Tuesday, July 28, 2009

The Ellensburg sky for the week of 8/1/09

Saturday: In Scotland, August 1 was known as Lammas, the festival of the first wheat harvest of the year. You can remember this by looking at Spica, named for the Latin word for “ear of wheat”, one fist held upright and at arm’s length above the west-southwest horizon at 9:30 p.m. It is also called a cross-quarter day, a day approximately half way between an equinox and a solstice.

Sunday: The solar system’s cleaner is one fist above the southeast horizon at 10 p.m. Oh, you may know it as Jupiter. But as the hole in Jupiter’s atmosphere can attest, Jupiter helps rid the solar system of objects potentially hazardous to life on Earth. Astronomers think that a comet or asteroid collided with Jupiter about two weeks ago, opening up a nearly Earth-sized scar on Jupiter.

Monday: Are you thirsty? The Big Dipper can hold your water late at night. The cup is facing upright about two fists above the north-northwest horizon at 11:30 p.m.

Tuesday: Had the script been written a little differently for a well known Robin Williams movie, we may have heard Mr. Williams shout, “Goooood Morning Orion the hunter”. Orion is typically thought of as a winter constellation. But, it makes its first appearance in the summer sky. The lowest corner of Orion’s body, represented by the star Saiph (pronounced “safe”), rises at 4:30 a.m., well before the Sun. By 5 a.m., Orion’s belt is about one fist above the east-southeast horizon.

Wednesday: The full moon occurs at about 6:00 this evening. When the Moon is full, it is difficult to see dim objects in the sky because of the sky glow. But why struggle to find dim objects when there is so much to see on the big, bright object in front of you? The lunar crater called Tycho is best seen during a full Moon. Tycho was formed about 109 million years ago when an asteroid struck the Moon, leaving a crater over 50 miles in diameter and ejected dust trails visible from Earth that radiate out hundreds of miles in all directions. For more lunar highlights, go to
http://nightsky.jpl.nasa.gov/docs/ObserveMoon.pdf, a resource of the Night Sky Network.

Thursday: Saturn is a half a fist above due west at 9:30 p.m.

Friday: Need a caffeine pick-me-up? Make it a double. Need an astronomy pick-me-up? Make it a double-double. Find Vega, in the constellation Lyra the lyre, nearly straight overhead at 11:00 tonight. Less than half a fist to the east (or left if you are facing south) of the bright bluish star Vega is the “star” Epsilon Lyra. If you look at Epsilon Lyra through binoculars, it looks like two stars. If you look at Epsilon Lyra through a large enough telescope, you will notice that each star in the pair is itself a pair of stars. Each star in the double is double. Hence, Epsilon Lyra is known as the double-double. The stars in each pair orbit a point approximately in the center of each respective pair. The pairs themselves orbit a point between the two pairs.

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

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