Posted on by Tammy Plotner

IYA Live Telescope Today: NGC 6302 – The “Bug” Nebula

“Baby, breakdown, go ahead give it to me… Breakdown, honey take me through the night. Breakdown, Im standing here, can you see? Breakdown, it’s all right… It’s all right… It’s all right.”. Oh, hi! Were you watching the IYA Live Telescope today? If you were, then you know that we encountered a real “bug” shortly after we aimed at NGC 6302. That’s right. A bipolar nebula caused our little telescope to go bipolar and blow a gasket. But don’t you worry! Dr. Bert “Can Do” is on the scene and fixing things up again. In the mean time, he did manage to capture some live footage of NGC 6302 before we went down and we’re here to share…

NGC 6302 (also called the Bug Nebula or Butterfly Nebula), is a bipolar planetary nebula in the constellation Scorpius. It is one of the most interesting and complex planetary nebulae observed. The spectrum of NGC 6302 shows its central star is one of the hottest objects in the galaxy, with a surface temperature in excess of 200,000 K, implying that the star from which it formed must have been very large. The central star has never been observed and is surrounded by a particularly dense equatorial disc composed of gas and dust. This dense disc is postulated to have caused the star’s outflows to form a bipolar structure (Gurzadyan 1997), similar to an hour-glass. This bipolar structure shows many interesting features seen in planetary nebulae such as ionization walls, knots and sharp edges to the lobes.

As it is included in the New General Catalogue, this object has been known since at least 1888. The earliest known study of NGC 6302 is Edward Emerson Barnard who, in 1907, drew and described it. (Meaburn et al. 2005). Since then it has been the focus of many works and displays many interesting characteristics worthy of study. Interest in recent years has shifted from discussions over the excitation method in the nebula (shock-excitation or photo-ionisation) to the properties of the large dust component.

NGC 6302 has a complex morphology which may be approximated as bipolar with two primary lobes, though there is evidence for a second pair of lobes that may have belonged to a previous phase of mass loss A dark lane runs through the waist of the PN obscuring the central star at all wavelengths. Observations of NGC 6302 suggest that there may be an orthogonal skirt (or chakram) similar to that found in Menzel 3. (Meaburn et al. 2005). The nebula is orientated at an angle of 12.8° against the plane of the sky.

This PN contains a prominent North-West lobe which extends up to 3?.0 away from the central star and is estimated to have formed from an eruptive event around 1,900 years ago. It has a circular part whose walls precisely follow a Hubble-type outflow (where outflow speed is proportional to distance from the central source). At an angular distance of 1?.71 from the central star, the flow velocity of this lobe is measured to be 263 km/s. At the extreme periphery of the lobe, the outward velocity exceeds 600 km/s. The western edge of the lobe displays characteristics suggestive of a collision with pre-existing globules of gas which modified the outflow in that region. (Meaburn et al. 2005)

The prominent dark lane that runs through the centre of the nebula has been shown to have an extraordinary dust chemistry, showing evidence for multiple crystalline silicates and features that have been interpreted by some to be the first extra-solar detection of carbonates. This detection has been disputed, due to the difficulties in forming carbonates in a non-aqueous environment. Other solid state features detected include crystalline water ice and quartz.

One of the most interesting characteristics of the dust detected in NGC 6302 is the existence of both oxygen-rich (i.e. silicates) and carbon-rich (i.e. poly-aromatic-hydrocarbons or PAHs) material. Stars are usually either O-rich or C-rich, the change from the former to the latter occurring late in the evolution of the star due to nuclear and chemical changes in the star’s atmosphere. When a star or nebula is observed to have a dual chemistry it is indicative of a recent change from O-rich chemistry to C-rich chemistry.

Look for the IYA Live Telescope to be up and running again soon, so keep on checking the link to the right and we’ll see you when skies are clear and dark in central Victoria! Ciao for now…

(Factual Information Source: Wikipedia)

Posted on by Tammy Plotner

IYA Live Telescope Today: NGC 6281

Did you get a chance to watch the IYA Live Telescope today? This time we went hunting galactic open star clusters and we found a beauty! NGC 6281 can be easily spotted in binoculars and small telescopes and we invite you along for the tour. No telescope? No problem. As always, we record a video clip for you so you can enjoy, too!

