Friday, December 2, 2011

Weekly SkyWatcher's Forecast - December 3-9, 2011

Written by Tammy Plotner

Friday, December 3 - Today in 1971, the Soviet Mars 3 became the first spacecraft to make a soft landing on the red planet, and two years later on this same date the Pioneer 10 mission became the first spacecraft to fly by Jupiter. One year later on this same date? Pioneer 11 did the same thing!

Tonight is a wonderful chance for binoculars and small telescopes to study the Moon. Craters Aristotle and Eudoxus to the north will be easily apparent, along with the Caucasus and Apennine mountain range. Are you looking for a slight telescopic lunar challenge? Then 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 the lighting conditions will be just right to explore its 1.6 km to 20.9 km (1-13 mile) wide and 177 km (110 mile) long expanse.

Now let's familiarize ourselves with the vague constellation of Fornax. Its three brightest stars form a shallow V just south of the Cetus/Eridanus border and span less than a handwidth of sky. Although it's on the low side for northern observers, there is a wealth of sky objects in this area.

Try having a look at the easternmost star - 40-light-year distant Alpha. At magnitude 4, it is not easy, but what you'll find there is quite beautiful. For binoculars, you'll see a delightful cluster of stars around this long-term binary - but telescopes will enjoy it as a great golden double star! First measured by John Herschel in 1835, the distance between the pair has narrowed and widened over the last 172 years and it is suspected its orbital period may be 314 years. While the 7th magnitude secondary can be spotted with a small scope - watch out - because it may also be a variable which drops by as much as a full magnitude!

Saturday, December 4 - Today in 1978, the Pioneer/Venus Orbiter became the first spacecraft to orbit Venus. And in 1996, the Mars Pathfinder mission was launched!

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 km (75 mile) long, 366 meter (1200 ft.) high feature slopes upward with the steepest angle on the lunar surface at 41 degrees. It will be a challenge under these lighting conditions, but look for 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.

A star for all seasons is Polaris. Take the opportunity to see what magnification gives the best view of its 8.9 magnitude companion. This one can be tough for small scopes during Full Moon, so try for the right magnification to balance things like sky contrast and image scale. This teaches lots of lessons that really make a difference in resolving even more desperate disparates!

Sunday, December 5 - Let’s begin this evening with some lunar exploration as crater Copernicus becomes visible to even the most modest of optical aids. Small binoculars will see Copernicus as a bright “ring” about midway along the lunar dividing line of light and dark called the “terminator”. Telescopes will reveal its 97 km (60 mile) expanse and 120 meter (1200 ft.) central peak to perfection. Copernicus holds special appeal as it’s the aftermath of a huge meteoric impact! At 3800 meters (12,600 feet) deep, its walls are around 22 km (14 miles) thick and over the next few days, the impact ray system extending from this tremendous crater will become wonderfully apparent.

Now let’s have a look at a splendid set of colors – 1 Arietis. Because this pair is faint, you will need to apply “stellar geometry” to track it down. To find it, start with Alpha and Beta and form a right triangle whose third point is less than a finger-width northwest of Beta. Center the scope at moderate powers on that locale, then use the finder to pick out the nearest 6th magnitude star – 1 Arietis. Look for a 7.8 magnitude green companion south-southeast of the 5.8 magnitude white primary.

Monday, December 6 - It’s a “Moon Gazer’s” night as our nearest astronomical neighbor continues to light up the night sky. Even from 383,000 km (238,000 miles) away! Don’t put away your telescopes and binoculars thinking there will be nothing to view, because one of the most “romantic” features on the lunar surface will be highlighted tonight.

The Sinus Iridium is one of the most fascinating and calming areas on the Moon. At around 241 km (150 miles) in diameter and ringed by the Juras Mountains, it’s known as the quiet name of “The Bay of Rainbows” but was formed by a cataclysm. Science speculates that a minor planet around 201 km (125 miles) in diameter once impacted our forming Moon with a glancing strike and the result of that impact caused “waves” of material to wash up to a “shoreline” forming this delightful C-shaped lunar feature. The effect of looking at a bay is stunning as the smooth inner sands show soft waves called “rilles”, broken only by a few small, impact craters. The picture is complete as Promentoriums Heraclides and LaPlace tower above the surface at 1800 meters (5900 ft.) and 3000 meters (9900 feet) respectively and appear as distant “lighthouses” set on either tip of Sinus Iridum’s opening.

For northern observers clamoring for brighter stellar action, look no further tonight than the incredible "Double Cluster" about four fingerwidths southeast of Delta Cassiopeiae. At a dark sky site, this incredible pair is easily located visually and stunning in any size binoculars and telescopes.

