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The Sky This Month - September 2006

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Written by Gary Boyle, Ottawa on
Post Date: 
Wed, 2006/09/06

Seasonal Change

As the days of September moves closer to the change of seasons at 00:03 hrs eastern on the 23rd, darkness creeps in earlier and earlier. After the 23rd, the hours of darkness will trump daylight hours. Here in Canada, the comfortable nights are coming to an end as the winter winds are only a couple of months away. Until then we have a good number of targets to nail down – so let’s get started.

This month we will focus on some of the Northern constellations. One of the most famous other than Ursa Major is the great “W” of Cassiopeia the Queen. Well up in the north east after sunset, this area plays host to numerous star clusters and other objects. We start our journey with NGC 281. The Pacman Nebula lies about 1.5 degrees east of Alpha Cass. This 7th magnitude object is a combination of a nebulous cloud and a star cluster. The Pacman is also home to many great Bok globules.

Next move over to NGC 457, the splendid group of stars. Termed as young, the ET Cluster’s 60 members take on the resemblance of one of the Double Cluster groups. Its brightest member is a red supergiant star, glowing at magnitude 8.6. The entire cluster lies some 9,000 light years (ly) from us. About a moon’s width north is the cluster NGC 436 – another rich grouping of suns.

As we move to the top of the great W, we come across M52. This scattered peppering of stars is estimated at 5,000 ly away and about 19 ly across itself, M52 dubbed the Scorpion is one of Charles Messier’s original discoveries. To locate this open cluster, draw a line from Alpha to Beta Cass and continue a little more than the two star separation.

A little to the north-east of M52, we come across a splash of light from the Bubble Nebula. NGC 7635 is about 11,000 ly from us with the bubble being the result of stellar winds blown from the nearby star.

Next we will look at the smaller version of M27. Catalogued as M76, it is widely known as the Little Dumbell. At a mere 3,400 ly, it only glows at a faint 10.1 magnitude. Strangely, this object has two NGCs associated with it. The main catalogue number is NGC 650, while NGC 651 is the eastern part of the nebula.

Cassiopeia is not only home to a wrath of open clusters but does harbour a couple of galaxies. I am speaking about NGC 147 and 185. Both are close to the 9.2 magnitude range and listed a few million light years away, they do sport different orientations. NGC 147 is an elongated structure, difficult to see except with averted vision, while NGC 185 is an E2 elliptical type.

Moving to the constellation Andromeda, we start off with the most observed and photographed galaxy – M31. At a mere 2.9 million ly, the mighty Andromeda Galaxy can be glimpsed naked eye from dark sky locations. Although it spans about three degrees of sky (six full moons), the unaided eye will only pick up the inner, brighter concentration. Any telescope will reveal its majestic structure and two satellite galaxies (M32 and M110) as well as the NGC 206 star cloud, but large telescopes and a detailed chart with the actual plates under index 1 and 2. These charts will allow you to spot globular clusters in M31. I have picked up a few of these with my 12.5 inch dobsonian telescope years ago.

Continue from M31 through Beta Andromeda and try to find NGC 404. This 10.1 magnitude galaxy resides only seven arc minutes from the second magnitude Beta star – Mirach. After you have caught NGC 404 in your sights, continue the same distance from M31 to Mirach till you come to M33, a lovely face-on galaxy with nebulous regions labeled as NGCs. At about the same distance as M31 and glowing at magnitude 5.7, it is sometimes a challenge seeing it naked eye due to its face-on orientation. Within a couple degrees from the Andromeda Galaxy is NGC 7662 - aka the Blue Snowball. At ninth magnitude, this gem sports a nice ring feature.

 

Click on image to open interactive site

To end off this region with a challenge, one of the more difficult objects to spot is Stephan’s Quintet. Catalogued as Hickson 92 and Arp 319, this grouping of five galaxies range from magnitude 13.3 to 14.7 can be found by first hunting down NGC 7331 in Pegasus at RA 22h 37m, Dec 34d 27m. This is a wonderful galaxy along with its close companions. Then slide over to RA 22h 36m, Dec 34d 00m and you should spot this faint group. Dark, moonless skies are a must to spot these objects, measured to be an astounding 350 million ly away.

As Jupiter slowly sinks in the west it is your last time to observe the king of planets. This month, Jupiter is sporting many single and double transits of its moon and trailing shadow onto the Jovian surface. Consult the RASC Observer’s Handbook for a list of events. But as one planet is saying goodbye in the west, a couple more are rising in southern skies. I am speaking about the two farthest planets of the solar system and no - one of them is not Pluto.

For seventy-six years, six months and six days, astronomy books have proudly referred to Pluto as the ninth and most distant sibling of our family of planets. However, this all came to an abrupt end during the week long, twenty-sixth General Meeting of the International Astronomical Union (IAU) held last month in Prague in the Czech Republic. Astronomers from around the world took in various paper sessions and drafted resolutions pertaining to other celestial business. Members then mulled over the idea of what the true definition of a planet should be. The number of planets briefly rose to twelve but on Aug 24 resolution 5a and 6a spelled out new terms to planetary status. After the dust had cleared, Pluto was knocked of the shelf and denoted to “dwarf status”. Pluto also has company with the largest asteroid Ceres and unnamed 2003 UB313.

Getting back to the main planets, Neptune is now well place in Capricorn and lies some 4.4 billion km from us. At magnitude 7.8, it can be picked up in simple binoculars. It sports a bluish tinge and arrears like a fuzzy star. Now slide on over to Aquarius and find Uranus shining at naked eye visibility of magnitude 5.7. Again this planet appears as a bright fuzzy star with a bluish green colour.

It appears that the Sun might be started its five year climb to Solar Max. Astronomers believe this could be an extremely active cycle, the greatest in the past fifty years. This – without say will be time to dust off the solar scope and prepare for amazing displays of the Aurora Borealis.

We have often looked at distant celestial objects but the Moon is the closest and most interesting venues to train a telescope on. As the nights go by, our natural satellite takes on a slightly different face as shadow lengths and depths paint amazing portraits. Click on the Lunar Picture of the Day (LPOD) for a sample of what you can reveal.

One sure tale sign that winter is around the corner is the Pleiades star cluster. M45 is now seen about 11:00 p.m. locally with mighty Orion appearing a few hours later. Well at least the bugs are pretty well gone.

Until next – clear skies everyone.

Gary Boyle

garyboyle@sympatico.ca