Author: Tammy Plotner

Do you think you’re seeing a Hubble Image? Then think again. Just revealed at last weekend’s NEAF gathering at Rockland College in Suffern, New York, this incredible image of IC 2944 was taken by Ken Crawford at Macedon Ranges Observatory and shows so much more than just pretty sky scenery. In this edition of the Universe Today Astronomy Photo of the week, we’ll take a deeper look into the science behind the picture as you discover an anomaly known as “Thackeray’s Globules”…

The photographic artistry of Ken Crawford takes us on a visual journey ever deeper into the busy star-forming region, IC 2944. While the view of this incredible emission nebula is some 6,000 light years away, Ken’s work takes us directly in for close up views of Thackeray’s Globules in ways that stagger the imagination.

IC 2948 is sprawling cloud of gas and dust that is illuminated and heated by a loose cluster of massive stars known as IC 2944. These stars are much hotter and much more massive than our Sun and their strong stellar winds carve out unique shapes in the noble hydrogen gases. These busy star forming HII regions are home to curious dark masses which we really don’t know a whole lot about – except their association. Dark globules like these have been known since Dutch-American astronomer Bart Jan Bok first began documenting them in 1947 and astronomer A.D. Thackeray first spied the globules in IC 2944 in 1950.

The largest of the globules in IC 2944 could possibly be two separate clouds that appear to partially overlap along our line of sight. Each cloud is nearly 1.4 light-years along its longest dimension and a combination of both clouds contain enough material to equal over 15 solar masses. When you take a closer look, you’ll see the globules appear almost shattered – as if strong forces were pulling them apart. In the case of IC 2944, seeing is believing because when radio astronomers observed the faint hiss of molecules within the globules, they realized Thackeray’s million year old discovery is in constant, aggressive motion, moving along in a supersonic dance. Like a water droplet sprayed against hot metal, this dance may be caused by the powerful ultraviolet radiation from the luminous, massive stars. When the region of glowing hydrogen gas is heated, it expands and streams against these dark masses, causing their annihilation.

According the research done by Bo Reipurth, Patrice Corporon, Michael Olberg and Guillermo Tenorio-Tagle: “We believe that the globules are the remnants of an elephant-trunk observed from behind, originating as a Rayleigh-Taylor instability in an expanding neutral shell powered by the hot HII region. The globule complex is now in an advanced stage of disintegration. We have found no evidence for star formation in any of the globules.”

Often known as the Running Chicken Nebula or the Lambda Cen Nebula, IC 2944 and IC 2948 is nestled between the Southern Cross and the star-thick Carina area on the southern border of Centaurus (RA 11:36.6 Dec -63:02). With an average magnitude of 4.5 and spanning around 75 arc minutes, its collection of bright stars is also referred to as Collinder 249 and was given the designation of Caldwell 100 by Sir Patrick Moore. Don’t expect to see a vision in either eyepiece or binoculars. The cluster is easy… But the nebula is very vague!

Image Details: IC 2944
Taken at: MACEDON RANGES OBSERVATORY
AP130 @ F6 / Paramount ME
Apogee Alta 16803
AstroDon – (5nm Ha & SII) & OIII 3nm Filters
Ha =180 minutes mapped to Green
SII =180 minutes Mapped to Red
OIII = 240 minutes Mapped to Blue
CCDAutoPilot for unattended imaging With MaxDL 4

Since the initial alert for the latest nova in Sagittarius, folks the world over have been anxious for darkness to arrive and their chance at spotting this cosmic wonder firsthand. Thanks to our good friends at Macedon Ranges Observatory, Universe Today readers are about to see the latest nova in Sagittarius revealed and learn just what is a nova.

One thing is certain, both professional and amateur astronomers have something in common – curiosity. Unfortunately, because many of us live where skies seem to be perpetually cloudy or don’t always have the equipment to view a late breaking astronomy alert object, it becomes even more imperative to be able to call upon others in different regions of the world. It certainly is a true pleasure to have friends down under! So now that we see it… What is a nova?

The word nova is Latin for “new star”. Astronomers assign the term nova to stars that have a rapid increase in brightness. These stars are usually far too dim to be seen unaided and may often become the brightest object – besides the Sun and Moon – in the sky!

Novae themselves are stars that have been quiet for many years, and suddenly decided to reignite their nuclear fusion process. All stars have fusion occurring in their core – processing hydrogen into helium and releasing energy. When this fuel is expended, stars like our sun simply shed their outer layer and continue on as small, hot, white dwarf stars. They are basically dead… Their fuel gone.

