Omega2 Scorpii
Variable star
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ω2 Scorpii, Latinised as Omega2 Scorpii, is a suspected[11] variable star in the zodiac constellation of Scorpius. A component of the visual double star ω Scorpii, it is bright enough to be seen with the naked eye having an apparent visual magnitude of +4.320.[2] The distance to this star, as determined using parallax measurements,[1] is around 291 light years. The visual magnitude of this star is reduced by 0.38 because of extinction from interstellar dust.[6]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 07m 24.32818s[1] |
| Declination | −20° 52′ 07.5518″[1] |
| Apparent magnitude (V) | +4.320[2] |
| Characteristics | |
| Evolutionary stage | horizontal branch[3] |
| Spectral type | G6/8III[4] |
| U−B color index | +0.494[2] |
| B−V color index | +0.850[2] |
| Astrometry | |
| Radial velocity (Rv) | −5.4[5] km/s |
| Proper motion (μ) | RA: +44.81[1] mas/yr Dec.: −45.42[1] mas/yr |
| Parallax (π) | 11.22±0.32 mas[1] |
| Distance | 291 ± 8 ly (89 ± 3 pc) |
| Absolute magnitude (MV) | −0.62[6] |
| Details | |
| Mass | 3.27[6] M☉ |
| Radius | 15.0[7] R☉ |
| Luminosity | 163[7] L☉ |
| Surface gravity (log g) | 2.62±0.11[8] cgs |
| Temperature | 5,363±42[8] K |
| Metallicity [Fe/H] | +0.03±0.05[8] dex |
| Age | 282[6] Myr |
| Other designations | |
| Jabhat al Akrab,[9] ω2 Sco, 10 Scorpii, BD−20°4408, HD 144608, HIP 78990, HR 5997, SAO 184135[10] | |
| Database references | |
| SIMBAD | data |
It is 0.05 degree north of the ecliptic, so can be occulted by the moon and planets.
This is a G-type giant star with a stellar classification of G6/8III.[4] With an estimated age of 282 million years,[6] it is an evolved, thin disk star that is currently on the red horizontal branch.[3] The interferometry-measured angular diameter of this star is 1.63 ± 0.10 mas,[12] which, at its estimated distance, equates to a physical radius of nearly 16 times the radius of the Sun.[13] It has 3.27 times the mass of the Sun,[6] and radiates 141 times the Sun's luminosity[14] The effective temperature of the star's outer atmosphere is 5,363 K.[8]
Names
In the Cook Islands, a traditional story is told of twins who flee their parents into the sky and become the pair of stars Omega2 and Omega1 Scorpii. The girl, who is called Piri-ere-ua "Inseparable", keeps tight hold of her brother, who is not named.[15] (The IAU used a version of this story from Tahiti to name Mu2 Scorpii.)
