Betelgeuse facts for kids

The pink arrow at the star on left labelled α indicates Betelgeuse in Orion

Image showing Betelgeuse (top left) and the dense nebulae of the Orion Molecular Cloud Complex (Rogelio Bernal Andreo)

Betelgeuse (from Arabic:إبط الجوزاء Ibṭ al-Jauzā’, meaning "the armpit of Orion") is a large red supergiant star in the Orion constellation. It is usually the ninth-brightest star in the night sky, and the second-brightest in Orion.

Betelgeuse is a semiregular variable star whose apparent magnitude varies between 0.2 and 1.2. This is the widest range of any first-magnitude star.

It is also one of the largest and most luminous observable stars. It has a radius between 950 to 1,000 times wider than the Sun. This means it is 1.322 to 1.392 billion kilometers in diameter. Betelgeuse was the first star other than the Sun whose size was known. The star's distance from Earth is about 640 light-years. Its average absolute magnitude is about −6.02.

Betelgeuse is less than 10 million years old. It evolves rapidly because of its high mass. It is moving through the interstellar medium at a speed of 30 km/s, creating a shock wave over 4 light-years wide.

Betelgeuse is now in a later stage of stellar evolution. It will rapidly go through its life cycle before exploding as a type II supernova sometime in the next million years.

An observation by the Herschel Space Observatory in January 2013 showed that the star's winds are crashing against the surrounding interstellar medium. Betelgeuse is one of the red supergiant stars to have a bow shock: others are Mu Cephei and IRC-10414. Betelgeuse can be seen at the upper left in Orion.

Alternate names

Betelgeuse is also called Alpha Orionis (α Orionis, abbreviated Alpha Ori, α Ori).

Related pages

Orion (constellation)
Rigel
119 Tauri, Antares, and Mu Cephei, other similar red supergiant stars

Images for kids

Sir John Herschel in 1846
1998/9 UV HST images of Betelgeuse showing asymmetrical pulsations with corresponding spectral line profiles
AAVSO V-band magnitude of Betelgeuse, between September 2018 and August 2020
NRAO's Very Large Array used to derive Betelgeuse's 2008 distance estimate
AAVSO V-band light curve of Betelgeuse (Alpha Orionis) from Dec 1988 to Aug 2002.
Radio image from 1998 showing the size of Betelgeuse's photosphere (circle) and the effect of convective forces on the star's atmosphere
Infrared image of Betelgeuse, Meissa and Bellatrix with surrounding nebulae
Orion OB1 Association
Image from ESO's Very Large Telescope showing the stellar disk and an extended atmosphere with a previously unknown plume of surrounding gas
Exterior view of ESO's Very Large Telescope (VLT) in Paranal, Chile
Interior view of one of the four 8.2-meter Unit Telescopes at ESO's VLT
tiny red circle]] in the middle is the size of the photosphere.
Hertzsprung–Russell diagram identifying supergiants like Betelgeuse that have moved off the main sequence
Celestia depiction of Orion as it might appear from Earth when Betelgeuse explodes as a supernova, which could be brighter than the supernova that exploded in 1006
An illustration of Orion (horizontally reversed) in al-Sufi's Book of Fixed Stars. Betelgeuze is annotated as Yad al-Jauzā ("Hand of Orion"), one of the proposed etymological origins of its modern name, and also as Mankib al Jauzā' ("Shoulder of Orion").