  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Microscopium |
| Right ascension | 20h 51m 00.75817s [1] |
| Declination | −37° 54′ 47.9922″ [1] |
| Apparent magnitude (V) | 5.50±0.01 [2] |
| Characteristics | |
| Spectral type | K3 III [3] or K3 II [4] |
| B−V color index | +1.38 [5] |
| Astrometry | |
| Radial velocity (Rv) | 16.5±2.9 [6] km/s |
| Proper motion (μ) | RA: −7.436 mas/yr [1] Dec.: −17.374 mas/yr [1] |
| Parallax (π) | 5.7348±0.0797 mas [1] |
| Distance | 569 ± 8 ly (174 ± 2 pc) |
| Absolute magnitude (MV) | −0.75 [7] |
| Details | |
| Mass | 1.81±0.44 [8] M☉ |
| Radius | 37.8±1.9 [9] R☉ |
| Luminosity | 417+16 −15 [1] L☉ |
| Surface gravity (log g) | 1.06 [10] cgs |
| Temperature | 4,318±51 [11] K |
| Metallicity [Fe/H] | −0.12 [10] dex |
| Rotational velocity (v sin i) | <1.0 [12] km/s |
| Other designations | |
| 28 G. Microscopii [13] , CD−38°14250, CPD−38°8121, GC 29053, HD 198357, HIP 102916, HR 7971, SAO 212488 [14] | |
| Database references | |
| SIMBAD | data |
HD 198357 (HR 7971; 28 G. Microscopii) is a solitary star located in the southern constellation Microscopium. It is faintly visible to the naked eye as an orange-hued point of light with an apparent magnitude of 5.50. [2] Gaia DR3 parallax measurements imply a distance of 569 light-years [1] and the object is currently receding with a heliocentric radial velocity of 16.5 km/s . [6] At its current distance, HD 198357's brightness is diminished by 0.18 magnitudes due to interstellar extinction [15] and it has an absolute magnitude of −0.75. [7]
HD 198357 has a stellar classification of K3 III, [3] indicating that it is an evolved K-type giant star. David Stanley Evans gave a classification of K3 II, indicating a more evolved bright giant. [4] It has 1.81 times the mass of the Sun [8] but it has expanded to 37.8 times the radius of the Sun. [9] It radiates 417 times the luminosity of the Sun [1] from its photosphere at an effective temperature of 4,318 K . [11] HD 198357 is slightly metal deficient with an iron abundance three-quarters that of the Sun or [Fe/H] = −0.12 [10] and it spins too slowly for its projected rotational velocity to be measured accurately. [12] HD 198357 has a peculiar velocity of 27.7+3.9
−4.1 km/s , indicating that it may be a runaway star (46% chance). [16]
