Iota1 Scorpii

For other stars with this Bayer designation, see ι Scorpii
ι1 Scorpii
Location of ι1 Scorpii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension 17h 47m 35.08113s[1]
Declination −40° 07′ 37.1893″[1]
Apparent magnitude (V) 3.03[2]
Characteristics
Spectral type F2 Ia[3]
U−B color index +0.26[2]
B−V color index +0.51[2]
Astrometry
Radial velocity (Rv)−26.00[4] km/s
Proper motion (μ) RA: +0.01[1] mas/yr
Dec.: −6.24[1] mas/yr
Parallax (π)1.69 ± 0.15 mas[1]
Distance1,900 ± 200 ly
(590 ± 50 pc)
Absolute magnitude (MV)−6.51±0.19[5]
Details
Mass12.11±0.66[6] M☉
Radius120.3[7] R☉
Luminosity35,070[6] L☉
Surface gravity (log g)0.5 to 1.0[8] cgs
Temperature6,910 or 7,103[8] K
Metallicity [Fe/H]−0.13 to −0.11[8] dex
Age17.0 ± 0.5[9] Myr
Other designations
ι1 Sco, CD−40° 11838, FK5 666, HD 161471, HIP 87073, HR 6615, SAO 228420
Database references
SIMBADdata

Iota1 Scorpii, Latinized from ι1 Scorpii, is a star in the southern constellation of Scorpius. With an apparent visual magnitude of 3.03,[2] this star can be seen with the naked eye. It is sometimes called by the proper name Apollyon.[10] Parallax measurements place it at a distance of roughly 1,930 light-years (590 parsecs) from Earth, with a 9% margin of error.[1] At the estimated distance, the apparent magnitude is diminished by 0.66 magnitudes due to interveining gas and dust between Earth and the star.[5]

This star has a stellar classification of F2 Ia,[3] with the 'Ia' luminosity class indicating this is a supergiant more luminous than typical supergiants. It has about 12 times the Sun's mass[11] and is 35,000 times more luminous.[6] The limb-darkened angular diameter of Iota1 Scorpii is estimated at 1.896±0.213 mas.[12] At the estimated distance, this corresponds to a physical radius of 120.3 R☉.[7] The effective temperature of the photosphere is 6,910 or 7,103 K,[8] which gives it a yellow-white hue typical of an F-type star.[13]

Iota1 Scorpii has a 10th magnitude companion at an angular separation of 37.5 arcseconds, which, at the distance of this star, gives it a projected separation of 20,000 Astronomical Units (AU). As the relative separation of the two stars along the line of sight to the Earth is not known, however, this distance represents only a minimum value for their separation.[14]

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