Most people know about the famous stars of the Winter Triangle: Betelgeuse, Sirius and Procyon that form an asterism from three different constellations visible in fall and winter.
A set of bright stars are visible from December to March forming an asterism known as the Winter Hexagon or the Winter Circle. It consists of seven stars, two of them part of the Winter Triangle. The hexagon is visible almost worldwide, except for the farthest reaches of South America and New Zealand. On a clear night, all of the seven stars are visible from New York City.
Capella, in Auriga the charioteer, is the sixth brightest star in the night sky. It is 42 light years away and shines at 0.08 magnitude. Capella is a system of four stars in two binary pairs. The first pair consists of two bright giant stars Capella Aa and Capella Ab. Each of them is about 1000 times larger in volume than our sun and two and a half times its mass, in a tight orbit around each other. The second pair, Capella H and Capella L, consists of two faint red dwarfs.
Aldeberan, the Eye of Taurus the Bull, is a red giant about 65 light years away. It is 80,000 times larger than our sun, twice as massive, and 500 times brighter. It is a binary system with a small faint red dwarf companion. As the 14th brightest star viewed from Earth, Aldeberan is a variable star that shines at different magnitudes averaging at 0.8.
Rigel in Orion the Hunter, the seventh brightest star viewed from Earth, is a blue-white supergiant about 800 light years away. It is 400,000 times larger than our sun, and about thirty times more massive. It shines at 0.12 magnitude and it is at least 120,000 times brighter than our sun. It has two companions, Rigel B and Rigel C.
Sirius in Canis Major the Great Dog, the brightest star in the night sky, shines at -1.44. It’s one of the closest stars to us at 8.6 light years away. It’s ten times larger than our sun, twice as massive, and twenty times brighter. Sirius is a binary with a white dwarf star Sirius B, also known as the Pup.
Procyon in Canis Minor the Little Dog, is eleven light years away and the eighth brightest star seen from Earth, shining at 0.35 magnitude. It is about eight times larger than our sun, one and a half times more massive, and 7 times brighter. Procyon is a binary with white dwarf companion Procyon B.
Pollux is the brightest star in the constellation Gemini, and the seventeenth brightest star in the sky at 1.14. The giant yelloworange star is 700 times larger than our sun, twice as massive, and 40 times brighter. Its “twin” Castor, 50 light years away, is one of the brightest stars in our night sky at magnitude 1.55. Castor consists of six stars in three binary pairs. Each of the two largest stars in the system Castor Ab and Castor Ba is eight times larger than our sun, and over twice as massive.