<P> Coordinates: 05 55 10.3053, + 07 ° 24 ′ 25.426" </P> <P> Betelgeuse, also designated Alpha Orionis (α Orionis, abbreviated Alpha Ori, α Ori), is the ninth - brightest star in the night sky and second - brightest in the constellation of Orion . Distinctly reddish, it is a semiregular variable star whose apparent magnitude varies between 0.0 and 1.3, the widest range of any first - magnitude star . Betelgeuse is one of three stars that make up the Winter Triangle asterism, and it marks the center of the Winter Hexagon . It would be the brightest star in the night sky if the human eye could view all wavelengths of radiation . </P> <P> Classified as a red supergiant of spectral type M1 - 2, the star is one of the largest and most luminous stars visible to the naked eye . If Betelgeuse were at the center of the Solar System, its surface would extend past the asteroid belt, wholly engulfing the orbits of Mercury, Venus, Earth, Mars, and possibly Jupiter . Calculations of its mass range from slightly under ten to a little over twenty times that of the Sun . It is calculated to be 640 light - years away, yielding an absolute magnitude of about − 6 . Less than 10 million years old, Betelgeuse has evolved rapidly because of its high mass . Having been ejected from its birthplace in the Orion OB1 Association--which includes the stars in Orion's Belt--this runaway star has been observed moving through the interstellar medium at a speed of 30 km / s, creating a bow shock over 4 light - years wide . Currently in a late stage of stellar evolution, the supergiant is expected to explode as a supernova within the next million years . </P> <P> In 1920, Betelgeuse became the first extrasolar star to have the angular size of its photosphere measured . Subsequent studies have reported an angular diameter (apparent size) ranging from 0.042 to 0.056 arcseconds, with the differences ascribed to the non-sphericity, limb darkening, pulsations, and varying appearance at different wavelengths . It is also surrounded by a complex, asymmetric envelope roughly 250 times the size of the star, caused by mass loss from the star itself . The angular diameter of Betelgeuse is only exceeded by R Doradus (and the Sun). </P>

To which group does the star betelgeuse belong