Wednesday, January 12, 2011

The Ellensburg sky for the week of 1/15/11

Saturday: Who can forget that memorable song by Three Dog Constellations Night, “The sky is black. The stars are white. Together we learn to find the light.” Well, maybe it didn’t go like that. This is good because not all stars are white. Most stars are too dim to notice a color. But, the stars in the constellation Orion provide a noticeable contrast. Betelgeuse, five fists held upright and at arm’s length above due south at 10:30 p.m. is a red giant. Rigel, the bright star about two fists to the lower right of Betelgeuse, is a blue giant.
By the way, the three dog constellations are Canis Major, the greater dog; Canis Minor, the lesser dog; and Canes Venatici, the hunting dogs. Canis Major contains Sirius, the brightest star in the nighttime sky.

Sunday: Jupiter is three fists above the southwest horizon at 7 p.m.

Monday: Some objects we can observe every day lead to very difficult scientific questions. The star that we call Epsilon Auriga varies in brightness for a two year period every 27 years. Scientists were not sure of the exact cause of this dimming. The most recent episode started in the summer of 2009 and will end this year. But recent images from NASA’s Spitzer Space Telescope, which sees infrared wavelengths, are helping scientists solve the puzzle. Epsilon Auriga is actually a binary system. The bright star in the Epsilon Auriga system is orbited by a smaller star which is surrounded by a huge cloud of sand grain-sized particles. This cloud, which is approximately the size of Jupiter’s orbit in diameter, causes the main star in the system, creatively called Epsilon Auriga A, to be only half as bright as its maximum. You can follow the cycle with the naked eye. Epsilon Auriga is about a fist to the upper right of Capella, one of the brightest stars in the sky. Capella is seven and a half fists above due east at 8 p.m.

Tuesday: How do you study the life cycle of a dog? Easy. Get a dog from the animal shelter, care for it for 15 years and study it. How do you study the life cycle of a star? Easy. Pick a star, watch it for a few billion years, and…. Wait a minute. Astronomers can’t observe something for a few billion years. Instead, they study stars that are at different points in their long life cycle and piece together the information from those different stars. What they do is like studying a one-year-old dog for a few minutes, then studying a different two-year-old dog for a few minutes, and so on. The sky in and near the constellation Orion provides an example of four objects at different points of star life.
First, find Rigel, the bright star in the lower right corner of the constellation Orion. This star, rapidly burning its fuel for a high energy but short lived existence, is three and a half fists above due south at 9:30 p.m. About one fist up and to the left are the three objects of Orion’s sword holder. The middle “star” is really a star forming region called the Orion nebula. There you’ll find baby Suns. Now, look about two fists to the right and a little below Rigel. You should be looking at a star that is about one tenth as bright as Rigel but still the brightest in its local region. The third star to the right of that star is Epsilon Eridani, the most Sun-like close and bright star. Betelgeuse, in the upper left corner of Orion, is a star at the end of its life that started out life a bit larger than the Sun.

Wednesday: It’s cold. The snow is blowing in your face. Food is scarce. Packs of wild animals are wondering around howling. Does this describe your house after someone broke your window during your New Year’s party? It also describes wolf packs around Native American villages. That’s why many tribes call January’s full moon, which occurs this morning at 5:36 the Full Wolf Moon. It is also called the Moon after Yule.

Thursday: Saturn finally makes its way into the late evening sky. It is a half a fist above the east horizon at midnight.

Friday: Venus is one and a half fists above the southeast horizon at 6:30 a.m.

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

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