The Ellensburg, WA sky for the week of September 26, 2020

Saturday:  Mnemonics are helpful for remembering astronomy facts. (Similarly, “Johnny Mnemonic”, the 1995 cyberpunk film, was helpful in getting Keanu Reeves’ career going.) After all, school children around the world are learning the order of the planets by remembering, “My very excellent mother just served us nine….” Oops, I guess that one needs updating. Well, here’s one that will not need updating for tens of thousands of years: the order of the stars in the Big Dipper. Because the nighttime stars are so far away from us, their actual motion through the sky, called their “proper motion” is not noticeable over even thousands of years. That is why the constellations have remained the same since ancient times. But two stars in the Big Dipper have a proper motion large enough such that in 100,000 years; the stars will no longer make a dipper shape. You can see this simulated at the American Museum of Natural History video found at https://youtu.be/sBfUBtdo8yo. Until then, you can remember the names of the seven dipper stars in order from handle to cup by remembering this helpful advice for teens: “AM, ask mom. PM, dad”. The stars are Alkaid, Mizar, Alioth, Megrez, Phad, Merek, and Duhbe. The Big Dipper is one fist held upright and at arm’s length above the northern horizon at 11:00 p.m. 

Sunday: To the people of Ancient Greece, the stars that are about five and a half fists above the east-northeastern horizon at 10:00 p.m. were known as Cassiopeia and Andromeda, a mythological queen and her daughter. But not all cultures imagined the same pictures in the sky. To the people of Polynesia, the stars of Cassiopeia and Andromeda represented a dolphin, called Kwu. Cassiopeia formed its tail, the brightest stars of Andromeda formed its fins, and its fainter stars outlined the dolphin’s body. 

Monday: At 8:00 p.m., Jupiter is two fists above due south. Saturn is a half a fist to the left of Jupiter.

Tuesday: You discovered Cassiopeia two nights ago. The astronomer Caroline Herschel discovered an open star cluster that looks like a rose over 200 years ago. This cluster, called Caroline’s Rose, is about 6,500 light years away and consists of about 1,000 stars that are one third the age of the Sun. For more information about Caroline’s Rose, go to http://tiny.cc/i0zxsz and have the story read to you. Caroline's Rose is five and a half fists above the northeastern horizon at 9:00 p.m. First find the somewhat bright star at the top of the sideways "W" of Cassiopeia. With that star in the lower left portion of your binocular field of view, the Rose is near the center of your field of view.

Wednesday: Venus is two and a half fists above the eastern horizon at 6:00 a.m., trying to earn its nickname as “the morning star”.

Thursday: “There’s water in them thar craters”, frozen water, that is. There has been speculation since the 1960s and indirect evidence since the 2000s of water on the Moon. Two years ago, astronomers studied data from the Moon Mineralogy Mapper, the Lunar Orbiter Laser Altimeter, Lyman-Alpha Mapping Project, and Diviner Lunar Radio Experiment. The light reflecting off the bottom of craters near the lunar South Pole showed characteristics of light reflecting off pure ice in their labs. The water likely came from comet impacts or other solar system objects with trace amounts of water ice. For more information about this discovery, see https://goo.gl/P4zvtU. Tonight’s Full Moon must be full of water because it is in the constellation Cetus the sea monster

Friday: Mars is near the Moon for the entire night. At 8:00 p.m., they are a half a fist above due east, with Mars being a finger width above the Moon. By midnight, the Moon has moved noticeably away from Mars. By tomorrow morning, they are in the western sky. 

Speaking of tomorrow morning, the CWU campus is closed. But astronomy learning lives on! The Physics Department is hosting a First Saturday VIRTUAL planetarium show tomorrow from noon to 1:00 p.m. Former CWU professor Tony Smith will give a show featuring stories and highlights about the stars and planets in the October sky. He will use the browser-based Worldwide Telescope program found at http://worldwidetelescope.org/webclient/. There will be a virtual planetarium show on the first Saturday of every month for the rest of the school year. Stay at home, practice good physical distancing, and visit http://tiny.cc/hpyxsz to register for the show and to attend online using Zoom.

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.