Betelgeuse
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Orion |
| Pronunciation |
/ˈbiːtəldʒuːz/, /ˈbɛtəldʒuːz/ or /ˈbiːtəldʒuːs/ |
| Right ascension | 05h 55m 10.30536s |
| Declination | +07° 24′ 25.4304″ |
| Characteristics | |
| Evolutionary stage | Red supergiant |
| Spectral type | M1–M2 Ia–ab |
| Apparent magnitude (V) | 0.50(0.0 - 1.3) |
| Apparent magnitude (J) | −3.00 |
| Apparent magnitude (K) | −4.05 |
| U−B color index | +2.06 |
| B−V color index | +1.85 |
| Variable type | SRc |
| Astrometry | |
| Radial velocity (Rv) | +21.91 km/s |
| Proper motion (μ) |
RA: 24.95 ± 0.08 mas/yr Dec.: 9.56 ± 0.15 mas/yr |
| Parallax (π) | 5.07 ± 1.10mas |
| Distance | 643 ± 146ly (197 ± 45pc) |
| Absolute magnitude (MV) | −5.85 |
| Details | |
| Mass |
11.6+5.0 −3.9 M☉ |
| Radius | 887±203 R☉ |
| Luminosity | 90000 – 150000 L☉ |
| Surface gravity (log g) | −0.5 cgs |
| Temperature | 3590 K |
| Metallicity [Fe/H] | +0.05 dex |
| Rotational velocity (v sin i) | 5 km/s |
| Age | 8.0 – 8.5 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Coordinates: 
05h 55m 10.3053s, +07° 24′ 25.426″
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.
The star is classified as a red supergiant of spectral type M1-2 and 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 and Mars. 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 crimson runaway has been observed moving through the interstellar medium at a supersonic 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.
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