HD 178845, also known as HR 7271 or rarely 49 G. Telescopii, is a binary star located in the southern constellation Telescopium. Gaia DR3 parallax measurements place the system 379 light years away[3][1] and both components are approaching the Solar System with heliocentric radial velocities of −26 km/s and −24 km/s respectively.[6][8] At its current distance, HD 178845A's brightness is diminished by 0.22 magnitudes due to interstellar dust.[12]
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Telescopium |
| A | |
| Right ascension | 19h 12m 46.13847s[1] |
| Declination | −50° 29′ 11.1095″[1] |
| Apparent magnitude (V) | 6.13[2] |
| B | |
| Right ascension | 19h 12m 45.51968s[3] |
| Declination | −50° 29′ 08.7448″[3] |
| Apparent magnitude (V) | 10.90±0.02[4] |
| Characteristics | |
| A | |
| Spectral type | G8 III[5] |
| B−V color index | +0.95[2] |
| Astrometry | |
| A | |
| Radial velocity (Rv) | −26.4±0.4[6] km/s |
| Proper motion (μ) | RA: +44.868 mas/yr[1] Dec.: −42.034 mas/yr[1] |
| Parallax (π) | 8.6125 ± 0.0283 mas[1] |
| Distance | 379 ± 1 ly (116.1 ± 0.4 pc) |
| Absolute magnitude (MV) | +0.68[7] |
| B | |
| Radial velocity (Rv) | −24.2±5.3[8] km/s |
| Proper motion (μ) | RA: +46.984 mas/yr[3] Dec.: −41.403 mas/yr[3] |
| Parallax (π) | 8.6162 ± 0.024 mas[3] |
| Distance | 379 ± 1 ly (116.1 ± 0.3 pc) |
| Details[9] | |
| A | |
| Mass | 2.35±0.08 M☉ |
| Radius | 9.13±0.16 R☉ |
| Luminosity | 47±0.9 L☉ |
| Surface gravity (log g) | 2.95±0.10 cgs |
| Temperature | 5,001±36 K |
| Metallicity [Fe/H] | +0.02±0.03 dex |
| Rotational velocity (v sin i) | 2.6±1.1[10] km/s |
| Age | 455+45 −46[1] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The primary has an apparent magnitude of 6.13,[2] placing it near the naked eye viewing limit and the companion has an apparent magnitude of 10.9,[4] making it readily visible in medium-sized telescopes. The system was first observed by astronomer Willem Hendrik van den Bos in 1930.[13] As of 1991, HD 178845B is located 7.2" away along a position angle of 320°.[14]
The primary is an evolved red giant with a stellar classification of G8 III.[5] It has 2.35 times the mass of the Sun[9] but at the age of 455 million years,[1] it has expanded to 9.1 times its radius.[9] It radiates 47 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 5,001 K,[9] giving it a yellow hue. It has a solar metallicity ([Fe/H] = +0.02[9]) and spins modestly with a projected rotational velocity of 2.6 km/s.[10]