| |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Pegasus |
| Right ascension | 21h44m 31.330s[1] |
| Declination | +14° 46′ 18.98″[1] |
| Apparent magnitude (V) | 5.92 - 5.95[2] |
| Characteristics | |
| Spectral type | G0 V CH-0.5[3] |
| U−B color index | +0.031[4] |
| B−V color index | +0.588[4] |
| Variable type | BY Dra[5] |
| Astrometry | |
| Radial velocity (Rv) | −16.68±0.09[6] km/s |
| Proper motion (μ) | RA: +231.108 mas/yr[1] Dec.: −113.200 mas/yr[1] |
| Parallax (π) | 55.148 ± 0.0348 mas[1] |
| Distance | 59.14 ± 0.04 ly (18.13 ± 0.01 pc) |
| Absolute magnitude (MV) | 4.70[7] |
| Details | |
| HN Peg A | |
| Mass | 1.085±0.091[5] M☉ |
| Radius | 1.002±0.018[5] R☉ |
| Luminosity (bolometric) | 1.090[7] L☉ |
| Surface gravity (log g) | 4.45[8] cgs |
| Temperature | 5,961[8] K |
| Metallicity [Fe/H] | −0.06[8] dex |
| Rotation | 4.84 d[9] |
| Rotational velocity (v sin i) | 12.81[10] km/s |
| Age | 237±33[5] Myr |
| HN Peg B | |
| Radius | 0.101[11] R☉ |
| Surface gravity (log g) | 4.81[11] cgs |
| Temperature | 1,115[11] K |
| Other designations | |
HN Peg, BD+14°4668, FK5 3737, GJ 836.7, HD 206860, HIP 107350, HR 8314, SAO 107364[12] | |
| Database references | |
| SIMBAD | HN Peg A |
| HN Peg B | |
HN Pegasi is the variable star designation for a young, Sun-like star in the northern constellationofPegasus. It has an apparent visual magnitude of 5.9,[4] which, according to the Bortle scale, indicates that it is visible to the naked eye from suburban skies. Parallax measurements put the star at a distance of around 59 light years from the Sun,[1] but it is drifting closer with a radial velocity of −16.7 km/s.[6]
This is a G-type main sequence star with a stellar classificationofG0 V CH-0.5[3] and an estimated age of just 237 million years. It has slightly more mass and a slightly larger radius than the Sun,[5] but a somewhat lower metallicity.[8] It is spinning relatively quickly, with an estimated rotation period of 4.84[9] days.
The surface magnetic field of the star has a complex and variable geometry. It is a BY Draconis variable star with an active chromosphere, which means there is a rotational modulation of its luminosity due to star spots. Much like the Sun, the star spot activity undergoes a periodic cycle of maxima and minima lasting roughly 5.5±0.3 yr.[5] Its apparent magnitude varies between a maximum of 5.92 and a minimum of 5.95 over a period of 24.9 days.[2] However, the rotation period is on average 4.84 days. The star shows an anti-solar pattern of rotation, with the rotation rate steadily increasing during each cycle before dropping back to the initial value upon the start of a new cycle.[9]
In 2007, the discovery of a brown dwarf companion was announced. HN Peg B was spotted using the Spitzer Space Telescope at an angular separation of 43.2 arc sec, showing a methane emission characteristic of T-type dwarfs. The separation corresponds to a projected physical distance of 795 AU,[13] which is uncommonly wide for such brown dwarf companions. The estimated mass of the object is 28 MJ. Based upon its spectrum, HN Peg B has relatively thin cloud decks.[11]
This star displays an emission of infrared excess that suggests there is a circumstellar disk of debris in orbit.[7] HN Pegasi is most likely a thin disk population star.[8] It is a member of the nearby Hercules-Lyra association of stars that share a common motion through space.[5]
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