Looking Up: See Betelgeuse, the ruby-red star
Last week’s column highlighted the "diamond in the sky," Sirius. This time around we will look at another beacon of the winter sky, which shines more like a ruby: Betelgeuse.
Betelgeuse is one of the luminaries of the constellation Orion, marking the upper left corner of the parallelogram of stars encompassing the famed stellar trio of "Orion’s Belt". You can see Orion in the south on February evenings.
The eighth brightest star in the night sky, Betelgeuse appears red-orange. Its fiery appearance is striking in a telescope of any size, suggesting a burning ember flaring from the black of space. Betelgeuse varies in brightness by 1.2 magnitude, at an irregular rate,
The star is classified as a Red Giant. Once a star that has at least 10 times the Sun’s mass has used up its hydrogen, it is believed to expand into an enormous sphere of gas, as it starts consuming its reservoir of helium. Betelgeuse is so huge, its surface extends possibly as far as the distance from our Sun to the orbit of Jupiter.
Betelgeuse is about 640 lights years from your backyard. Being so huge and so close, the star was the first (besides the Sun) to be measured in angular diameter, in 1920.
Another name for it is Alpha Orionis. The principal stars of each of the 88 constellations are listed in star catalogs and star atlases by the Greek alphabet; for the most part, in order of brightness from the most bright (Alpha) to the least (Omega).
I like "Betelgeuse" better, although no one asked me! Other variations of the name are Betelguex, Betelgeuze and Beteiguex.
Brilliant blue-white Rigel (Beta Orionis) shines at the lower right corner of the Orion figure. The prominent star at the lower left is Saiph; the prominent star at the upper right corner is Bellatrix. The three stars marking the "Belt" are from left, Alnitak, Alnilam and Mintaka.
Right below Alnitak is a patch of stars, marking "Orion’s Sword." The middle one appears hazy; binoculars quickly show this as a small, cloudy patch, the Great Nebula of Orion, listed as M42. This is a region where stars are being formed.
Two American Navy cargo ships were named for the star, both used in World War II. They were the USS Betelgeuse (AKA-11) and USS Betelgeuse (AK-260). The French also had a super tanker named Betelgeuse which exploded as it was discharging oil off Ireland in 1979. Fifty persons were killed.
Other bright red stars include Aldebaran, located to the upper right of Orion, and Antares, which shines in constellation Scorpius and seen in the summer evening sky. Red/orange stars are actually very common, and a slow sweep through a dark night sky with a small telescope will reveal many.
First quarter Moon is on Feb. 23
Keep looking up!
— Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at news@neagle.com. Please mention in what newspaper or web site you read this column.