The Ellensburg Sky for the week of 12/13/08

Saturday: The Geminid meteor shower peaks late tonight and early 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 about 50 meteors per hour near the peak. Most of the dim meteors in the sky tonight and tomorrow morning will be obscured by the light of the waning gibbous moon.
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 boiled off by many close passes by the Sun.

Sunday: Jupiter is rapidly fading toward the southwest horizon. The much brighter planet Venus is to the upper right of Jupiter. Venus is most likely the first object you’ll find in the southwest sky because it is the brightest point of light in the sky. It is a fist above the southwest horizon at 6 p.m. Jupiter is nearly a fist to the lower right of Venus.

Monday: Who could forget this holiday classic? “Away in the manger, no crib for its bed. The Moon near Praesepe in Cancer instead.” Oh. You have forgotten it already. Well, that’s probably for the better. At least this song has meaning this morning because the Moon is in the constellation Cancer near the open star cluster called Praesepe (Latin for “manger”). Watching over the manger are Asellus Borealis and Asellus Australis, the northern and southern donkey stars, respectively. The donkeys and the manger are less than a fist to the upper left of the moon, too dim to be seen with the naked eye through the glare of the Moon.

Tuesday: 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.

Wednesday: Capella, the bright star in the constellation Auriga the charioteer, is straight overhead at 11:30 p.m.

Thursday: Saturn is about a fist to the upper left of the Moon this morning. They are four fists above the south-southwest horizon at 7 a.m.

Friday: This morning’s last quarter moon is in the constellation Virgo.

The positional information in this column about stars and any planet except Mercury is accurate for the entire week.