Thursday, December 5, 2013
The Ellensburg sky for the week of 12/7/13
Saturday: The earliest sunset of the year occurs today and 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: The Christmas season is a time of love, joy, and Lovejoy. Comet Lovejoy, that is. The “Comet of the Century”, Comet ISON, disintegrated as it passed near the Sun. So it is time to focus on the “Comet of the Season”. Comet Lovejoy is visible with the naked eye under very dark skies and visible with binoculars even as dawn approaches. Go outside at 6 a.m. this morning and look three fists held upright and at arm’s length above the east-northeast horizon. You should see a keystone-shaped set of four moderately bright stars. These represent part of the constellation of Hercules. Find the brightest of the four stars, the one in the upper right corner, and put it at the bottom of your binocular field of view. Comet Lovejoy will be near the middle of your field of view with its tail stretching from upper left to lower right. For a detailed chart to help you find Comet Lovejoy, go to http://goo.gl/TWQIHw.
Monday: Venus is more than one fist above the southwest horizon at 5 p.m. You can’t miss it because it is brighter than it has been all year.
Tuesday: Do you like to look in 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: If trying to find Comet Lovejoy frustrated you, there are easier morning targets. Mars is four fists above the south-southeast horizon at 6 a.m. Saturn is one fist above the southeast horizon.
Thursday: 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 moon will be in the waxing gibbous phase, reflecting sunlight that 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 3200 Phaethon and the Geminid shower, go to http://goo.gl/LuwGW.
Friday: Today is Friday the 13th and you know what that means. Bad luck as evidenced by many paper cuts from people trying to tear that day off of their desk calendar as quickly as possible. Celebrate the day by looking at Aldebaran, the 13th brightest star in the nighttime sky. It is three fists above the east horizon at 7 p.m. Jupiter is in the same part of the sky, less than one fist above the east-northeast horizon.
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 https://nightsky.jpl.nasa.gov/planner.cfm.