Wednesday, March 7, 2012

The Ellensburg Sky for the week of 3/10/12

Saturday: Don't forget to set you clocks ahead one hour tonight for the annual ritual called daylight savings. Daylight savings originated in the United States during World War I to save energy for the war effort. But a recent study by two economists shows that switching to daylight savings time may actually lead to higher utility bills. When the economists compared the last three years of energy bills in the section of Indiana that just started observing daylight savings, they discovered that switching to daylight savings cost Indiana utility customers $8.6 million in electricity. In an even more important consequence of daylight savings, Stanley Coren of the University of British Columbia discovered a 7% jump in traffic accidents on the Monday after we "spring ahead". Blame it on the lost hour of sleep. And, sky watchers will lose even more sleep because the sky does not get dark for an additional hour.
You won’t need to be very wide-awake to find a bright planet conjunction every night this week. Venus passes by Jupiter in the early evening sky throughout the week. Tonight Jupiter is less than a half a fist to the upper left of the very bright Venus. They are three fists held upright and at arm’s length above the west horizon at 7 p.m. Because of daylight savings, they’ll be at this altitude (number of degrees above the horizon) at 8 p.m. the rest of the week. If anyone you know needs evidence that objects in the night sky actually move with respect to each other, the motion of Venus compared to Jupiter is a highly visible example.
Before you go inside tonight, be sure to look for Mercury, a half a fist above the west horizon. By the end of the week, it will be too close to the Sun to be easily visible.

Sunday: Mercury is the naked eye planet we know the least about. You may not have even knowingly seen it until reading yesterday’s exciting section of “What’s up in the sky”. That global lack of knowledge is rapidly going away because NASA’s Messenger probe has been orbiting Mercury for one year as of this week. It is the first visitor since 1974 to the planet that one Messenger scientist called the most under-appreciated planet. The number one question scientists hope to answer is why Mercury has such a large iron core compared to its size. The number one question you may be asking is “Why is Mercury noticeably closer to the horizon since yesterday?”. Since Mercury is so close to the Sun, it moves very fast in its orbit so it changes positions in the sky much faster than anything other than the Moon.

Monday: Mars is three and a half fists above the east-southeast horizon at 9 p.m.

Tuesday: Antares is one and a half fists above due south and about a half a fist to the lower left of the Moon at 6 a.m. this morning.

Wednesday: This morning’s almost last quarter Moon is in the constellation Ophiuchus, the serpent bearer.

Thursday: Saturn is one fist above the east-southeast horizon at 11 p.m.

Friday: Ask someone which day in March has the same duration day and night. Go ahead, ask someone. Why are you still reading this? I can wait. If that person said the first day of spring, they are wrong. Today, three days before the first day of spring, is the date in which day and night are closest in duration. There are two main reasons for this. First, the atmosphere acts like a lens, bending light from the Sun above the horizon when the Sun is actually below the horizon. This makes the Sun appear to rise before it actually rises and appear to set after is actually sets. Second, spring starts when the center of the Sun passes through the point called the vernal equinox. But, the Sun is not a point. The upper edge of the Sun rises about a minute before the center of the Sun and the lower edge sets a minute after the center of the Sun. Thus, even if we didn’t have an atmosphere that bends the sunlight, daytime on the first day of spring would still be longer than 12 hours.

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

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