Sunday, January 29, 2012

Weekly SkyWatcher's Forecast - January 29-February 4, 2012

Greetings, fellow SkyWatchers! There's plenty of Moon to study this week, so grab your telescopes and binoculars and let's blast off and learn!

Sunday, January 29 - Tonight let's head towards the Moon and the southern quadrant and explore "The Sea of Nectar"...

At around 1000 meters deep, Mare Nectaris covers an area of the Moon equal to that of the Great Sandhills in Saskatchewan, Canada. Like all maria, it is part of a gigantic basin which is filled with lava, and there is evidence of grabens along the western edge of the basin. While Nectaris' basaltic flows appear darker than those in most maria, it is one of the older formations on the Moon, and as the terminator progresses you'll be able to see where ejecta belonging to Tycho crosses its surface. For a real challenge, look for an ancient and ruined crater which lies on the southern shore of Mare Nectaris. To binoculars, Fracastorius will look like a shallow, light colored ring, but a telescope will reveal its northern wall is missing - perhaps melted away by the lava flow which formed the mare. This is all that remains of a once grand crater which was more than 117 kilometers in diameter. The tallest of its eroded walls still stand at an impressive 1758 meters, placing them as high as the base elevation of Mt. Hood, yet in places nothing more than a few ridges and low hills still stand to mark the crater's remains. Power up and look for interior craterlets. Be sure to mark your lunar observing challenge notes with your observations!

Now, take a look at Mars. While it’s been on the move, it has also been dimming slightly. Right now it’s around magnitude +0.5. Be sure to check out surface details and enjoy fine points like the polar caps.

Monday, January 30 - We'll begin our lunar studies tonight by exploring the edges of a feature that's about the same size as the state of New Mexico - Mare Serenitatus. On its southwest border stand the Haemus Mountains - which will continue on beyond the terminator. Look in their midst for the sharp punctuation of Class I Menelaus. This small crater has a brilliant west inner wall and deeply shadowed floor. Menelaus is fine crater to watch for expansive ray systems as the terminator progresses. While the Montes Haemus look pretty impressive, they are foothills compared to the Apennines which have yet to emerge. Look at Serenitatus' northwest edge to view some real mountains. These are the Montes Caucasus, rising up to 17,000 feet above the plains. Look closely at the maps and you will find that near these mountain ranges are the homes of the Apollo 11, Apollo 15, Apollo 16 and Apollo 17 landers, as well as Luna 21. It is an area that you can deeply appreciate for its historical significance. Like its earthly counterpart, the Caucasus Mountain Range has peaks that reach upwards of six kilometers - summits as high as Mount Elbrus! Nearby and slightly smaller than its terrestrial namesake, the lunar Apennine mountain range extends some 600 kilometers with peaks rising as high as five kilometers. Be sure to look for Mons Hadley, one of the tallest peaks you will see at the northern end of this chain. It rises above the surface to a height of 4.6 kilometers, making that single mountain about the size of asteroid Toutatis.

Tuesday, January 31 - Today in 1961, Mercury Redstone 2 launched, carrying Ham the chimpanzee into a suborbital flight and to fame. In 1966, Luna 9 was launched. In 1958, the first US satellite - Explorer 1 - was launched and met a milestone as it proved the Earth was surrounded by intense bands of radiation which we now refer to as the Van Allen Belts.

In 1971 Apollo 14 was headed towards the Moon - and so are we as we take a look at the lunar poles by returning to previous study crater Plato. North of Plato you will see a long horizontal area of grey floor - Mare Frigoris - the "Cold Sea." North of it you will note a "double crater." This elongated diamond-shape is Goldschmidt, and the crater which cuts across its western border is Anaxagoras. The lunar north pole isn't far from Goldschmidt, and since Anaxagoras is just about one degree outside of the Moon's theoretical "arctic" area, the lunar sunrise will never go high enough to clear the southernmost rim. As proposed with yesterday's study, this "permanent darkness" must mean there is ice! For that very reason, NASA's Lunar Prospector probe was sent to explore here. Did it find what it was looking for? Answer - Yes. The probe discovered vast quantities of cometary ice which has hidden inside the crater's depths untouched for millions of years. If this sounds rather boring to you, then realize this type of resource may aid our plans to eventually establish a manned base on the lunar surface.

