Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Scorpius |
Right ascension | 17h 48m 10.47559s [1] |
Declination | −31° 42′ 11.5636″ [1] |
Apparent magnitude (V) | 4.79 [2] |
Characteristics | |
Spectral type | B8 Ib/II [3] |
B−V color index | −0.028±0.023 [2] |
Astrometry | |
Radial velocity (Rv) | −13.3±2.8 [2] km/s |
Proper motion (μ) |
RA: +6.845
[1]
mas/
yr Dec.: −8.161 [1] mas/ yr |
Parallax (π) | 6.5831 ± 0.3618 mas [1] |
Distance | 500 ± 30
ly (152 ± 8 pc) |
Absolute magnitude (MV) | −1.37 [2] |
Details | |
Mass | 3.93±0.08 [4] M☉ |
Radius | 3.2 [5] R☉ |
Luminosity | 565+59 −53 [4] L☉ |
Surface gravity (log g) | 3.38 [6] cgs |
Temperature | 11066+77 −76 [4] K |
Rotational velocity (v sin i) | 24 [4] km/s |
Other designations | |
Database references | |
SIMBAD | data |
HD 161840 is a single, [8] blue-white hued star in the southern zodiac constellation of Scorpius. It is faintly visible to the naked eye with an apparent visual magnitude of 4.79. [2] With an annual parallax shift of 6.5 mas [1] it is located roughly 500 light years from the Sun. It is moving closer with a heliocentric radial velocity of −13 km/s. [2]
There has been some uncertainty as to the classification of this stage. Houk (1979) lists a stellar class of B8 Ib/II for HD 161840, [3] which corresponds to a B-type bright giant/lesser supergiant mix. Multiple studies still use an older classification of B8 V, [8] [6] [4] suggesting instead this is a B-type main-sequence star. Garrison and Gray (1994) assigned it a class of B8 III-IV, [9] which would put it on the subgiant/ giant star track. It has an estimated 3.93 [4] times the mass of the Sun and 3.2 [5] times the Sun's radius. The star is radiating 565 [4] times the Sun's luminosity from its photosphere at an effective temperature of 11,066 K. [4]