Thursday, December 8, 2011

The Ellensburg sky for the week of 12/10/11

What's up in the sky 12/10/11

Today: “Red Moon, you saw me sleeping alone. Before the Sun rises up. Before I turn on my phone.” Early risers will see a total lunar eclipse this morning, low in the western sky. During a total lunar eclipse, the Moon enters the earth’s shadow. Total lunar eclipses are not as obvious as total solar eclipses because light still reaches the Moon even when it is directly behind the Earth. That is because the Earth’s atmosphere acts like a lens and bends rays of light that would normally miss the Moon such that they hit the Moon. That doesn’t mean the Moon looks the same during a total lunar eclipse as it does during a normal full Moon. Sunlight is white. White light is the sum of all of the colors in the visible spectrum (red, orange, yellow, green, blue, indigo and violet). Our atmosphere scatters the blue component of the Sun’s white light. That is why our sky is blue. When the Sun or Moon is near the horizon, the light passes through a lot of the atmosphere meaning a lot of the blue light is scattered and the Sun or Moon looks redder than when it is high in the sky. During a total lunar eclipse, sunlight passes through a large slice of the Earth’s atmosphere. The remaining light that reaches the Moon is reddish. Thus, the Moon looks red during a total lunar eclipse. From our perspective in Washington, the Moon will start to enter the Earth’s shadow at 4:45 a.m. Totality starts a little after 6 a.m. By 7 a.m., the total eclipse will be over.

Sunday: Jupiter is five fists above due south at 9 p.m.

Monday: The Geminid meteor shower peaks at 10 a.m. tomorrow morning but will remain highly active throughout the next two nights. 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. Unfortunately, the Moon will be out throughout the night, obscuring most of the meteorites.
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 a comet source for this shower since 1862 when the shower was first observed. Finally, 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. For more information about 3200 Phaethon, go to

Tuesday: On these cold mornings, it is difficult to 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

Wednesday: Sirius, the brightest star in the night sky, is one fist above due southeast at 10 p.m.

Thursday: Mars is one fist above due east at midnight.

Friday: Regulus is less than a fist to the upper left of the Moon at 11 p.m.

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

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