page_title: Brown dwarf
section_title: Formation and evolution
hierarchical_section_title: Brown dwarf / Formation and evolution
caption_attribution_description: English: The HH 1165 jet launched by a brown dwarf in the outer periphery of the sigma Ori cluster. Traced by emission from singly ionized sulfur, which appears green in the image, the jet extends 0.7 light years (equivalent to 0.2 parsecs) northwest of the brown dwarf.Image use
context_page_description: A brown dwarf is a type of substellar object that has a mass between those of the heaviest gas giant planets and the least massive stars, i.e. about 13 to 75–80 times that of Jupiter, or about 2.5×10²⁸ kg to 1.5×10²⁹ kg. Below this range are the sub-brown dwarfs, and above it are the red dwarfs. 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 to helium in their cores. They are, however, thought to fuse deuterium. If their mass is > 65 MJ they may also fuse lithium. It is also debated whether brown dwarfs would be better defined by their formation processes rather than by their 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, such as 2M1207b, MOA-2007-BLG-192Lb, and 2MASS J044144b.
context_section_description: Brown dwarfs form similar to stars and are surrounded by protoplanetary disks, such as Cha 110913-773444. As of 2017 there is only one known proto-brown dwarf that is connected with a large Herbig-Haro object. This is the brown dwarf Mayrit 1701117, which is surrounded by a pseudo-disk and a Keplerian disk. Mayrit 1701117 launches the 0.7 light-year long jet H 1165, mostly seen in ionized sulfur.
  Disks around brown dwarfs have been found to have many of the same features as disks around stars; therefore, it is expected that there will be accretion-formed planets around brown dwarfs. Given the small mass of brown dwarf disks, most planets will be terrestrial planets rather than gas giants. If a giant planet orbits a brown dwarf across our line of sight, then, because they have approximately the same diameter, this would give a large signal for detection by transit. The accretion zone for planets around a brown dwarf is very close to the brown dwarf itself, so tidal forces would have a strong effect.
  The brown dwarf Cha 110913-773444, located 500 light years away in the constellation Chamaeleon, may be in the process of forming a miniature planetary system. Astronomers from Pennsylvania State University have detected what they believe to be a disk of gas and dust similar to the one hypothesized to have formed the Solar System. Cha 110913-773444 is the smallest brown dwarf found to date (8 MJ), and if it formed a planetary system, it would be the smallest known object to have one.
caption: The HH 1165 jet launched by the brown dwarf Mayrit 1701117 in the outer periphery of the sigma Orionis cluster
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