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Betelgeuse is a red supergiant star in the constellation of Orion. It is usually the tenth-brightest star in the night sky and, after Rigel, the second-brightest in its constellation. It is a distinctly reddish, semiregular variable star whose apparent magnitude, varying between +0.0 and +1.6, has the widest range displayed by any first ...
Rigel is an intrinsic variable star with an apparent magnitude ranging from 0.05 to 0.18. [5] It is typically the seventh-brightest star in the celestial sphere, excluding the Sun, although occasionally fainter than Betelgeuse. [31] Rigel appears slightly blue-white and has a B-V color index of −0.06. [32]
A line from Rigel through Betelgeuse points to Castor and Pollux (α Gem and β Gem). Additionally, Rigel is part of the Winter Circle asterism. Sirius and Procyon, which may be located from Orion by following imaginary lines (see map), also are points in both the Winter Triangle and the Circle. [6]
Bellatrix is the third-brightest star in the constellation of Orion, positioned 5° west of the red supergiant Betelgeuse (Alpha Orionis). It has the Bayer designation γ Orionis, which is Latinized to Gamma Orionis. With a slightly variable magnitude of around 1.6, it is typically the 25th-brightest star in the night sky.
The solar radius is usually defined as the radius to the layer in the Sun 's photosphere where the optical depth equals 2/3: [1] 695,700 kilometres (432,300 miles) is approximately 10 times the average radius of Jupiter, 109 times the radius of the Earth, and 1/215th of an astronomical unit, the approximate distance between Earth and the Sun.
Alpha Centauri (α Centauri, α Cen, or Alpha Cen) is a triple star system in the southern constellation of Centaurus. It consists of three stars: Rigil Kentaurus (α Centauri A), Toliman (α Centauri B), and Proxima Centauri (α Centauri C). [ 14 ] Proxima Centauri is the closest star to the Sun at 4.2465 light-years (1.3020 pc).
The hot supergiant Rigel emits 60% of its light in the ultraviolet, while the cool supergiant Betelgeuse emits 85% of its light at infrared wavelengths. With both stars prominent in the constellation of Orion, one can easily appreciate the color difference between the blue-white Rigel (T = 12100 K) and the red Betelgeuse (T ≈ 3800 K). [5]
The distance between the two varies between 8.2 and 31.5 astronomical units as they orbit every 50 years. [25] Sirius appears bright because of its intrinsic luminosity and its proximity to the Solar System. At a distance of 2.64 parsecs (8.6 ly), the Sirius system is one of Earth's nearest neighbours. Sirius is gradually moving closer to the ...