Friday, November 25, 2011

Weekly SkyWatcher's Forecast - November 26 - December 2, 2011

Written by Tammy Plotner

Friday, November 26 - Today in 1965 marked the launch of the first French satellite - Asterix 1. Today is also the seventh anniversary of the discovery of the meteorites SAU 005 & 008: the "Mars Meteorites." These meteorites are known to be of Martian origin because of gases preserved in the glassy material of their interior. They were hurled into space some 600,000 years ago when a probable asteroid impact on Mars tossed them high enough to escape the planet's gravity, and they were captured by our gravity these many thousands of years later. They are just two of the 32 meteorites found on Earth which have been positively determined from their chemical compositions to be of Martian origin.

Tonight let's return again to Cassiopeia and start at the central-most bright star, Gamma. Four degrees southeast is our marker for this starhop, Phi Cassiopeiae. By aiming binoculars or telescopes at this star, it is very easy to locate an interesting open cluster, NGC 457, because they will be in the same field of view.
This bright and splendid galactic cluster has received a variety of names over the years because of its uncanny resemblance to a figure. Some call it an "Angel," others see it as the "Zuni Thunderbird;" I've heard it called the "Owl" and the "Dragonfly," but perhaps my favorite is the "E.T. Cluster," As you view it, you can see why! Bright Phi and HD 7902 appear like "eyes" in the dark and the dozens of stars that make up the "body" appear like outstretched "arms" or "wings." (For E.T. fans? Check out the red "heart" in the center.)

All this is very fanciful, but what is NGC 457, really? Both Phi and HD 7902 may not be true members of the cluster. If 5th magnitude Phi were actually part of this grouping, it would have to have a distance of approximately 9300 light-years, making it the most luminous star in the sky, far outshining even Rigel! To get a rough of idea of what that means, if we were to view our own Sun from this far away, it would be no more than magnitude 17.5. The fainter members of NGC 457 comprise a relatively young star cluster that spans about 30 light-years. Most of the stars are only about 10 million years old, yet there is an 8.6 magnitude red supergiant in the center. No matter what you call it, NGC 457 is an entertaining and bright cluster that you will find yourself returning to again and again. Enjoy!

Saturday, November 27 - Tonight let's take advantage of early dark and venture further into Cassiopeia. Returning to Gamma, we will move towards the southeast and identify Delta. Also known as Ruchbah, this long-term and very slight variable star is about 45 light-years away, but we are going to use it as our marker as we head just one degree northeast and discover M103. (And speaking of degrees, today is also the birthday of Anders Celsius - born in 1701.)

As the last object in the original Messier catalog, M103 (NGC 581) was actually credited to Mechain in 1781. Easily spotted in binoculars and small scopes, this rich open cluster is around magnitude 7, making it a prime study object. At about 8000 light-years away and spanning approximately 15 light-years, M103 offers up superb views in a variety of magnitudes and colors, with a notable red in the south and a pleasing yellow and blue double to the northwest.

Viewers with telescopes and larger binoculars are encouraged to move about a degree and half east of M103 to view a small and challenging chain of open clusters, NGCs 654, 663 and 659! Surprisingly larger than M103, NGC 663 is a lovely fan-shaped concentration of stars with about 15 or so members that resolve easily to smaller aperture. For the telescope, head north for NGC 654, (difficult, but not impossible to even a 114mm scope) which has a bright star on its southern border. South of NGC 663 is NGC 659 which is definitely a challenge for small scopes, but its presence will be revealed just northeast of two conspicuous stars in the field of view.

Sunday, November 28 - Tonight we'll start off with binoculars in the northeast quadrant of the Moon for a more detailed look at Mare Crisium - the "Sea of Crises" - home to a gravitational anomaly called a mascon. This "mass concentration" could possibly be fragments of the asteroid or comet whose impact with the lunar surface created the basin buried beneath the lava flow. How do we know it is there? A mascon creates an area of high gravity and causes changes in the orbits of lunar probes. This excess gravity has even been known to cause low orbiting lunar satellites to either crash land or be flung out into space!

Once again utilizing early darkness, let's go back to Cassiopeia. Remembering Alpha's position as the westernmost star, go there with your finderscope or binoculars and locate bright Sigma and Rho (each has a dimmer companion). They will appear to the southwest of Alpha. It is between these two stars that you will find NGC 7789 (RA 23 57 24.00 Dec +56 42 30.0).

