Wednesday, October 14, 2015
The Ellensburg WA sky for the week of 10/17/15
Saturday: The Milky Way makes a faint white trail from due northeast through straight overhead to due southwest at 9 p.m. Starting in the northeast, the Milky Way “passes through” the prominent constellations Auriga the charioteer, Cassiopeia the queen, and Cygnus the swan with its brightest star, Deneb, nearly straight overhead. After Cygnus, you’ll see Aquila the eagle with its brightest star Altair about four and a half fists held upright and at arm’s length above the southwest horizon.
Sunday: Four planets are crowded near the east-southeast horizon at 6:30 this morning. Venus, the brightest planet, is three fists above the east-southeast horizon. Jupiter is about a half a fist to the lower left of Venus. Mars is visible in the same small telescope field of view as Jupiter, less than a pinky thickness to the lower left of the gas giant. Mercury is a more challenging target, a half a fist above the east horizon.
Monday: Halloween is next week so make sure you load up on peanut clusters, almond clusters, and open star clusters. That last one will be easy (and cheap… actually free) because two of the most prominent open star clusters in the sky are easily visible in the autumn sky. The sideways V-shaped Hyades Cluster is two fists above due east at 10 p.m. Containing over 300 stars; the Hyades cluster is about 150 light years away and 625 million years old. The Pleiades Cluster, a little more than three fists above due east, is larger at over 1000 stars and younger. Compared to our 5 billion year old Sun, the 100 million year age of the Pleiades is infant-like. The moon will help you find these clusters. This morning at 6:30 a.m., the Pleiades cluster is less than one fist to the upper right of the moon and the Hyades cluster is about one fist to the upper left of the moon. Tomorrow morning, the moon sits in the “V” of the Hyades cluster.
Tuesday: Saturn is about a half a fist above the southwest horizon at 7 p.m.
Wednesday: The Orionid meteor shower consists of the Earth colliding with pieces of the remains of Halley's Comet's tail. This shower peaks tonight after midnight. This is not a meteor shower that typically results in a meteor storm. There will be about 15-20 meteors per hour, many more meteors than are visible on a typical night but not the storm that some showers bring. Luckily, the moon is new so it won’t be obscuring many meteors. Meteor showers are named after the constellation from which the meteors appear to originate. These meteors appear to come from a point in Orion, the hunter. This point is about one fist above due east at midnight. You can follow this point throughout the night as it will remain one fist above the prominent reddish star Betelgeuse (pronounced Bet'-el-jews). The Orionid meteors are fast - up to 40 miles per second. If you fall asleep tonight, you can catch the tail end of the shower every night until early November. For more information, go to http://goo.gl/8f8J50.
Thursday: The weather forecast calls for blue skies… on Pluto. Recent images just sent back from the New Horizons spacecraft show Pluto’s atmospheric haze backlit by the Sun. Astronomers were surprised to see that the atmospheric haze was a rich blue color, similar to that of the Earth’s atmosphere. The reason for the blue color is similar, as well. Particles in Pluto’s thin atmosphere scatter the blue component of sunlight just like the nitrogen particles in the Earth’s atmosphere scatter the blue component of sunlight and make the sky appear blue. Pluto’s atmosphere is too thin to look blue from its surface. But obviously thick enough to look blue while backlit by the Sun. For more information about Pluto’s blue sky, go to http://goo.gl/meIzTj.
Friday: “It’s a wonderful day in the neighborhood.” Constellations can be considered neighborhoods in the nighttime sky. But, the stars in those constellations are not necessarily neighbors in real life. For example, the bright stars in the constellation Cassiopeia range from 19 to over 10,000 light years away from Earth. One constellation that consists of real neighbors is Ursa Major. Or, more specifically, the Big Dipper. Five stars in the Big Dipper are all moving in the same direction in space, are about the same age and are all about 80 light years from Earth. “Please won’t you be my neighbor?” Skat, the third brightest star in the constellation Aquarius is a neighbor to these five Big Dipper stars, all of which are about 30 light years from each other. They are thought to have originated in the same nebula about 500 million years ago. Just like human children do, these child stars are slowly moving away from home. Skat is about three fists above due south at 10 p.m. The much brighter Fomalhaut is a fist and a half below Skat. And, it’s not fun being below Skat.
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 http://nightsky.jpl.nasa.gov/planner.cfm.