33 Boötis
Star in the constellation Boötes
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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.[2] The object is moving closer to the Earth with a heliocentric radial velocity of −13 km/s,[2] and is catalogued as a member of the Pleiades supercluster.[9]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Boötes |
| Right ascension | 14h 38m 50.225s[1] |
| Declination | +44° 24′ 16.21″[1] |
| Apparent magnitude (V) | 5.39[2] |
| Characteristics | |
| primary | |
| Evolutionary stage | main sequence[3][1] |
| Spectral type | A1 V[4] |
| B−V color index | 0.030±0.003[2] |
| companion | |
| Evolutionary stage | brown dwarf[5] |
| Spectral type | M5-M8[5] |
| Astrometry | |
| Radial velocity (Rv) | −23.8±2.6[1] km/s |
| Proper motion (μ) | RA: −67.847 mas/yr[1] Dec.: −18.424 mas/yr[1] |
| Parallax (π) | 17.1844±0.1516 mas[1] |
| Distance | 190 ± 2 ly (58.2 ± 0.5 pc) |
| Absolute magnitude (MV) | 1.61[2] |
| Orbit[5] | |
| 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[5] M☉ |
| Radius | 1.84[1] R☉ |
| Luminosity | 21.2[5] L☉ |
| Surface gravity (log g) | 4.18[6] cgs |
| Temperature | 9,224[1] K |
| Rotational velocity (v sin i) | 86[7] km/s |
| Age | 142[7] Myr |
| B | |
| Mass | 60+27 −21[5] MJup |
| Radius | 1.696[5] RJup |
| Luminosity | (1.05–0.52)×10−3[5] L☉ |
| Temperature | 2,700±100[5] K |
| Other designations | |
| 33 Boo, BD+45°2204, FK5 540, HD 129002, HIP 71618, HR 5468, SAO 45153[8] | |
| Database references | |
| SIMBAD | data |
This is an ordinary A-type main-sequence star with a stellar classification of A1 V.[4] 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.[10] 33 Boötis is 142 million years old[7] with a projected rotational velocity of 86 km/s.[7] The star has 2.07 times the mass of the Sun,[5] 1.84 times the Sun's radius and is radiating 21.2 times the luminosity of the Sun from its photosphere[5] at an effective temperature of 9,224 K.[1]
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.[a] The companion was detected in 2025 from observations with the Subaru and Keck telescopes, as well as Hipparcos and Gaia astrometry.[5]
Notes
- Calculated using the equations a(1 + e) and a(1 − e) for apoastron and periastron, respectively, where a is the semi-major axis and e is the eccentricity.