Thursday, December 10, 2009

The Ellensburg sky for the week of 12/12/09

Saturday: Jupiter is two and a half fists held upright and at arm’s length above the south-southwest horizon at 6 p.m. It is by far the brightest object in this region of the sky. Neptune, the dimmest planet in the sky is near Jupiter, allowing you to use Jupiter as a marker to find it with binoculars. Place Jupiter in the lower right hand portion of your binocular field of view. There will be a diagonal line of three stars near the middle of the field of view. The upper right star should be the brightest. Neptune is to the upper left of this line of three stars, a little bit farther above the stars than Jupiter is below them.

Sunday: The Geminid meteor shower peaks at 9 p.m. and should remain highly active through tomorrow morning. Meteor showers are named after the constellation from which the meteors appear to originate. These meteors appear to come from a point in Gemini the twins. This point is about three fists held upright and at arm’s length above the east-northeast horizon at 9 p.m. tonight. You can follow this point throughout the night as it will remain near the bright star Castor, the right hand star of the “twin” stars Pollux and Castor. This shower is typically one of the best ones of the year producing bright, medium speed meteors with up to 80 meteors per hour near the peak. Since we are so close to the new moon, the sky will be very dark meaning good viewing conditions.
Most meteor showers occur when the Earth passes through the orbital trail of a comet. The broken off comet fragments collide with the earth and burn up in the atmosphere. Astronomers had searched for the comet source since 1862 when the shower was first observed. In 1983, astronomers discovered the object that created the fragments that cause the meteor shower. To their surprise, it was a dark, rock that looked like an asteroid, not a shiny icy comet. Astronomers named this object Asteroid 3200 Phaethon. But, they still don’t know if it an asteroid or if it is a comet with all of its ice sublimated away by many close passes by the Sun.
If you are interested in participating in astronomy research by counting meteors, the International Meteor Organization would love to hear from you. Careful observations from observers around the world are critical for the study of meteors and their relationship to the rest of the solar system. Go to for more information on how to participate and about meteor showers in general.

Monday: On these cold mornings, it is difficult tom get going. You just want to plop into a chair and sit still. But, are you really sitting still? You’re moving at about 700 miles per hour due to the rotation of the Earth on its axis and 66,000 miles per hour due to the revolution of the Earth around the Sun. If that’s not enough, the entire solar system is orbiting the center of the galaxy at a whopping 480,000 miles per hour! So while you may be sitting still with respect to your living room (and all of the over achievers in your house), you are NOT sitting still with respect to the center of the galaxy. For more information about this concept, go to

Tuesday: Mars is two and a half fists above due east at 11 p.m.

Wednesday: Tonight’s Moon is new. Don’t bother looking for it. The new moon is the phase where the Moon is directly between the Earth and the Sun. Hence the side of the Moon facing Earth is not receiving any sunlight and cannot be seen.

Thursday: Mercury will be as far away from the Sun in the sky as it will get this orbital cycle. This "farthest away" point is known as the planet's greatest elongation. Since Mercury is in evening sky, it is east of the Sun. Thus, this evening’s elongation is known as the greatest eastern elongation. (If you care to remember this in general, remember both eastern and evening start with the letter "e".) Tonight and tomorrow will be the best nights to observe Mercury for the next few months. Mercury is about a half a fist above the southwest horizon at 5:00 p.m., just to the upper left of the crescent moon. Over the next two weeks, Mercury will toward the Sun in the sky. By mid-January, it will be visible in the morning sky.

Friday: When you were growing up, you may have heard “Don’t make waves.” The red supergiant star Betelgeuse must not have listened. According to data from the Japanese Akari satellite, Betelgeuse creates a shockwave as it moves through the surrounding cloud of gas and dust. If viewed through a telescope sensitive to infrared radiation, this shockwave would appear to be the size of the full Moon as seen from Earth. Betelgeuse is four fists above the southeast horizon at 10 p.m.

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

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