Global InformationV723 Monocerotis information
 A visual band light curve for V723 Monocerotis, adapted from Jayasinghe et al. (2021)[1] | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Monoceros |
| Right ascension | 06h 29m 04.659s[2] |
| Declination | −05° 34′ 20.23″[2] |
| Apparent magnitude (V) | 8.21 - 8.42[3] |
| Characteristics | |
| Spectral type | G0II[4] |
| Variable type | Ellipsoidal[5] |
| Astrometry | |
| Proper motion (μ) | RA: −1.347 mas/yr[2] Dec.: 16.140 mas/yr[2] |
| Parallax (π) | 2.1748 ± 0.0331 mas[2] |
| Distance | 1,500 ± 20 ly (460 ± 7 pc) |
| Absolute magnitude (MV) | +0.93[6] |
| Orbit[1] | |
| Period (P) | 59.9398 d |
| Eccentricity (e) | 0 (fixed) |
| Inclination (i) | 87.0+1.7 −1.4° |
| Argument of periastron (ω) (secondary) | 0 (fixed)° |
| Details | |
| Giant star | |
| Mass | 0.44±0.06[5] M☉ |
| Radius | 22.5±1.0[5] R☉ |
| Luminosity | 173±8[1] L☉ |
| Surface gravity (log g) | 1.7±0.1[1] cgs |
| Temperature | 3,800±100[5] K |
| Metallicity [Fe/H] | −0.9±0.1[1] dex |
| Rotational velocity (v sin i) | 15±2[5] km/s |
| Age | 5.4+5.1 −2.6[1] Gyr |
| Stripped subgiant | |
| Mass | 2.8±0.3[5] M☉ |
| Radius | 8.3±0.4[5] R☉ |
| Temperature | 5,800±200[5] K |
| Rotational velocity (v sin i) | 70±10[5] km/s |
| Other designations | |
V723 Mon, BD−05 1649, HD 45762, HIP 30891, SAO 133321, PPM 189220[7] | |
| Database references | |
| SIMBAD | data |
V723 Monocerotis is a variable star in the constellation Monoceros. It was proposed in 2021 to be a binary system including a lower mass gap black hole candidate nicknamed "The Unicorn".[1] Located 1,500 light years from Earth, it would be the closest black hole to our planet, and among the smallest ever found.[8][9]
Located in the Monoceros constellation, V723 Monocerotis is an eighth-magnitude ellipsoidal variable yellow giant star roughly the mass of the Sun, but 25 times its radius. The accompanying black hole was proposed to have a mass 3 times the mass of the Sun, corresponding to a Schwarzschild radius of 9 kilometers.[10][11]
Follow-up work in 2022 argued that V723 Monocerotis does not contain a black hole, but is a mass-transfer binary containing a red giant and a subgiant star that has been stripped of much of its mass.[5]
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