Monday, July 26, 2010

The Ellensburg sky for the week of 7/31/10

Saturday: Mars and Saturn are neighbors in the sky all week. They are one fist held upright and at arm’s length above the west horizon at 9:30 p.m. Saturn is on top, the brighter of the two. They will easily fit into the field of view of typical binoculars. The much brighter Venus is a fist to the lower right of Mars and Saturn.

Sunday: In Scotland, August 1 was known as Lammas, the festival of the first wheat harvest of the year. You can remember this by looking at Spica, named for the Latin word for “ear of wheat”, one fist held upright and at arm’s length above the west-southwest horizon at 9:30 p.m. It is also called a cross-quarter day, a day approximately half way between an equinox and a solstice.

Monday: When you think of the Solar System, the main objects that come to mind are the planets and the Sun. But much of the evidence of how the Solar System formed comes from meteors, comets, and asteroids. Scientists have been analyzing the small chunks of rocks and ice that fall to Earth. More recently, astronomers have been studying the rocks and ice in outer space with telescopes and space probes. For example, in July, 2005, the NASA mission Deep Impact smashed into a comet to study its structure. For more information about this rather cold “Hot Topic”, go to

Tuesday: What are some of the signs of August? 1. Hot weather. 2. Back to school sales. 3. A chain email saying Mars will look as big as a full moon this month. The first two are true. The third one never was and never will be. In August of 2003, Mars was as close to Earth as it had been in all of written history. With the right telescope magnification, it could look as large as the moon without magnification. But, even then, Mars did not appear even as large as Jupiter always does. This year, Mars is about half its maximum apparent size. Compare it with Saturn in a small telescope. Mars and Saturn are still one above the west horizon at 9:30 p.m. Mars apparent diameter is much less than Saturn’s.

Wednesday: Had the script been written a little differently for a well known Robin Williams movie, we may have heard Mr. Williams shout, “Goooood Morning Orion the hunter”. Orion is typically thought of as a winter constellation. But, it makes its first appearance in the summer sky. The lowest corner of Orion’s body, represented by the star Saiph (pronounced “safe”), rises at 4:30 a.m., well before the Sun. By 5 a.m., Orion’s belt is about one fist above the east-southeast horizon.

Thursday: Jupiter is a fist above the east-southeast horizon at 11:30 p.m.

Friday: Need a caffeine pick-me-up? Make it a double. Need an astronomy pick-me-up? Make it a double-double. Find Vega, in the constellation Lyra the lyre, nearly straight overhead at 11:00 tonight. Less than half a fist to the east (or left if you are facing south) of the bright bluish star Vega is the “star” Epsilon Lyra. If you look at Epsilon Lyra through binoculars, it looks like two stars. If you look at Epsilon Lyra through a large enough telescope, you will notice that each star in the pair is itself a pair of stars. Each star in the double is double. Hence, Epsilon Lyra is known as the double-double. The stars in each pair orbit a point approximately in the center of each respective pair. The pairs themselves orbit a point between the two pairs.

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

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