What's Up this Week: December 25 – December 31, 2006
Written by Fraser Cain
It's a holiday week and even the stars are celebrating! Are you ready to join me in the last week of the 2006 observing season? Then head out into the night, because…
Here's what's up!
Monday, December 25 – Wishing you all the very best for the holiday season! Like a present, Sir Isaac Newton was born this day in 1642. Newton invented his own mathematics (calculus) and used it to describe a huge amount of what we now consider modern physics. Even young children are aware of his simple laws of motion and gravity. It wasn't until the age of the Great Observatories that another physics genius, Einstein by name, came along and things changed again!
Did you get a new telescope or binoculars? Then let's head off towards the lunar surface as soon as the sky gets dark to turn up some very simple features. Beginning in the north, look for the deep grey oval of crater Endymion. As you move slowly south, note a small, shadowed grey patch marking Mare Struve where a series of craters begins. Moving toward the lunar south, these are Messala, Bernoulli, Geminus, and Cleomides. Do you see smaller craters Debes and Tralles caught on Cleomides' west? Now we've arrived at the isolated sea Mare Crisium. The two tiny dark ovals south of "the Sea of Crises" are Firmicus and Apollonius. Now for Mare Fecunditatis, with huge Langrenus and Vendelinus along its eastern shore. Can you spot the faded Petavius further south, with its central peak?
In keeping with the season, tonight's astronomical object is a celebration of both starlight and asterism. Located 10 degrees east of Betelgeuse, you'll have to wait until later for it to be seen to advantage – but that only means exploring a few other fine studies to keep you "looking up!"
There are a number of very fine dark sky studies present tonight. Using low power, start at Beta Ceti and look around three finger-widths north-northeast for a large 8th magnitude planetary nebula. Due to its size and brightness, NGC 246 can be found in binoculars, but its incomplete annulus is only detectable in large scopes. Most observers will see a large, pale, seemingly uniform, bubble of vaguely bluish light incorporating a pair of 11th magnitude stars.
Returning to Beta, drop south-southeast around four finger-widths to one of the finest galaxies in the night sky – NGC 253, the Sculptor Galaxy. At a combined magnitude of 7.1, this large, highly tilted, spindle-shaped galaxy is a delight in large scopes! Featuring a broad range of knots, voids, broken lanes, and spiral arms, use no more power than necessary to darken the background sky – then power up for the details. Discovered by Caroline Herschel on September 23, 1783, using a small reflector, this 10 million light-year distant galaxy is a real treat!
Now head slightly more than a fist width northeast of Betelguese to put you in the area for NGC 2264 – also known as "the Christmas Tree" cluster. This bright asterism of two dozen bright and 100 fainter stars is embroiled in a faint nebulosity visible only through very dark skies, but its delightful "Christmas Tree" shape, adorned with stars, can be seen through the smallest binoculars or telescopes. The very brightest of these stars, S Monoceros, is 5th magnitude and shows clearly in the finderscope as a double. Steady skies will reveal that the "star" at the top of our "tree" is also a visual double and home to the beautiful, dark "Cone Nebula." Many of the stars will also appear to have companions arrayed in faint hues of silver and gold.
This is one of many presents from the Cosmos!
Tuesday, December 26 – Tonight let's enjoy the serenity of the crescent Moon well above the western horizon. Tonight's challenge is an unusual series of craters known as the Rheita Valley. One-third the way up from the southern cusp, you will see on the terminator a group of three craters running north to south – Metius, Fabricus and Jannsen. From Metius, look northeast for a small crater with thick walls and small central peak. This is Rheita. Along Rheita's west wall is a long runnel cutting through the rugged terrain. This 230 mile long feature, with a 100 mile southern extension, looks as though it might have been the result of a series of impacts much older than Rheita itself. Note how each impact overlays the next – ending near southern crater Young.