In 1862, Alvan Graham Clark, Jr. was at the eyepiece and made an unusual discovery. While watching Sirius, Clark uncovered the intense star's faint companion while testing an 18 inch refractor being built at Dearborn Observatory. The scope itself was built by Clark, his father and his brother. Imagine his excitement when it turned up the white dwarf - Sirius B! Friedrich Bessel had proposed its existence back in 1844, but this is the first time it was confirmed visually.

Why not try your own hand at turning up this difficult double star? If you have problems finding the companion, don't worry. Back in 1948, the first test photos using the Hale 5-meter (200-inch) telescope at Mt. Palomar were being taken. Believe it or not, problems with the configuration and mounting of the mirror meant that it was almost 2 years later before the first observing run was made by a scheduled astronomer!

Wednesday, February 1 - Let's begin our lunar studies tonight with a deeper look at the "Sea of Rains." Our mission is to explore the disclosure of Mare Imbrium, home to Apollo 15. Stretching out 1123 kilometers over the Moon's northwest quadrant, Imbrium was formed around 38 million years ago when a huge object impacted the lunar surface creating a gigantic basin. The basin itself is surrounded by three concentric rings of mountains. The most distant ring reaches a diameter of 1300 kilometers and involves the Montes Carpatus to the south, the Montes Apenninus southwest, and the Caucasus to the east. The central ring is formed by the Montes Alpes, and the innermost has long been lost except for a few low hills which still show their 600 kilometer diameter pattern through the eons of lava flow. Originally the impact basin was believed to be as much as 100 kilometers deep. So devastating was the event that a Moon-wide series of fault lines appeared as the massive strike shattered the lunar lithosphere. Imbrium is also home to a huge mascon, and images of the far side show areas opposite the basin where seismic waves traveled through the interior and shaped its landscape. The floor of the basin rebounded from the cataclysm and filled in to a depth of around 12 kilometers. Over time, lava flow and regolith added another five kilometers of material, yet evidence remains of the ejecta which was flung more than 800 kilometers away, carving long runnels through the landscape.

Thursday, February 2 - We start tonight's lunar tour with a northern landmark that can even be spotted with unaided vision - Plato. Located in the northern hemisphere of the Moon, its dark ellipse is unmistakable. Plato's floor consists of 2700 square miles of lava fill and is considered by some observers as the darkest single low-albedo feature on the Moon. Because of its low reflectivity, this crater has the distinction of being one of the only mountain-walled plains that doesn't "disappear" as the Moon grows full. With Plato in the center of the field note the pyramid-like peak of Pico due south in northeastern Mare Imbrium. East of Pico is an unnamed dorsum - or lava wave - terminating just above crater Piazzi Smyth to the south. Power up in a telescope and check out the triangular peak near its end.

Now let's go to the lunar surface to have a look through binoculars or telescopes at tremendous impact region located to the lunar west of Plato. Sinus Iridum is one of the most fascinating and calming areas on the Moon. At around 241 kilometers in diameter and ringed by the Juras Mountains, it's known by the quiet name of the Bay of Rainbows, but was formed by a cataclysm. Astronomers speculate that a minor planet around 200 kilometers in diameter impacted our forming Moon at a glancing angle, and the result of the impact caused "waves" of material to wash up to a "shoreline," forming this delightful C-shaped lunar feature. The impression of looking at an earthly bay is stunning as the smooth inner sands show soft waves called "rilles," broken only by a few small impact craters. The picture is completed by Promontoriums Heraclides and LaPlace, which tower above the surface, at 1800 meters and 3000 meters respectively, and appear as distant "lighthouses" set on either tip of Sinus Iridum's opening. For a great telescopic challenge, imagine that Sinus Iridum is a mirror focusing light - this will lead your eye to crater Helicon. The slightly smaller crater southeast of Helicon is Leverrier. Be sure to power up to capture the splendid north-south oriented “wave -like” ridge which flows lunar east. Enjoy this serene lunar feature ...

