1 Scorpii

This article is about b Scorpii and is not to be confused with β Scorpii.

1 Scorpii, or b Scorpii, is a single^[9] star in the southern zodiac constellation of Scorpius. It has an apparent magnitude of 4.63,^[1] which is bright enough to be faintly visible to the naked eye on a dark night. The star shows an annual parallax shift of 6.59 mas from Earth's orbit, which equates to a distance of roughly 490 light years. It is a probable (89% chance) member of the Sco OB2 moving group.^[10][9]

1 Scorpii

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Scorpius[1]
Right ascension	15h 50m 58.74452s[2]
Declination	−25° 45′ 04.6649″[2]
Apparent magnitude (V)	4.63[1]
Characteristics
Spectral type	B1.5 Vn[3]
B−V color index	−0.072±0.003[1]
Astrometry
Radial velocity (Rv)	−3.0±4.7[4] km/s
Proper motion (μ)	RA: −14.20[2] mas/yr Dec.: −25.12[2] mas/yr
Parallax (π)	6.59±0.27 mas[2]
Distance	490 ± 20 ly (152 ± 6 pc)
Absolute magnitude (MV)	−1.27[1]
Details
Mass	8.3±0.2[5] M☉
Radius	3.7[6] R☉
Luminosity	3,890[6] L☉
Temperature	24,000[6] K
Rotational velocity (v sin i)	310[7] km/s
Age	10.3±5.3[5] Myr
Other designations
b Sco, 1 Sco, CD−25°11131, HD 141637, HIP 77635, HR 5885, SAO 183854[8]
Database references
SIMBAD	data

This is a B-type main-sequence star with a stellar classification of B1.5 Vn,^[3] where the 'n' suffix indicates "nebulous" absorption lines being induced by rapid rotation. It has a projected rotational velocity of 310 km/s, which is giving the star an oblate shape with an equatorial bulge that is 13% wider than the polar radius.^[7] There is some weak evidence that this is a Be star with a gaseous disk that is being viewed edge-on.^[11]

1 Scorpii is a young star at around 10^[5] million years old, with 8.3^[5] times the mass of the Sun and 3.7 times the Sun's radius.^[6] The star is radiating 3,890 times the Sun's luminosity from its photosphere at an effective temperature of about 24,000 K.^[6]