Sunday, April 15, 2012

The Ellensburg Sky for the week of 4/21/12

Saturday: Remember the old saying: April showers bring… meteors. The Lyrid meteor shower peaks tonight. The meteors appear to come from a point to the right of the bright bluish star Vega in the constellation Lyra the lyre. This point is about three fists held upright and at arm’s length above the east-northeast horizon at midnight tonight and close to straight overhead near dawn. The best time to look is just before dawn since that is when the radiant, or point from which the meteors appear to come, is high in the sky. This year, the Moon is new so expect to see up to 20 bright meteors per hour. Typically, this is one of the least interesting major meteor showers of the year. However, it is also one of the most unpredictable. As recently as 1982, there were 90 meteors visible during a single hour. In addition, the Lyrid meteor shower has historical interest because it was one of the first ones observed. Chinese records say “stars fell like rain” in the shower of 687 B.C. As your Mother might say, dress warm and sit in a comfortable chair for maximum enjoyment. Meteors are tiny rocks that hit the Earth and burn up in the atmosphere.

Sunday: You know Metis and Thebe and Adrastea and Amalthea. Io and Ganymede and Callisto and Europa. But do you recall? There are 65 Jovian moons in all. Less than 50 years ago, Jupiter was thought to have only 12 moons. But, astronomers are red-nosed with delight that the advent of supersensitive electronic cameras has caused the number of discovered moons to rapidly increase. Jupiter’s 65 moons range in size from Ganymede, with a diameter of 5,262 kilometers, to S/2002 J12 and S/2003 J9, with a diameter of only one kilometer. Our moon has a diameter of 3,475 kilometers. (One kilometer is 0.62 miles.) Saturn is second place in the moon race with 62. Uranus is next with 27. Then comes Neptune with 13, Mars with 2, and Earth with 1. Even dwarf planets have moons. Pluto has 4, Eris has 1, and Haumea has 2. Eris is an outer solar system object that was discovered in 2005 and named in September of 2006. Because astronomers thought it was larger than Pluto, people called it the tenth planet for a while. (More recent measurements show Eris to be a little smaller than Pluto.) Haumea, the newest dwarf planet with a moon, was discovered in 2004 and officially named a dwarf planet on September 17, 2008. Jupiter, the “mooning” champ, is a half a fist above the west horizon at 9 p.m. Go to for more information about Solar System moons.

Monday: Are you thirsty. I’ll wait while you get some water. I will NOT wait while Corvus the crow gets you some water. The Greco-Roman god Apollo made this mistake. He sent Corvus the crow to get some water in the cup known as Crater. Some figs distracted Corvus and he waited for them to ripen so he could eat them. When Corvus got back late, Apollo put Corvus and Crater in the sky with the gently tipping cup just out of the reach of the perpetually thirsty crow. Corvus is a trapezoid-shaped constellation about two fists above due south at 11 p.m. Crater is just to the right of Corvus.

Tuesday: Venus is about a half a fist to the upper right of the Moon at 9 p.m. Both objects are low in the western sky.

Wednesday: “Water, water everywhere nor any drop to drink” is from The Rime of the Ancient Mariner. (No not Ichiro.) But is could be the slogan of our solar system. Astronomers used to think that the solar system was dry with earth being the only place to find water. It turns out that the solar system has an abundance of water; Comets are made of water ice. Some astronomers think they be the source of some, or even most, of Earth’s water. Jupiter’s Moon Europa has a crust of frozen water covering a large ocean containing more water than all of the Earth’s oceans. Even the Moon, thought to be dry as a bone, has frozen ice deep in its polar craters. Take a swim in the watery last quarter Moon this morning. Once you dry off, visit to read more about solar system water.

Thursday: At 10 p.m., Mars is about five and a half fists above the south horizon and Saturn is about two and a half fists above the southeast horizon. Saturn is slightly brighter and orange compared to the bluish star Spica to its lower right.

Friday: How many of you know your 12 nearest neighbors? I thought so. Why don’t you go out and meet them right now. I’ll wait. Yes, of course bring them cookies. No, not those stale ones you hate.
Are you back already? That means you didn’t really go out and meet your 12 nearest stellar neighbors, did you? Including the Sun, there are 12 stars within 10 light years of Earth. The most well known are the Sun (obviously); Proxima Centauri, the nearest star other than the Sun; Alpha Centauri, a bright binary star visible from the tropics and the Southern Hemisphere; and Sirius, the brightest star in the nighttime sky. Sirius is the largest and most luminous star in our neighborhood. It is one and a half fists above the southwest horizon at 9 p.m.

The positional information in this column about stars and planets is typically accurate for the entire week.

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