The Ellensburg WA sky for the week of 4/29/17

Saturday: As the rock group Journey once thought of singing, “Wheel in the sky keeps on turnin’. Know where the Dipper’ll be tomorrow.” Every night, the Big Dipper and Cassiopeia make a wheel in the sky that turns around the North Star in a counter clockwise direction. Every year on May 3 at 10 p.m., the Big Dipper is straight overhead and W-shaped Cassiopeia is low on the northern horizon. Every year on May 4 at 10 p.m., the Big Dipper is straight overhead and W-shaped Cassiopeia is low on the northern horizon. Every year on May 5 at 10 p.m., the Big Dipper is straight overhead and W-shaped Cassiopeia is low on the northern horizon. Every year on May 6 at 10 p.m., well, you get the idea. Of course, there are subtle charges in the position from night to night. Each northern constellation moves about one degree counter clockwise from one night to the next. But this is not going to change their position in the sky drastically over a few days. So if you know where the Big Dipper is tonight, you DO know where it’ll be tomorrow. If you are really struggling to understand this concept, Don’t Stop Believin’ in yourself. Just keep studying Faithfully.

Sunday: Mars is a little more than one fist held upright and at arm’s length above the west-northwest horizon at 9 p.m.

Monday: Jupiter is nearly three fists above due south at 11:30 p.m.

Tuesday: You know Metis and Thebe and Adrastea and Amalthea. Io and Ganymede and Callisto and Europa. But do you recall? There are 67 Jovian moons in all. (As of July 2013.) Just 60 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 67 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 14, Mars with 2, and Earth with 1. Even dwarf planets have moons. Pluto has 5, 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. Go to http://goo.gl/Xkoeq for more information about Solar System moons.

Wednesday: At 5 a.m., Saturn is two fists above the south horizon and the very bright Venus is about a half a fist above the eastern horizon.

Thursday: Mother’s Day is a little over a week away. What are you going to get her? Get her a Gem(ma). The star Gemma, also known as Alphekka, is the brightest star in the constellation Corona Borealis, the Northern Crown. Gemma, Latin for jewel is the central gemstone for the crown. It is four fists held upright and at arm’s length above due east at 10 p.m.

Friday: The Eta Aquarid meteor shower peaks tonight and tomorrow morning. But since this meteor shower has a fairly broad peak range, there will be many more meteors than in the typical pre-dawn sky throughout the month of May. Meteor showers are named after the constellation from which the meteors appear to originate. The meteors appear to come from a point in the constellation Aquarius near the star Eta. This point is about one fist above the east horizon at 4 a.m. The Moon is new tonight so it won’t be lighting the sky and obscuring the dimmer meteors. So you could be rewarded with many bright, fast meteors. The Eta Aquarid meteors slam into the Earth at about 40 miles per second. They often leave a long trail. The Eta Aquarid meteors are small rocks that have broken off Halley’s Comet. For more information about the Eta Aquarids, go to http://earthsky.org/?p=3954.

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.