Wednesday, April 20, 2011

The Ellensburg sky for the week of 4/23/11

Saturday: You know Metis and Thebe and Adrastea and Amalthea. Io and Ganymede and Callisto and Europa. But do you recall? There are 63 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 63 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 61. Uranus is next with 27. Then comes Neptune with 13, Mars with 2, and Earth with 1. Even dwarf planets have moons. Pluto has 3, 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, was discovered in 2004 and officially named a dwarf planet on September 17, 2008. Saturn, in second place on the moon list, is three fists held upright and at arm’s length above the east horizon at 9 p.m. Go to for more information about moons.

Sunday: 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. Corvus got distracted by some figs 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.

Monday: “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.

Tuesday: 50 years ago this morning, Jupiter and Saturn were in line with the constellation Capricornus the sea goat. What does this mean for a person born on that day? Maybe they like swimming as symbolized by the water reference. Maybe they were raised in crowded conditions as symbolized by the two largest planets being in one constellation. Or maybe the location of the planets on the day you were born has nothing to do with what you become as an adult. Maybe you turn out to be a great person, loved by those close to you, because of the choices you make and the hard work that you do. That’s what I think. Take that, astrology!

Wednesday: Sirius, the brightest star in the nighttime sky, is one and a half fists above the southwest horizon at 8:30 p.m.

Thursday: Vega is one fist above the northeast horizon at 9:30 p.m.

Friday: Hydra the water snake rears its ugly head in the southwest sky at 10 p.m. First find Procyon. This bright star is two and a half fists above the west-southwest horizon. Next, find Saturn and Regulus right next to each other, five fists above the southwest horizon. Now, draw an imaginary line between Procyon and Regulus. Just below the midway point of that line, you should see a clump of stars that make the shape of a crooked house. This is the head of Hydra. The brightest star in the constellation, called Alphard, is three fists above the south horizon, midway between Regulus and the horizon. There are no other bright stars in the area. So it makes sense that the name Alphard means “the solitary one”.
As you may have noticed, Hydra is just below Corvus and Crater. Apollo put Hydra in the sky to keep Corvus from drinking the water from the cup.

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

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