HN Pegasi
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Pegasus |
| Right ascension | 21h 44m 31.32919s[1] |
| Declination | +14° 46′ 18.9806″[1] |
| Apparent magnitude (V) | 5.940[2] |
| Characteristics | |
| Spectral type | G0 V CH-0.5[3] |
| U−B color index | +0.031[2] |
| B−V color index | +0.588[2] |
| Variable type | BY Dra[4] |
| Astrometry | |
| Radial velocity (Rv) | −16.68±0.09[5] km/s |
| Proper motion (μ) | RA: +229.93[1] mas/yr Dec.: −113.46[1] mas/yr |
| Parallax (π) | 55.91 ± 0.45[1] mas |
| Distance | 58.3 ± 0.5 ly (17.9 ± 0.1 pc) |
| Absolute magnitude (MV) | 4.70[6] |
| Details | |
| HN Peg A | |
| Mass | 1.085±0.091[4] M☉ |
| Radius | 1.002±0.018[4] R☉ |
| Luminosity (bolometric) | 1.090[6] L☉ |
| Surface gravity (log g) | 4.45[7] cgs |
| Temperature | 5,961[7] K |
| Metallicity [Fe/H] | −0.06[7] dex |
| Rotation | 4.84[8] |
| Rotational velocity (v sin i) | 12.81[9] km/s |
| Age | 237±33[4] Myr |
| HN Peg B | |
| Radius | 0.101[10] R☉ |
| Surface gravity (log g) | 4.81[10] cgs |
| Temperature | 1,115[10] K |
| Other designations | |
HN Pegasus is the variable star designation for a young, Sun-like star in the northern constellation of Pegasus. It has an apparent visual magnitude of 5.9,[2] which, according to the Bortle scale, indicates that it is visible to the naked eye from suburban skies. Parallax measurements made by the Hipparcos spacecraft put the star at a distance of around 58 light years.[1]
This is a G-type main sequence star with a stellar classification of G0 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,[4] but a somewhat lower abundance of elements other than hydrogen and helium.[7] It is spinning relatively quickly, with an estimated rotation period of 4.84[8] 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.[4] 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.[8]
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 minutes, showing a methane emission characteristic of T-type dwarfs. The separation corresponds to a projected physical distance of 795 AU,[12] 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.[10]
This star displays an emission of infrared excess that suggests there is a circumstellar disk of debris in orbit.[6] HN Pegasus is most likely a thin disk population star.[7] It is a member of the nearby Hercules-Lyra association of stars that share a common motion through space.[4]
References
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- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ 10.0 10.1 10.2 10.3 Lua error in package.lua at line 80: module 'strict' not found.
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