Thursday, August 2, 2018
The Ellensburg WA sky for the week of 8/4/18
Saturday: Enjoy four planets visible to the naked eye at 9 p.m. tonight. Venus is one fist above the west horizon. Jupiter is two fists above the southwest horizon. Saturn is two fists above the south-southeast horizon. Mars is less than a half a fist above due south east.
Sunday: Did you think you saw one of Jupiter's moons last night during your naked eye viewing of the sky? You can't see Jupiter's moons without binoculars or a small telescope. That bright point of light you see a pinky-width to the lower left of Jupiter is Zubenelgenubi, the second brightest star in the constellation Libra. Take a look again tonight at 10 p.m., one and a half fists above due southwest.
Monday: Mizar is a well-known binary star in the constellation Major. You can find it at the bend in the Big Dipper handle, one fist above due north at 5 a.m. Its name is Arabic for waistband. Mizar has an optical double called Alcor, which is less than a pinky width away and can easily be seen with the naked eye. Optical doubles are stars that are close together in the sky but do not orbit a common center of mass as true binary stars. Not wanting to deceive sky gazers who call Alcor and Mizar a binary star, two stars that DO orbit a common center of mass, Mizar actually is a binary. It was the first binary star system discovered by telescope. Mizar A and Mizar B are about 400 astronomical units apart from each other and about 80 light years from Earth. 400 astronomical units is about 10 times the distance between the Sun and Pluto.
Tuesday: It is not winter yet. But Orion, thought of as a winter constellation, is just above the east-southeast horizon at 5 a.m. By the actual winter, it will be visible in the evening sky.
Wednesday: The Perseid meteor shower hits its peak for the next few early mornings with Sunday and Monday mornings being the peak of the peak. The meteors appear to come from a point just below the W of the constellation Cassiopeia. This point is about two and a half fists held upright and at arm’s length above the northeast horizon at 11 p.m. By dawn, this point is about seven fists above the northeast horizon. If you fall asleep or forget to set your alarm, you will be able to observe this shower from about 11 p.m. to dawn for the next few nights in about the same location in the sky. The Perseid shower is one of the longest lasting showers. The Moon will be new or close to new for the next few nights. For tips about optimizing your viewing this year, go to http://earthsky.org/?p=2087. As your Mother might say, dress warm and sit in a comfortable chair for maximum enjoyment. These meteors are sand to pea-sized bits of rock that fell off of Comet Swift-Tuttle. They are traveling about 40 miles per second as they collide with the Earth and burn up in the atmosphere.
Thursday: Many big city dwellers never see the milky white, nearly continuous band of stars known as the Milky Way. As cities grow and add more lights, it has become harder to see the bulk of the Milky Way galaxy, our home in the universe. But, there are two easy ways to see the Milky Way. The first way is to look in the mirror. You are part of the Milky Way. The second way is to look from due north through the point straight overhead (called the zenith) to due south from 10:30 p.m. to 1 a.m. for the next two weeks. This is the time of year when the Milky Way is highest in the sky and away from the city lights on the horizon.
Friday: Mars is as close to Earth and as bright as it has been in many years this summer. Enjoy the show one and a half fists above due south at midnight tonight.
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.