33 Boötis
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Boötes |
| Right ascension | 14h 38m 50.225s |
| Declination | +44° 24′ 16.21″ |
| Apparent magnitude (V) | 5.39 |
| Characteristics | |
| primary | |
| Evolutionary stage | main sequence |
| Spectral type | A1 V |
| B−V color index | 0.030±0.003 |
| companion | |
| Evolutionary stage | brown dwarf |
| Spectral type | M5-M8 |
| Astrometry | |
| Radial velocity (Rv) | −23.8±2.6 km/s |
| Proper motion (μ) | RA: −67.847 mas/yr Dec.: −18.424 mas/yr |
| Parallax (π) | 17.1844±0.1516 mas |
| Distance | 190 ± 2 ly (58.2 ± 0.5 pc) |
| Absolute magnitude (MV) | 1.61 |
| Orbit | |
| Period (P) | 25.6+4.4 −3.1 yr |
| Semi-major axis (a) | 11.1+1.3 −1.0 AU |
| Eccentricity (e) | 0.87+0.10 −0.22 |
| Inclination (i) | 98+20 −10° |
| Longitude of the node (Ω) | 122.5+176 −6.2° |
| Periastron epoch (T) | 2463402+1111 −7509 JD |
| Argument of periastron (ω) (secondary) | 176+164 −156° |
| Details | |
| A | |
| Mass | 2.07±0.24 M☉ |
| Radius | 1.84 R☉ |
| Luminosity | 21.2 L☉ |
| Surface gravity (log g) | 4.18 cgs |
| Temperature | 9,224 K |
| Rotational velocity (v sin i) | 86 km/s |
| Age | 142 Myr |
| B | |
| Mass | 60+27 −21 MJup |
| Radius | 1.696 RJup |
| Luminosity | (1.05–0.52)×10−3 L☉ |
| Temperature | 2,700±100 K |
| Other designations | |
| 33 Boo, BD+45°2204, FK5 540, HD 129002, HIP 71618, HR 5468, SAO 45153 | |
| Database references | |
| SIMBAD | data |
33 Boötis is a star with a brown dwarf companion in the northern constellation Boötes, located 190 light years away from the Sun. It is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of 5.39. The object is moving closer to the Earth with a heliocentric radial velocity of −13 km/s, and is catalogued as a member of the Pleiades supercluster.
This is an ordinary A-type main-sequence star with a stellar classification of A1 V. It is a source of X-ray emission, but early A-type stars are not expected to be X-ray sources, so this may indicate it has an undetected companion. 33 Boötis is 142 million years old with a projected rotational velocity of 86 km/s. The star has 2.07 times the mass of the Sun, 1.84 times the Sun's radius and is radiating 21.2 times the luminosity of the Sun from its photosphere at an effective temperature of 9,224 K.
33 Boötis is orbited by a brown dwarf with roughly 60 times the mass of Jupiter and 1.7 times the radius. It takes roughly 26 years to complete one highly-eccentric orbit, coming as close as 1.4 AU at periastron and as distant as 21 AU at apoastron. The companion was detected in 2025 from observations with the Subaru and Keck telescopes, as well as Hipparcos and Gaia astrometry.