Wednesday, September 12, 2012
The Ellensburg sky for the week of 9/15/12
Saturday: “Excuse me, do you have the time?”
“No, but the Big Dipper does.”
You can use the orientation of the Big Dipper to tell time with a precision of about 15-30 minutes. First, find the two stars at the far end of the Big Dipper cup, the stars that do not touch the handle. Draw an imaginary line segment starting at the North Star and passing through the two Big Dipper cup stars. Now, draw a big circle around the North Star. Your circle is a 24-hour clock. Number the circle from 0 hours at the top, counterclockwise to 12 hours at the bottom of the circle, and back up to 24 hours at the top. (O hours and 24 hours are the same on this clock because the day is 24 hours long.) The hour number on the big circle closest to where your imaginary line intersects this circle is called your raw time. Due to the location of the Big Dipper compared to the rest of the stars, the time nearest the intersection (the raw time) is correct for March 6. For any other night, subtract two times the number of months the current date is after March 6 from the raw time. For example, let’s say the imaginary line between the North Star and the Dipper stars is pointed to the right. That means the raw time is 18 hours or 6 p.m. If you made this observation on October 6, which is seven months after March 6, you would subtract two times seven or 14 hours from the raw time. Thus, the time for November 6 is 18 hours minus 14 hours or 4 hours. In other words, 4 a.m. Don’t forget to convert for daylight savings time if needed. For a more complete set of instructions, go to http://goo.gl/02HmA. There is a simple “star clock” template and instructions at http://goo.gl/SFKrE. Use this paper star clock whenever you watch is broken.
Sunday: Saturn is about a half a fist above the west-southwest horizon at 8 p.m.
Monday: Let me tell you the story of the ghostly white figure that rises early in the morning around Halloween. It appears to be a huge dim glow of white light that rises up from the east in the pre-dawn sky. No, I’m not writing about the ROTC student who has early morning physical training. I’m describing 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 sky with no haze or light pollution to see the zodiacal light that will be visible for the next week or so. At its brightest, the zodiacal light rivals the light of the central Milky Way.
Tuesday: To celebrate the start of school at CWU tomorrow, let’s sing a song of the season. “Oh the weather outside is grand. And the fire is rightfully banned. There is really no place to go. Let it snow, let it snow, let it snow. On Mars.” The Mars Reconnaissance Orbiter has discovered evidence of carbon dioxide snow clouds high above the surface of Mars. Carbon dioxide, also called “dry ice”, exists in Mars south polar ice cap and requires temperatures of nearly 200 degrees below zero Fahrenheit to form. Astronomers were not sure how this polar cap gets replenished but the discovery of carbon dioxide clouds may provide an answer. For more information, go to http://goo.gl/shMTf. Mars is less than one fist held upright and at arm’s length above the southwest horizon at 8 p.m.
Wednesday: Venus is three fists above the east horizon at 6 a.m.
Thursday: “One world, group hug, love everyone” philosophy: political borders are human-made and can’t be seen from space. Real world, pragmatic discovery: some human-made political borders CAN be seen from space. Since 2003, India has illuminated its border with Pakistan to prevent illegal crossings. In August, astronaut Ron Garan took a picture of the boarder from the International Space Station. For more information, including the photo, go to http://goo.gl/mY8xG.
Friday: Jupiter is a half a fist above the east-northeast horizon at 11 p.m.
The positional information in this column about stars and planets is typically accurate for the entire week.