The sun is a very stable star in the prime of its life. Many stars fluctuate periodically and are called variable stars. Astronomers use cameras to do photometry to precisely determine the stars’ brightnesses. For some stars, this variation can be seen with just your eyes.

The star in the left shoulder of the constellation Orion, the Hunter, is called Betelgeuse. It has been in the news lately because it is currently fainter than it has been in the past. Betelgeuse is a red giant star that is approaching the end of its life with a fluctuation period of about 425 days. It can be almost as faint as Bellatrix (right shoulder, magnitude 1.55) and brighter than Rigel (right knee, magnitude 0). Currently it is at magnitude 1.5.

Come to the observatory on the first Friday each month from sunset-10 p.m. This is the season to see Betelgeuse: humbleisd.net/observatory.

Aaron Clevenson
Author: Aaron ClevensonEmail: This email address is being protected from spambots. You need JavaScript enabled to view it.
I am the observatory director at the Insperity Observatory in Humble ISD. I am also an adjunct astronomy professor at Lone Star College-Montgomery where I teach solar system astronomy and stars and galaxies astronomy. I am the author of the astronomy textbook, “Astronomy for Mere Mortals.” I am a past president of the North Houston Astronomy Club, and was the chair of Astronomy Day in Southeast Texas in 2015 and 2016. He is an observing program director with The Astronomical League, coordinates their Master Observer Progression Awards, and has authored six of their observing programs.

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