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IK Pegasi
 Location of IK Pegasi. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Pegasus |
| Right ascension | 21h 26m 26.66066s[1] |
| Declination | +19° 22′ 32.3169″[1] |
| Apparent magnitude (V) | 6.08[2] |
| Characteristics | |
| A | |
| Spectral type | A8m:[3] or kA6hA9mF0[4] |
| U−B color index | 0.03[5] |
| B−V color index | 0.235±0.009[2] |
| Variable type | Delta Scuti[3] |
| B | |
| Spectral type | DA[6] |
| Astrometry | |
| Radial velocity (Rv) | −9.7±0.2[2] km/s |
| Proper motion (μ) | RA: +80.964[1] mas/yr Dec.: +16.205[1] mas/yr |
| Parallax (π) | 21.1287 ± 0.1410 mas[1] |
| Distance | 154 ± 1 ly (47.3 ± 0.3 pc) |
| Absolute magnitude (MV) | 2.75[2] |
| Details | |
| A | |
| Mass | 1.65[7] M☉ |
| Radius | 1.47+0.07 −0.09[1] R☉ |
| Luminosity | 6.568±0.051[1] L☉ |
| Surface gravity (log g) | 4.25[7] cgs |
| Temperature | 7,624+237 −181[1] K |
| Metallicity | 117[7][8] |
| Rotational velocity (v sin i) | < 32.5[8] km/s |
| Age | 50–600[7] Myr |
| B | |
| Mass | 1.15[9] M☉ |
| Radius | 0.006[6] R☉ |
| Luminosity | 0.12[nb 1] L☉ |
| Surface gravity (log g) | 8.95[6] cgs |
| Temperature | 35,500[9] K |
| Other designations | |
| AB: IK Peg, BD+18° 4794, HD 204188, HIP 105860, HR 8210, SAO 107138.[5] | |
| B: WD 2124+191, EUVE J2126+193.[10][11] | |
| Database references | |
| SIMBAD | data |
IK Pegasi (or HR 8210) is a binary star system in the constellation Pegasus. It is just luminous enough to be seen with the unaided eye, at a distance of about 154 light years from the Solar System.
The primary (IK Pegasi A) is an A-type main-sequence star that displays minor pulsations in luminosity. It is categorized as a Delta Scuti variable star and it has a periodic cycle of luminosity variation that repeats itself about 22.9 times per day.[7] Its companion (IK Pegasi B) is a massive white dwarf—a star that has evolved past the main sequence and is no longer generating energy through nuclear fusion. They orbit each other every 21.7 days with an average separation of about 31 million kilometres, or 19 million miles, or 0.21 astronomical units (AU). This is smaller than the orbit of Mercury around the Sun.
IK Pegasi B is the nearest known supernova progenitor candidate. When the primary begins to evolve into a red giant, it is expected to grow to a radius where the white dwarf can accrete matter from the expanded gaseous envelope. When the white dwarf approaches the Chandrasekhar limit of 1.4 solar masses (M☉),[12] it may explode as a Type Ia supernova.[13]
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