As part of the constellation of Perseus, this double delight is around 7000 light-years away and less than 100 light-years separates the pair. While open clusters in this area are not really a rarity, what makes the "Double Cluster" so inviting is the large amount of bright stars within each of them. Well known since the very beginnings of astronomy, take the time to have a close look at both Chi (NGC 884) and H Persei very carefully. Note how many colorful stars you see, and the vast array of double, multiple and variable systems!

Tuesday, December 7 - Today is the birthday of Gerard Kuiper. Born 1905, Kuiper was a Dutch-born American planetary scientist who discovered moons of both Uranus and Neptune. He was the first to know that Titan had an atmosphere, and he studied the origins of comets and the solar system.

Take the time tonight to once again return to the Moon and explore with binoculars or telescopes the area to the south around another easy and delightful lunar feature, the crater Gassendi. At around 110 km (70 miles) in diameter and 2010 meters (6600 feet) deep, this ancient crater contains a triple mountain peak in its center. As one of the most “perfect circles” on the Moon, the south wall of Gassendi has been eroded by lava flows over a 48 km (30 mile) expanse and offers a great amount of details to telescopic observers on its ridge and rille covered floor. For those observing with binoculars? Gassendi’s bright ring stands on the north shore of Mare Humorum… An area about the size of the state of Arkansas!

Wednesday, December 8 - Today in history (1908) marks "first light" for the 60" Hale Telescope at Mt. Wilson Observatory. Not only was it the largest telescope of the time, but it ended up being one of the most productive of all. Almost 100 years later, the 60" Hale is still in service as a public outreach instrument.

The waxing Moon will dominate the early evening skies, but tonight is an excellent opportunity for binoculars and telescopes to explore crater Tycho. Named for Danish astronomer, Tycho Brahe, this fantastic impact crater will be very impressive in even the most modest of optical aids. Spanning 85 km (56 miles), this lunar feature is very prominent and unmistakable in the southern hemisphere of the Moon. Tycho’s highly conspicuous ray systems support its impact crater theory and span hundreds of kilometers across the lunar surface. Tycho is also one of the youngest of the major features at an astounding age of only 50 million years old!

On January 9, 1968 Surveyor 7 (the last lunar robot of its kind) landed quietly on Tycho’s slopes at sunrise. Because previous Surveyor missions had provided the Apollo program with all the data necessary to their goals, Surveyor 7′s presence was scientific only. Two weeks later, when the Sun set on the landing site, Surveyor 7 had provided over 21,000 photographs, determined physical and chemical properties associated with the Southern Highland area and recorded the laser beams aimed toward it from two separate Earth observatories.

Thursday, December 9 - Southern Hemisphere viewers, you're in luck for a meteor shower. This is the maximum of the Puppid-Velid meteor shower. With an average fall rate of about 10 per hour, this particular meteor shower could also be visible to those far enough south to see the constellation of Puppis. Very little is known about this shower except that the streams and radiants are very tightly bound together. Since studies of the Puppid-Velids are just beginning, why not take the opportunity to watch? Viewing will be possible all night long and although most of the meteors are faint, this one is known to produce an occasional fireball.

Tonight the very gibbous Moon will command the skies and give unaided observers an opportunity to use their imaginations. Since the dawn of mankind, we have been gazing at the Moon and seeing fanciful shapes in the lunar features. Tonight as the Moon rises is your chance to catch “The Rabbit In The Moon”. The “Rabbit” is a compilation of all the dark maria. The Oceanus Procellarum forms the “ear” while the Mare Humorum makes the “nose”. The “body” is Mare Ibrium and the “front legs” appear to be Mare Nubium. Mare Serentatis is the “backside” and the picture is complete where Mare Tranquilitatus and Mare Fecunditatis shape the “hind legs” with Crisium as the “tail”.

See the Moon with an open mind and open eyes — and find the “Rabbit”!

For telescopes and binoculars, the lunar surface will provide a bright but superior view of crater Grimaldi. Named for Italian physicist and astronomer, Francesco Grimaldi, this deep grey oval is one of the darkest albedo features on the Moon – only reflecting about 6% of the light. Approximately 430 km (140-145 miles) long, it’s easy to spot along the terminator and just slightly south of the center of the lunar limb. Tonight is the best time to view its mountained walls, for they will disappear and Grimaldi will take on the appearance of a small mare in the light of the full Moon.

Until next week, may all your journeys be at light speed! ~Tammy

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