Your guide star to finding NGC 6281 is Mu Scorpii. About a finger-width east you will find large open galactic star cluster NGC 6281. At magnitude 5.4, you’ll find this sky gem punctuated by a wide pair of 6th magnitude stars. This brightly scattered cluster of three dozen members shows no real nucleus but is easily recognized at low magnifications.

Recent studies have found possible light variations of the member star HD 153919 – identified as an X-ray source. The nebulousity associated with this cluster is also an active HII region and of interest to astronomers wanting to study using Hubble instruments: “We propose a WFPC2 FUV imaging survey of 6 Galactic open clusters with ages ranging from 1 Myr to 300 Myr complemented with NUV/optical imaging of the same fields. No such survey has ever been attempted before in the FUV at the resolution of WFPC2 (indeed, no WFPC2 FUV images of any Galactic open cluster exist in the HST archive) and, since WFPC2 will be retired in SM4 and none of the other HST instruments can do FUV imaging of bright objects, this is the last chance to do such a survey before another UV telescope is launched.” says Dr. Jesus Maiz Apellaniz, “This survey will provide a new perspective on young intermediate age Galactic clusters and a key template for the study of star formation at high redshift, where the intensity peak we observe in the optical/NIR from Earth is located in the FUV in its rest frame. For clusters still associated with an H II region, UV imaging maps the continuum emission of the ionized gas and the radiation scattered by background dust and, combined with optical nebular images, can be used to determine the 3-D structure of the H II region. For all young clusters, FUV+NUV+optical photometry can be used to study the UV excesses of T-Tauri stars. For clusters older than ~40 Myr, the same photometric combination is the easiest method to detect companion white dwarfs which are invisible using only the optical and NIR. WFPC2 is also an excellent instrument to discover close companions around bright stars and improve our knowledge of their multiplicity fraction. Finally, for all clusters, the combination of high-spatial-resolution UV and optical photometry can be used to simultaneously measure the temperature, extinction, extinction law, distance, and existence of companions (resolved and unresolved) and, thus, produce clean HR diagrams with resolved cluster membership and much-reduced systematic uncertainties.”

As always, be sure to enjoy the views from our IYA Live Telescope whenever the skies are clear and dark in Central Victoria by clicking on the link to your right! And have fun… We do!

Posted on by Tammy Plotner

Planetary Line Up Graces Pre-Dawn Sky June 19-21, 2009… Make A Date!


What could be more fun that practicing some astronomy that doesn’t require dragging out a lot of special equipment or even going to a special location? That’s right… It’s conjunction time again. All it takes is knowing the right time and where to look to enjoy! Step inside and learn…

A great line-up of planets will light up the pre-dawn sky later this week. From June 19 to 21, Mercury, Venus, Mars, and the Moon will put on quite a show, according to the editors of StarDate magazine.

Starting before dawn on June 19, look for Venus blazing as the ‘morning star’ due east around an hour to 45 minutes before local sunrise. Fainter Mars will be a little to its lower left, with Mercury a good bit farther to the lower left. Although Mercury looks like a bright star, it will be so low in the sky that you may need binoculars to pick it out of the lower sky haze.

The little Pleiades star cluster will stand to the upper right of Mercury, forming the shoulder of the constellation Taurus, the Bull.

The Moon will be well to the upper right of Venus and Mars on the morning of the 18th, and directly above them on the 19th. It moves closer to the Pleiades on the 20th, and a little left of Mercury on the 21st, when it will be the slimmest of crescents.

(Information and video courtesy of The University of Texas at Austin McDonald Observatory. Many thanks!)

Posted on by Tammy Plotner

IYA Live Telescope Today: Messier 80

Did you get a chance to watch the IYA Live Telescope Today? Our target was the extremely compact and bright globular cluster, M80 in the constellation of Scorpius. What a treat! Of course, if you didn’t get a chance to watch it live, we made sure to capture a quick video for you to share….

