Thursday, June 1, 2017

The Ellensburg WA sky for the week of 6/3/17

Saturday: Cygnus the swan flies tonight. Deneb, the brightest star in the constellation, whose name means “tail” in Arabic, is two fists above the northeast horizon at 10 p.m. Cygnus’ wings make a vertical line one half a fist to the right of Deneb. Its head, marked by the star Albireo, is two fists to the right of Deneb. While Deneb is at the tail of Cygnus, it is at the head of the line of bright stars. It is 160,000 times more luminous than the Sun making it one of the brightest stars in the galaxy. It does not dominate our night sky because it is 2,600 light years away, one of the farthest naked eye stars. If Deneb were 25 light years away, it would shine as bright as a crescent moon. Compare that to Vega, which is 25 light years away. Vega is three and a half fists above the east-northeast horizon at this time.

Sunday: Venus is about a half a fist above the east horizon at 4 a.m. You can use it to find Uranus this morning. Get Venus in the bottom of your binocular filed of view. Uranus will be in the middle part of your field of view.

Monday: Jupiter is three and a half fists above the south-southeast horizon at 10 p.m.

Tuesday: While the NASA probe Dawn is off exploring the largest main-belt asteroid Ceres, you can explore the second largest asteroid Vesta. NASA has released Vesta Trek, a free web-based application that allows you to zoom in, “fly” over the surface, measure craters sizes, and see what Vesta looks like in different wavelengths of light. Go to for more information about Vesta Trek and the Dawn mission.

Wednesday: As the weather warms up, people start thinking about swimming in a nice cool body of water. Recently, astronomers have discovered evidence an ocean about 20 miles beneath the surface of Saturn’s moon Enceledas. NASA’s Cassini probes measured variations in how the moon’s gravity pulled on the orbiting spacecraft. These variations can be explained by a large amount of liquid water under one section of the ice because liquid water is denser than an equal volume of ice. While you need a very large telescope to see Enceledas, Saturn is one fist above the southeast horizon at 10:30 p.m.

Thursday: Tonight’s full Moon is in the constellation Ophiuchus. At 10:30 p.m., the Moon and Saturn are more than one fist apart in the sky. By 4:30 a.m., they are less than three quarters of a fist apart. That’s because the Moon is close enough to us such that its actual motion affects its position in the sky. For the distant stars and outer planets, heir only noticeable motion throughout the night is due to the Earth’s rotation.

Friday: Summer is nearly here. How do I know? Because the days are very long. Because the temperature is rising. Because kids are getting out of school. Also, because the Summer Triangle is fairly high in the eastern sky at 11 p.m. Vega, the third brightest star visible from Ellensburg, is about five fists above the east horizon. Deneb, at the tail of Cygnus the swan is about three and a half fists above the northeast horizon. The third star in the triangle, Altair, in Aquila the eagle is two fists above the east horizon.
If you want to put somebody off, tell her or him to wait until Deneb sets. At Ellensburg’s latitude of 47 degrees, Deneb is a circumpolar star meaning it never goes below the horizon.

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

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