Zeta1 Scorpii
Star in the constellation Scorpius
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Zeta1 Scorpii (Zeta1 Sco, ζ1 Scorpii, ζ1 Sco) is a binary star[7] in the constellation of Scorpius, composed by an B-type hypergiant star as the primary, and a secondary of which little is known. It has an apparent visual magnitude which varies between 4.66 and 4.86.[3] It is a member of the Scorpius OB1 association, and potentially of the open star cluster NGC 6231,[11] also known as the "Northern jewel box" cluster.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 53m 59.72713s[1] |
| Declination | −42° 21′ 43.3073″[1] |
| Apparent magnitude (V) | 4.705[2] (4.66 to 4.86)[3] |
| Characteristics | |
| Spectral type | B1.5 Ia+[4] |
| U−B color index | −0.567[2] |
| B−V color index | +0.480[2] |
| Variable type | Luminous blue variable[5] |
| Astrometry | |
| Radial velocity (Rv) | −26.0[6] km/s |
| Proper motion (μ) | RA: −0.094 mas/yr[1] Dec.: −3.368 mas/yr[1] |
| Parallax (π) | 0.5855±0.1176 mas[1] |
| Distance | approx. 6,000 ly (approx. 1,700 pc) |
| Absolute magnitude (MV) | −8.5[4] |
| Details | |
| Mass | 36 to 53[4] M☉ |
| Radius | 159+83 −34[7] R☉ |
| Luminosity (bolometric) | (1.0–1.6)×106[7] L☉ |
| Surface gravity (log g) | 1.7[4] cgs |
| Temperature | 17,000–19,000[7] K |
| Rotational velocity (v sin i) | 60[8] km/s |
| Age | 6.5±0.1[9] Myr |
| Other designations | |
| ζ1 Sco, CD−42 11633, CPD−42 7545, GC 22730, HD 152236, HIP 82671, HR 6262, PPM 322342, SAO 227375.[10] | |
| Database references | |
| SIMBAD | data |
Characteristics
ζ1 Scorpii's primary is a luminous blue variable according to its luminosity and spectral appearance,[13] yet is has not shown the characteristic types of variability, hence is classified as a dormant LBV.[5] It has around 36 times as massive as the Sun[4] and is one of the most luminous stars known in the Galaxy, with an estimated bolometric luminosity between 1 and 1.6 million times that of the Sun and a radius around 160 times that of the Sun.[7] The stellar wind from this supergiant is expelling matter from the star at the rate of 1.55 × 10−6 solar masses per year, or roughly the equivalent to the Sun's mass every 640,000 years.[4]
The secondary has been detected using interferometry, and its discovery was announced in 2021. As of 2021[update], it has an angular separation of 11.54±0.10 mas along a position angle of 283.22°+0.76°
−0.34°. It is 6.3 magnitudes fainter than the primary.[7]
ζ1 Scorpii forms a naked eye double with ζ2 Scorpii, but the stars are merely coincidentally near in the line of sight from Earth. ζ2 is a mere 135 light-years distant and much less luminous in real terms. ζ1 Scorpii can also be distinguished from ζ2, due to the latter's orange hue especially in long-exposure photographs.