2MASS J12195156+3128497
Brown dwarf in the constellation Coma Berenices
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2MASS J12195156+3128497 (abbreviated to 2MASS J1219+3128) is a rapidly-rotating brown dwarf of spectral class L8, located in the constellation Coma Berenices about 66 light-years from Earth. With a photometrically measured rotation period of 1.14 hours, it is one of the fastest-rotating known brown dwarfs announced by a team of astronomers led by Megan E. Tannock in March 2021. With a rotational velocity of about 80 km/s (50 mi/s), it is approaching the predicted rotational speed limit beyond which it would break apart due to centripetal forces. As a consequence of its rapid rotation, the brown dwarf is slightly flattened at its poles to a similar degree as Saturn, the most oblate planet in the Solar System.[5] Its rapid rotation may enable strong auroral radio emissions via particle interactions in its magnetic field, as observed in other known rapidly-rotating brown dwarfs.[2]
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Coma Berenices |
| Right ascension | 12h 19m 51.561s[1] |
| Declination | +31° 28′ 49.71″[1] |
| Characteristics | |
| Spectral type | L8[2] |
| Apparent magnitude (J) | 15.913±0.082[1] |
| Apparent magnitude (H) | 14.907±0.074[1] |
| Apparent magnitude (K) | 14.305±0.072[1] |
| Astrometry | |
| Radial velocity (Rv) | −19.0±4.2[2] km/s |
| Proper motion (μ) | RA: −233.0±23.7[3] mas/yr Dec.: −49.6±14.7[3] mas/yr |
| Distance | 66.2±9.8 ly (20.3±3.0[4] pc) |
| Details[2] | |
| Mass | 0.047+0.022 −0.025 M☉ |
| Radius | 0.100+0.027 −0.013 R☉ |
| Surface gravity (log g) | 5.1±0.5 cgs |
| Temperature | 1,330±140 K |
| Rotation | 1.14+0.03 −0.01 h |
| Rotational velocity (v sin i) | 79.0±3.4 km/s |
| Age | 0.9+12.8 −0.8 Gyr |
| Other designations | |
| WISE J121951.32+312849.5, UGCS J121951.36+312849.4, SDSS J121951.45+312849.4, TIC 139087399[1] | |
| Database references | |
| SIMBAD | data |
Discovery
2MASS J1219+3128 was first catalogued as a point source in June 2003 by the Two Micron All-Sky Survey (2MASS) organized by the University of Massachusetts Amherst and the Infrared Processing and Analysis Center under the California Institute of Technology.[6] It was discovered to be a brown dwarf of the spectral class L8 by K. Chiu and collaborators, based on near-infrared observations obtained from the Sloan Digital Sky Survey (SDSS) at Apache Point Observatory in New Mexico, United States. Their discovery and classification of 71 L and T dwarfs including 2MASS J1219+3128 (designated alternatively as SDSS J121951.45+312849.4) was published in The Astronomical Journal in June 2006.[7]
Distance
The distance of 2MASS J1219+3128 from Earth has not yet been measured with trigonometric parallax, so instead it is calculated from the spectrophotometric relation of spectral type and near-infrared absolute magnitude.[4] Schmidt et al. (2010) estimate a spectrophotometric distance of 18.1 ± 3.7 parsecs (59 ± 12 ly) from combined SDSS iz-band and 2MASS JHK-band photometry[3] whereas Buenzli et al. (2014) estimate a spectrophotometric distance of 20.3 ± 3.0 parsecs (66.2 ± 9.8 ly) from 2MASS H-band photometry.[4]
Proper motion
2MASS J1219+3128 has a net proper motion of 238.2 mas/yr with position angle 257.98 degrees,[a][b] indicating motion in south-west direction on the sky.[3]
See also
The other two discoveries of rapidly-rotating brown dwarfs, presented in Tannock et al. (2021):[2]
- 2MASS J04070752+1546457 – L3.5 spectral class brown dwarf with a period of 1.23±0.01 h
- 2MASS J03480772−6022270 – T7 spectral class brown dwarf with a period of 1.080+0.004
−0.005 h
