What's Up this Week: September 18 – September 24, 2006
Written by Fraser Cain
Greetings, fellow SkyWatchers! As the week opens, we're treated to several lovely views of the waning Moon and the bright winter objects just before dawn. Early evening dark skies mean an opportunity to galaxy hunt and study planetary nebulae. Mark your calendar to enjoy a weekend meteor shower, too! It's time to dust off the scopes and head out, because…
Here's what's up!
Monday, September 18 – Why not step outside this morning before leaving for work? If it's before the dawn, you'll be rewarded as Saturn and the Moon make a lovely pre-dawn picture.
Tonight we're heading north for a galaxy and cluster pairing – NGC 6946 and NGC 6939. Located in western Cepheus, you'll find them about a finger-width southwest of Eta.
Discovered by William Herschel on September 9th, 1798, 10 million light-year distant face-on spiral NGC 6946 spreads itself pretty thin in modest instruments. Lacking a bright core, this oval mist orients southwest to northeast. Larger telescopes will reveal traces of spiral arms – especially rotating southwest. This galaxy would appear extraordinary if we weren't looking though Milky Way obscuration to view it!
Through smaller scopes, northwestern open cluster NGC 6939 appears like a tight little formation of 11th and 12th magnitude stars similar in pattern to a very small M11. It is well resolved in larger scopes.
Tuesday, September 19 – If you're up early this morning, be sure to look at the Moon with bright Regulus nearby. On this day in 1848, William Boyd was observing Saturn and discovered the planet's eighth moon – Hyperion. Since you're up, have a look at the Saturn. Large telescopes can reveal 14.0 magnitude Hyperion, and even a small scope can observe Tethys, Dione, and Rhea.
Tonight's dark sky provides a superb opportunity to trace the expanse of the Milky Way from the tail of the Scorpion through distant Perseus, but start early to make the most of it. Whether by eye, binocular, rich field refractor or dobsonian reflector, take the time to wander and wonder!
Begin southwest and see if you can spot "X" the core of our galaxy. Now trace the trail past the Small Sagittarian Star Cloud (M24) then off to the larger Scutum Star Cloud. Continuing northeast, look for the Cygnus rift – a dark lane that is also known as Barnard 186. Continue through Lacerta and into southern Cepheus and on to bright and easily recognized Cassiopeia… and finally distant Perseus on the far side of the dome of the sky. Amazing, isn't it?
Now with binoculars – or rich field refractor – repeat the same journey. How many old friends of the night sky can you recognize by sight?
Wednesday, September 20 – On this night in 1948, the 48" Schmidt telescope at Mt. Palomar was busy making its first photographic plate of a distant galaxy. The astrophotographer was the same man who had ground and polished the scope's massive corrector plate, Don Hendricks. Tonight we'll join his vision as we take a return look at the fantastic M31 – The Great Andromeda Galaxy.
Seasoned amateurs can easily point out the 2.9 million year-old gauzy light of M31. But, perhaps you've never tried. Believe it or not, this is one easy galaxy to see even without a telescope! Look overhead, can you clearly see the five stars making up tiny Delphinus? If so, look east-northeast to the diamond-shaped pattern of even brighter stars that stretches a hand span across the sky. This is the "Great Square of Pegasus." The northeasternmost star of the Great Square is Alpheratz, and from that star we start our hop. Stay with the bright chain of stars that extend east-northeast from Alpheratz and look four finger-widths away for bright Beta Andromedae. Next along that chain is three finger-width distant, brighter Mirach. Now head two more finger-widths north past fainter Mu to see an even dimmer star – Nu. Look for a faint smudge nearby. This is no cloud – it's the Great Andromeda Galaxy! And you didn't even need a telescope…
Now get out those binoculars and enjoy one of the finest, largest, and brightest galaxies in the sky!
Thursday, September 21 – This morning before dawn, look for one of the most inspiring events you may ever witness – the Moon occulting Venus. For some viewers, this may only be a close conjunction, so please check IOTA for details specific to your area.
One of the most interesting features of the autumn sky is how slowly the stars and constellations seem to proceed across the heavens. This is an illusion after summer solstice in the northern hemisphere because skydark arrives earlier each night, making the progress of the constellations across the sky seem to "freeze." Tonight Capella can be seen just rising to the northeast while Antares settles southwest. Four planets – Jupiter, Pluto, Neptune, and Uranus are still above the horizon – with Jupiter now very low to the west-southwest. Descending to the northwest is Ursa Major, the "Big Dipper." Across the sky is Piscis Austrinus and lonely, but bright, Fomalhaut beginning its rise. Seven stars of the first magnitude now grace the heavens. Against this backdrop, one of the darkest skies of the month is now upon us.
