Tuesday, May 18, 2010

The Ellensburg sky for the week of 5/22/10

Saturday: Saturn is one fist held upright and at arm’s length above the Moon at 10 p.m.

Sunday: Ophiuchus (pronounced O-fee-u’-kus) the serpent holder rises just before sunset this evening. By 11, p.m., the leading star, Yed Prior or “the preceding star of the hand” is three fists held upright and at arm’s length above the southeast horizon.

Monday: Spica, the brightest star in the constellation Virgo, is about one fist above the Moon at 10 p.m.

Tuesday: 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.

Wednesday: Mercury is at greatest western elongation this morning. This means Mercury is farthest from the Sun in the morning sky for this orbit. Typically, that means it is a good time to view Mercury. But, Mercury still remains low in the morning sky for this western elongation. It is less than a half a fist above the east-northeast horizon at 5 a.m.

Thursday: Tonight’s full moon is in the constellation Scorpius the scorpion. Since this is the time for “May flowers”, the May full moon is called the Full Flower Moon. At 11 p.m., the bright star Antares is about a finger width to the right of the Moon.

Friday: 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.

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

No comments: