FU Orionis
Barnard 35, a part of the Lambda Orionis Ring seen by the Spitzer Space Telescope. FU Orionis is the bright star at lower right. | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Orion |
| Right ascension | 05h 45m 22.362s |
| Declination | +09° 04′ 12.31″ |
| Apparent magnitude (V) | 8.94 |
| Characteristics | |
| Spectral type | uncertain + K5+2 −1 |
| B−V color index | 1.41 |
| Variable type | FU Ori |
| Astrometry | |
| Proper motion (μ) | RA: +2.218±0.079 mas/yr Dec.: −2.834±0.065 mas/yr |
| Parallax (π) | 2.4029±0.0497 mas |
| Distance | 1,360 ± 30 ly (416 ± 9 pc) |
| Details | |
| FU Orionis north | |
| Mass | 0.6 M☉ |
| Radius | 10.42 R☉ |
| Temperature | 5095.1 K |
| FU Orionis south | |
| Mass | 1.2 M☉ |
| Temperature | 4350 K |
| Age | ~2 Myr |
| Other designations | |
| FU Ori, BD+09°5427 | |
| Database references | |
| SIMBAD | data |
FU Orionis is a variable and binary star system in the constellation of Orion, that in 1937 rose in apparent visual magnitude from 16.5 to 9.6, and has since been around magnitude 9. The name FU Orionis is a variable star designation in the Argelander system, which are assigned sequentially as new variables are discovered. FU Orionis is about 1,360 light years distant and is associated with the molecular cloud Barnard 35.
For a long time this variable was considered unique, but in 1970 a similar star, V1057 Cygni, was discovered, and a number of additional examples have been discovered since then. These stars constitute the FU Orionis class of variable stars, GCVS type FU, often nicknamed FUors. These stars are pre–main sequence stars which display an extreme change in magnitude and spectral type.