunar feature that goes beyond simply incredible – it’s downright weird. Start your journey by identifying Kepler, and head due west across Oceanus Procellarum until you encounter the bright ring of crater Reiner. Spanning 30 kilometers, this crater isn’t anything showy…just shallow-looking walls with a little hummock in the center. But, look further west and a little more north for an anomaly – Reiner Gamma.

Well, it’s bright. It’s slightly eye-shaped. But what exactly is it? Having no appreciable elevation or depth, Reiner Gamma could very well be an extremely young feature caused by a comet. Only three other such features are known to exist – two on the lunar far side and one on Mercury. They are high albedo surface deposits with magnetic properties. Unlike a lunar ray, consisting of material ejected from below the surface, Reiner Gamma can be spotted during the daylight hours – when ray systems disappear. And, unlike other lunar formations, it never casts a shadow.

Reiner Gamma is also a magnetic deviation on a barren world that has no magnetic field, so how did it form? Many ideas have been proposed, such as solar storms, volcanic activity, or even seismic waves. But the best explanation? It is the result of a cometary strike. Evidence exists that a split-nucleus comet, or cometary fragments, once impacted the area, and the swirl of gases from the high-velocity debris may have somehow changed the regolith. On the other hand, ejecta from such an impact could have formed around a magnetic “hot spot,” much like a magnet attracts iron filings.

No matter which theory is correct, the simple act of viewing Reiner Gamma and realizing it is different from all other features on the Moon’s Earth-facing side makes this journey well worth the time!

Sunday, September 14 – With a nearly Full Moon, skies are light-trashed tonight, so if you’d like to visit another object that only requires your eyes, then look no further than Eta Aquilae (RA 19 52 28 37 Dec +01 00 20), about one fistwidth due south of Altair…

Discovered by Pigot in 1784, this Cepheid variable varies by over a magnitude in a period of 7.17644 days. During this time it will reach of maximum of magnitude 3.7, and then decline slowly over five days to a minimum of 4.5… Yet it only takes two days to brighten again! This period of expansion and contraction makes Eta unique. To help gauge these changes, compare Eta to Beta on Altair’s same southeast side. When Eta is at maximum, it will about equal Beta in brightness.

Wishing you clear skies and a super weekend!!

This week’s awesome images are Kepler Crater by Wes Higgins, Luna 2 courtesy of NASA, Reiner Gamma from the Clementine Lunar Browser and Eta Aquilae – Credit: Palomar Observatory, courtesy of Caltech. Many thanks!

Posted on by Tammy Plotner

Australian Telescope Leads the World In Astronomy Research

The AAT - Photograph courtesy of Chris McCowage

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While the Anglo-Australian Telescope is far from being the world’s largest, or even located in the world’s best observing site, it’s still the world’s most productive in terms of astronomy research. According to recently released productivity ratings, the number of scientific papers resulting from observations made with the AAOmega fibre-fed optical spectrograph, SPIRAL Integral Field Unit, IRIS2, University College London Echelle Spectrograph (UCLES), or Ultra High Resolution Facility (UHRF) made the AAT the number one ranked 4-metre-class telescope in the world for more than two years between 2001 and 2003. But what’s going on today is even more important…

When we think of research telescopes, some of the world’s top rated are the Hubble Space Telescope (located in Earth orbit), Keck (more than twice the AAT’s size) in Hawaii, the Very Large Telescope (VLT, which comprises four telescopes twice the size of the AAT) in Chile, the Sloan Digital Sky Survey and the 2MASS telescope. So where does that leave the humble Anglo-Australian? Try number five. “The AAT has a remarkable track record of scientific productivity and impact,” says Prof. Matthew Colless, Director of the Anglo-Australian Observatory. “This is an extraordinary achievement.”

When the Anglo-Australian Observatory opened for business in the early 1970’s, the 4 meter telescope was the standard by which all others were judged. Since that time, research telescope aperture has more than doubled and while the AAT can’t compete in some respects, it has advantages that give it an edge for research. While it isn’t Mauna Kea, Australia still offers up some of the best skies to study our Galaxy and other nearby galaxies and the ability to undertake long-term observations and programs that just won’t work with other observatories. Add to that some very unique instrumentation such as Echidna – a fibre positioner for FMOS, UKidna – A multi-fibre positioner for the UKST, OZPOZ – a fibre positioner for ESO and part of FLAMES, DAZLE – The Dark Age z (redshift) Lyman-alpha Explorer, MOMFOS – Multi-Object Multi-Fibre Optical Spectrograph, ODC – Optical Detector Controllers and AAOmega – next generation optical spectrograph for the AAT and you have a recipe for research. This explains why demand for the telescope remains strong, with 2.5 times as many applications for telescope time as can actually be handled. “The AAO believes that the AAT can maintain this high level of productivity and impact for another decade.” says Prof. Colless.