Now head for 5.7 magnitude NGC 752 – easily found in finderscope or binoculars around three finger-widths south of Gamma Andromedae. Missed by Messier – but probably a discovery of Hodierna over 100 years earlier – William Herschel cataloged it September 21, 1786. Although bounded by a spiral of brighter stars to the north, the brightest actual members of this 1300 light-year distant and one billion year-old cluster are of the 9th magnitude – within reach of all equipment.
Wednesday, December 27 – Born today in 1571 was Johannes Kepler – astronomer and assistant to Tycho Brahe. Kepler used Brahe's copious notes of Mars' positions to formulate his three laws of planetary motion.
For telescope users, the Moon gives a wonderful opportunity to revisit ancient crater Posidonius. Its 84 kilometer by 98 kilometer expanse is easily seen in the most modest of optical instruments and it offers a wealth of detail in its eroded walls and 1768 meter high central peak. Be sure to continue southward from Posidonius to the edge of Mare Serenitatis to view the Apollo 17 landing area!
Now let's head towards M34 about halfway between Algol (Beta Persei) and Almach (Gamma Andromedae). No doubt about it, Giovanni Batista Hodierna discovered this large, 5.5 magnitude open cluster at least 110 years before Charles Messier recorded it on August 25th 1764. One look at the cluster explains why – this 80 plus member, 1400 light-year distant group is very compressed – even presenting a faint nebulous patch to the unaided eye on a good dark night. Through binoculars, its dozen bright members make it plain that you are seeing a cluster of stars. Look for numerous doubles in this curiously "cross-shaped" cluster – an area joined by numerous fainter arcs and groupings.
Thursday, December 28 – Today we celebrate the birth of Arthur S. Eddington. Born in 1882 – Eddington was a key theoretical astrophysicist who explained how stars form out of accretion disks. Eddington also coined the astronomical phrase "expanding universe" to describe the mutual recession of distant galaxies.
For moon watchers tonight, let's celebrate 35 years of space exploration as the Apollo 11 landing site becomes visible. For telescopes and binoculars the landing area will be found near the terminator at the southern edge of Mare Tranquillitatis. For those of you who like a real challenge, try spotting small craters Armstrong, Aldrin, and Collins just east of the easy craters Sabine and Ritter. No scope? No problem! Look at the Moon. The dark round area you see on the northeastern limb is Mare Crisium. The dark area below that is Mare Fecunditatis. Now look mid-way along the terminator for the dark area that is Mare Tranquillitatis. We were there…
Now we'll head further south telescopically to identify the unusually shaped crater Hypatia. Can you spot its rima on the southern shore of Tranquillitatis? Perhaps the bright pockmark of Moltke on its north edge will help. Hypatia sits on the northern shore of a rugged area known as Sinus Asperitatis. Do you see Alfraganus on the terminator? Follow the terrain to Theophilus and look west for Ibyn-Rushd with crater Kant to the northwest and the beautiful peak of Mons Penck to its east.
Unseen today, but of symbolic and aesthetic interest, is the fact that the planets, Jupiter, Mars, Mercury, Venus, Neptune, and Uranus are near alignment. Jupiter now precedes the Sun in rising by two hours and is found near Antares in Scorpio. Its rival, Mars, rises a little more than an hour later. Mercury roasts within six degrees of the Sun and cannot be seen without great care. Venus disappears about an hour after sunrise and at magnitude -3.9, should be visible unaided. Neptune sets less than 3 hours after the Sun and Uranus joins all the others 90 minutes later. All six planets now form very close to a right angle in space. Add Pluto now north of Mercury and that makes seven. Who's missing? Saturn still needs morning skies for best seeing conditions…and don't forget the Earth beneath your feet. That great rotating orb is about to complete another anthropocentric anniversary of revolution around everybody's favorite star – Sol!
