Brown dwarf

brown dwarfsbrown dwarvesPlanetarT-typeL-typevery low-mass brown dwarfBDblack dwarfbrown brown dwarf star
Brown dwarfs are substellar objects that occupy 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, or approximately 2.5 kg to about 1.5 kg.wikipedia
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Luhman 16

Luhman 16 (WISE 1049-5319)Luhman 16B
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. Since then, over 1,800 brown dwarfs have been identified, even some very close to Earth like Epsilon Indi Ba and Bb, a pair of brown dwarfs gravitationally bound to a Sun-like star 12 light-years from the Sun, and Luhman 16, a binary system of brown dwarfs at 6.5 light-years from the Sun.
Luhman 16 (WISE 1049−5319, WISE J104915.57−531906.1) is a binary brown-dwarf system in the southern constellation Vela at a distance of approximately 6.5 ly from the Sun.

Sub-brown dwarf

subfree planetsub-brown
Brown dwarfs are substellar objects that occupy 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, or approximately 2.5 kg to about 1.5 kg. Below this range are the sub-brown dwarfs (sometimes referred to as rogue planets), and above it are the lightest red dwarfs (M9 V). In April 2010, two newly discovered ultracool sub-brown dwarfs (UGPS 0722-05 and SDWFS 1433+35) were proposed as prototypes for spectral class Y0.
A sub-brown dwarf or planetary-mass brown dwarf is an astronomical object that formed in the same manner as stars and brown dwarfs (i.e. through the collapse of a gas cloud) but that has a mass below the limiting mass for thermonuclear fusion of deuterium (about ).

2M1207b

2M1207 b
There are planets known to orbit brown dwarfs: 2M1207b, MOA-2007-BLG-192Lb, and 2MASS J044144b.
2M1207b is a planetary-mass object orbiting the brown dwarf 2M1207, in the constellation Centaurus, approximately 170 light-years from Earth.

Substellar object

substellarsmaller solid objectssub-stellar object
Brown dwarfs are substellar objects that occupy 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, or approximately 2.5 kg to about 1.5 kg. Below this range are the sub-brown dwarfs (sometimes referred to as rogue planets), and above it are the lightest red dwarfs (M9 V).
This definition includes brown dwarfs and former stars similar to EF Eridani B, and can also include objects of planetary mass, regardless of their formation mechanism and whether or not they are associated with a primary star.

Teide 1

In 1995, the study of brown dwarfs changed substantially with the discovery of two indisputable substellar objects – Teide 1 and Gliese 229B – which were identified by the presence of the 670.8 nm lithium line.
Teide 1 was the first brown dwarf to be verified, in 1995.

Epsilon Indi

ε IndEpsilon Indi Ba, Bbε Indi
Since then, over 1,800 brown dwarfs have been identified, even some very close to Earth like Epsilon Indi Ba and Bb, a pair of brown dwarfs gravitationally bound to a Sun-like star 12 light-years from the Sun, and Luhman 16, a binary system of brown dwarfs at 6.5 light-years from the Sun.
Epsilon Indi (ε Indi, ε Ind) is a star system approximately 12 light-years from Earth in the constellation of Indus consisting of a K-type main-sequence star, ε Indi A, and two brown dwarfs, ε Indi Ba and ε Indi Bb, in a wide orbit around it. The brown dwarfs were discovered in 2003.

Jill Tarter

Dr. Jill TarterJill Cornell Tarter
In 1975, Jill Tarter suggested the term "brown dwarf", using "brown" as an approximate color.
It was in her PhD thesis where she coined the term "brown dwarf" while researching small-mass objects that fail to stably fuse hydrogen.

Jupiter mass

M J mass of Jupitermass
Brown dwarfs are substellar objects that occupy 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, or approximately 2.5 kg to about 1.5 kg. Below this range are the sub-brown dwarfs (sometimes referred to as rogue planets), and above it are the lightest red dwarfs (M9 V).
It may also be used to describe the masses of brown dwarfs, as this unit provides a convenient scale for comparison.

MOA-2007-BLG-192Lb

b
There are planets known to orbit brown dwarfs: 2M1207b, MOA-2007-BLG-192Lb, and 2MASS J044144b.
The planet was discovered orbiting the brown dwarf or low-mass star MOA-2007-BLG-192L.

Lithium burning

burnedfuse lithiumlithium-6 fusion
They are, however, thought to fuse deuterium ( 2 H) and to fuse lithium ( 7 Li) if their mass is above a debated threshold of and, respectively.
Lithium is generally present in brown dwarfs and not in low-mass stars.

List of exoplanet extremes

least massive planetlowest metallicity planet-bearing starmost distant known planet
HR 2562 b is listed as the most-massive known exoplanet (as of December 2017) in NASA's exoplanet archive, despite having a mass more than twice the 13-Jupiter-mass cutoff between planets and brown dwarfs.