Messier 80 (also known as M80 or NGC 6093) is a globular cluster in the constellation Scorpius. It was discovered by Charles Messier in 1781.

M80 is located midway between Alpha Scorpii (Antares) and Beta Scorpii in a field in the Milky Way that is rich in nebulae. It can be viewed with modest amateur telescopes as a mottled ball of light. With an apparent diameter of about 10′ and at an estimated distance of 32,600 light-years, M80’s spatial diameter is about 95 light-years and contains several hundred thousand stars. It is among the more densely populated globular clusters in the Milky Way Galaxy. M80 contains a relatively large amount of blue stragglers, stars that appear to be much younger than the cluster itself. It is thought these stars have lost part of their outer layers due to close encounters with other cluster members or perhaps the result of collisions between stars in the dense cluster. Images from the Hubble Space Telescope have shown districts of very high blue straggler densities, suggesting that the center of the cluster is likely to have a very high capture and collision rate.

On May 21, 1860, a nova was discovered in M80 that attained a magnitude of +7.0. The nova, variable star designation T Scorpii, reached an absolute magnitude of -8.5, briefly outshining the entire cluster.

As always, you can join us whenever the skies are clear and dark in Central Victoria by clicking on the live remote cam link under the IYA telescope logo to your right. Have a great time!

(Factual Information Source: Wikipedia)

Posted on by Tammy Plotner

Summer Fun – The Celestron Optics Kit

For anyone who does astronomy outreach work, is interested in practicing binocular astronomy or is just looking for a great teaching tool, I’ve got something you really need to take another look at – the Celestron 10X50 UpClose Binoculars and Green Laser Pointer Optics Kit; great for binocular astronomy. Almost a year ago I did a review on this product, and I’m back to tell you how it’s held up against another year of service.

When I first researched the Celestron Optics Kit I was looking for inexpensive binoculars that anyone could handle for our guests at the Observatory. During a public night or an outreach program, we may have a hundred or more guests and, let’s face it, providing several pairs of binoculars can be expensive for a non-profit organization. When doing something of this nature, you face two dilemmas. One… When you can afford them, they are invariably low quality and you’ve just disappointed the person you were trying to teach binocular astronomy… and… Two… When you get a good pair of binoculars they cost so much that you’re afraid to let smaller children handle them. (Which is equally wrong, because kids are people, too!)

Of course, since the green laser pointer came along a few years ago, all of us have learned a lot of aiming tricks. They can be aimed (carefully) through an optical finderscope to project a beam in the sky, they can be rigidly mounted on a telescope or binocular body as a finder, they can be used to point things out, or… in my case… I quickly learned that even a novice (right down to my five and six year old grandchildren) can follow the visible beam to where you target it, to its end with binoculars. Then the beam is switched off and the object is in the binoculars! With a mind for safety, it’s a simple and fun way to teach anyone to use binoculars for deep sky observing.

But the green laser wasn’t what I was after… It was the binoculars, wasn’t it?

Another aspect of the binocular astronomy classes we give is providing a monthly star chart to our guests that highlights a few objects for them to locate on their own. It’s just a simple handout – one I print out at home before any program and we stand around in the dark and share a red flashlight as I teach them how to read it and point out the marker stars with the green laser. Yep. We share the red flashlight… A simple tool that should be in the hands of every single person that even remotely takes an interest in reading an astronomy chart outside at night… And one that I just don’t happen to have ten extra to pass around.

But the red flashlights wasn’t what I was after… It was the binoculars, wasn’t it?

So, back to basics. I needed multiple pairs of binoculars that could withstand hard use (like accidentally being dropped on concrete, run over by a Jeep or left out overnight) and perform well. After many years, and many pairs of personal binoculars, I’d love to put Nikon, Oberwerk or Fujinons in every one’s hands, but the reality check is not every one’s hands are ready for these types of binoculars. What I needed was something I knew from experience that could withstand being dropped, was water-proofed and provided an excellent view. In that case, experience tells me Celestron and a great all-purpose astronomy binocular size is 10X50.

