The Ellensburg, WA sky for the week of February 20, 2021

Saturday: Tonight is a great night to look for the Big Dipper. Tomorrow will be a great night to look for the Big Dipper. In fact, every night for many centuries will be great nights to look for the Big Dipper. But the Big Dipper’s shape slowly changes over many, many, many, many centuries. (Have I reached my word count yet?) Tens of thousands of years ago, it didn’t look like a dipper and tens of thousands of years from now, it will no longer look like a dipper. For a short video simulation of the changing Big Dipper, go to https://youtu.be/txJH8RlIoXQ. For a look at the current Dipper, face northeast at 8:00 p.m. The lowest star, Alkaid, is two fists held upright and at arm's length above the horizon. 

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. Look for the ghostly patch after twilight for the next few weeks.

Monday: Mars is five and a half fists above due southwest at 7:00 p.m.

Tuesday: Mercury and Saturn are just above the east-southeastern horizon at 6:15 a.m. Mercury is the slightly brighter of the two and to the left of Saturn.

Wednesday: On these late winter mornings, it is still difficult to get going. You just want to plop into a chair and sit still. But, are you really sitting still? You’re moving at about 700 miles per hour due to the rotation of the Earth on its axis and 66,000 miles per hour due to the revolution of the Earth around the Sun. If that’s not enough, the entire solar system is orbiting the center of the galaxy at a whopping 480,000 miles per hour! So while you may be sitting still with respect to your living room (and all of the overachievers in your house), you are NOT sitting still with respect to the center of the galaxy. For more information about this concept, go to https://nightsky.jpl.nasa.gov/docs/HowFast.pdf. 

Thursday: Are you lonesome tonight? Alphard in the constellation Hydra is. Also spelled Al Fard, Arabic for “the solitary one”, Alphard is in a region of the sky without any bright stars. Alphard really ought to have a lot of friends. It is an orange giant star like better known stars such as Arcturus and Aldebaran. It pulsates, making it interesting to astro-seismologists. And it is on the flag of Brazil. There’s no reason for it to be lonely. Go introduce yourself to Alphard, three and a half fists above due south at 11:00 p.m.

Friday: Two bright stars, Vega and Deneb, are hugging the northern horizon together at 11:00 p.m. Vega, the brighter of the two, is about a half a fist above the northeastern horizon. Supergiant Deneb to two and a half fists to the left of Vega, closer to due north.

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.