Absolutely one of the finest of rich galactic opens bordering on a loose globular, NGC 7789 has a population of about 1000 stars and spans a mind-boggling 40 light-years. At well over a billion years old, the stars in this 5000 light-year distant galactic cluster have already evolved into red-giants or super-giants. Discovered by Caroline Herschel in the 18th century, this huge cloud of stars has an average magnitude of 10, making it a great large binocular object, a superb small telescope target, and a total fantasy of resolution for larger instruments.

Tonight in 1659, Christian Huygens was busy at the eyepiece - but he wasn't studying Saturn. This was the first time any astronomer had seen dark markings on Mars! And speaking of the planets, did you notice just how close Jupiter is to tonight’s Moon? Keep watching as the planet moves to the other side tomorrow night!

Monday, November 29 - Today in 1961, Mercury 5 launched Enos the Chimp into fame!

We begin our binocular and small telescope explorations tonight by looking near the center of the lunar terminator to identify and take a closer look at Mare Fecunditatis. Its expanse covers 1463 kilometers in diameter. The combined area of this mare is equal in size to the Great Sandy Desert in Australia—and almost as vacant in interior features. It is home to glasses, pyroxenes, feldspars, oxides, olivines, troilite and metals in its lunar soil, which is called regolith. Studies show the basaltic flow inside of the Fecunditatis basin perhaps occurred all at once, making its chemical composition different from other maria. The lower titanium content means it is between 3.1 and 3.6 billion years old. Stretching out across an area about equal in size to the state of California, the Sea of Fertility’s western edge is home to features we share terrestrially – grabens. These down-dropped areas of landscape between parallel fault lines occur where the crust is stretched to the breaking point. On Earth, these happen along tectonic plates, but on the Moon they are found around basins. The forces created by lava flow increase the weight inside the basin, causing a tension along the border which eventually fault and cause these areas. Look closely along the western shore of Fecunditatis where you will see many such graben features. They are also bordered by parallel fault lines and are quite similar to such terrestrial features as Death Valley in the western United States.

Now aim towards the earthen shore of Mare Fecunditatus and identify the flat, bright oval of a previous study, Langrenus. This is an opportunity to challenge yourself by identifying two small craters just slightly northwest of the mare’s central point – Messier and Messier A – named for the famous French comet hunter – Charles Messier. Scan along the terminator over Mare Fecunditatis about 1/3 its width from west to east for a pair of emerging bright rings. These twin craters will be difficult in binoculars, but not hard for even a small telescope and intermediate power. The easternmost crater is somewhat oval in shape with dimensions of 9 by 11 kilometers.

At high power, Messier A to the west appears to have overlapped a smaller crater during its formation and it is slightly larger at 11 by 13 kilometers. For a challenging telescopic note, you’ll find another point of interest to the northwest. Rima Messier is a long surface crack which runs diagonally across Mare Fecunditatis’ northwestern flank and reaches a length of 100 kilometers. Keep the Messiers in mind, for in a few days you will see a pair of “rays” extending out from them.

Now how about journeying with me once again to Cassiopeia? We will start our studies with the western-most of the bright stars - Beta. Also known as "Caph," Beta Cassiopeiae is approximately 45 light-years away and is known to be a rapid variable. Viewers with larger telescopes are challenged to find the 14th magnitude optical companion to Caph at about 23" in separation. Tonight, using our previous study stars Alpha and Beta, we are going to learn to locate a Messier object with ease! By drawing an imaginary line between Alpha and Beta, we extend that line the same distance and angle beyond Beta and find M52.

Found on September 7, 1774 by Charles Messier, this magnitude 7 galactic cluster is easily seen in both binoculars and small telescopes. Comprised of roughly 200 members, this open cluster is roughly 3,000 light-years distant and spans approximately 10-15 light-years. Containing stars of several different magnitudes, larger telescopes will easily perceive blue components as well as orange and yellow. Also known as NGC 7654, M52 is a young, very compressed cluster whose approximate age is about the same as the Pleiades.

For those with large telescopes wanting a challenge? Try spotting a faint patch of nebulosity just 36' to the southwest. This is NGC 7635, more commonly known as the "Bubble Nebula." Best of luck!

Tuesday, November 30 - Just as a curiosity, on this day in 1954, Elizabeth Hodges was struck by a five kilogram meteorite in Alabama. Duck!