So, here I am… Staring at the Celestron 10X50 UpClose Binoculars and Green Laser Pointer Optics Kit for $59 and then the reality check really comes home. For this price I can order five… And get five pairs of binoculars, five green laser pointers and five red flashlights… All for about what five pairs of binoculars would cost! Click. Ordered. Now I find out they’ve gone down to $29.95 and guess who’s ordering more?

Yep. We are. And here’s the reason why…

handnavigationEvery year we see thousands of visitors each summer and teach the night sky. Lessons begin as simply as learning navigation directions – like degrees – with hand spans and finger widths. When it comes down to nuts and bolts, the more experienced people you have with you armed with green lasers, the more effective any program can be, because a lot of seeing the laser beam has to do with the angle you are looking at it. (And unless you’re using one that will bore through concrete, no typical green laser pointer is going to cut through moonlight, ok?) In this case, we can easily do a presentation where we can point out constellations with the green lasers and responsible adults can also assist in the program by pointing out particular stars or objects for us to name. By having several flashlights available, small groups of kids can work together with charts and adults at the same time to learn constellations on their own. When it’s time to practice astronomy, we use the same “follow the beam” trick, they learn and have a great time!

outreachSo how do the binoculars hold up to exuberance, youth and use? Like the fabled Timex watch… If you think a 5 year old would be hard on equipment, try handing it to a group of teenagers. (Word of warning? Never trust them with your laser.) While most of them are respectful, the fact remains that these original 5 pairs of Celestron UpClose 5X10 binoculars have had the right eye diopter twisted like Chubby Checker, the interpupillary distance adjusted in and out more times than my waist size and the focuser spun around more times than the big wheel on the Price Is Right. They’ve had mascara cleaned off the lenses with a t-shirt, knocked off the observing table and left outside. In general… They’ve been used. But you know what? They still perform. All five pair have kept their collimation. Not one pair shows any signs of getting moisture inside and every last one of them still operates just the way they did when they came out of the box.

Are the laser pointers and flashlights still using the original batteries? Oddly enough, two of the flashlights and one of the laser pointers still is. None of the flashlights malfunctioned with time, but we did have two laser pointers that have to be “warmed up” to use. (Don’t ask me why, but they work brighter after they’ve been on for a few minutes.) Also, when the weather dipped down below the freezing point, the lasers also needed to be kept warm (like in an internal coat pocket) to function quick and easy. Sure, these low power green lasers aren’t going to stun the crowds with their light sabre-like qualities and shoot down passing aircraft, but they are highly efficient at being a simple beam pointer and work just fine. Just try to find one for what this whole kit costs!

Am I disappointed in the Celestron 10X50 UpClose Binoculars and Green Laser Pointer Optics Kits? Not hardly – and you won’t be either. Combined with a simple star chart and a starry night, you’ll be in for a whole lot of summer fun for about what a large pizza would cost. It is an exceptional bargain at $29.95 and one I highly recommend. As a matter of a fact, I recommend it so much that OPT is even going to give three of these kits away to Universe Today readers to keep so you can test it out yourself! From now until June 25 at 12:00 pm PDT you can send an email with the title of this review in the subject line and your name in the body of the email and Universe Today will randomly choose a winner to get your own Celestron Green Laser Pointer Optics Kit for free! All you have to do is pay for shipping, ok?

Put ’em to the test and see if you don’t agree. The Celestron 10X50 UpClose Binoculars and Green Laser Pointer Optics Kit is an exceptionally rugged and good performing astronomy binocular and having a red flashlight and green laser is a huge bonus.

The Celestron 10X50 UpClose Binoculars and Green Laser Pointer Optics Kit were purchased for this review from Oceanside Photo and Telescope and three free kits will be provided to randomly chosen winners by Fraser Cain of UniverseToday.

