User:Sadalsuud/Beetle1geuse
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Betelgeuse (/ˈbiːtəldʒuːz/ or /ˈbɛtəldʒuːz/),[1] also known by its Bayer designation Alpha Orionis (α Orionis, α Ori), is the eighth brightest star in the night sky and second brightest in the constellation of Orion, outshining Rigel (Beta Orionis) only rarely. Distinctly reddish, it is a semiregular variable star whose apparent magnitude varies between 0.2 and 1.2, the widest range of any first-magnitude star. Betelgeuse marks the upper right vertex of the Winter Triangle asterism and the center of the Winter Hexagon.
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Orion |
Pronunciation | /ˈbiːtəldʒuːz/ or /ˈbɛtəldʒuːz/[1] |
Right ascension | 05h 55m 10.3053s[2] |
Declination | +07° 24′ 25.426″[2] |
Characteristics | |
Spectral type | M2Iab[2] |
Apparent magnitude (V) | 0.42 (0.3 to 1.2)[2][3] |
Apparent magnitude (J) | -2.99 ± 0.10[2] |
U−B color index | 2.06[4] |
B−V color index | 1.85[4] |
Variable type | SR c (Semi-Regular)[2] |
Astrometry | |
Radial velocity (Rv) | +21.91[2] km/s |
Proper motion (μ) | RA: 24.95 ± 0.08[5] mas/yr Dec.: 9.56 ± 0.15[5] mas/yr |
Parallax (π) | 5.07 ± 1.10 mas[5] |
Distance | 643 ± 146 [5] ly (197 ± 45 [5] pc) |
Absolute magnitude (MV) | −6.02[6][note 1] |
Details | |
Mass | 7.7–20[7] M☉ |
Radius | 950–1200[7][8] R☉ |
Luminosity | 120,000±30,000[7] L☉ |
Surface gravity (log g) | -0.5[9] cgs |
Temperature | 3,140-3,641[7][10][11] K |
Metallicity | 0.05 Fe/H[12] |
Rotation | 5 km/s[11] |
Age | ~7.3×106 [6][13] years |
Other designations | |
Database references | |
SIMBAD | data |
The star is classified as a red supergiant of spectral type M2Iab and is one of the largest and most luminous known stars. If it were at the center of the Solar System its surface would extend past the asteroid belt, possibly to the orbit of Jupiter and beyond, wholly engulfing Mercury, Venus, Earth and Mars. Its distance in 2008 was estimated at 640 light-years, yielding a mean absolute magnitude of about −6.02. 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 also includes the late type O and B stars in Orion's belt, Alnitak, Alnilam and Mintaka—this crimson runaway has been observed racing through the interstellar medium at a supersonic speed of 30 km/sec, creating a bow shock over 4 light-years wide. Currently in a late stage of stellar evolution, the supergiant is expected to proceed through its expected life cycle before exploding as a type II supernova within the next million years.
In 1920, Betelgeuse was the first star (after the Sun) to have its photosphere measured. Since then, researchers have used a number of telescopes to measure this stellar giant, each with different technical parameters, often yielding conflicting results. Studies since 1990 have produced an apparent diameter ranging from 0.043 to 0.056 arcseconds, an incongruity largely caused by the star's perceived tendency to periodically change shape. Because of limb darkening, variability, and angular diameters that vary with wavelength, the star remains a perplexing mystery. Adding to the computational challenges, Betelgeuse has a complex, asymmetric envelope caused by colossal mass loss obscuring its surface—an envelope that is roughly 250 times the size of the star itself—with stellar companions possibly orbiting within this circumstellar nebula magnifying the star's eccentric behavior.