The Ellensburg WA sky for the week of 12/3/16

Saturday: Venus is a fist held out at arm’s length below the Moon, in the south-southwest sky at 4:45 p.m. Mercury is the more challenging object to find, less than a half a fist above due southwest at this time.

Sunday: Mars is less than a half a fist to the left of the Moon at 9 p.m. They are both just above the west-southwest horizon.

Monday: The earliest sunset of the year occurs throughout the next week: 4:13 p.m. This seems odd because the shortest day of the year, the winter solstice, isn’t for about two more weeks. 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 sunrise and sunset times depend on more than its apparent southward motion in the sky. 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 leading edge of the analemma, the first section to go below the horizon. For a slightly different explanation about this, go to http://goo.gl/kjnHP. Or just go watch the sunset. But don’t stare at the Sun.

Tuesday: Most constellations don’t look like the object their name refers to. That’s because most constellations don’t have such a simple to object to emulate as Triangulum does. Triangulum is shaped like a… wait for it…. Wait for it…. A thin isosceles triangle. Metallah is the only named star in the constellation. In Latin this star is called Caput Trianguli, the head of the triangle. Triangulum is seven fists above due south horizon at 9 p.m. It is pointing down and to the right with Metallah being the southernmost star at this time of night. The Triangulum Galaxy can be seen with binoculars about a half a fist to the right of Metallah.

Wednesday: Jupiter is three and a half fists above the south-southeast horizon at 7 a.m.

Thursday: It’s getting too cold to see frogs in the wild. Some rich politicians see them on their dinner plate. But this is a great time to see frogs in the sky. Ancient Arabs referred to the stars that we now call Fomalhaut and Diphda as Ad-difdi al-awwal and Ad-difda at-tani. This means the first frog and the second frog, respectively. Both frogs are low in the southern sky at 7 p.m. Fomalhaut is one fist above the horizon and one fist to the east of due south. The slightly dimmer Diphda a little more than two fists above the horizon and one fist to the west of due south.

Friday: Cosmic rays are high-energy subatomic particles. When they strike the Earth, they interact with the atmosphere, creating a cascade of other particles including muons. These muons pass through almost everything. So muons (HUH), what are they good for? Absolutely nothing? Wrong. They are good for probing the interior of places too fragile or too dangerous to enter. Scientists observed the pattern of muons passing through the Fukushima nuclear reactor to determine the location and orientation of the damaged fuel rods. For more muon application, go to https://stardate.org/radio/program/cosmic-rays-iii.

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.