Friday, May 17, 2013

The Ellensburg sky for the week of 5/18/13

Saturday: Saturn is nearly three fists held upright and at arm’s length above the south-southeast horizon. With the naked eye, and through binoculars, Saturn looks to be a dull orange color. This is because of the different gasses in the atmosphere. But a close up view reveals even more colors - brown, yellow, and even blue – emphasizing different gases, cloud layers, and wind patterns. For a true-color close-up view of Saturn and Titan, its largest moon, go to

Sunday: The questions who, what, where, and when can only be asked with a “W”. At 11 p.m., the W-shaped constellation Cassiopeia is about two fists above due north. The middle star in the W was used as a navigation reference point during the early space missions. The American astronaut Gus Grissom nicknamed the star Navi, his middle name Ivan spelled backwards. After he died in the Apollo 1 fire, the star name was kept as a memorial.

Monday: Mercury, Venus, and Jupiter are clustered low in the west-northwest sky after sunset for most of the week. At 9 p.m. tonight, Jupiter is about a fist above the horizon, Venus is a half a fist above the horizon, and Mercury is to the lower right of Venus. As the week goes on, Venus and Mercury move upward in the sky and Jupiter moves downward. By Thursday, the rapidly moving Mercury has passed up Venus. By next week, both Venus and Mercury are above Jupiter.

Tuesday: Spica remains less than a half a fist to the left of the moon throughout the night.

Wednesday: Saturn remains about a half a fist or less above the moon throughout the night.

Thursday: 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.

Friday: 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”.

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

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