Thursday, May 6, 2021

The bright stars of winter have arrived

The Eastern Sky 9:00PM December 17th. Submitted

The Eastern Sky 9:00PM December 17th. Submitted

by Mike Usher

For some reason the brightest stars in the sky make their appearance in the winter. We already met Betelgeuse and Rigel last time; now extend the line formed by Orion’s belt stars upwards to find Aldebaran. It is the orange eye of Taurus the Bull who seems to be forever fighting Orion. Turn your gaze to the left to find the bright star Capella, commonly nicknamed the goat star as ancient artists depicted Auriga holding a goat. Drop back towards the horizon to see two about equally bright stars Castor and Pollux, part of Gemini. To the right and slightly downwards is Procyon and to the right of that is the brightest of all stars Sirius. If you start at Aldebaran proceed counter-clockwise to the above mentioned stars and finish at Rigel and then Betelgeuse you will see you have followed a giant “G” shape in the sky!

Notice how bright stars, particularly Sirius, sparkle and flash different colors while near the horizon. This is caused by our atmosphere being thicker and rather unstable near the horizon. Inexperienced star gazers almost invariably wonder if they could possibly be  UFO’s, particularly since the stars are close to fixed objects such as trees which makes the motion of the stars more obvious. Planets don’t twinkle as much as they are tiny disks instead of dimensionless points of light, but even they will twinkle if the air is unstable enough. Just this summer I was with two teenagers who spotted Venus very close to the horizon twinkling; first words out of their mouths were “Is that a UFO?”

Next week when the Moon is not visible, notice that Aldebaran lies inside a “V” shaped group of stars that form the base of Taurus’ horns. These stars form the Hyades, one of the few open star clusters easily visible to the naked eye. Aldebaran is not a member but merely lies along the same line-of-sight less than half the distance away.

The most obvious star cluster in the sky is above Aldebaran, just barely on our chart tonight. These are the famous Pleiades, a group of perhaps a thousand members of which six are easily visible to the eye and as many as 14 to the very sharp-eyed in a very dark sky. They have a very long observational history going back to the 23rd century BC Babylonia, are mentioned by Homer in the Iliad and Odyssey and mentioned three times in the Bible. For a bit a trivia to amaze your friends “Subaru” is the Japanese word for Pleiades! See you next time!


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