Friday, February 3 - Tonight we celebrate the success of Luna 9, also known as Lunik 9. On this day in 1966, the unmanned Soviet lunar probe became the first to achieve a soft landing on the Moon's surface and successfully transmit photographs back to Earth. The lander weighed in at 99 kg, and the four petals, which formed the spacecraft, opened outward. Within five minutes of landing, antennae sprang to life and the television cameras began broadcasting back the first panoramic images of the surface of another world, proving that a landing would not simply sink into the lunar dust. Last contact with the spacecraft occurred just before midnight on February 6, 1966.

Tonight you can view the area of the first successful landing on the Moon as you turn your scopes towards Oceanus Procellarum - the Ocean of Storms. While the area will be brightly lit and it will be difficult to pick out small features, Procellarum is the long, dark expanse that runs from lunar north to south. On its western edge, about one quarter the length from lunar north to south is where you would find the remains of Luna 9. While no earthly-bound telescope could ever hope to achieve resolution of mission remains, it is still a wonderful way to improve your skills and enjoy a bit of history at the same time. Now, let’s talk about Oceanus Procellarum…

Encompassing most of the northwest quadrant and stretching across 2,102,000 square kilometers of area, it rivals the Bering Sea in sheer size. No wonder it was considered an ocean! Created by lava floods, but never contained within an impact basin, it's similar to Earth's Siberian Traps great upwellings of lava from our shared primeval history. Formed in the Imbrian geological period, it could be anywhere from 3 billion to 4 billion years old. Oceanus Procellarum's name could refer to its vivid volcanic past, but there is a story behind the name "Ocean des TempUtes"... It originated from a myth claiming stormy weather ahead if it was visible during the second quarter. While the Moon doesn't play a role in our Earthly weather, what could cause such a myth to arise? Factually, if skies are clear enough to see the Ocean of Storms during the night, they'll allow heat to escape directly into our upper atmosphere. Rising air can cause clouds to form. Water vapor molecules cool and begin coalescing faster than they can be scattered by thermal energy condensing and forming clouds where only one of two things can happen. Water molecules will either evaporate, changing back into vapor, or join to grow liquid drops whose critical mass will fall back to Earth as either rain or snow. Tempestuous weather? Perhaps...

Saturday, February 4 - Today is the birthday of Clyde Tombaugh. Born in 1906, Tombaugh was the discoverer of Pluto and it happened 24 years and two weeks after his birth.

Tonight our lunar studies take us back to the Oceanus Procellarum and landmark crater Kepler. To the north you will see equally bright Aristarchus - quite probably one of the youngest of the prominent features at around 50 million years old. It's hard to miss the blinding beacon of Aristarchus! Its albedo is double that of other lunar features and it is so dazzling that it can usually be spotted with the unaided eye and quite frequently with binoculars during earthshine. Power up in the telescope and take a look around the southeastern edge for the Aristarchus plateau - an elevated area that contains a number of volcanic features, such as sinuous rilles. This is also home to other lunar transient phenomena, and even Lunar Prospector measured radon gas emissions from this area. Watch Aristarchus as the Moon grows full, because it will also develop a ray system.

Now, grab your telescope and look west of Aristarchus for less prominent crater Herodotus. Just to the north you will see a fine white thread known as Vallis Schroteri—or Schroter's Valley. Winding its way across the Aristarchus plain, this feature is about 160 kilometers long, from 3 to 8 kilometers wide, and about 1 kilometer deep - but what is it? Schroter's Valley a prime example of a collapsed lava tube—created when molten rock flowed over the surface. This may have been from a major meteor strike, such as the formation of Aristarchus crater, or early volcanic activity. What is left is a long, narrow cave on the surface which only shows well when the lighting is correct. Like many sinuous rilles covering the surface, collapse has occurred. If intact tubes can be found on the lunar surface they could conceivably provide shelter for future settlers!

Before you call it a night, it’s time to note Mars’ position. It’s starting to begin retrograde motion, moving slowly each night out of Virgo and back into the constellation of Leo.

Written by Tammy Plotner. If you'd like to know what's happening all year, then check out the book The Night Sky Companion 2012.

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