Friday, December 8, 2017
The Ellensburg WA sky for the week of 12/16/17
Saturday: “Lately, I’ve been, I’ve been losing sleep. Dreaming about the things that we could be. But baby, I’ve been, I’ve been praying hard, said no more counting dollars. We’ll be counting 9,096 stars, yeah we’ll be counting 9,096 stars.” Luckily, artistic judgment prevailed over scientific precision in the OneRepublic hit “Counting Stars”. According to the Yale Bright Star Catalog, there are 9,096 stars visible to the naked eye across the entire sky if you are observing from a very dark site. In the northern United States, where a part of the sky is never visible, that number drops to about 6,500. In the middle of a small city at mid-latitudes, like Ellensburg, that number drops to a few hundred. No wonder someone has been losing sleep. Learn more about the star count at http://goo.gl/nt8d80.
Sunday: Today is Saturnalia, an ancient Roman festival in honor of their god Saturn, the god of agriculture and time. The holiday featured a break from work and school, a public banquet, and private gift giving. Some of these customs influenced the secular aspects of Christmas celebrations. After Sheldon hugged Penny on The Big Bang Theory, Leonard said, “It’s a Saturnalia miracle.” See the miracle on YouTube. It would be nearly a miracle if you saw the planet Saturn today. It sets just a few minutes after the Sun. It won’t be easily visible again until it shows up in the morning sky in mid-January.
Monday: Fomalhaut, the southernmost bright star for the northern latitudes, is one and a half fists above due south at 5 p.m.
Tuesday: Jupiter is two fists held upright and at arm’s length above the southeast horizon at 7 a.m. Less than a pinky-width below it is the bright star Zubenelgenubi. Even though it is the second brightest star in Libra, its name means Southern Claw in Arabic, an artifact of the time that it was considered part of Scorpius the scorpion. Zubenelgenubi is a visual binary, consisting of a white and yellow star that are about arc minutes apart from each other in the sky. This is about the same angular diameter of a medium sized dark spot, or mare, on the Moon and can be observed with the naked eye under good sky conditions. In actuality, they are at least 5,500 astronomical units apart from each other, about 130 times the distance between the Sun and Pluto.
Wednesday: Do you look into a nursery and say, “it’s a boy” or “it’s a girl”? Not me. I say, “It’s a star”. Of course, I like looking into a stellar nursery – a star-forming region such as the Orion Nebula in the middle of Orion’s sword holder. The Orion Nebula looks like a fuzzy patch to the naked eye. Binoculars reveal a nebula, or region of gas and dust, that is 30 light years across. The center of the nebula contains four hot “baby” stars called the Trapezium. These hot stars emit the ultraviolet radiation that causes the Nebula’s gas to glow. The Orion Nebula is two and a half fists above the southeast horizon at 9 p.m.
Thursday: At 8:28 a.m., the Sun reaches its lowest point in the sky with respect to the background stars. This point is called the Winter Solstice. During the day that the Sun reaches this point, your noontime shadow is longer than any other day of the year. Also, the Sun spends less time in the sky on the day of the Winter Solstice than any other day making this the shortest day of the year. Even though it is the shortest day of the year, it is not the day with the latest sunrise or the earliest sunset. The latest sunrise is during the first week in January and the earliest sunset is during the second week in December. The Sun is at its southernmost point with respect to the background stars on the day of the winter solstice. This means the Sun spends the least amount of time above the horizon on that day. But, the Sun rise and set time depends on more than its apparent vertical motion. It also depends on where the Sun is on the analemma, that skinny figure-8 you see on globes and world maps. During the second week in December, the Sun is not quite to the bottom of the analemma. But, it is on the first part of the analemma to go below the horizon. During the first week in January, it is on the last part of the analemma to rise above the horizon. For more information on this, go to http://goo.gl/KpbkTf.
Friday: Headline from the tabloids: Earth sends robot to Mars in order to take a selfie. In January 2014, the Mars Curiosity rover took a picture of its night sky that included the Earth and moon. Both would easily be visible to the naked eye for a human standing on Mars. Since you can’t go to Mars, go to http://goo.gl/DqprKF look at the picture. Then go outside and look two and a half fists above the south-southeast horizon to see Mars. Mars and Jupiter are moving towards each other in the morning sky.
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.