Posted on by Tammy Plotner

Weekend SkyWatcher’s Forecast – June 12-14, 2009

Greetings, fellow SkyWatchers! Are you ready for a great weekend? Then it’s time to do some challenging studies as we take on one of the most difficult globular clusters in the sky – Palomar 5. Need something you can spot with your eyes or binoculars? Then try the planet Mercury… But get up early! Maybe a weekend meteor shower that’s known for spitting out bright bolides is more to your liking… Still feeling challenged? Then let’s try our hand at some Herschel studies and blow some dust off the galaxies! Time to get out the scopes and the star charts and I’ll see you in the back yard.

gillFriday, June 12, 2009 – Today, remember the 1843 birth of Sir David Gill on this date, who took measurements of solar and stellar parallax, computed the distances of the Sun and other stars from Earth, and was first to use photography in mapping the heavens. To determine parallaxes, Gill perfected the heliometer, a telescope that uses a split image to measure the angular separation of celestial bodies. He later redetermined the solar parallax with such precision that almanacs used his value as late as 1968!

Completing astronomical projects is very challenging, and tonight we’ll hunt down a difficult globular cluster study by using M5 as a guide. Palomar 5 is by no stretch of the imagination easy. For GoTo systems, aiming is easy, but for large telescopes, starhopping instructions are critical. From M5 drop south for double 5 Serpens, and again south and slightly west for another, fainter double. Don’t confuse it with eastern 6 Serpens. A half degree west you’ll encounter an 8th magnitude star, with 7th magnitude 4 Serpens a half degree south. Continue south another half degree, for a triangle of 9th magnitude stars. The southern apex star is home to Palomar 5 (RA 15 16 05 Dec +00 06 41).

pal5

Discovered by Walter Baade in 1950, this 11.7 magnitude, Class XII globular was first believed to be a dwarf elliptical galaxy, possibly a member of our Local Group. Later studies showed Palomar 5 to be a globular cluster but one being ripped apart by the tidal forces of the Milky Way—at 60,000 light-years from the galactic center! Palomar 5’s members are escaping, leaving trails spanning 13,000 light years – a several billion year process. Telescopes of 6’’ can distinguish a few individual members northwest of the 9th magnitude marker star, but even ones as large as 31’’ fail to show more than a handful of resolvable stars. This may be the toughest locating job you’ll ever tackle, but be sure to make a quick sketch of the region to complete your studies. Good luck!

maxwellSaturday, June 13, 2009 – Before dawn, Mercury reaches its highest morning elevation, and you’ll find the asteroid Psyche less than half a degree north of the Moon. Look a finger-width south of Luna, and you’ll see Neptune and Jupiter separated by less than a degree! Perhaps they’re saluting the 1831 birth on this date of James Clerk Maxwell? Maxwell calculated that the speed of propagation of an electromagnetic field is approximately the speed of light, thereby inferring that light is an electromagnetic phenomenon. Born on the same day but 28 years before him was Thomas Young, who had demonstrated the wave nature of light.

For us, tonight’s light waves will be from Herschel II.76, also known as NGC 5970. Begin by identifying Beta and Delta Serpentis, and look for finderscope Chi between them. Less than a degree southwest, you will see a similar-magnitude double star. Hop about one-third degree northwest, and you’ll find the galaxy just a fraction southwest of a 7th magnitude star (RA 15 38 302 Dec +12 11 11).

5970

NGC 5970 isn’t particularly easy for smaller scopes (even near 11th magnitude), because of its low surface brightness, but its structure makes it a distant cousin of the Milky Way. At 105 million light year-distant, it’s no great surprise we see it as faint, for its light left around the time the dinosaurs ruled Earth. Stretching across 85,000 light-years of space, the nuclear region, obscuring dust regions, and the stellar population of this grand spiral have been extensively studied. And—like us—it is also part of its own Local Group. Although smaller telescopes will make out a slightly elongated mist, in mid-to-large apertures NGC 5970 will appear oval-shaped with a bright core and evidence of a central bar. Although the edges of the galaxy seem well-defined, look closely at the narrower ends, where material seems more wispy. Seen averted, the nucleus will sometimes take on a stellar appearance yet lose this property with direct vision. Be sure to mark your Herschel notes on this one!

