Thursday, May 14, 2009

The Ellensburg sky for the week of 5/16/09

Saturday: Saturn is four fists held upright and at arm’s length above the southwest horizon at 10:30 p.m.

Sunday: Jupiter is less than a half a fist to the lower right of the last quarter Moon at 5 a.m.

Monday: Late spring and early summer is a good time to look for star clusters. Last week, you learned about M3, the third object cataloged by French astronomer Charles Messier over 200 years ago. One of the best clusters is the globular cluster in the constellation Hercules, also called M13. (Hummm. Guess what number that object is in Messier’s catalog.) Globular clusters are compact groupings of a few hundred thousand stars in a spherical shape 100 light years across. (For comparison, a 100 light year diameter sphere near out Sun would contain a few hundred stars.) The globular cluster in Hercules is six fists above due east at 11 p.m. First find Vega, the bright bluish star about four fists above the east-northeast horizon. Two fists to the upper right of Vega is a keystone shape. Aim your binoculars at the two stars that form the uppermost point of the keystone. The globular cluster is one third of the way south of the uppermost star on the way to the rightmost star of the keystone. It looks like a fuzzy patch on the obtuse angle of a small obtuse triangle. If you don’t know what an obtuse angle is, you should not have told your teacher, “I’ll never need to know this stuff”.

Tuesday: When it is sitting low in the western sky, many people mistake the star Capella for a planet. It is bright. It has a slight yellow color. But, Capella is compelling on its own. It is the fourth brightest star we can see in Ellensburg. It is the most northerly bright star. It is a binary star consisting of two yellow giant stars that orbit each other every 100 days. At 10 p.m., Capella is two fists above the northwest horizon. If you miss it tonight, don’t worry. Capella is the brightest circumpolar star meaning it is the brightest star that never goes below the horizon from our point of view in Ellensburg.

Wednesday: The Moon interacts with Mars and Venus in the morning sky for the next two days. At 5 a.m., Venus is about a fist to the lower left of the Moon. Mars is about a half a fist to the lower left of Venus.

Thursday: Mars, Venus and the Moon make a nearly equilateral triangle in the eastern sky just before sunrise. Venus is the bright point of light on the right side of the triangle. Mars is the lowest point of light in the triangle.

Friday: Spica, the brightest star in the constellation Virgo, is known as the Horn Mansion one of 28 mansions, or constellations, in the Chinese sky. Spica is about three fists above the south horizon at 11 p.m.

The positional information in this column about stars and planets is typically accurate for the entire week.

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