On the lunar surface tonight, let’s begin with a look at Mare Serenitatus – the “Serene Sea”. On its northeast shore, binoculars will have no trouble spotting the shallow ring of crater Posidonius. Almost flat from eons of lava flows, this crater shows numerous variations in texture along its floor in small telescopes. This huge, old, mountain-walled plain is considered a class V crater and could be as much as 3 billion years old. Spanning 84 by 98 kilometers, you can plainly see Posidonius is shallow – dropping only 2590 meters below the surface. Tonight it will resemble a bright, elliptical pancake on the surface to smaller optics with its ring structure remaining conspicuous to binoculars throughout all lunar phases. However, a telescope is needed to appreciate the many fine features found on Posidonius’ floor. Power up to observe the stepped, stadium-like wall structure and numerous resolvable mountain peaks joining its small, central interior crater. It has its own interior rimae that is especially prominent to the east and a smashing view of trio Posidonius O, I and B on the north crater rim. Adding crater Chacornac to the southeast makes things even more interesting! Did you spot the small punctuation of Daniell to the north?

Now, look a bit south of and east of Posidonius and almost parallel to the terminator for a curious feature known as the Serpentine Ridge, or more properly as Dorsa Smirnov and the accompanying Dorsa Lister. Can you detect the very tiny crater Very in its center? This thin, white line wanders across the western portion of Mare Serenitatus for a distance of about 134 kilometers. In some places it rises as high as 305 meters above the smooth sands. This lunar “wrinkle” is an amazing 10 kilometers wide! Power up in a telescope. The northern portion of the Serpentine Ridge is Dorsa Smirnov until it branches west and becomes Dorsa Lister. If the shadow play is good at your time, you might be lucky enough to resolve Dorsum Nicol, which connects the two. Only about 51 kilometers long, Dorsum Nichol will appear almost as a circular, crater-like feature – but it isn’t. As part of the Mare Serenitatis / Mare Tranquilitatis border, it’s not much more than a just an area where the two distinct lava flows cooled and contracted, causing the surface to heave up, but you’ll also find it’s connected to the Rima Plinius as well.

Tonight when the Moon has sufficiently set, we will haunt Cassiopeia one last time - with studies for the seasoned observer. Our first challenge of the evening will be to return to Gamma where we will locate two patches of nebulosity in the same field of view. IC 59 and IC 63 are challenging because of the bright influence of the star, but by moving the star to the edge of the field of view you may be able to locate these two splendid small nebulae. If you do not have success with this pair, why not move on to Alpha? About one and a half degrees due east, you will find a small collection of finderscope stars that mark the area of NGC 281 (RA 00 52 25.10 Dec +56 33 54.0). This distinctive cloud of stars and ghostly nebulae make this NGC object a fine challenge!

The last things we will study are two small elliptical galaxies that are achievable in mid-sized scopes. Locate Omicron Cassiopeiae about 7 degrees north of M31 and discover a close galactic pair that is associated with the Andromeda group - NGC 185 (RA 00 38 57.40 Dec +48 20 14.4) and NGC 147 (RA 00 33 11.79 Dec +48 30 24.8).

The constellation of Cassiopeia contains many, many more fine star clusters, and nebulae - and even more galaxies. For the casual observer, simply tracing over the rich star fields with binoculars is a true pleasure, for there are many bright asterisms best enjoyed at low power. Scopists will return to "rock with the Queen" year after year for its many challenging treasures. Enjoy it tonight!

Wednesday, December 1 - Tonight on the lunar surface, all of Mare Serenitatis and Mare Tranquillitatis will be revealed, and so it is fitting we should take an even closer look at both the “Serene” and “Tranquil” seas. Formed some 38 million years ago, these two areas of the Moon have been home to most of mankind’s lunar exploration. Somewhere scattered on the basalt landscape on the western edge of Tranquillitatis, a few remains of the Ranger 6 mission lie tossed about, perhaps forming a small impact crater of their own. Its eyes were open, but blinded by a malfunction…forever seeing nothing. To the southwest edge lie the remnants of the successful Ranger 8 mission which sent back 7137 glorious images during the last 23 minutes of its life. Nearby, the intact Surveyor 5 withstood all odds and made space history by managing to perform an alpha particle spectrogram of the soil while withstanding temperatures considerably greater than the boiling point. Not only this, but it also took over 18,000 pictures!

