Thursday, October 1, 2009

The Ellensburg sky for the week of 10/3/09

Saturday: Shine on, shine on harvest moon, up in the sky. It’s just like a full moon in January, February, June and July. The only difference is that near the Autumnal Equinox (also known as the first day of fall), the full moon rises near sunset resulting in a full night of light for the harvest. The harvest moon looks like a dull orange color while it is near the horizon because of the dust kicked up from the harvest. The dust scatters the white light reflecting off of the Moon resulting in slightly more of the red and orange components of the white light reaching your eyes. Although the Moon has a dull yellow color whenever it is near the horizon owing to light scattering off of dust and atmospheric particles, the effect is more noticeable for the harvest Moon. Tonight’s full moon is in the constellation Pisces the fish.
If you keep your old copies of “What’s Up in the Sky?” each week (and who doesn’t?), you will notice that last year’s harvest moon was also in the constellation Pisces. So was the year before’s harvest moon. And the year before that. The harvest moon won’t always be in Pisces. But, it will be in Pisces or a constellation that borders Pisces. That is because the Sun is always in (meaning in line with) the constellation Virgo on the first day of autumn. Since the full moon is always 180 degrees from the Sun in the sky, the harvest moon will be in nearly the same place each year. I say “nearly” because the moon’s orbit has a slight wobble so it does not follow the exact same path in consecutive years.

Sunday: Mercury, Venus, and Saturn close together low in the eastern sky for the next few mornings. This morning at 6:30 am, Venus, the brightest of the three, is a fist and a half held upright and at arm’s length above the east horizon. Mercury, the second brightest, is a fist above the east horizon and Saturn is just below it.

Monday: Jupiter is two and a half fists above due south at 9 p.m.

Tuesday: Mars finally rises in the evening sky… assuming you define 11:56 p.m. as “evening”. By 1 a.m., it is a fist above the east-northeast horizon.

Wednesday: The Draconid meteor shower peaks tonight and tomorrow night. The meteors appear to come from a point in the head of Draco, the dragon constellation. This point is about five fists above the northwest horizon at 10 p.m. tonight. This point remains near the trapezoid-shaped head of Draco throughout the night. Typically, this is a minor shower. However, Draconid meteors are slow moving which means you will have a easy time differentiating true Draconid meteors, from Comet 21P/Giacobini-Zinner, from stray grains of dust that happen to enter the Earth’s atmosphere near where we see the constellation Draco. As your Mother might say, dress warm and sit in a comfortable chair for maximum enjoyment.

Thursday: This morning, Mercury, Venus, and Saturn are within a circle smaller than your fist held at arm’s length. They are about a fist above the east horizon at 6:30 a.m. Saturn and Mercury are about a third of a degree apart, less than the width of a pencil held at arm’s length.

Friday: Do you know how it is when people drive by a collision? They don’t want to look but they can’t help it. The CWU astronomy club and physics department will be feeding on that morbid human curiosity by hosting an LCROSS collision party in Lind Hall on the southeast corner of the CWU campus this morning starting at 3:30 a.m. LCROSS stands for Lunar Crater Observation and Sensing Satellite. This morning (October 9) at 4:30 a.m. Pacific Daylight Time, LCROSS will crash into the crater Cabeus near the Moon’s South Pole. A trailing part of the satellite will analyze the ejected dust for signs of water. Locally, CWU physics professor Michael Braunstein will be tracking the collision at the CWU Observatory on the roof of Lind Hall (weather permitting). The NASA feed will be showing in room 204 starting at 3:30 a.m. There will be various smaller telescopes available for general sky observing, as well. The event will end, and nap time will begin, at 5:00 a.m. For more information about LCROSS, go to

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

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