Wednesday, September 30, 2015
The Ellensburg WA sky for the week of 10/3/15
Saturday: Since Halloween is later this month; the stores are filled with bags of candy clusters. Instead, take time to look at a star cluster. The Hyades cluster is an open star cluster that represents the V-shaped face of Taurus the bull. It is one of the biggest and nearest star clusters with about 200 stars 150 light years away. The Hyades cluster was the first cluster to be the subject of detailed motion studies. These studies allowed astronomers to pinpoint the distance to the Hyades and provide important information about the scale of the universe. Aldebaran, nearly two fists held upright and at arm’s length above the east horizon at 11 p.m., is a foreground star and not a part of the Hyades cluster.
Sunday: 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 all around the country 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 nearly 100,000 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 than in 100,000 years, the stars will no longer make a dipper shape. 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 north horizon at 11 p.m.
Monday: Along with the not-so-subtle drug reference in their name, The Doobie Brothers made an astronomy reference in their song lyrics: “Old black water, keep on rollin’, Mississippi moon won’t you keep on shining on me.” Astronomers now think that some of the water on Earth may be older than the Solar System. The chemical signature of the water indicates it came from a very cold source, just a few degrees above absolute zero. The early Solar System was much warmer than this meaning the water came from a source outside the Solar System. For more information about the old Earth water, go to http://goo.gl/QsEu5P.
Tuesday: Winter is coming to the morning sky. The “winter constellations” such as Orion, Taurus, and Gemini are high above the southern horizon at 6 a.m. They are called winter constellations because they are high in the sky during the evening viewing hours of the winter months.
Wednesday: The Draconid meteor shower peaks for the next three nights. The meteors appear to come from a point in the head of Draco, the dragon constellation. This point is about five fists above the northwest horizon at 10 p.m. tonight. This point remains near the trapezoid-shaped head of Draco throughout the night. Typically, this is a minor shower. However, Draconid meteors are slow moving which means you will have a easy time differentiating true Draconid meteors, from Comet 21P/Giacobini-Zinner, from stray grains of dust that happen to enter the Earth’s atmosphere near where we see the constellation Draco. The moon will be below the horizon for most of the peak viewing time so this might be your lucky meteor watching week. For everything you need to know about the Draconid meteor shower, go to http://goo.gl/HGkw0w.
Thursday: The east-southeast horizon is crowded with Solar System objects this morning. The Moon is just over three fists above the horizon. The bright point of light below the Moon is Venus. Just to the upper left of Venus is its moon Regulus. Oops. Regulus is actually a star that just happens to be near Venus in the morning sky. The red planet Mars is a fist to the lower left of Venus. (Wow, I’ve sure mentioned Venus a lot in today’s overview. Hmmm. Venus.) Jupiter is right below Mars, at about two fists above the horizon. The elusive Mercury is a half a fist above the east horizon, nearly lost in the glare of the soon-to-be rising Sun. Over the next three mornings, the Moon will hop down the ladder of planets to the horizon.
Friday: Saturn is one fist above the southwest horizon at 7 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 http://nightsky.jpl.nasa.gov/planner.cfm.