Friday, December 29 – Tonight is a wonderful chance for binoculars and small telescopes to study the Moon. Craters Aristotle and Eudoxus to the north are easily apparent, along with the Caucasus and Apennine mountain ranges. For those seeking a bit of a telescopic challenge, look no further than the Valles Alpes. More commonly known as the "Alpine Valley" this deep gash cut across the northern surface will be easily visible and lighting conditions will be just right to explore its 1.6 to 21 kilometer wide and 177 kilometer long expanse. Using it as your guide, start at the western point and drop south along the Montes Alpes where you will see three bright peaks – Mons Blanc, Promontorium DeVille and Promontorium Agassiz. Can you see lonely Mons Piton in the grey sands of Mare Imbrium? Now look east for Astronomical League challenge Cassini with its interior A and B craters. Further southeast you'll spy small Theaetetus.
If you'd like to stay out a bit longer, then have a look at another fine double for moonlit nights – Eta Persei. Eta is challenge for smaller binoculars, because the faint secondary puts this one squarely into the class of small scope studies. Eta A is a K-type star appearing golden-yellow to the eye. Larger scopes will reveal the 8.5 magnitude secondary's A-type blue tint. The overall impression is of a widely disparate version of summer's famous Alberio! You'll find this one about a fist width northwest of Alpha Persei.
Saturday, December 30 – Be sure to take out your telescopes and have a look at the Moon tonight. One of the most sought-after and unusual features will be visible to small telescopes in the southern half of the Moon near the terminator – Rupes Recta. Also known as "The Straight Wall," this 130 kilometer long, 366 meter high feature slopes upward with the steepest angle on the lunar surface at 41 degrees. A challenge under these conditions, use triple ring craters Ptolemy, Alphonsus and Arzachel to guide you. The "Straight Wall" will appear as a very thin line stretching across the edge of Mare Nubium. Look for bright crater Birt along the west to help spot it.
Now let's go east and take a high power look at companion craters. Starting at the northern point of Rupes Recta, you'll find yourself at Promontorium Taenarium. Just to the west of the point is splendid Alpetragius with its huge central peak. To the southeast is Arzachel, which sports a similar size central peak along with rimae and interior craterlets. Southwest is small Thebit with a very formidable puncture on its west wall. Further south will bring you to eroded old Purbach. Note how the sands of time have made its western area much higher than the east. On its south wall lies Regiomontanus. See how many details you can find in this old crater!
For a really superb treat, let's go to Almach – the third and westernmost bright star in Andromeda. Gamma Andromedae is actually an exquisite double. At magnitude 4.8, its beautiful blue companion would make a fine addition to many of the fainter constellations in the night sky – but it took the presence of the deep golden magnitude 2.3 primary to make it the beauty we see tonight. This lovely colored pair is a "must" for any size telescope!
Sunday, December 31 – Today is the birthday of Robert G. Aitken. Born in 1864, Aitken was a prolific American observer who discovered and catalogued more than 3100 double and binary stars.
Before we head out to view the Moon, let's have a look at a fine triple star system – Iota Cassiopeiae. Iota is easily found by making a mental line between Delta and Epsilon – the two easternmost stars of the Cassiopeia "W." Now go northeast a little less than the same distance between them. Resolvable through small scopes, this splendid and disparate triple is close! Magnitude 7.6 Iota B is 2.6 arc seconds southwest of magnitude 4.7 Iota A. The more comfortably spaced 8.4 magnitude turquoise C star is found 7.1 arc seconds east-southeast of the primary. The colors are warm-yellow, aqua, and turquoise and it takes a steady night to separate that B star!
Before the year ends, let's journey one last time to the lunar surface on the south shore of Mare Nubium and look for ancient crater Pitatus. Although we have been here before, what may transpire as you view this area will be well worth your time. During lunar sunrise, a break between Pitatus and westward neighbor Hesiodus can cause a beautiful phenomenon known as the "Hesiodus Sunrise Ray." For a very brief moment, a shaft of sunlight will shine through this break and create an experience you will never forget.
And now we wish you a most Happy New Year and we'll see you tomorrow…
May all your journeys be at light speed… ~Tammy Plotner.
Filed under: What's Up
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