Wednesday, January 1, 2014
The Ellensburg sky for the week of 1/4/14
Saturday: If the Sun looks big today, your eyes are not playing tricks on you. The Earth is at perihelion at about 4 a.m. today. If you dig out your Greek language textbook, you’ll see that peri- means “in close proximity” and helios means “Sun”. So, perihelion is when an object is closest to the Sun in its orbit, about 1.5 million miles closer than its average distance of 93 million miles. Since it is winter in the Northern Hemisphere now, the seasonal temperature changes must not be caused by the Earth getting farther from and closer to the Sun. Otherwise, we’d have summer when the Earth is closest to the Sun. The seasons are caused by the angle of the sunlight hitting the Earth. In the winter, sunlight hits the Earth at a very low angle, an angle far from perpendicular or straight up and down. This means that a given “bundle” of sunlight is spread out over a large area and does not warm the surface as much as the same bundle in the summer.
Sunday: Venus is less than half a fist held upright and at arm’s length above the southwest horizon at 5 p.m. By the end of the week, it will be lost in the glare of the Sun for most viewers.
Monday: Jupiter is nearly three fists above the east horizon at 7 p.m. It is in an area of the sky with many bright stars. Pollux and Castor is a fist to the left of Jupiter. Procyon is about two fists below it and Betelgeuse is two fists to the right of it.
Tuesday: Orion stands tall in the southern sky. At 10:30 p.m., the middle of Orion’s belt is four fists above due south. And talk about belt tightening! Alnilam, the middle star in the belt, is losing mass at a rate of about 100 thousand trillion tons a day. That’s a 1 followed by 17 zeros tons per day.
Wednesday: Do you typically get eight hours sleep? Perfect. I asked you to look at something at 10:30 last night. Now I’ll ask you to look at two things at 6:30 this morning. Saturn is about two fists above the south-southwest horizon and Mars is nearly four fists above the south horizon. Don’t confuse Mars with Spica, a star of similar brightness nearby. Mars is reddish and higher above the horizon.
Thursday: Listen, do you want to know a secret? Do you promise not to tell? Whoa oh, oh. The Beatles certainly didn’t write this song about the Barringer meteorite crater in Arizona. Astronomers are studying this 50,000-year-old impact to learn more about our planet’s violent history as well as the physics of impacts throughout the solar system. If you’d like to be let in on some of these secrets, go to http://goo.gl/sqbBe.
Friday: Have you ever looked down on the ground and spotted a penny? In Yakima? While you were standing in Ellensburg? If you have, then you may be able to see the star Hamal as more than just a point of light. It has an angular diameter that can be directly measured from Earth. Hamal, the brightest star in the constellation Aries the ram, has the same angular diameter as a penny 37 miles away. (For comparison, the moon is about half the diameter of a penny held at arm’s length.) Hamal is three and a half fists above due west at 11 p.m.
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.