Now let’s go to the southwest edge of Tranquillitatis and visit with the Apollo 11 landing area. Although we can never see the “Eagle” telescopically, we can find where it landed. For telescopes and binoculars the landing area will be found near the terminator along the southern edge of Mare Tranquillitatis. No scope? No problem. Find the dark round area on the lunar northeastern limb – Mare Crisium. Then locate the dark area below that – Mare Fecundatatis. Now look mid-way along the terminator for the dark area that is Mare Tranquillitatis. The bright point west where it joins Mare Nectaris further south is the target for the first men on the Moon. We were there! Telescopically, start tracing the western wall of Tranquillitatis and looking for the small circles of craters Sabine and Ritter which are easily revealed tonight.

Once located, switch to your highest magnification. Look in the smooth sands to the east to see a parallel line of three tiny craters. From west to east, these are Aldrin, Collins, and Armstrong – the only craters to be named for the living. It is here where Apollo 11 touched down, forever changing our perception of space exploration.

“That’s one small step for [a] man, one giant leap for mankind.”

Born today in 1811 was Benjamin (Don Benito) Wilson. He was the namesake of Mt. Wilson, California - home to what once were the largest telescopes in the world - the 60" Hale and the 100" Hooker. Later, three solar telescopes were added on the mountain - two of which are still in use - as well as the CHARA array and active interferometers. It was here that Edwin Hubble first realized the "nebulae" were distant galaxies and discovered Cepheid variables in them. As we approach the end of our SkyWatching year together, let us wait until the Moon sets and pretend the skies are still as dark as they were on Mt. Wilson as we aim our binoculars and telescopes towards one of the most elusive galaxies of all - M33.

Located about one-third the distance between Alpha Triangulum and Beta Andromedae (RA 01 33.9 Dec +30 39), this member of our Local Group was probably first seen by Hodierna, but was recovered independently by Messier some 110 years later. Right on the edge of visibility unaided, M33 spans about 4 full moon widths of sky, making it a beautiful binocular object and a prime view in a low power telescope.

Smaller than the Milky Way and the Andromeda Galaxy, the Triangulum galaxy is about average in size, but anything but average to study. So impressed was Herschel that he gave it its own designation of H V.17 after having cataloged one of its bright star forming regions as H III.150! In 1926, Hubble also studied M33 at Mt. Wilson with the Hooker telescope during his work with Cepheid variables. Larger telescopes often "can't see" M33 with good reason - it overfills the field of view - but what a view! Not only did Herschel discover a region much like our own Orion Nebula, but the entire galaxy contains many NGC and IC objects (even globular clusters) that can be seen with a larger scope.

Although M33 might be 3 million light-years away, tonight it's as close as your own dark sky site...

Thursday, December 2 - The Moon will dominate the early evening hours, but why not enjoy its features as we scan the terminator in binoculars to enjoy the Caucasus Mountains and outstanding craters Aristillus and Autolycus to the north. Just south of this outstanding pair is a rather curious dark area known as Palus Putredinus, or the “Rotten Swamp”. On September 13, 1959 European observers witnessed the impact of Lunik 2 in this area.

Today in 1934, the largest mirror in telescope history began its life as the blank for the 200" telescope was cast in Corning, NY. The 200" would play another important role as Edwin Hubble continued on at Palomar Observatory. Thanks to his work there, we now understand "Hubble's Law" - the expansion of the Universe. Tonight – when the Moon has sufficiently set - let us honor that great mind as we take a look at a galaxy that's receding from us - NGC 1300.

Located about a thumb's width north of Tau4 Eridani (RA 03 19.7 Dec -19 25), this is probably the most incredible barred spiral you will ever encounter. At magnitude 10, it will require at least a 4.5" telescope in northern latitudes, but can probably be spotted with binoculars in the far south.

At 75 million light-years away, NGC 1300's central bar alone is larger than the Milky Way, and this galaxy has been intensively studied because the manner of its formation was so similar that of to our own. Although it is so distant, it is seen face-on - allowing us a look at how this formation occurs without looking through the gas and dust which block our own central view. Enjoy this one's fantastic structure!

Image Credits: NGC 457 - Adam Block/NOAO/AURA/NSF, Serpentine Ridge - Peter Lloyd and "Lunar History" courtesy of Lunar Phase Pro. Thank you for sharing!

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