Thursday, August 23, 2018

The Ellensburg WA sky for the week of 8/25/18

Today: Arcturus is four fists held upright and at arm’s length above the west-southwest horizon at 8:30 p.m. This star, whose name means bear watcher, is the brightest in the sky’s northern hemisphere. It follows Ursa Major, the Great Bear, around the North Star. Arcturus is the closest giant star to Earth. It is one of the few stars whose diameter can be measured directly rather than being inferred from its density and mass, which, themselves are derived from other parameters.

Sunday: This morning will be the best morning to observe Mercury for the next few weeks. Mercury is a little less than one fist above the east-northeast horizon at 5:30 a.m. Over the next few weeks, Mercury will move toward the Sun in the sky. By mid October, it will be visible in the evening sky.

Monday: Have you ever gone to a family reunion, looked around and asked, “How in the world are we related to each other?” Astronomers look around the Solar System and wonder if there is life anywhere else that we are related to. The Mars Science Laboratory landed on Mars in 2012 to investigate whether it ever had conditions favorable for life. The Venus Express studied the atmosphere of Venus from 2006 to 2014. The Cassini Mission continues to study the plume of complex organic chemicals streaming from Saturn’s moon Enceladus. NASA and the European Space Agency are planning missions to study Europa, the Jovian moon with an ice-covered ocean. And many astronomers consider the methane haze in the atmosphere in Saturn’s moon Titan similar to that of the early Earth. To learn more about the search for life in the Solar System and beyond, go to, a NASA-sponsored popular science magazine. While you won’t see anyone waving back, you can see Venus, Mars, Jupiter, and Saturn in the early night sky. Start with Venus, a half a fist above the west-southwest horizon at 8:30 p.m. Then move on to Jupiter, one and a half fists above the southwest horizon.

Tuesday: Deneb is nearly straight overhead at 11 p.m. When you look at Deneb, you are seeing light that left Deneb about 1,800 years ago.

Wednesday: Are you ready for more planets? Saturn is two fists above dus south at 8:40 p.m. At this time, Mars is one fist above the east-southeast horizon.

Thursday: All stars rotate. Our Sun takes a little less than an Earth month to make one rotation. Astronomers have started to study the relationship between mass, stellar rotation, and planetary formation by aiming NASA’s Kepler space telescope toward the Pleiades open star cluster. All 1,000 stars in this group is nearly the same age, 125 million years old. Since all of the stars are the same age and formed from the same set of materials, astronomers have the ideal “laboratory” to isolate the role star mass plays on star rotation and evolution. Read more about the findings at See the Pleiades for yourself, one fist above the east-northeast horizon at 11:30 p.m.

Friday: Yes, I know the total solar eclipse was one year ago. But one of the best photos was just released this week. It was, or more accurately, they were taken from a Southwest Airlines flight from Portland, Oregon to St. Louis, Missouri. Se and read more about the composite photograph at

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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