Sunday, June 14, 2009 – As the new hours of the day begin and you wait on dawn, keep watch for the peak of the Ophiuchid meteor shower with the radiant near Scorpius. The fall rate is poor, with only 3 per hour, but fast moving bolides are common. This meteor stream will last for 25 days. While you’re out, see if you can spot Mercury! What planet is the Moon near now?

Tonight, let’s go south in Libra and have a look at the galaxy pairing NGC 5903 and NGC 5898.

You’ll find these about 3 degrees northeast of Sigma, and just north of a pair of 7th magnitude stars (RA 15 18 36 Dec -24 04 05). Although northernmost NGC 5903 seems to be nothing more than a faint elliptical with a brighter concentration toward the center and an almost identical elliptical—NGC 5898—to the southwest, you’re probably asking yourself. . .why the big deal over two small ellipticals?

5903field

First off, NGC 5903 is Herschel III.139 and NGC 5898 is Herschel III.138—two more to add to your studies. And second? The Very Large Array has studied this galaxy pair in the spectral line of neutral hydrogen. The brighter of the pair, NGC 5898, shows evidence of ionized gas that has been collected from outside its galactic realm, while NGC 5903 seems to be running streamers of material toward it. A double-galaxy, double-accretion event!

But there’s more. . .

Look to the southeast, and you’ll double your pleasure and double your fun as you discover two double stars instead of just one! Sometimes we overlook field stars for reasons of study, but don’t do it tonight! Even mid-sized telescopes can easily reveal this twin pair of galaxies sharing ‘‘their stuff,’’ as well as a pair of double stars in the same low power field of view. (Psst. . .slim and dim MCG 043607 and quasar 1514-241 are also here!) Ain’t it grand?

Until next week? Stay challenged and you’ll always stay interested!

This week’s awesome images are (in order of appearance): Sir David Gill (historical image), Palomar 5 (credit—Palomar Observatory, courtesy of Caltech), James Clerk Maxwell (historical image), NGC 5970 (credit—Palomar Observatory, courtesy of Caltech) and NGC 5903 and NGC 5898 field (credit—Palomar Observatory, courtesy of Caltech). We thank you so much!

Posted on by Tammy Plotner

Kid’s Astronomy – The Cup and the Raven…

With the Moon now gone from the early evening sky and the lightning bugs beginning to twinkle in the summer fields, isn’t it time you stopped to do a little stargazing? If you’re outside when the skies begin the get dark, the first star you will see overhead is the brilliant orange Arcturus, which will point the way to blue/white Spica as the skies get dark. If you listen to the wind, you’ll hear the night birds beginning to call… and maybe even the voice of the stars telling you about the Cup and the Raven!

web_corvus_rot“Legend tells us that the constellation of Crater is the cup of the gods. A cup befitting the god of the skies… Apollo. And who holds this cup, dressed in black? The Raven… Corvus. Once upon a time, the Raven – or Crow – had beautiful silver feathers… so shiny they appeared almost white. They were the sacred birds of Apollo, god of the skies, and were able to speak in a human voice. Soon enough, Apollo fell in love with a beautiful maiden, Virgo, and he sent the Raven to spy upon her. When the Raven returned with the news that Virgo did not return his love, Apollo became very angry and turned the bird’s feathers black for bringing back such bad news.”

virgo__corvus

“With his beautiful silver feathers gone, the Raven became very hard to see among the stars. As night falls, only a star here and there appears to mark his place in the sky. Wanting to gain back favor, the Raven asked Apollo to set him a task. The great god of the sky then told the crow to fetch him a cup of water in his golden goblet – Crater.

However, the end of the tale is a sad one. It is the story of a creature sent to fetch water for his master, only to tarry too long waiting on a fig to ripen. When he realized his mistake, the sorry Raven returned to Apollo with his cup and brought along the serpent Hydra in his claws as well. Angry, Apollo tossed them into the sky for all eternity. The Raven’s beautiful voice was taken away as it is forever to be punished by being perpetually thirsty and thus its rough caw.”

hydra-corvus-crater

Virgo did not escape the wrath of Apollo either, for he decided if he could not have her? No man could. And so he tossed her into the stars to forever remain a virgin and it is to the south that all of this story’s players remain to this day.”

