European Southern Observatory infrared image of 2M1207 (bluish) and companion planet 2M1207b (reddish), taken in 2004. | |
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Centaurus |
Right ascension | 12h 07m 33.47s[1] |
Declination | −39° 32′ 54.0″[1] |
Apparent magnitude (V) | 20.15[2] |
Characteristics | |
Spectral type | M8IVe[1] |
V−R color index | +2.1[2] |
R−I color index | +2.1[2] |
Astrometry | |
Proper motion (μ) | RA: −64.040±0.087[3] mas/yr Dec.: −23.678±0.072[3] mas/yr |
Parallax (π) | 15.4624 ± 0.1163 mas[3] |
Distance | 211 ± 2 ly (64.7 ± 0.5 pc) |
Details | |
Mass | ~0.025[4] M☉ |
Radius | ~0.25[5] R☉ |
Luminosity | ~0.002[5] L☉ |
Temperature | 2550 ± 150[5] K |
Age | 5·106 to 10·106[5] years |
Other designations | |
2MASSW J1207334−393254, 2MASS J12073346-3932539, TWA 27[1] | |
Database references | |
SIMBAD | data |
2M1207, 2M1207A or 2MASS J12073346–3932539 is a brown dwarf located in the constellation Centaurus; a companion object, 2M1207b, may be the first extrasolar planetary-mass companion to be directly imaged, and is the first discovered orbiting a brown dwarf.[5][6]
2M1207 was discovered during the course of the 2MASS infrared sky survey: hence the "2M" in its name, followed by its celestial coordinates. With a fairly early (for a brown dwarf) spectral type of M8,[1] it is very young, and probably a member of the TW Hydrae association. Its estimated mass is around 25 Jupiter masses.[4] The companion, 2M1207b, is estimated to have a mass of 5–6 Jupiter masses.[7] Still glowing red hot, it will shrink to a size slightly smaller than Jupiter as it cools over the next few billion years.
An initial photometric estimate for the distance to 2M1207 was 70 parsecs.[4] In December 2005, American astronomer Eric Mamajek reported a more accurate distance (53 ± 6 parsecs) to 2M1207 using the moving cluster method.[8] The new distance gives a fainter luminosity for 2M1207. Recent trigonometric parallax results have confirmed this moving cluster distance, leading to a distance estimate of 53 ± 1 parsec or 172 ± 3 light years.[4]
Like classical T Tauri stars, many brown dwarfs are surrounded by disks of gas and dust which accrete onto the brown dwarf.[9][10] 2M1207 was first suspected to have such a disk because of its broad Hα line. This was later confirmed by ultraviolet spectroscopy.[10] The existence of a dust disk has also been confirmed by infrared observations[11] and with ALMA.[12] In general, accretion from disks are known to produce fast-moving jets, perpendicular to the disk, of ejected material.[13] This has also been observed for 2M1207; an April 2007 paper in the Astrophysical Journal reports that this brown dwarf is spouting jets of material from its poles.[14] The jets, which extend around 109 kilometers into space, were discovered using the Very Large Telescope (VLT) at the European Southern Observatory. Material in the jets streams into space at a few kilometers per second.[15]
2M1207b shows weak accretion from a disk, inferred from emission lines of hydrogen and helium in medium-resolution NIRSpec data. Surprisingly 2M1207b does not show absorption due to methane, which was predicted to be present for this object. It was suggested that very young objects have a L/T-transition starts at a later spectral type.[16]
Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
circumstellar disk | 9.4±1.5 AU | 35+20 −15° |
— | |||
b | 5–6 MJ | ≥49.8 ± 1.1[18] | 633-20046 | 0.02-0.98 | 13-150° | — |