Wednesday, February 15, 2012

The Ellensburg Sky for the week of 2/18/12

What's up in the sky 2/18/12

Today: “Happy Birthday to you. Happy Birthday to you. Happy Birthday dear Pluto. Happy Birthday to you.” On this day in 1930, Clyde Tombaugh discovered Pluto, the solar system object formerly known as a planet.

Sunday: It’s getting dark. The last remnant of twilight has disappeared. Suddenly, you notice a large softly radiant pyramid of light in the western sky. The base of this ghostly triangle is along the west horizon and the peak stretches two or three fists above the horizon. It is not really a ghost. It is an effect called the zodiacal light. This light comes from sunlight reflecting off dust grains in our solar system. The effect is the most visible when the band of constellations called the zodiac makes a steep angle with the horizon. You need a clear dark sky with no haze or light pollution to see the zodiacal light. At its brightest, the zodiacal light rivals the light of the central Milky Way.

Monday: This President’s Day weekend, let’s remember Abraham Lincoln: 16th president, country lawyer, man on the penny, and astronomer. Astronomer? Well, maybe not an astronomer, but someone who used observational evidence from the sky to solve a problem. In 1858, Lincoln defended Duff Armstrong, a family friend who was accused of murder. The prosecution thought they had a strong case because their primary witnesses claimed to have observed the killing by the light of the nearly full moon. Let’s listen in on the trial courtesy of the 1939 film, Young Mr. Lincoln.
Lincoln: How’d you see so well?
Witness: I told you it was Moon bright, Mr. Lincoln.
Lincoln: Moon bright.
Witness: Yes.
(Dramatic pause as Lincoln reaches for something)
Lincoln: Look at this. Go on, look at it. It’s the Farmer’s Almanack (sic). You see what it says about the Moon. That the Moon… set at 10:21, 40 minutes before the killing took place. So you see it couldn’t have been Moon bright, could it?
Lincoln used the known information about Moon rising and setting times for August 29, 1858 as evidence in a trial. This is one of the earliest uses of forensic astronomy. You may confirm Lincoln’s findings on the Moon set time by going to, the US Naval Observatory website, and filling out Form A. For more information about Lincoln’s “almanac trial”, go to

Tuesday: Tonight’s Moon is new. Don’t bother looking for it. The new moon is the phase where the Moon is directly between the Earth and the Sun. Hence the side of the Moon facing Earth is not receiving any sunlight and cannot be seen.

Wednesday: Venus is two and a half fists held upright and at arms length and Jupiter is four fists above the southwest horizon at 7 p.m.

Thursday: Saturn is just barely above the horizon at a reasonable viewing hour. It is a half a fist above the east-southeast horizon at 11 p.m.

Friday: The space shuttles have been retired. But that does not mean NASA has stopped thinking about the future of space flight. Here is a small NASA poster summarizing the future of American Human spaceflight: Mars is one of the possible destinations. If Mars is your viewing destination tonight, look three and a half fists above the east-southeast horizon at 10 p.m.

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

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