Over a period of time, the the AAO has produced some of the most inspiring astronomy images ever seen – those taken by David Malin. These are the most extraordinary wide-field astrophotographs made with professional telescopes anywhere and every effort has been made to capture the true colours of distant stars, galaxies and nebulae using innovative photographic techniques and CCD detectors. The images have detailed captions and the full NGC 2000.0 catalogue entry. Galaxy images also carry NASA/IPAC Extragalactic Database (NED) data links. They are a standard of astronomers everywhere. But, progress hasn’t stopped. The AAT’s prime focus has recently been upgraded to accommodate a new generation of highly sensitive CCD detectors. The first colour images made with the new facility are now available, currently only in digital form. Most of the photographic images have recently been digitally re-mastered from the original 3-colour separations. This has allowed the AAO to create new, high resolution versions of many existing images and some new pictures that could not be made photographically.

Just this year a “uniquely ambitious, far-sighted” project won an Australian and UK astronomy team the first Group Achievement Award from the UK’s Royal Astronomical Society. Led by Professor Matthew Colless (Anglo-Australian Observatory) in Australia and Professor John Peacock (University of Edinburgh) in the UK, the thirty-three-member team spent ten years mapping the distribution in space of 220,000 galaxies using the 3.9-m Anglo-Australian Telescope (AAT) in New South Wales — a project called the 2-degree Field Galaxy Redshift Survey (2dFGRS). “The scale of this project made it ground-breaking,” said Matthew Colless. “For the first time we were able to map the positions of a huge number of galaxies and see the subtle effects that reveal the different types of matter in the universe.”

What was needed was for the area of sky surveyed to be much bigger than, rather than the same size as, the “walls” and “strings” of galaxies being detected. Almost ten times larger than any previous survey, the 2dFGRS was the first study to meet this crucial condition. The survey measured patterns in the distribution of galaxies, on scales from 100 million to 1 billion light-years. Two wedge-shaped pieces of sky were surveyed, so when the galaxies within them were mapped out, the result looked like a bow-tie cut from a sponge: a network of voids and dense regions. The size of the 2dF Galaxy Redshift Survey was made possible only by technological advances developed at the Anglo-Australian Observatory (AAO). The 2dF spectrograph used robotic technology to place optical fibres onto the telescope’s focal plane, where each fibre could collect the light from a single galaxy. By using up to 400 optical fibres, this system allowed the light from up to 400 galaxies to be captured simultaneously.

And the AAT is ensuring that it doesn’t fall behind the times with future technological advancement either….

“We are currently investing $4 million in refurbishing the telescope to ensure that it can operate reliably and efficiently for another ten years, and more than $6 million in a major new instrument, the 400-fibre HERMES high-resolution Spectrograph,” says Prof. Colless. “The primary science drivers for HERMES are ‘Galactic archaeology’ surveys to uncover the formation history of the Milky Way,’ he adds. ‘Extragalactic surveys using the AAOmega instrument and galactic surveys using HERMES will be the flagship science carried out on the AAT over the next 5-10 years. AAOmega and HERMES, and other upgrades to existing instruments, will provide astronomers with powerful tools that will enable them to do competitive, high-impact research using the AAT throughout the coming decade.”

Original Source: SpaceInfo.com

Posted on by Tammy Plotner

The Dragon Slayer – NGC 5985, NGC 5982, NGC 5981 by Ken Crawford

Draco Trio - By Ken Crawford

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There are wonderful tales which surround the circumpolar Draco constellation. According to Greek legend, Draco represents the dragon killed by Cadmus before founding the city of Thebes – or perhaps it represented the dragon which guarded the golden fleece and was eventually killed by Jason and his famous Argonauts. To the Romans, it was simply a creature killed by Minerva and tossed into the sky as stars to be remembered. The Egyptians called it Tawaret. But the most famous of all representations of Draco was one of the twelve labors that Hercules had to overcome. Many of us will never see the jewels that hide within the boundaries of this sprawling constellation, but thanks to the Herculean efforts of Ken Crawford – we can share in its mysteries…

