Friday, December 5, 2014
The Ellensburg sky for the week of 12/6/14
Saturday: The earliest sunset of the year occurs throughout the next week: 4:13 p.m. This seems odd because the shortest day of the year, the winter solstice, isn’t for about two more weeks. The Sun is at its southernmost point with respect to the background stars on the day of the winter solstice. This means the Sun spends the least amount of time above the horizon on that day. But, the sunrise and sunset times depend on more than its apparent southward motion in the sky. It also depends on where the Sun is on the analemma, that skinny figure-8 you see on globes and world maps. During the second week in December, the Sun is not quite to the bottom of the analemma. But, it is on the leading edge of the analemma, the first section to go below the horizon. For a slightly different explanation about this, go to http://goo.gl/kjnHP. Or just go watch the sunset. But don’t stare at the Sun.
Sunday: Jupiter is one and a half fists held upright and at arm’s length above the east horizon at 11 p.m.
Monday: Saturn is nearly one fist above the southeast horizon at 7 a.m.
Tuesday: Do you look into a nursery and say, “it’s a boy” or “it’s a girl”? Not me. I say, “It’s a star”. Of course, I like looking into a stellar nursery – a star-forming region such as the Orion Nebula in the middle of Orion’s sword holder. The Orion Nebula looks like a fuzzy patch to the naked eye. Binoculars reveal a nebula, or region of gas and dust, that is 30 light years across. The center of the nebula contains four hot “baby” stars called the Trapezium. These hot stars emit the ultraviolet radiation that causes the Nebula’s gas to glow. The Orion Nebula is three fists above the southeast horizon at 11 p.m.
Wednesday: Warrant, the American glam metal band (as labeled by Wikipedia) was singing about carbon stars in its 1991 hit “I Saw Red”. The lyrics for the astronomy version are “Then I saw red, when I looked up in the sky, I saw red, Orion’s bright star it was by.” R Leporis, also known as Hind’s Crimson Star, is one of the reddest stars in the sky. It is a star near the end of its life that has burned its helium nuclei into carbon. Convective currents, like those in a pot of boiling water, bring this carbon to the surface. There it forms a layer of soot that scatters away the light from the blue end of the visible spectrum leaving the light from the red end of the spectrum to reach our eyes. For more information about Hind’s Crimson Star and a list of other deep red stars, go to http://goo.gl/EnhRe4. Hind’s Crimson star is one fist to the lower right of Rigel, the brightest star in Orion. You’ll need binoculars or a small telescope to see it Hind’s Crimson star. But you can easily spot Rigel three fists above the southeast horizon at 10 p.m.
Thursday: Speaking of red, “I spoke red”, the red planet is visible in the early evening sky. Mars is a little more than one fist above the southwest horizon at 6 p.m.
Friday: The Geminid meteor shower peaks for the next two nights. Meteor showers are named after the constellation from which the meteors appear to originate. These meteors appear to come from a point in Gemini the twins. This point is about three fists held upright and at arm’s length above the east-northeast horizon at 9 p.m. tonight. You can follow this point throughout the night, as it will remain near the bright star Castor, the right hand star of the “twin” stars Pollux and Castor. This shower is typically one of the best ones of the year producing bright, medium speed meteors with up to 80 meteors per hour near the peak. This year, the nearly full moon will obscure some of the dimmer meteors.
Most meteor showers occur when the Earth passes through the orbital trail of a comet. The broken off comet fragments collide with the earth and burn up in the atmosphere. Astronomers had searched for a comet source for this shower since 1862 when the shower was first observed. Finally, in 1983, astronomers discovered the object that created the fragments that cause the meteor shower. To their surprise, it was a dark, rock that looked like an asteroid, not a shiny icy comet. Astronomers named this object Asteroid 3200 Phaethon. But, they still don’t know if it an asteroid or if it is a comet with all of its ice sublimated away by many close passes by the Sun. For more information about the Geminid shower, go to http://earthsky.org/space/everything-you-need-to-know-geminid-meteor-shower.
The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to http://nightsky.jpl.nasa.gov/planner.cfm.