Alpha Trianguli

α Trianguli
Location of α Trianguli (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Triangulum
Right ascension 01h 53m 04.90710s[1]
Declination +29° 34′ 43.7801″[1]
Apparent magnitude (V) +3.42[2]
Characteristics
Spectral type F5III[3] to F6IV[4] + M[5]
U−B color index +0.06[2]
B−V color index +0.48[2]
Variable type Ellipsoidal[4]
Astrometry
Radial velocity (Rv)−12.6[6] km/s
Proper motion (μ) RA: 10.82[1] mas/yr
Dec.: −234.24[1] mas/yr
Parallax (π)51.50 ± 0.23 mas[1]
Distance63.3 ± 0.3 ly
(19.42 ± 0.09 pc)
Absolute magnitude (MV)1.98[7]
Orbit[8]
Period (P)1.767 days
Eccentricity (e)0.065
Semi-amplitude (K1)
(primary)		10.64 km/s
Details
α Tri A
Mass1.70[5] M☉
Radius3.22[5] R☉
Surface gravity (log g)3.91[9] cgs
Temperature6,288[9] K
Metallicity [Fe/H]−0.09[7] to 0.00[9] dex
Rotational velocity (v sin i)81.6[10] km/s
Age1.6[7] Gyr
α Tri B
Mass0.11[5] M☉
Radius0.14[5] R☉
Other designations
Mothallah, Ras al Muthallah, Caput Trianguli, α Trianguli,[11] 2 Trianguli, HR 544, HD 11443, BD+28°312, FK5 64, HIP 8796, SAO 74996.[12]
Database references
SIMBADdata

Alpha Trianguli (α Trianguli, abbreviated Alpha Tri, α Tri) is a spectroscopic binary star in the constellation of Triangulum. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 63.3 light-years (19.4 parsecs) distant from the Sun.[1] The brighter or primary component is named Mothallah /məˈθælə/.[13]

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