Stellar evolution

evolvedevolvingevolution
Early theories concerning the nature of the lowest-mass stars and the hydrogen-burning limit suggested that a population I object with a mass less than 0.07 solar masses or a population II object less than would never go through normal stellar evolution and would become a completely degenerate star.
These are known as brown dwarfs.

Stellar classification

spectral typeK-typeG-type
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.
Red dwarfs are a deep shade of orange, and brown dwarfs do not literally appear brown, but hypothetically would appear dim grey to a nearby observer.

Black dwarf

Sun will have cooled
The objects now called "brown dwarfs" were theorized to exist in the 1960s by Shiv S. Kumar and were originally called black dwarfs, a classification for dark substellar objects floating freely in space that were not massive enough to sustain hydrogen fusion.
These objects are now generally called brown dwarfs, a term coined in the 1970s.

GD 165

In 1988, however, a faint companion to a star known as GD 165 was found in an infrared search of white dwarfs.
GD 165 is a system of a white dwarf and a brown dwarf of spectral types DA4 + L4, located in constellation Boötes at approximately 103 light-years from Earth.

WISE J031624.35+430709.1

T-class brown dwarfs, such as WISE 0316+4307, have been detected over 100 light-years from the Sun.
WISE J031624.35+430709.1 is a brown dwarf of spectral class T8, located in constellation Perseus at approximately 106 light-years from Earth.

WISE 1828+2650

Of these, fourteen are classified as cool Ys. One of the Y dwarfs, called WISE 1828+2650, was, as of August 2011, the record holder for the coldest brown dwarf – emitting no visible light at all, this type of object resembles free-floating planets more than stars.
WISE 1828+2650 (full designation WISEPA J182831.08+265037.8) is a brown dwarf or rogue planet of spectral class >Y2, located in constellation Lyra at approximately 47 light-years from Earth.

Kelu-1

Kelu 1
Wide-field searches have identified individual faint objects, such as Kelu-1 (30 ly away).
Kelu-1 is a system of two brown dwarfs of spectral types L2 and L4 located in constellation Hydra at approximately 61 light-years from Earth.

ULAS J133553.45+113005.2

In 2009, the coolest known brown dwarfs had estimated effective temperatures between 500 and 600 K, and have been assigned the spectral class T9. Three examples are the brown dwarfs CFBDS J005910.90-011401.3, ULAS J133553.45+113005.2, and ULAS J003402.77−005206.7.
ULAS J133553.45+113005.2 (also called ULAS1335) is a T-type brown dwarf in the constellation of Virgo.

UGPS J0722-0540

UGPS 0722−05UPGS 0722-05
In April 2010, two newly discovered ultracool sub-brown dwarfs (UGPS 0722-05 and SDWFS 1433+35) were proposed as prototypes for spectral class Y0.
UGPS J072227.51-054031.2 (designation often abbreviated to UGPS 0722-05) is a brown dwarf of late T type, located approximately 4.1 pc from Earth.

Kelvin–Helmholtz mechanism

gravitational contractionKelvin–Helmholtz heatingKelvin–Helmholtz timescale
As the cloud contracts it heats due to the Kelvin–Helmholtz mechanism.
This mechanism is evident on Jupiter and Saturn and on brown dwarfs whose central temperatures are not high enough to undergo nuclear fusion.

WISE 0855−0714

In April 2014, WISE 0855−0714 was announced with a temperature profile estimated around 225 to 260 K (−48 to −13 °C; −55 to 8 °F) and a mass of.
WISE 0855−0714 (full designation WISE J085510.83−071442.5 ) is a sub-brown dwarf 2.23 parsecs (7.27 light-years) from Earth, the discovery of which was announced in April 2014 by Kevin Luhman using data from the Wide-field Infrared Survey Explorer (WISE).

ULAS J003402.77−005206.7

ULAS J0034-00
In 2009, the coolest known brown dwarfs had estimated effective temperatures between 500 and 600 K, and have been assigned the spectral class T9. Three examples are the brown dwarfs CFBDS J005910.90-011401.3, ULAS J133553.45+113005.2, and ULAS J003402.77−005206.7.
ULAS J003402.77-005206.7 (also ULAS J0034-00) is a T-type brown dwarf in the constellation of Cetus.

Jupiter

Jovianplanet JupiterGiove
Like the Sun, Jupiter and Saturn are both made primarily of hydrogen and helium.
A "Jupiter mass" ( or ) is often used as a unit to describe masses of other objects, particularly extrasolar planets and brown dwarfs.

HR 2562 b

HR 2562 b is listed as the most-massive known exoplanet (as of December 2017) in NASA's exoplanet archive, despite having a mass more than twice the 13-Jupiter-mass cutoff between planets and brown dwarfs.
Initially categorised as brown dwarf, its exact mass is unknown, and is thought to be 30 ± 15 Jupiter masses, and its luminosity is about two one-thousandths of a percent of a solar luminosity.