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Brown dwarf is a substellar object that occupies the mass range between the heaviest gas giant planets and the lightest stars, having masses between approximately 13 to 75–80 times that of Jupiter (MJ), or approximately 2.5×1028 kg to about 1.5×1029 kg. Below this range are the sub-brown dwarfs, and above it are the lightest red dwarfs (M9 V). Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.

Unlike the stars in the main sequence, brown dwarfs are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) to helium in their cores. They are, however, thought to fuse deuterium (2H) and to fuse lithium (7Li) if their mass is above a debated threshold of 13 MJ and 65 MJ, respectively. It is also debated whether brown dwarfs would be better defined by their formation processes rather than by their supposed nuclear fusion reactions.

Stars are categorized by spectral class, with brown dwarfs designated as types M, L, T, and Y.[ Despite their name, brown dwarfs are of different colors. Many brown dwarfs would likely appear magenta to the human eye, or possibly orange/red. Brown dwarfs are not very luminous at visible wavelengths.

There are planets known to orbit brown dwarfs: 2M1207b, MOA-2007-BLG-192Lb, and 2MASS J044144b.

At a distance of about 6.5 light years, the nearest known brown dwarf is Luhman 16, a binary system of brown dwarfs discovered in 2013. HR 2562 b is listed as the most-massive known exoplanet (as of December 2017) in NASA’s exoplanet archive, despite having a mass (30±15 MJ) more than twice the 13-Jupiter-mass cutoff between planets and brown dwarfs. — Wikipedia

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Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.

Observations detect a brown dwarf orbiting the...
on June 15, 2021 at 3:10 pm
An international team of astronomers reports the discovery of a companion to the M dwarf star known as TOI–1278. The newly found object turns out to be a brown dwarf nearly 20 times as massive as Jupiter. The finding is detailed in a paper published June 8 on the arXiv pre-print server.
Astronomers probe layer-cake structure of brown...
on June 10, 2021 at 12:45 pm
Brown dwarfs are the cosmic equivalent of tweeners. They're too massive to be planets and too small to sustain nuclear fusion in their cores, which powers stars. Many brown dwarfs are nomadic. They do not orbit stars but drift among them as loners.
Astronomers detect substellar companion of HD...
on May 12, 2021 at 1:00 pm
Using the Harlan J. Smith Telescope, astronomers have discovered that the star HD 47127 has a substellar companion. The newly identified object, designated HD 47127 B, appears to be a brown dwarf or a brown dwarf binary. The finding is reported in a paper published May 4 on arXiv.org.
Using exoplanets as dark matter detectors
on April 22, 2021 at 5:08 pm
In the continuing search for dark matter in our universe, scientists believe they have found a unique and powerful detector: exoplanets.
Clock's running out on climate change. California...
on April 20, 2021 at 3:59 pm
Solar panels, wind turbines and electric cars will go far in helping California and the Biden administration meet their aggressive climate goals—but not far enough. As time runs short, scientists and government officials say the moment to break out the giant vacuums has arrived.