Tuesday, March 2, 2010

The Ellensburg sky for the week of 3/6/10

Saturday: “The crow rises in the southeast” said spy number one. “I’m sorry. I don’t recognize that code” replied spy number two. Spy one exclaimed, “That’s because it’s not a code, you idiot. I’m talking about the constellation Corvus the crow.” This very bad spy movie dialogue is to remind you that Corvus had a very bad life. According to one myth, Corvus brought the god Apollo the news that his girlfriend was seeing someone else. In a classic case of punishing the messenger, Apollo turned the formerly beautifully colored crow black. The box-shaped Corvus is one fist held upright and at arm’s length above the southeast horizon at 10 p.m.

Sunday: This morning’s last quarter Moon is in the constellation Ophiuchus the serpent bearer. At 6 a.m., the bright star Antares is about a half a fist to the right of the Moon.

Monday: 2009 was the International Year of Astronomy. Even though 2009 was over, astronomy lives on in the “Hot Topic” of the month. For March, the hot topic is observing at night… and in the day. Technology has expanded the amount of information astronomers can learn from observing the sky. Up until the mid 1900s, we studied the sky using a very narrow portion of the electromagnetic spectrum – visible light waves. It was like studying music by listening only to notes of medium pitch. The invention of the radio telescope opened up a new source of information, long wavelength radiation. It also opened a new time to observe the sky – the day time. Radio waves from outer space are not blocked by the sunlit sky like visible light from outer space is. Since then, astronomers have started gathering gamma ray, x-ray, ultraviolet, infrared, and microwave radiation. Finally, the entire symphony rather than a few notes. But technology has also negatively impacted our view of the nighttime sky through light pollution. The dim light of a distant galaxy is facing more and more competition from businesses that use inefficient lighting that lights the sky as much as it lights the ground. Many communities, including Ellensburg, have passed or are working on ordinances to reduce this costly and sky-robbing stray lighting. Go to http://astronomy2009.nasa.gov/topics_mar.htm for more information about the March “Hot Topic”.

Tuesday: Saturn is three fists above the southeast horizon at 10 a.m.

Wednesday: Venus is a half a fist above the west horizon at 6:30 p.m.

Thursday: How many of you will be stationary at 1 a.m. this morning? You. And you. And Mars, too. The Earth is closer to the Sun than Mars is. Thus, the Earth moves faster in its orbit around the Sun. About once every year and a half, the Earth passes Mars as Mars lollygags in its orbit. As the Earth passes Mars, Mars appears to move backwards in the sky. You notice a similar occurrence while driving. When you pass a car, it appears to be moving backwards with respect to you. On a nearly circular “track” like the solar system, as a fast inner planet passes a slow outer planet, the outer planet appears to move backward, or westward, with respect to the background stars. Once the Earth has passed Mars by a sufficient amount, after about two months, Mars starts moving forward, or eastward, again. When something goes from moving backward to moving forward, it is stationary for a moment. That moment for Mars comes at 1 a.m. today. This backward motion with respect to the stars is called retrograde motion. If you are stationary and looking up at the sky at this time, Mars is three and a half fists above the west horizon.

Friday: Sunspot activity on the Sun is starting to increase. On the Sun-like star Corot-2a, there is always a lot of sunspot activity. Amazing as it may seem, astronomers can measure sunspot activity on stars that are dozens of light years away. They do so by measuring how much the Corot-2a’s light dips when the close-in planet Corot-2b passes in front of it. Sunspots are relatively cool and dark portions of a star. When the planet passes in front of a region of high sunspot activity, Corot-2a’s light dims less because the planet is blocking a relatively dark portion of the star.

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

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