Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main-sequence stars. Their mass is approximately 13 to 80 times that of Jupiter (MJ)—not big enough to sustain nuclear fusion of ordinary hydrogen (1H) into helium in their cores, but massive enough to emit some light and heat from the fusion of deuterium (2H). The most massive ones can fuse lithium (7Li).
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.
A sub-brown dwarf or planetary-mass brown dwarf is an astronomical object that formed in the same manner as stars and brown dwarfs but that has a planetary mass, therefore by definition below the limiting mass for thermonuclear fusion of deuterium . Some researchers call them rogue planets whereas others call them planetary-mass brown dwarfs. They are sometimes categorized as Y spectral class brown dwarfs.
Omega Cassiopeiae is a binary star system in the northern constellation of Cassiopeia. It has a combined apparent visual magnitude of +4.99, which means it is a faint star but visible to the naked eye. Based upon an annual parallax shift of 4.65 mas as seen from Earth, this system is located roughly 730 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction of 0.16 due to interstellar dust.
HD 136118 is a star in the Serpens Caput section of the Serpens constellation. The star is too dim to be readily visible to the naked eye, having an apparent visual magnitude of 6.93. It is located at a distance of 165 light years from the Sun based on parallax, and is drifting closer with a radial velocity of −3 km/s.
HD 149382 is a hot subdwarf star in the constellation of Ophiuchus with an apparent visual magnitude of 8.943. This is too faint to be seen with the naked eye even under ideal conditions, although it can be viewed with a small telescope. Based upon parallax measurements, this star is located at a distance of about 246 light-years from the Earth.
2MASS J12373919+6526148 is a brown dwarf object with late spectral type T in the constellation of Draco, nearly 34 light-years away from the Sun. The substellar object could likely host a very low-mass companion, possibly in the planetary regime. This has been inferred from unusual Hα emission that it exhibited in the past.
HD 175167 is a star with an exoplanet companion in the southern constellation of Pavo. It is too faint to be visible with the naked eye at an apparent visual magnitude of 8.01. The system is located at a distance of 232 light-years from the Sun based on parallax measurements, and it is drifting further away with a radial velocity of 5 km/s. It shows a high proper motion, traversing the celestial sphere at an angular rate of 0.190 arcsec yr−1.
2MASS J15074769−1627386 is a brown dwarf in the constellation Libra, located about 23.9 light-years from Earth. It was discovered in 1999 by I. Neill Reid et al. It belongs to the spectral class L5; its surface temperature is 1,300 to 2,000 kelvins. As with other brown dwarfs of spectral type L, its spectrum is dominated by metal hydrides and alkali metals. Its spectrum also has a weak silicate absorption band and highly variable water absorption band, indicating a complicated clouds and haze structures.
2MASS J00361617+1821104 is a brown dwarf, located in 28.6 light-years from Earth in the constellation Pisces. It was discovered in 2000 by I. Neill Reid et al. Kinematically, it does not belong to any known moving group, been grouped with other "field stars".
WISEPA J025409.45+022359.1 is a brown dwarf of spectral class T8, located in constellation Cetus at approximately 22.3 light-years from Earth.
Luhman 16 is a binary brown-dwarf system in the southern constellation Vela at a distance of 6.51 light-years from the Sun. These are the closest-known brown dwarfs and the closest system found since the measurement of the proper motion of Barnard's Star in 1916, and the third-closest-known system to the Sun. The primary is of spectral type L7.5 and the secondary of type T0.5 ± 1. The masses of Luhman 16 A and B are 35.4 and 29.4 Jupiter masses, respectively, and their ages are estimated to be 400–800 million years. Luhman 16 A and B orbit each other at a distance of about 3.5 astronomical units with an orbital period of approximately 26.6 years.
LHS 6343 is a star system in the northern constellation of Lyra. It appears exceedingly faint with a combined apparent magnitude of 13.435. Based on its stellar properties, the system is thought to be about 119.4 light-years away.
2MASS J11011926–7732383 AB is a brown dwarf binary about 600 light-years distant in the Chamaeleon. constellation. The wide binary pair is separated by about 240 astronomical units. The system was the first discovery of a brown dwarf binary with a separation greater than 20 au. The discovery gave fundamental insights into the formation of brown dwarfs. Previously it was thought that such wide binary brown dwarfs are not formed or at least are disrupted at ages of 1-10 Myrs. Together with other wide binaries, such as Oph 162225-240515 or UScoCTIO 108, the existence of this system was inconsistent with the ejection hypothesis, a proposed hypothesis in which brown dwarfs form in a multiple system, but are ejected before they gain enough mass to burn hydrogen. The ejection hypothesis predicted a maximum separation of 10 au for brown dwarf binaries.
2MASS J15104761–2818234, sometimes shortened to 2M1510, is a triple or possibly quadruple brown dwarf system, consisting of the eclipsing binary 2M1510A and the wide companion 2M1510B. 2M1510A was found to be an eclipsing binary in the first light data of the SPECULOOS telescopes. It is only the second eclipsing binary brown dwarf found so far, the other is 2M0535-05. The system verified theoretical models for how brown dwarfs cool. The system is located 120 light-years away from earth in the constellation Libra.
HIP 79098 is a binary star in the constellation Scorpius. It has a visual apparent magnitude of +5.88, being visible to the naked eye under very dark skies. From parallax measurements by the Gaia spacecraft, it is located approximately 500 light-years from Earth.
19 Leonis Minoris is a spectroscopic binary located in the northern constellation Leo Minor. It has an apparent magnitude of 5.1, making it one of the brighter members of the constellation. The system is relatively close at a distance of 94 light years but is drifitng closer with a heliocentric radial velocity of 8.6 km/s.
