2MASS J09393548−2448279 (abbreviated 2MASS 0939−2448)[5] is a probable system of two nearby T-type brown dwarfs, located in constellation Antlia at 17.4 light-years from Earth.[2] The two stars orbit at a distance of 0.0928 AU

2MASS J09393548−2448279

Observation data Epoch J2000      Equinox J2000
Constellation	Antlia
Right ascension	09h 39m 35.48s
Declination	−24° 48′ 27.9″
Characteristics
Spectral type	T8[1]
Apparent magnitude (J)	15.61 ± 0.09[1]
Apparent magnitude (H)	15.96 ± 0.09[1]
Apparent magnitude (K)	16.83 ± 0.09[1]
Astrometry
Proper motion (μ)	RA: +573.4 ± 2.3[2] mas/yr Dec.: −1044.7 ± 2.5[2] mas/yr
Parallax (π)	187.3 ± 4.6 mas[2]
Distance	17.4 ± 0.4 ly (5.3 ± 0.1 pc)
Details
2MASS 0939-2448 A
Mass	20–50[1] MJup
Radius	1.22+0.1 −0.09[3] RJup
Luminosity	0.000002[4][3] L☉
Surface gravity (log g)	4.88+0.2 −0.4[3] cgs
Temperature	611+17 −24[3] K
Metallicity	−0.3–0.0[1]
Age	2–10[1] Gyr
2MASS 0939-2448 B
Mass	20–40[1] MJup
Radius	0.09[1] R☉
Temperature	600–700[1] K
Metallicity	−0.3–0.0[1]
Age	2–10[1] Gyr
Other designations
2MASS J09393548−2448279[5]
Database references
SIMBAD	data
2MASS 0939−2448 Location of 2MASS 0939−2448 in the constellation Antlia

Discovery

2MASS 0939−2448 was identified as a brown dwarf through analysis of data from the 2MASS survey by Tinney et al. The discovery was published in 2005.[5]

Properties

Model calculations suggest that 2MASS 0939−2448 is a system of two brown dwarfs with effective temperatures of about 500 and 700 K and masses of about 25 and 40 Jupiter masses; it is also possible that it is a pair of identical objects with temperatures of 600 K and 30 Jupiter masses.[1]

Dimmest known brown dwarf

From publication of the discovery in 2005 till at least 2008, 2MASS 0939−2448, or its dimmer component, was the dimmest brown dwarf known.[6] Later dimmer objects, including (sub)brown dwarfs and rogue planets of new spectral class Y, were discovered, using data from WISE and from other surveys. In 2011–2014, the dimmest known of these objects was WISE 1828+2650, and from 2014 the dimmest one is WISE 0855−0714.

References

• Faherty, Jacqueline K.; Burgasser, Adam J.; Walter, Frederick M.; Van der Bliek, Nicole; Shara, Michael M.; Cruz, Kelle L.; West, Andrew A.; Vrba, Frederick J.; Anglada-Escud, Guillem (2012). "The Brown Dwarf Kinematics Project (BDKP). III. Parallaxes for 70 Ultracool Dwarfs". The Astrophysical Journal. 752 (1): 56. arXiv:1203.5543. Bibcode:2012ApJ...752...56F. doi:10.1088/0004-637X/752/1/56. S2CID 18160586.
• Smart, R. L.; Tinney, C. G.; Bucciarelli, B.; Marocco, F.; Abbas, U.; Andrei, A.; Bernardi, G.; Burningham, B.; Cardoso, C.; Costa, E.; Crosta, M. T.; Daprá, M.; Day-Jones, A.; Goldman, B.; Jones, H. R. A.; Lattanzi, M. G.; Leggett, S. K.; Lucas, P.; Mendez, R.; Penna, J. L.; Pinfield, D.; Smith, L.; Sozzetti, A.; Vecchiato, A. (2013). "NPARSEC: NTT Parallaxes of Southern Extremely Cool objects. Goals, targets, procedures and first results". Monthly Notices of the Royal Astronomical Society. 433 (3): 2054–2063. arXiv:1306.4527. Bibcode:2013MNRAS.433.2054S. doi:10.1093/mnras/stt876. S2CID 1376087.

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