Nu Capricorni
Star in the constellation Capricornus
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Nu Capricorni is a star in the southern constellation of Capricornus. It has the proper name Alshat, pronounced /ˈælʃæt/;[12] Nu Capricorni is the Bayer designation. This star is visible to the naked eye with an apparent visual magnitude of +4.76.[3] It is calculated to be a distance of 268 light-years (82 pc) distant from the Sun based on parallax.[2]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Capricornus[1] |
| Right ascension | 20h 20m 39.816s[2] |
| Declination | −12° 45′ 32.69″[2] |
| Apparent magnitude (V) | +4.76[3] |
| Characteristics | |
| Evolutionary stage | main sequence[4][2] |
| Spectral type | B9 IV[5] or B9.5 V[6] |
| U−B color index | −0.11[3] |
| B−V color index | −0.04[3] |
| Astrometry | |
| Radial velocity (Rv) | −1.00[7] km/s |
| Proper motion (μ) | RA: +14.130 mas/yr[2] Dec.: −15.123 mas/yr[2] |
| Parallax (π) | 12.1737±0.1597 mas[2] |
| Distance | 268 ± 4 ly (82 ± 1 pc) |
| Absolute magnitude (MV) | +0.32[1] |
| Details | |
| Mass | 2.37[8] M☉ |
| Radius | 3.04±0.08[9] R☉ |
| Luminosity | 89±4[9] L☉ |
| Surface gravity (log g) | 3.88±0.08[9] cgs |
| Temperature | 10,200±220[9] K |
| Metallicity [Fe/H] | −0.15±0.04[1] dex |
| Rotational velocity (v sin i) | 24[10] km/s |
| Age | 115[8] Myr |
| Other designations | |
| Alshat, ν Cap, Nu Cap, 8 Cap, BD−13°5642, HD 193432, HIP 100310, HR 7773, SAO 163468, ADS 13714, WDS J20207-1246A[11] | |
| Database references | |
| SIMBAD | data |
Nu Capricorni is 6.6 degrees north of the ecliptic and so is within the margin of occultations of few if any planets but is well within that of the Moon.[13] The celestial latitude of either of the Alpha Capricorni main stars is about 6.93 degrees by comparison.[14]
Characteristics
The star is a blue-white hued B-type main-sequence star.[15] With an estimated age of 115 million years,[8] it is spinning with a projected rotational velocity of 24 km/s.[10] It has 2.4[8] times the mass of the Sun and 3 times the Sun's radius.[9] The star is radiating 89 times the luminosity of the Sun from its photosphere at an effective temperature of 10,200 K.[9] It has a nearly Sun-like composition of elements.[15]
It has an optical companion, named Nu Capricorni B, a magnitude 11.8 star at an angular separation of 54.1 arcseconds from the primary.[6] Gaia Data Release 2 shows the companion to be much further away from Earth, forming a binary system only in the line-of-sight.[16]
Nomenclature
ν Capricorni, Latinised to Nu Capricorni, is the system's Bayer designation, abbreviated Nu Cap or ν Cap.
The star bore the traditional name Alshat, from the Arabic الشاة aš-šā[t], meaning 'the sheep' that was to be slaughtered by the adjacent Beta¹ Capricorni (Dabih).[17] In 2016, the IAU organized a Working Group on Star Names (WGSN)[18] to catalog and standardize proper names for stars. It approved the name Alshat on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.[12]