To deep sky observers, the group of NGC 5985, NGC 5982 and NGC 5981 is commonly known as the “Draco Trio”. Two barred spirals at different angles and a face on elliptical all in the same field of view is a rare sight and makes for a beautiful celestial portrait. The beautiful spiral is NGC 5985. The proper designation for the elliptical galaxy is NGC 5982. The catalog number for the edge-on is NGC 5981. While these galaxies span huge amounts of light years apart, they share telescopic space at RA: 15h 38m 40s Dec: +59°21’22” as a center and share photons in the eyepiece at around 25 arc minutes. While the Draco group is far too small to be considered its own galaxy cluster and has never been classified as a compact group, oddly enough all three are around 100 million light years away from the Sol System.

I did mention there were mysteries here, didn’t I? Then let’s explore them…

Take a closer look at the grand spiral, NGC 5985. It’s a Seyfert. According to research done by Simões Lopes (et al) it may also harbor a wonderful black hole right in there with its active galactic nucleus. “This result demonstrates a strong correlation between the presence of circumnuclear dust and accretion onto the central, supermassive black hole in elliptical and lenticular galaxies. Current estimates suggest the dust settling or destruction time is on order of 108 yr, and therefore the presence of dust in ~50% of early-type galaxies requires frequent replenishment and similarly frequent fueling of their central supermassive black holes. The observed dust could be internally produced (via stellar winds) or externally accreted, although there are observational challenges for both of these scenarios. Our analysis also reveals that approximately one-third of the early-type galaxies without circumnuclear dust have nuclear stellar disks. These nuclear stellar disks may provide a preferred kinematic axis to externally accreted material, and this material may in turn form new stars in these disks. The observed incidence of nuclear stellar disks and circumnuclear dust suggests that episodic replenishment of nuclear stellar disks occurs and is approximately concurrent with the fueling of the central AGN.”

But that’s not all, because there’s a quasar there, too. According to a 2001 study done by one of my heroes – Halton Arp and David Russell; “The distribution on the sky of clusters of galaxies shows significant association with relatively nearby, large, active galaxies. The pattern is that of clusters paired equidistant across a central galaxy with the apparent magnitudes and redshifts of their constituent galaxies being closely matched. The clusters and the galaxies in them tend to be strong X-ray and radio emitters, and their redshifts occur at preferred redshift values. The central, low-redshift galaxies often show evidence of ejection in the direction of these higher redshift clusters. In all these respects the clusters resemble closely quasars which have been increasingly shown for the last 34 years to be similarly associated with active parent galaxies. New, especially significant pairings of quasars are presented here, which are, at the same time, associated with Abell clusters of galaxies. It is argued here that, empirically, the quasars are ejected from active galaxies. They evolve to lower redshift with time, forming stars, and fragmenting at the end of their development into clusters of low-luminosity galaxies. The cluster galaxies can be at the same distance as their lower redshift parents because they still retain a component of their earlier, quasar intrinsic redshift.”

Now, let’s take a look at the quiet little elliptical – NGC 5982. Just this year it was studied by Del Burgo (et al) for its dust shell. According to the report: “Shells in Ellipticals are peculiar faint sharp edged features that are thought to be formed by galaxy mergers. We use Spitzer data in the wavelength range from 3.6 to 160 μm and HST/ACS optical data. After subtracting the galaxy models, residual images are used to identify the shells. We detect for the first time shells from mid-infrared data. The very different distributions of dust, warm gas and HI gas together with the presence of shells and a kinematically decoupled core suggest a minor merger in NGC 5982.”

Ah, ha! So, it’s always the quiet ones that get ya’, huh? Then it might interest you to know that NGC 5982 may also contain its own black hole, a peculiar population of stars, a low luminosity active galactic nucleus and may have even been a product of a black hole merger! What more, new globular clusters may have formed during these interactions without the benefits of gaseous materials. Simply too cool…

Now… How about the wild looking edge-on, NGC 5981? Science loves to examine what it just can’t quite see and in the case of this highly inclined spiral, we’ve found out that the stellar disc just might be cut off – or foreshortened. According to a 2007 work done by Florido (et al); “This is the first work reporting observations of the truncation of a stellar disc, in both the optical and the NIR spectral ranges. No galaxy has been observed at both wavelengths with the required depth. The optical radial profiles of spiral galaxy discs seem to suggest a double exponential behaviour, whilst NIR profiles seem to show a real truncation. NGC 6504 has a real truncation in both the optical and the NIR radial profiles. A double exponential does not fit the observed optical profile. The truncation radius is larger in the V band than in the NIR by ~10 arcsec, about 3 kpc (equivalent to about 10%).”

