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Sirius (star)

Sirius A / B
Sirius is located in 100x100
Sirius

The position of Sirius (circled).
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Canis Major
Sirius (/ˈsɪriəs/) system
Right ascension 06h 45m 08.91728s
Declination −16° 42′ 58.0171″
Apparent magnitude (V) −1.46
Sirius A
Right ascension 06h 45m 08.917s
Declination −16° 42′ 58.02″
Apparent magnitude (V) −1.47
Sirius B
Right ascension 06h 45m 09.0s
Declination −16° 43′ 06″
Apparent magnitude (V) 8.44
Characteristics
Sirius A
Evolutionary stage Main sequence
Spectral type A0mA1 Va
U−B colour index −0.05
B−V colour index +0.00
Sirius B
Evolutionary stage White dwarf
Spectral type DA2
U−B colour index −1.04
B−V colour index −0.03
Astrometry
Radial velocity (Rv) −5.50 km/s
Proper motion (μ) RA: −546.01 mas/yr
Dec.: −1223.07 mas/yr
Parallax (π) 379.21 ± 1.58mas
Distance 8.60 ± 0.04 ly
(2.64 ± 0.01 pc)
Sirius A
Absolute magnitude (MV) 1.42
Sirius B
Absolute magnitude (MV) 11.18
Orbit
Companion α CMa B
Period (P) 50.1284 ± 0.0043 yr
Semi-major axis (a) 7.4957 ± 0.0025″
Eccentricity (e) 0.59142 ± 0.00037
Inclination (i) 136.336 ± 0.040°
Longitude of the node (Ω) 44.40 ± 0.071°
Periastron epoch (T) 1994.5715 ± 0.0058
Argument of periastron (ω)
(secondary)
149.161 ± 0.075°
Details
α CMa A
Mass 2.063 ± 0.023 M
Radius 1.711 R
Luminosity 25.4 L
Surface gravity (log g) 4.33 cgs
Temperature 9,940 K
Metallicity [Fe/H] 0.50 dex
Rotation 16 km/s
Age 237-247 Myr
α CMa B
Mass 1.018 ± 0.011 M
Radius 0.0084 ± 3% R
Luminosity 0.056 L
Surface gravity (log g) 8.57 cgs
Temperature 25,200 K
Age 228+10
−8
 Myr
Other designations
Dog Star, Aschere, Canicula, Al Shira, Sothis, Alhabor, Mrgavyadha, Lubdhaka, Tenrōsei,α Canis Majoris (α CMa), 9 Canis Majoris (9 CMa), HD 48915, HR 2491, BD−16°1591, GJ 244, LHS 219, ADS 5423, LTT 2638, HIP 32349
Sirius B: EGGR 49, WD 0642-166, GCTP 1577.00
Database references
SIMBAD The system
A
B

Sirius (/ˈsɪri.əs/, a romanization of Greek Σείριος, Seirios, lit. "glowing" or "scorching") is a star system and the brightest star in the Earth's night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The system has the Bayer designation Alpha Canis Majoris (α CMa). What the naked eye perceives as a single star is a binary star system, consisting of a white main-sequence star of spectral type A0 or A1, termed Sirius A, and a faint white dwarf companion of spectral type DA2, called Sirius B. The distance separating Sirius A from its companion varies between 8.2 and 31.5 AU.

Sirius appears bright because of its intrinsic luminosity and its proximity to Earth. At a distance of 2.6 parsecs (8.6 ly), as determined by the Hipparcos astrometry satellite, the Sirius system is one of Earth's near neighbours. Sirius is gradually moving closer to the Solar System, so it will slightly increase in brightness over the next 60,000 years. After that time its distance will begin to increase and it will become fainter, but it will continue to be the brightest star in the Earth's night sky for the next 210,000 years.


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