Unlike our own Sun, most stars are a binary system – two stars that closely orbit each other. If one of these stars should happen to be a white dwarf and the other starts to evolve into a red giant, the white dwarf can begin attracting gas towards itself by means of gravity. What type of gas? Hydrogen! When the hydrogen stolen from the red giant reaches the surface of the incredibly hot white dwarf, it rapidly ignites. What’s born is an incredibly huge nuclear explosion on the white dwarf’s surface and we see it as a nova!

Using a 12″ Ritchey Chretien Optical Systems telescope, Joe Brimacombe set to work imaging the latest nova for us to see. By comparing this photo with the 19 April Sagittarius Image you can see how quickly the white dwarf ignited!

Nova Sgr 19April2008 Joseph Brimacombe Image details are as follows: STL11000 camera; BRC 250; image scale 1.46 asec/px; image is 97 amin across; nova is centre star; stack 6 x 300 Ha; false colour.

If southern skies stargazers thought there was nothing to the north to be interested in, then think again. There’s a surprising number of galaxies both close to home and towards the farthest reaches of our Universe in the constellation of Ursa Major. It you think the larger of this 42 million light year distant galactic pair is a little warped, you’d be right. But there’s more than two cosmic cannibals in this astronomy picture.

Originally discovered by Sir William Herschel during this very same month 211 years ago, NGC 3718 became the future study of an astronomer named Halton Arp. For 28 years Dr. Arp was staff astronomer at the Mt. Palomar and Mt. Wilson observatories and while there, he produced his well known catalog of Peculiar Galaxies that are disturbed or irregular in appearance. Needless to say, NGC 3718 became Arp 214: “”Barred spiral, (with a) sharp nucleus, narrow absorption lanes through center”.

But it’s not quiet and it’s alone in the field. Joining warped NGC 3718 around 150,000 light years away is NGC 3729 – another massive galaxy which may be causing its neighbor’s peculiarities. While the warping of galactic discs is common, the process is not quite yet understood. It’s highly possible that tidal forces exerted by neighboring galaxies could be at work and in the case of this pair, it seems to carry through.

NGC 3718 contains an active galactic nucleus (AGN) and is known as a Seyfert Galaxy type 1.9 – one which may contain a massive black hole and is known for violent stars. Through HI mapping, NGC 3718 displays a tidal “tail” which begins on its eastern frontier and extends north towards its companion, NGC 3729. Is this just a case gravitational relationship? One galaxy consuming another? Let’s find out…

It is commonly accepted that when galaxies pass each other that tidal forces draw out the companion galaxy’s stars, gas, and dust in the formation of a spectacular tail. Just as it is commonly accepted that a merger of two spiral galaxies results in a remnant with an elliptical-like surface-brightness profile. In the case of NGC 3718, it would appear (according to interferometer data), the disk warp is evolving into a polar ring. No doubt, its molecular gas content is consistent with elliptical galaxy structure, but the distribution is warping the inner disk. At the same time, 2MASS data shows Arp 214’s main support against gravitational collapse comes from pressure due to random motion of stars as seen in an elliptical galaxy rather than from rotation. The origin of the unusual combination of properties makes the whole scene not only beautiful to look at, but most unique.

But don’t stop there… A closer examination of this picture will also show another another compact set of interacting galaxies as well – Hickson 56. Instead of two, there are five which share similarities with the closer cousins. Located some 400 million light years distant, this Hickson compact group has several catalogue designations including UGC 6527, VV 150, Markarian 176 and Arp 322 and were originally observed by Lord Rosse. According to Halton Arp, “Much print has been dedicated to explaining discordant redshifts in compact groups as unrelated background galaxies. But no one has analyzed the accordant galaxies. It is shown here that when there is a brightest galaxy in the group, the remainder with differences of less than 1000 km s−1 are systematically redshifted. This is the same result as obtained in all other well-defined groups and demonstrates again an increasing intrinsic redshift with fainter luminosity.”

So what’s Paul Hickson take? “Group 56 consists of five galaxies, three of which appear to be in contract and interacting. Two of these three galaxies (B and D) are <a href=”http://www.universetoday.com/11970/galaxy-caught-stealing-gas/”radio source galaxies. Infrared emission is also detected from this interacting system.” Much like it’s closer counterpart, Hickson 56 displays a notable stream of “galaxy stuff” linking its B and C components. An examination of the C galaxy reveals an asymmetric halo but D has a less complex outer luminosity profile. Last, but not least, both the A and D galaxies are Seyfert. More galaxies that have – or are – interacting in the past, present and future.