But, just because its equipment is a little shorter than most, does that mean it doesn’t produce as many stars? Not hardly. It just means its peanut-shaped central bulge may be embedded in a dark halo. Thanks to the work of Joop Schaye who also took a look at NGC 5981, we know a little more about these properties. “We study global star formation thresholds in the outer parts of galaxies by investigating the stability of disk galaxies embedded in dark halos. The disks are self-gravitating, contain metals and dust, and are exposed to UV radiation. We find that the critical surface density for the existence of a cold interstellar phase depends only weakly on the parameters of the model and coincides with the empirically derived surface density threshold for star formation. Furthermore, it is shown that the drop in the thermal velocity dispersion associated with the transition from the warm to the cold gas phase triggers gravitational instability on a wide range of scales. The presence of strong turbulence does not undermine this conclusion if the disk is self-gravitating. Models based on the hypothesis that the onset of thermal instability determines the star formation threshold in the outer parts of galaxies can reproduce many observations, including the threshold radii, the column densities, and the sizes of stellar disks as a function of disk scale length and mass.”

While we’ll never see the Draco Trio in the telescope eyepiece as well as what this incredible image by Ken Crawford presents, we welcome the Dragon Slayer for the opportunity it gives us to take a closer look at another cosmic mystery. Is the Draco Group really a galaxy group? Perhaps. According to independent research papers done by both Giuricin and Garcia, this small group of friends collectively known as the NGC 5866 Group (because it’s the brightest) is located to the northwest of both the M101 Group and its companion galaxies which makes it proximity. Also nearby is the M51 Group, home to the Whirlpool Galaxy, the Sunflower Galaxy, and several others. The distances to these three groups was gathered by studying their individual members and science has found they are similar – and perhaps part of a much larger, more loose association than we’ve yet discovered.

But we’re learning…

Many thanks to AORAIA member Ken Crawford for the use of the spectacular image and the awesome research challenge it posed! My gratitude for the inspiration and the learning challenge…

Posted on by Tammy Plotner

UT Reader Promotes IYA in “Canoe Africa”

Canoe Africa Team

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If you haven’t heard of UT reader, Brian Sheen, you will over the next few months. Brian is not only a reader here, but he’s also a member of the Roseland Observatory in Cornwall and he’s about to embark on an adventure that most of us only dream about. Four men, one canoe, one river, 2,500 miles, in six months…

Brian Sheen
Brian Sheen
Canoe Africa is a unique project ready to launch by the UK astronomer just as soon as the proverbial waters reach safe levels. Brian and a small team of scout leaders will begin their journey on foot in the mountains of Guinea, at the source of one of the longest rivers in the world – the Niger. Then it’s into a dugout canoe to travel almost 2,500 miles passing through the countries of Guinea, Mali, Niger, Benin and Nigeria, with their epic journey stopping about 100 miles away from wilds of the Niger Delta. Along the way they will meet with local scout troops for support and company in their journey, but there’s much more to the story than just a deliverance.

Brian is no stranger to long distance canoeing, nor is this his first time in West Africa. Forty years ago he was there providing relief with the Red Cross during the Niger Crisis, and returned again in 1981 to canoe 150 miles through the Delta from Onitsha to Port Harcourt. While the team will be promoting the UK Scouting Movement, astronomer Sheen also sees this as a unique opportunity to promote the International Year of Astronomy. “The vision of the International Year of Astronomy (IYA2009) is to help the citizens of the world rediscover their place in the Universe through the day- and night time sky, and thereby engage a personal sense of wonder and discovery. All humans should realize the impact of astronomy and basic sciences on our daily lives, and understand better how scientific knowledge can contribute to a more equitable and peaceful society.”

