HD 170642
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  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Corona Australis |
| Right ascension | 18h 32m 21.33140s[1] |
| Declination | −39° 42′ 14.4023″[1] |
| Apparent magnitude (V) | 5.16±0.01[2] |
| Characteristics | |
| Spectral type | A3 V[3] or A3 Van[4] |
| B−V color index | +0.08[5] |
| Astrometry | |
| Radial velocity (Rv) | −6±4.2[6] km/s |
| Proper motion (μ) | RA: +32.47 mas/yr[1] Dec.: −37.47 mas/yr[1] |
| Parallax (π) | 14.23±0.23 mas[1] |
| Distance | 229 ± 4 ly (70 ± 1 pc) |
| Absolute magnitude (MV) | +0.93[7] |
| Details | |
| Mass | 2.25[8] M☉ |
| Radius | 2.59±0.13[9] R☉ |
| Luminosity | 32.6[10] L☉ |
| Surface gravity (log g) | 3.96[11] cgs |
| Temperature | 8,938±161[12] K |
| Metallicity [Fe/H] | +0.24[11] dex |
| Rotational velocity (v sin i) | 177±1[13] km/s |
| Age | 480[8] Myr |
| Other designations | |
| 13 G. Coronae Australis[14], CD−39°12696, CPD−39°8114, GC 25285, HD 170642, HIP 90887, HR 6942, SAO 210277[15] | |
| Database references | |
| SIMBAD | data |
HD 170642, also designated as HR 6942 or rarely 13 G. Coronae Australis, is a single star[16] located in the southern constellation Corona Australis. It is faintly visible to the naked eye as a white hued star with an apparent magnitude of 5.16.[2] The object is located relatively close at a distance of 229 light years based on Hipparcos parallax measurements,[1] but it is approaching the Solar System with a somewhat constrained heliocentric radial velocity of −6 km/s.[6] At its current distance, HD 170642's brightness is diminished by 0.28 magnitudes due to interstellar dust.[17] It has an absolute magnitude of +0.93.[7]
This is an ordinary A-type main-sequence star with a stellar classification of A3 V.[3] Other sources include broad/nebulous absorption lines due to rapid rotation.[18][4] It has 2.25 times the mass of the Sun and is estimated to be 480 million years old.[8] HD 170642 has a radius of 2.59 R☉.[9] When combined with an effective temperature of 8,938 K,[12] it radiates 32.6 times the luminosity of the Sun[10] from its photosphere. The star is metal enriched, having an iron abundance 74% greater than the Sun's.[11] Like many hot stars HD 170642 spins rapidly, having a projected rotational velocity of 177 km/s.[13]