Can you find the stars that make up this sad tale? Then look for one of the brightest stars to the south this time of year, Spica. To its west you will see the the crooked box shape of Corvus and further west the faint U-shape of the goblet, Crater. On a dark night, look below them for the long, faint chain of stars that forms Hydra, the water snake. Explore it these constellations with binoculars! What treasures are hidden inside?

Many thanks to Torsten Bronger for the Corvus constellation map, Hubblesite for the historical Corvus image, Animation by Michelet B., and Constellation Mythology map courtesy of the University of Michigan. We thank you!

Posted on by Tammy Plotner

IYA Live Telescope – Kaguya Impact: 18:30 UT / THE MOON

The Japanese lunar orbiter Kaguya will end its two-year mission with a controlled impact on the Moon’s surface on June 10th at 18:30 Universal Time. The impact location is near the southeast limb at 80ºE, 63ºS. If you live in Asia and Australia, you may have the opportunity to observe the impact event… And if you don’t? Then watch on our IYA Live Telescope! We’re focused on the Moon right now and keeping our fingers crossed the clouds stay away….

Thanks for stopping by! We opened up all the extra room we had on our server for the day to accomodate as many people as possible.
Well, we tried our best – and here’s the results.

Did we catch it? Doesn’t look that way… But neither did telescopes 5 times larger than what we’re using. The point is, we tried! One of our friendly photographers was also on the job, so once he’s reviewed his footage for the night, perhaps he managed to catch a flash. If so, we’ll share!

In the meantime, thank you so much for tuning in and we’ll keep those cameras rollin’!

Posted on by Tammy Plotner

Beauty and the Beast: The Corona Australis Nebula by Eddie Trimarchi

The Corona Australis Nebula by Eddie Trimarchi

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Embedded in the Southern Crown some 424 light years away from us resides an area of incredible beauty surrounded by a dark and dusty beast. The three nebulae NGC 6726-27, and NGC 6729 were first discovered by Johann Friedrich Julius Schmidt, during his observations at Athens Observatory in 1861… a time when what they were was poorly understood. At first glance, one might believe this association of stars to be purely coincidental – a chance meeting of moving stars passing through a dust cloud, much like the Pleiades. But, thank heavens for an astronomer named Marth who independently recovered it in 1864 and began to study it, because there’s a whole lot more here than just a pretty picture.

When Marth recovered Schmidt’s three nebulous regions from his vantange point in Malta, he began a series of observations that would last for several years and lead to findings that would cause astronomers to take second looks at this incredible region known as the Corona Australis Nebula. Why? Because by 1916 both Schmidt and Marth had identified a variable star (R CrA) and a variable nebula within it. Within months, astronomers also realized also noticed that the behaviour of R CrA (variability and environment) was similar to T Tauri.

Buried in its yellowish cocoon near the two bright reflection nebulae, R CrA is a young star still accreting interstellar material on to its surface. But what materials? “The 3 micrometers absorption due to H2O ice was detected in three types of sources including protostars, T Tauri-like stars, and background field stars.” says Masuo Tanaka (et al), “This scattered distribution suggests the significant contribution of the circumstellar hot dust to the H-K color and/or sublimation of H2O ice at the inner region of the circumstellar disk due to heating by protostars. Among them, the optical depth of CO ice in IRS 2 is the largest so far detected. It is found that the absorption feature of each source has almost the same central frequency and FWHM which coincide with the calculated values of small grains with dominant CO mantle. On the other hand, the column density of CO ice is found to be substantially smaller than that of H2O ice.”

However, when examined in infrared, two distinct red patches can also be seen hiding inside the beast – Herbig Haro objects. Are these what account for the variability of the nebula? “We suggest that these variations are the result of variable obscuration, possibly linked to dust shells physically associated to the system.” says L.P. Vaz (et al), “NGC 6729 is part of a nebulous region that contains both variable stars R CrA and detached Herbig Be eclipsing binary TY Coronae Australis. We present the non-eclipse-related photometric variability of the system.” Regions that are constantly changing, yet show visible signs of star formation occurring deep inside the dark dust clouds… Coughed out from the hidden star-forming beast (often in pairs) and sent flying in an opposite direction.

