What's up in the sky 11/21/20
Today: “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 light years 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 held upright and at arm’s length above due south at 7:00 p.m. The much brighter Fomalhaut is a fist and a half below Skat. And, it’s not fun being below Skat.
Sunday: Venus, the brightest point of light in the sky, is about one and a half fists above the southeast horizon at 6:30 a.m. Mercury is to the lower left of Venus, between Venus and the horizon.
Monday: Are you thankful that you live in a solar system with multiple planets? You should be. A giant planet like Jupiter cleans up planetary debris that could have collided with Earth and hindered the formation of complex life. Any inhabitants of the planets orbiting Upsilon Andromedae are thankful for this, as well. Upsilon Andromedae, a star in the constellation Andromeda, was the first Sun-like star discovered to have multiple planets orbiting it. So far, all of its planets are giant planets like Jupiter. But, the system is likely to also contain smaller planets. The dim star, but certainly not its planets, is barely visible straight overhead at 9:00 p.m. Jupiter has set by then. You can see it one and a half fists above the south-southwestern horizon at 5:30 p.m. Saturn is less than a half a fist to the upper left of Jupiter.
Tuesday: Deneb Kaitos, Arabic for whale’s tail, is two and a half fists above due south at 8:30 p.m. This is the brightest star in the constellation Cetus the sea monster. Or, if you are less prone to hyperbole, Cetus the whale.
Wednesday: Mars is about a half a fist from the Moon tonight. At 6:00 p.m., it is right above the Moon. You can watch their relative positions change slightly throughout the night, until they set at 3:00 tomorrow morning.
Thursday: Some of us have a lot to be thankful for on Thanksgiving. But, probably not as much as Andromeda had to be thankful for. According to Greek mythology, the beautiful princess Andromeda was chained to a rock next to the ocean. Cetus the sea monster was about to devour her in order to punish her family. Her mother Queen Cassiopeia and her father King Cepheus didn’t know what to do. It seemed that all was lost. But, along came Andromeda’s boyfriend, the great warrior Perseus. Even though Perseus’ standing as the son of King Zeus and the slayer of Medusa was probably enough to win Andromeda under normal circumstances, Andromeda’s impending death-by-sea-monster was not a normal circumstance. So, Perseus drove his sword into the sea monster’s neck and killed it. This was the first time in recorded history that a set of parents actually welcomed an uninvited Thanksgiving visit from the boyfriend. Perseus is about five fists above the east-northeastern horizon and Andromeda is about seven fists above the eastern horizon at 7:00 p.m.
Friday: We are just a few days away from the earliest sunsets of the year in Ellensburg. (No, the earliest sunsets are not on the first day of winter.) So this is a good time to learn how to quantify the darkness of the sky. First find the Great Square, the main part of the constellation Pegasus. It is six fists above due south at 7:00 p.m. Find the dimmest star that you can see inside or near the square. Then compare that star to the chart at https://www.skyandtelescope.com/observing/how-dark-is-your-night-sky/. The larger the magnitude number, the dimmer the star. When the sky is exceptionally dark, you can see more stars and more interesting deep-sky objects such as star clusters and nebulae.
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.
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