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]
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]