Let's have a look at another fine planetary nebula – NGC 7662. At 9.0 magnitude, this one is more commonly known as the "Blue Snowball" and can be found about three finger-widths east of Omicron Andromedae, or a little less than a hand span northwest of Alpha Pegasi. Similar in size to M57, even low power with a small scope easily reveals the planetary nature of this very fine study. Power up and you'll discover that the annulus of this roughly circular planetary is definitely brighter inside than out. Large telescopes will highlight NGC 7662's blue coloration and reveal a bright inner globe surrounded by faint outer ring!
Friday, September 22 – Today the place to be is Suriname or French Guyana for an annular eclipse of the Sun. But take heart if you live in western Africa or eastern South America, for you will still be treated to a partial. Please check the webpages of "Mr. Eclipse" – Fred Espenak – for details on times and locations. For the rest of us? It's New Moon! Tonight's destination starts out easy – but gets tougher. Head for Eta Pegasi and slightly more than 4 degrees north-northeast for NGC 7331.
This beautiful, 10th magnitude, tilted spiral galaxy is very much how our own Milky Way would appear if we could travel 50 million light-years away and look back. Very similar in structure both to ourselves and the "Great Andromeda," this particular galaxy gains more and more interest as scope size increases – yet it can be spotted with larger binoculars. At around 8" in aperture, a bright core appears and the beginnings of wispy arms. In the 10" to 12" range, spiral patterns begin to emerge and with good seeing conditions, you can see "patchiness" in structure as nebulous areas are revealed, and the western half is deeply outlined with a dark dustlane. But hang on…because the best is yet to come!
Return to NGC 7331 with all the aperture you have. What we are about to look at is truly a challenge and requires dark skies, optimal position and excellent conditions. Now breathe the scope about one half a degree south-southwest and behold one of the most famous galaxy clusters in the night.
In 1877, French astronomer – Edouard Stephan was using the first telescope designed with a reflection coated mirror when he discovered something a bit more with NGC 7331. He found a group of nearby galaxies! This faint gathering of five is better known as "Stephan's Quintet" and its members are no further apart than the diameter of our own Milky Way galaxy.
Visually in a large scope, these members are all rather faint, but their proximity is what makes them such a curiosity. The Quintet is made up of five galaxies numbered NGC 7317, 7318A, 7318B, 7319 and the largest, 7320. Even with a 12.5" telescope, this author has never seen them as much more than tiny, barely there objects that look like ghosts of rice grains on a dinner plate.
So why bother?
What our backyard equipment can never reveal is what else exists within this area – more than 100 star clusters and several dwarf galaxies. Some 100 million years ago, two of the galaxies collided and left long streamers of their materials which created star forming regions of their own, and this tidal pull keeps them connected. The stars within the galaxies themselves are nearly a billion years old, but between them lay much younger ones. Although we cannot see them, you can make out the soft sheen of the galactic nuclei of our interacting group.
Enjoy their faint mystery!
Saturday, September 23 – On this day in 1846, Johann Galle of the Berlin Observatory added an eighth planet to the solar system's number. While at the eyepiece, Galle identified the planet Neptune and – for the first time in history – mathematics played a role in a planet's discovery. Would you like to try for Neptune? The planet now resides a little more than a degree northwest of 4.3 magnitude Iota Capricorni.
On this day in 1962, the prime time cartoon "The Jetsons" premiered. Think of all the technology this inspired as tonight we relax and watch the Alpha Aurigid meteor shower. Face northeast and look for the radiant near Capella. The fall rate is around 12 per hour. They are fast and leave persistent trails.
If you have binoculars or scope out tonight, then have a go at NGC 7686 two finger-widths north of Lambda Andromedae. At 5.6 magnitude, this large open cluster contains about three dozen mixed magnitude stars, with a brighter non-member in the foreground.
Sunday, September 24 – On this day in 1970, the first unmanned, automated return of lunar material to the Earth occurred when the Soviet's Luna 16 returned with three ounces of another world.
Tonight's skies remain dark, so let's take this opportunity to have a look at two objects from one of the more obscure catalogs…
Set your sights on Alpha Pegasi and drop due south less than 5 degrees to pick up NGC 7479. Discovered by William Herschel in 1784, this 11.0 magnitude barred spiral galaxy experienced a supernova as recently as 1990. While the 16th magnitude event near its nucleus is no longer visible, modest telescopes will easily pick out the bright core and elongation of the central bar. Larger aperture will find this one a real treat as the spiral arms curl over and under the central structure, resembling a ballet dancer en pointe. Congratulations! You've just observed Caldwell 44.
NGC 7814 is easy enough to find. Start at Gamma Pegasi and use the finderscope to center on a star around 3 degrees northwest. In the scope, look southeast to see NGC 7814 as a scratch of light in the low power field. Magnify and enjoy! This galaxy has a deeply concentrated nucleus and a very prominent dissecting dark dustlane. This one is also known by another name…Caldwell 43.
May all your journeys be at light speed… ~Tammy Plotner with Jeff Barbour.
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