Sunday, March 14, 2010

The Ellensburg sky for the week of 3/20/10

Saturday: Look up in the sky. It’s a plane. It’s a bird. No, it’s the vernal equinox. The vernal equinox!? Spring starts at 12:33 p.m. Pacific Daylight Time The first day of spring is often called the vernal equinox. This label for the day is misleading. The vernal equinox is actually the point in the sky where the Sun’s apparent path with respect to the background stars (called the ecliptic) crosses the line that divides the stars into north and south (called the celestial equator). This point is in the constellation Pisces the fishes. At the vernal equinox, the Sun is moving from the southern region of background stars to the northern region. Since the Sun crosses the vernal equinox in the middle of the day, tomorrow will actually be the first full day of spring.
Because the Earth slowly wobbles like a spinning top, the vernal equinox is slowly moving into the constellation Aquarius. By the year 2597, the vernal equinox will reach the constellation Aquarius and the “Age of Aquarius” will begin. Until then, we’ll be in “the age of Pisces”.

Sunday: Saturn is opposition tonight. That doesn’t mean that Saturn is in the minority party in the senate. Opposition means that Saturn is on the opposite side of the Earth as the Sun. When an object is in opposition, it is at its highest point in the sky during the darkest time of the day. Thus, opposition is typically the best time to observe a planet. Saturn is about four and a half fists held upright and at arm’s length above the south horizon at 1 a.m. It is two fists above the east-southeast horizon at 9 p.m.
If you remember this column from March 7, 2009, you know that Saturn was also in opposition on March 8, 2009. Thus, it was in opposition about two weeks earlier last year. Two weeks is about one twenty-fourth of a year. This implies that it takes Saturn about 24 years to make one orbit around the Sun and get back in line with the same stars again. Saturn’s actual orbital period of 30 years matches this approximation quite well.

Monday: Look very low due north at 9:45 p.m. It’s a plane. It’s a bird. It’s the vernal equinox. (Oops, I already used that joke.) It’s a spotlight on the ridge. No, it’s not a spotlight on the ridge. It is the star Deneb of the constellation Cygnus the swan. Deneb is the second brightest circumpolar star. Circumpolar stars never rise or set. They are always above the horizon.

Tuesday: This morning’s first quarter moon is in the constellation Gemini the twins.

Wednesday: Mars is less than a half a fist to the upper left of the Moon at 10 p.m.

Thursday: Do you ever stare off into space and wonder if there is life out there? Your search may be successful if you stare in the direction of Orion for the next billion years or so. The Herschel Space Observatory has discovered signs of such life-enabling molecules as water, carbon monoxide, and methanol, among others in the Orion Nebula, a star forming region about 1,500 light years away. This does not mean life will definitely form there, just that the conditions are more favorable there than many other places in the galaxy. The Orion Nebula is about three fists above the southwest horizon at 9 p.m. For more information about the Herschel discovery, go to

Friday: Tomorrow night at 8:30 p.m. local time hundreds of millions of people around the world will come together to call for action on climate change by turning off unnecessary lights and other electric devices for one hour. To find out more about this event, called Earth Hour, go to

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

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