How does Universe Today tie into this? Thanks to being a constant reader, Brian discovered the Celestron Sky Scout and the Coronado PST. When he wrote me telling me what he was going to do and asking for help locating a French version of the Celestron SkyScout, not only did I find him the correct update, but I found more support for his project as well. Thanks to Michelle Meskill from Celestron International, Celestron Life: IYA has donated speakers for the journey as well! Now, not only will the Celestron SkyScout speak in French when needed – but is now able to reach large groups of people at once!

Map Provided by BBC
Map Provided by BBC

Brian will soon be on his way down the River Niger with binoculars, solar scope, Celestron SkyScout and more. We wish him the best of luck on his IYA Journey and look forward to bringing you further updates on our fearless UT reader and his African Astronomy Adventures during the coming months. Brille sur…

Posted on by Tammy Plotner

The Fire Cracker Galaxy – NGC 6946 by Dietmar Hager

The FireCracker Galaxy - NGC 6946 by Dietmar Hager

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It’s time to take a look back to what was happening 210 years ago on the night of September 9th. Sir William Herschel was at the eyepiece of his telescope in Slough. While he was viewing in real time, what he was viewing occurred more than 10 million years ago – the fireworks that ignited in NGC 6946.

At one time, it was widely believed that NGC 6946 was a member of our Local Group; mainly because it could be easily resolved into stars. There was a reddening observed in it, believed to be indicative of distance – but now know to be caused by interstellar dust. But it isn’t the shrouding dust cloud that makes NGC 6946 so interesting, it’s the fact that so many supernova and star-forming events have sparkled in its arms in the last few years that has science puzzled! So many, in fact, that they’ve been recorded every year or two for the last 60 years…

Most normally, bursts of star formation happen in galaxies which have nearby companions to lend materials. Yet, NGC 6946 appears to be alone in the field. According to a 2000 study done by Pisano (et al) ” Such gas-rich companions could include material left over from the galaxy assembly process which could persist into the current day around an isolated galaxy such as NGC 6946. NGC 6946 is prolifically forming stars, has a nuclear starburst, and has widespread high-velocity clouds associated with the disc. All of these features could be explained by the accretion of low-mass Hi clouds by NGC 6946. Our survey recovered two previously detected dwarf galaxies associated with NGC 6946, but otherwise found no signatures of interactions in the NGC 6946 system. The companions are small enough, and distant enough from NGC 6946 that they should have minimal effect on the main galaxy. Some tidal debris may be expected due to interaction between the two dwarf galaxies, but none is observed. This could be because it is at low column densities, or because the dwarf galaxies are more separated than they appear on the sky. This study of the system suggests that NGC 6946 is a gravitationally bound system with two dwarf galaxies in stable orbits about the larger primary galaxy.”

But, that was some 8 years ago and 16 events into the past. According to studies done by Eva Schinnerer (et al) in 2006, NGC 6946 has been “Caught in the Act” as a Bar-driven Nuclear Starburst Galaxy. “The data, obtained with the IRAM Plateau de Bure Interferometer (PdBI), allow the first detection of a molecular gas spiral in the inner ~10” (270 pc) with a large concentration of molecular gas (MH2~1.6×107 Msolar) within the inner 60 pc. This nuclear clump shows evidence for a ringlike geometry with a radius of ~10 pc as inferred from the position-velocity diagrams. Both the distribution of the molecular gas and its kinematics can be well explained by the influence of an inner stellar bar of about 400 pc length. A qualitative model of the expected gas flow shows that streaming motions along the leading sides of this bar are a plausible explanation for the high nuclear gas density. Thus, NGC 6946 is a prime example of molecular gas kinematics being driven by a small-scale, secondary stellar bar.”

Now, for the really cool part – understanding barred structure. Thanks to the Hubble Space Telescope and a study of more than 2,000 spiral galaxies – the Cosmic Evolution Survey (COSMOS) – astronomers understand that barred spiral structure just didn’t occur very often some 7 billion years ago in the local universe. Bar formation in spiral galaxies evolved over time. A team led by Kartik Sheth of the Spitzer Science Center at the California Institute of Technology in Pasadena discovered that only 20 percent of the spiral galaxies in the distant past possessed bars, compared with nearly 70 percent of their modern counterparts. This makes NGC 6946 very rare, indeed… Since its barred structure was noted back in Herschel’s time and its age of 10 billion years puts it beyond what is considered a “modern” galaxy.