What’s the chances of seeing some these galaxies yourself? Not bad at all. For the average-to-large telescope, NGC 3718 (RA 11 32 56 Dec +53 01 55) is roughly magnitude 10 to 11 (depending on whose scale you’re looking at) and is noted as a soft, even haze with a dark dustlane seen upon aversion. NGC 3729 (RA 11 34 Dec +53 08), despite its magnitude billing is low surface brightness and requires a large telescope and aversion to detect. As for Hickson 56 (RA 11 32 46 Dec +52 56 28), you’re going to need major aperture and excellent skies to even see a hint of this quintuplet.

Thanks to the photographic magic of Dietmar Hager of Austria, we’re able to enjoy this cosmic portrait. Using a 9″ TMB refractor, the image was captured with a SXV H16 CCD camera and processed with AstroArt Software, Maxim DL and Registax. When Dietmar isn’t busy being a trauma surgeon, he certainly takes outstanding astrophotos and is a member of the MRO imaging team. We thank him for sharing!

It’s big. It’s bright. It’s the Moon! Even though the dark skies will be trashed thanks to the influence of this weekend’s Moon, there’s still a lot of astronomy we can practice together. Grab your telescopes or binoculars and let’s head out, because… Here’s what’s up!

Friday, April 18 – Tonight, if you’re looking at the Moon near the southern cusp you’ll spy two outstanding features. The easiest is crater Schickard – a class V mountain-walled plain spanning 227 kilometers. Named for German astronomer Wilhelm Schickard, this beautiful old crater with subtle interior details has another crater caught on its northern wall which is named Lehmann. But, look further south for one of the Moon’s most incredible features – Wargentin. Among the many strange things on the lunar surface, Wargentin is unique. Once upon a time, it was a very normal crater and had been so for hundreds of millions of years, then it happened: either a fissure opened in its interior, or the meteoric impact which formed it caused molten lava to begin to rise. Oddly enough, Wargentin’s walls did not have large enough breaks to allow the lava to escape, and it continued to fill the crater to the rim. Often referred to as “the Cheese,” enjoy Wargentin tonight for its unusual appearance…and be sure to note Nasmyth and Phocylides as well.

Saturday, April 19 – Despite the Moon’s overpowering light, you may have noticed brilliant blue-white Spica very near the Moon tonight. Take the time to look at this glorious helium star, which shines 2300 times brighter than the Sun which lights tonight’s Moon. Roughly 275 light-years away, Alpha Virginis is a spectroscopic binary. The secondary star is about half the size of the primary and orbits it about every four days from its position of about 18 million kilometers from center to center… That’s less than one-third the distance at which Mercury orbits the Sun (here are some planet Mercury facts). The two stars can actually graze during an eclipse. Oddly enough, Spica is also a pulsating variable and the very closeness of this pair make for fine viewing – even without a telescope!

While we’re out, have a look at R Hydrae about a fingerwidth east of Gamma – which is itself a little more than fistwidth south of Spica. R Hydrae (RA 13 29 42 Dec -23 16 52) is a beautiful, red, long-term variable first observed by Hevelius in 1662. Located about 325 light-years from us, it’s approaching – but not so very fast. Be sure to look for a visual companion star as well.

Sunday, April 20 – Tonight’s Full Moon is often referred to as the “Pink Moon” of April. As strange as the name may sound, it actually comes from the herb moss pink or wild ground phlox. April is the time of blossoming and the “pink” is one of the earliest widespread flowers of the spring season. As always, it is known by other names as well, such as the Full Sprouting Grass Moon, the Egg Moon, and the coastal tribes referred to it as the Full Fish Moon. Why? Because spring was the season the fish swam upstream to spawn.

While skies are bright, let’s take this opportunity to have a look at Alpha Canis Minoris, now heading west. If you’re unsure of which bright star is, you’ll find it in the center of the diamond shape grouping in the southwest area of the early evening sky in the northern hemisphere. Known to the ancients as Procyon, “The Little Dog Star,” it’s the eighth brightest star in the night sky and the fifth nearest to our solar system. For over 100 years astronomers have known this brilliant star was not alone – it had a companion, and a very unusual one. 15,000 times fainter than the parent star, Procyon B is an example of a white dwarf whose diameter is only about twice that of Earth. But its density exceeds two tons per cubic inch! (Or, a third of a metric ton per cubic centimeter.) While only very large telescopes can resolve this second closest of the white dwarf stars, even the moonlight can’t dim its beauty.