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The Sky This Month - November 2012

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Written by Gary Boyle on
Post Date: 
Tue, 2012/11/06

The Big “W”

In astronomical and mythological terms, the Queen of the night belongs to Cassiopeia. Locating the Queen is as simple as looking up on these cool November nights and finding the five suns that form the distinctive letter ‘W’. These stars range in brightness from magnitude 2.5 to 3.4 and are circumpolar, meaning the constellation can be found all year round from our location as it circles some thirty degrees from the North Star – Polaris. Cassiopeia is ranked twenty-fifth in area. Within the 598 square degrees of sky lay many Royal jewels in the form of open star clusters and even a very red carbon star.

Gamma Cassiopeia is a hot blue B class star whose surface temperate is around 25,000 Kelvin and has a luminosity of 70,000 times that of our Sun. Nicknamed Navi, Gamma Cassiopeia is slowly evaporating a couple of nearby gas clouds. These interstellar victims are catalogued IC 59 and IC 63 and are located twenty-one arc minutes from mean ‘ole Gamma. However these nebulae might be a challenge to observe visually.

Move your scope a little less than two degrees to the bright, scattered open cluster NGC 225. This great looking brightly scattered cluster is made up of about 20 stars and seems to have a bit of nebulosity embedded at in the middle which only shows up in photographs. NGC 225 is located 2,140 light years from us.

Next we move to the last star of the ‘W’ or Beta Cassiopeia. Going by its traditional name Caph, which is Arabic meaning the “palm”. Caph is a class F2 giant star burning at 6,700 Kelvin. It resides at 54 light years and possess a close companion that orbits every 27 days. Now move close to three degree of sky to another dense open cluster named NGC 7789.

This fine looking object has a magnitude ranking of 6.7 and lies 7,600 light years away. Other nick names are "The White Rose" Cluster or "Caroline's Rose". The great    Walter Scott Houston referred to NGC 7789 as: "one of those rare objects that is impressive in any size instrument." And he was so right on this one. Going on, Scotty described the view through a 16 inch scope as “the whole field is scattered with diamond dust.”

Once you have finished with The White Rose cluster, nudge your scope fifty arc minutes to Rho Cassiopeia. This giant G2 star has a very slow rotation rate in the order of once every two Earth years. In fact during the summer of 1946, Rho Cass suddenly dropped from 4th to 6th magnitude and altered its spectral class. Astronomers are not sure when, but the star will eventually undergo a supernova explosion.

Moving farther north near the border with Cepheus we find a wonderful pairing of an open cluster and a nebula all within the width of the full moon. First we locate M52 which was one of Charles Messier’s original discoveries back in 1774. The rich cluster lies some 5,000 light years away and measures about 19 light years in width. Astronomers estimate its age to be about 35 million years old. Just off to the side is NGC 7635, the Bubble Nebula. Measuring 6 light years wide, this cosmic bubble was formed by intense stellar winds by the hot young central star. Wide angle photography is needed to fully capture and enjoy these contrasting objects.

With simply your naked eye, stars for the most part, appear the colour white. This is far from the truth when a telescope is used. These distant suns come in an array of colour which helps depict the temperature they are burning at. For instance, blue ones burn extremely hot while the red ones are much cooler. Our Sun is a yellow star, burning at 5,800 Kelvin. The spectral class of stars helps classify these individual objects via temperature. With this in mind, hunt down the variable WZ Cassiopeia. This is a great example of a red carbon star.

Last month we looked a couple of comets what is sure to dazzle in a few months from now. Let us look at a present day spectacle. Comet 168P/Hergenrother had an outburst back in September and is now splitting apart. The comet's fragmentation event was initially detected on October 26 by a team of astronomers from the Remanzacco Observatory, using the Faulkes Telescope North in Haleakala, Hawaii. The comet is now well placed high in the sky above Pegasus and in Andromeda. Comet 168P is glowing between 9th and 10 magnitude and getting fainter. Will this comet have one more outburst as it recedes from us – who knows?

The Leonid meteor shower occurs on the 17th but with an hourly rate (ZHR) of only 15, there could be a long gap between sightings. The shower starts around 10 p.m. local time when the radiant (area where the meteors appear to ordinate) is above the eastern horizon. Jupiter is the lonely bright planet that is up all night. The King of the Planet is pretty well at the highest point on the ecliptic and the best time to observe it subtle feature or image it for everlasting memories. Refer to pages 242 and 243 of the 2012 RASC Observer’s Handbook for an ephemeras of numerous satellite and shadow crossing. Posted times are in Universal Time (UT) so calculate you local time accordingly. Venus and Saturn will form a nice pairing on the 27th and 28th very early in the morning.

For planning purposes the new moon lunation 1112 occurs on the 13th. On this date there will be a total solar eclipse across the Pacific Ocean, making landfall on the northern tip of Australia. Totality will last about four minutes. Two weeks later on the 28, the full Beaver Moon will undergo a penumbral eclipse at which time the central and western portions of Canada will only see a slight shading of the moon as it enters the outer portion of the cone of darkness.

Do not forget to turn your clocks back one hour (where applicable) at 2 a.m. Sunday morning on the 4th. This will also affect the conversion to Universal Time.

Until next month, clear skies everyone.

Gary Boyle