Science believes bars in galaxies have been forming steadily over the last 7 billion years, more than tripling in number. “The recently forming bars are not uniformly distributed across galaxy masses, however, and this is a key finding from our investigation,” Sheth explained. “They are forming mostly in the small, low-mass galaxies, whereas among the most massive galaxies, the fraction of bars was the same in the past as it is today.” The findings, Sheth continued, have important ramifications for galaxy evolution. “We know that evolution is generally faster for more massive galaxies: They form their stars early and fast and then fade into red disks. Low-mass galaxies are known to form stars at a slower pace, but now we see that they also made their bars slowly over time,” he said. Bars form when stellar orbits in a spiral galaxy become unstable and deviate from a circular path. “The tiny elongations in the stars’ orbits grow and they get locked into place, making a bar,” explained team member Bruce Elmegreen of IBM’s research Division in Yorktown Heights, N.Y. “The bar becomes even stronger as it locks more and more of these elongated orbits into place. Eventually a high fraction of the stars in the galaxy’s inner region join the bar.”

Added team member Lia Athanassoula of the Laboratoire d’Astrophysique de Marseille in France: “The new observations suggest that the instability is faster in more massive galaxies, perhaps because their inner disks are denser and their gravity is stronger.” Bars are perhaps one of the most important catalysts for changing a galaxy. They force a large amount of gas towards the galactic center, fueling new star formation, building central bulges of stars, and feeding massive black holes. “The formation of a bar may be the final important act in the evolution of a spiral galaxy,” Sheth said. “Galaxies are thought to build themselves up through mergers with other galaxies. After settling down, the only other dramatic way for galaxies to evolve is through the action of bars.” (HubbleSite News Release)

Yet the studies of NGC 6946 haven’t stopped. In 2005, Gemini II also took a look at this crazy galaxy. “In order to sustain this rate of supernova activity, massive, quickly evolving stars must form or be born at an equally rapid rate in NGC 6946,” said Gemini North Associate Director, Jean-René Roy. “Its stars are exploding like a string of firecrackers!” And with it in 2007, hydrogen halos… Says Rense Boomsma: “A halo of neutral hydrogen is found around an increasing number of spiral galaxies. It is not well understood how hydrogen halos are formed. The orientation of nearby spiral galaxy NGC 6946 enables us to measure vertical gas velocities in the disk of the galaxy and therefore measure how the gas gets into the halo. We find hydrogen with high velocities toward regions where stars are formed. This correlation suggests that the formation of a hydrogen halo is related to massive star formation. A similar close connection is seen in the nearby spiral galaxy NGC 253. For some hydrogen clouds in NGC 6946 we have indications that they have been accreted from outside the galaxy.”

Will we ever understand everything there is to know about galaxies like NGC 6946? Perhaps not in our lifetimes. However, one of the best parts is knowing that it is a galaxy that you can observe and study with larger backyard telescopes. Located in the constellation of Cepheus (RA 20:34.8 Dec +60:09) and billed at magnitude 8.9 (but beware, it’s low surface brightness!), this small barred spiral will show some structure in 10″ or larger scopes with decent skies. Who knows what your night may reveal?

Our many thanks to AORAIA member, Dr. Dietmar Hager of Stargazer Observatory for the use of this incredible image and the challenge of researching the information!

Link to original full size image.

Posted on by Tammy Plotner

Weekend SkyWatcher’s Forecast – September 5 – 7, 2008

Greetings, fellow Skywatchers! The weekend has arrived at last and with it… more lunar challenge studies. Are you ready to dance with the pie-eyed piper as we seek out Piccolomini? You’ll find it to the southwest of the shallow ring of Fracastorius on Mare Nectaris’ southern shore. How about seeing double as we take on a few binary stars? It’s time to get out your binoculars and telescopes as we head to the Moon because… Here’s what’s up!

Friday, September 5, 2008 – Tonight let’s discover beauty on our own Moon as we have a look at one of the last lunar challenges of the year which occurs during the first few days of the Moon’s appearance – Piccolomini. You’ll find it to the southwest of the shallow ring of Fracastorius on Mare Nectaris’ southern shore. Piccolomini is a standout lunar feature – mainly because it is a fairly fresh impact crater. Its walls have not yet been destroyed by later impacts, and the interior is nicely terraced. Power up and look carefully at the northern interior wall where a rock slide may have rumbled toward the crater floor. While the floor itself is fairly featureless, the central peak is awesome. Rising a minimum of two kilometers above the floor, it is even higher than the White Mountains in New Hampshire!

