Thursday, May 26, 2011

The Ellensburg sky for the week of 5/28/11

Saturday: The constellation Aquila the eagle is starting its migration across the summer evening sky this month. Aquila, marked by its bright star Altair, rises above the east horizon at about 11 p.m. Not all animal migrations are fully understood by scientists. We might be inclined to attribute bird migrations to instinct. This answer certainly did not satisfy the theologian C. S. Lewis. In his short work “Men Without Chests”, he wrote, “to say that migratory birds find their way by instinct is only to say that we do not know how migratory birds find their way”. In science (and theology), Lewis is telling us to look for real causes and not simply labels such as instinct. The cause for Aquila’s migration is the Earth orbiting the Sun. As the Earth moves around the Sun, certain constellations move into the evening sky as others get lost in the glare of the setting Sun.

Sunday: The Moon tries to get in on the morning planet action over the next few days. This morning at 4:30, Jupiter can be seen a half a fist to the lower right of the Moon.

Monday: Cygnus the swan flies tonight. Deneb, the brightest star in the constellation, whose name means “tail” in Arabic, is two fists above the northeast horizon at 10 p.m. Cygnus’ wings make a vertical line one half a fist to the right of Deneb. Its head, marked by the star Albireo, is two fists to the right of Deneb. While Deneb is at the tail of Cygnus, it is at the head of the line of bright stars. It is 160,000 times more luminous than the Sun making it one of the brightest stars in the galaxy. It does not dominate our night sky because it is 2,600 light years away, one of the farthest naked eye stars. If Deneb were 25 light years away, it would shine as bright as a crescent moon. Compare that to Vega, which is 25 light years away. Vega is three and a half fists above the east-northeast horizon at this time.

Tuesday: At 4:30 a.m., Venus is a half a fist to the right of the Moon, just above the east-northeast horizon. Mars is to the upper

Wednesday: Are you feeling lucky today? Then go outside and yell to the sky “come and get me!” Asteroid 2009 BD will nearly oblige. This asteroid, discovered in 2009, is about 30 feet across and will come within 200,000 miles of hitting the Earth today. While 200,000 miles seems like a lot, it is only 90% of the Earth-Moon distance. Asteroid 2009 BD is somewhat rare in that it has nearly the same orbit as the Earth. Its orbit is a little bit larger and a little bit more elliptical meaning it often gets close to hitting the Earth. If an asteroid this size hit the Earth, scientists estimate it would cause approximately the same amount of damage as an atomic bomb.

Thursday: The month of June is named after Juno, the queen of the Roman gods and the mythological protector of the Roman state. In ancient Rome, the month began when the crescent moon was first seen in the evening sky from Capitoline Hill in Rome. If we still started months this way, June wouldn’t begin until about two weeks from now.

Friday: Saturn is four fists above the south-southwest horizon at 10 a.m.

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

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