Tuesday, January 12, 2010

The Ellensburg sky for the week of 1/16/10

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 about a half a fist to the left of the Moon at 6:30 p.m. They are one fist above the west-southwest horizon.

Monday: Sometimes objects we can observe every day provide very difficult scientific questions. The star Epsilon Auriga is star that 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 of which started last summer. But recent images from NASA’s Spitzer Space Telescope, which sees infrared wavelengths, are helping scientists solve the puzzle. The bright star in the Epsilon Auriga system is orbited by another star which is surrounded by a huge cloud of sad grain-sized particles. This cloud, which is approximately the size of Jupiter’s orbit in diameter, causes Epsilon Auriga to be only half as bright. 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: Mars is three fists above due east at 9 p.m.

Wednesday: Saturn is one fist above the east horizon at 11:30 p.m.

Thursday: 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.

Friday: Friday: Spica, the brightest star in Virgo, is three fists above the south horizon at 6 a.m.

Wait a minute. We got all the way to the end of the week with no Moon phase summary? How can that be? There are 29.5 days between the same Moon phase in two different cycles. That means about 7.5 days between the phases new, first quarter, full and last quarter. Since a week is seven days, there are some weeks in which none of the main phases occur. This week, the Moon was always in the waxing crescent phase.

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

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