Beta LyraeWhen you’ve caught up on your studies, let’s have a look at Beta and Gamma Lyrae, the lower two stars in the “Harp.” Beta is actually a quickly changing variable which drops to less than half the brightness of Gamma in around 12 days. For a few days the pair will seem of almost equal brightness; then you will notice the star closest to Vega begins to fade away. Beta is one of the most unusual spectroscopic stars in the sky, and it is possible that its eclipsing binary companion may be a prototypical “collapsar” (Yep – a black hole!) rather than an actual luminous body.

Double DoubleNow use the telescope for a pair of stars which are very close – Epsilon Lyrae (RA 18 44 20 Dec +39 40 12). Known to most of us as the “Double Double,” look about a fingerwidth northeast of Vega. Even the slightest optical aid will reveal this tiny star as a pair, but the real treat is with a telescope – because each component is a double star! Both sets of stars appear as primarily white, and each pair is very close in magnitude. What is the lowest power that you can use to split them?

Stargazer JackSaturday, September 6, 2008 – Today celebrates the founding of the Astronomical and Astrophysical Society of America. Started in 1899, it is now known as the American Astronomical Society. Also on this date, in 2006, the milestone 1500th episode of Jack Horkheimer’s Star Gazer series aired. The long-running short program on public television has led thousands of people, young and old, to “keep on looking up!” For a lifetime of achievement in public outreach, we salute you, Mr. Horkheimer!

Tonight when you have had a look at the Serpentine Ridge, drop south along the terminator and see if you can identify the very old crater Abulfeda, west of Theophilus.

Abulfeda - W. HigginsThis charming crater was named for Prince Ismail Abu’l Feda, who was a Syrian geographer and astronomer born in the late thirteenth century. Spanning 62 kilometers, its rocky walls show what once was a great depth, but the crater is now filled-in by lava, and drops to a mere 3110 meters below the surface. While it doesn’t appear very large to the telescope, that’s quite big enough to entirely hide Mt. Siple – one of the highest peaks in Antarctica! If conditions are steady, power up and take a look at Albulfeda’s smooth-appearing floor. Can you see many smaller strikes? If the lighting is correct, you might even spot one far younger than the others!

Ranger 9 CamerasSunday, September 7 – For binoculars and telescopes, tonight’s Moon will provide a piece of scenic history as we take an in-depth look at crater Albategnius. This huge, hexagonal, mountain-walled plain will appear near the terminator about one-third the way up from the south limb. This 136 kilometer wide crater is approximately 4390 meters deep, and its west wall will cast a black shadow on the dark floor. Albategnius is a very ancient formation, which partially filled with lava at one point in its development. It is home to several wall craters like Klein (which will appear telescopically on its southwest wall). Albategnius holds more than just the distinction of being a prominent crater – it holds a place in history. On May 9, 1962 Louis Smullin and Giorgio Fiocco of the Massachusetts Institute of technology aimed a red laser toward the lunar surface and Albategnius became the first lunar object to be illuminated by a laser and then detected from Earth!

Ranger 9 ImageOn March 24, 1965 Ranger 9 took this “snapshot” of Albategnius (in the lower right of the lunar image) from an altitude of approximately 2500 kilometers. Companion craters in the image are Ptolemaeus and Alphonsus, which will be revealed for us tomorrow night. Ranger 9 was designed by NASA for one purpose – to achieve a lunar impact trajectory and send back high-resolution photographs and high-quality video images of the lunar surface. It carried no other scientific experiments, and its only destiny was to take pictures right up to the moment of final impact. It is interesting to note that Ranger 9 slammed into Alphonsus approximately 18.5 minutes after the lunar photo was taken. They called that…a “hard landing.”

As the week progresses, watch as the Moon draws closer for a near event with Jupiter by Wednesday. While the pair will still be separated by around two degrees it will still be an awesome sight that doesn’t require a telescope to enjoy!

Wishing you clear skies…

This week’s awesome images are Crater Piccolomini – Credit: Oliver Pettenpaul (LPOD), Beta Lyrae – Credit: Palomar Observatory, courtesy of Caltech, Beta Lyrae – Credit: Palomar Observatory, courtesy of Caltech, Crater Abulfeda – Credit: Wes Higgins, Ranger 9 Image of Lunar Surface and Image of Lunar Surface – Credit: NASA. We thank you!!