Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Telescopium |
HD 187420 | |
Right ascension | 19h 52m 37.72117s[1] |
Declination | −54° 58′ 15.6700″[1] |
Apparent magnitude (V) | 5.71±0.01[2] |
HD 187421 | |
Right ascension | 19h 52m 39.13201s[3] |
Declination | −54° 58′ 35.1997″[3] |
Apparent magnitude (V) | 6.37±0.01[2] |
Characteristics | |
HD 187420 | |
Spectral type | G8/K0 III[4] |
U−B color index | +0.67[5] |
B−V color index | +0.92[5] |
HD 187421 | |
Spectral type | A1/3 V[4] |
U−B color index | +0.13[5] |
B−V color index | +0.10[5] |
Astrometry | |
HD 187420 | |
Radial velocity (Rv) | −17.9±1.2[6] km/s |
Proper motion (μ) | RA: +18.630 mas/yr[1] Dec.: +3.076 mas/yr[1] |
Parallax (π) | 8.0046 ± 0.0705 mas[1] |
Distance | 407 ± 4 ly (125 ± 1 pc) |
Absolute magnitude (MV) | −0.33[7] |
HD 187421 | |
Radial velocity (Rv) | −21.5±1.9[8] km/s |
Proper motion (μ) | RA: +19.549 mas/yr[3] Dec.: +2.252 mas/yr[3] |
Parallax (π) | 7.8714 ± 0.037 mas[3] |
Distance | 414 ± 2 ly (127.0 ± 0.6 pc) |
Absolute magnitude (MV) | +2.69[7] |
Details | |
HD 187420 | |
Mass | 3.00±0.04[1] M☉ |
Radius | 11.6±0.6[9] R☉ |
Luminosity | 88.3+1.4 −1.5[1] L☉ |
Surface gravity (log g) | 2.59[10] cgs |
Temperature | 5,140±122[11] K |
Metallicity [Fe/H] | −0.17[12] dex |
Rotational velocity (v sin i) | 2.4±1.2[13] km/s |
Age | 377±37[1] Myr |
HD 187421 | |
Mass | 2.31[14] M☉ |
Radius | 2.72±0.14[9] R☉ |
Luminosity | 37.1+2.4 −2.0[11] L☉ |
Surface gravity (log g) | 3.92[14] cgs |
Temperature | 9,099±309[14] K |
Metallicity [Fe/H] | +0.20[15] dex |
Rotational velocity (v sin i) | 170±2[16] km/s |
Age | 560[14] Myr |
Other designations | |
HD 187420: 71 G. Telescopii[17], CD−55°8312, CPD−55°9221, GC 27482, HD 187420, HIP 97816, HR 7548, SAO 246311, CCDM J19526-5458A, WDS J19526-5458A[18] | |
HD 187421: 72 G. Telescopii[17], CD−55°8313, CPD−55°9222, GC 27483, HD 187421, HIP 97819, HR 7549, SAO 246312, CCDM J19526-5458B, WDS J19526-5458B[19] | |
Database references | |
SIMBAD | HD 187420 |
HD 187421 |
HD 187420 (HR 7548; 71 G. Telescopii) and HD 187421 (HR 7549; 72 G. Telescopii), are the components of a binary star located in the southern constellation Telescopium. Gaia DR3 parallax measurements place the stars at a distance of 407 and 414 light years respectively.[1][3] The two are separated by 23″, and they are approaching the Solar System with heliocentric radial velocities of −17.9 km/s and −21.5 km/s respectively.[6][8]
HD 187420 is the primary of the system. It has an apparent magnitude of 5.71,[2] making it faintly visible to the naked eye as a yellowish-orange-hued star. However, its brightness is diminished by 0.17 magnitudes due to interstellar dust.[20] Meanwhile, the secondary HD 187421 has an apparent magnitude of 6.37,[2] placing it near the limit for naked eye visibility. It too suffers from extinction, which makes it 0.25 magnitudes dimmer.[20] The stars have absolute magnitudes of −0.33 and +2.69 respectively.[7] HD 187421 is located 23.5" away from HD 187420 along a position angle of 148° as of 2016.[21] They were first observed as a double star in 1826 by astronomer James Dunlap.[22]
HD 187420 has a stellar classification of G8/K0 III,[4] indicating that it is an evolved star with the characteristics of a G8 and K0 giant star. It has 3 times the mass of the Sun but at the age of 377 million years,[1] it has expanded to 11.6 times the radius of the Sun. It radiates 88.3 times the luminosity of the Sun[1] from its photosphere at an effective temperature of 5,140 K.[11] HD 187420 is metal deficient at [Fe/H] = −0.17[12] and spins modestly with a projected rotational velocity of 2.4 km/s.
HD 187421 is an A-type star with the characteristics of an A1 and A3 main sequence star, which corresponds to a classification of A1/3 V.[4] It has 2.31 times the mass of the Sun[14] and 2.72 times the Sun's radius.[9] It radiates 37.1 times the luminosity of the Sun[11] from its photosphere at an effective temperature of 9,099 K,[14] giving it a white hue. HD 187421 is particularly metal enriched at [Fe/H] = +0.2[15] and is estimated to be 560 million years old.[14] Like many hot stars it spins rapidly, having a projected rotational velocity of 170 km/s.[16]