Just how long ago were these expelled? According to recent research the primary TY CrA star is difficult to pinpoint, but may be around 3.16 million years old zero-age main sequence, and its secondary star is a pre-main-sequence star located at the base of the Hayashi tracks. It simply isn’t very evolved yet and could be as young as 1.64 million years or as old as 3 million. “All genuine Herbig stars in our sample are located between the birthline and the zero-age main sequence (ZAMS) in the Hertzsprung-Russell diagram (HRD), in accordance with what is expected for pre-main sequence stars.” says M.E. van den Ancker (et al), “The region in the HRD close to the birthline is relatively devoid of stars when compared to the region closer to the ZAMS, in agreement with the expected evolutionary time scales. The Herbig Ae/Be stars not associated with star forming regions were found to be located close to the ZAMS.”

But it is the combination of the beauty of new star formation and the beast of the dust that make the Corona Australis Nebula such a wonderful area for study. By studying polarization, we learn so much more about what is hidden inside. For example, dark dust clouds with embedded star clusters have a more complex distribution of polarization direction than do clouds without clusters, and it is believed that young stars and dense gases are a major factor in the enhanced dispersion of polarization angle – not just quantity of stars. Yet we can take an even closer look! “Polarization mapping of the reflection nebula NGC 6729 reveals parallel bands of polarization vectors across the premain sequence stars R and T Cr A. These bands can be explained by dust discs in which the grains are aligned by toroidal magnetic fields. The dust discs are oriented parallel to each other (in projection and possibly in space) in a north-south direction, which is orthogonal to the axis of the CO bipolar outflow from R Cr A observed by Levreault. Optical jets are associated with both stars, two with R Cr A and one with T Cr A, which are either parallel or antiparallel to each other; however, the optical jets are not orthogonal to the planes of the discs, but are inclined at about 60 deg.” says D. Ward-Thompson of Durham University, “A model is suggested in which the optical jets are collimated by a small inner circumstellar disc, which has decoupled from the magnetic field in outer regions because of ambipolar diffusion, and whose orientation is determined principally by the angular momentum. The large outer interstellar disc, in which the grains are aligned by a toroidal magnetic field, is inclined obliquely to the inner disc and is responsible for the collimation of the CO bipolar outflow.”

Is is the dark clouds of the beast hiding the beauty of star formation that causes the variability? “Measurable changes in the surface brightness of the reflection nebula associated with R CrA occur over intervals as short as 24 hours. These and other more extreme variations are demonstrated with CCD images obtained over a 23-day period. During this time span R CrA brightened by 1.3 mag.” says J.A. Graham, “The alterations in the appearance of the nebula NGC 6729 are apparently caused by the shadowing effects of clouds which are very close to the star, probably well within 1 Au. The spectrum of R CrA may itself vary slightly from night to night, and these changes are echoed by the surrounding nebula with an observable time delay.”

Will we ever know everything there is to know about the Beauty and the Beast? What we do know is: “The the Corona Australis molecular cloud complex is one of the nearest regions with ongoing and/or recent star formation. It is a region with highly variable extinction, containing, at its core, the Coronet protostar cluster. There are now 55 known optically detected members, starting at late B spectral types. At the opposite end of the mass spectrum, there are two confirmed brown dwarf members and seven more candidate brown dwarfs. The Corona Australis molecular cloud complex is today known as one of the nearest regions with ongoing and/or recent intermediate- and low-mass star formation.” says Ralph Neuhauser of Astrophysikalisches Institut und Universitats-Sternwarte, “In between the stars R and T CrA, there is the reflection nebula NGC 6729, and the stars TY CrA and HD 176386 illuminate the nebula NGC 6726/6727. Studying lines of CN, CH, and CH in the direction of TY CrA, find that the dust in the region which is attenuating the UV emission is highly processed and strong extended emission is possibly due to polycyclic aromatic hydrocarbons (PAHs).”

Our thanks to Eddie Trimarchi of Southern Galactic for sharing this awesome photo with us!