Brown Dwarf

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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.

  • Radio observations detect new brown dwarf
    on October 13, 2020 at 12:30 pm

    Using the Low-Frequency Array (LOFAR) radio telescope, an international team of astronomers has discovered a new radio source that turns out to be a cold brown dwarf. The object, designated BDR 1750+3809, is so far the first radio-selected brown dwarf, which proves that such sources can be also directly identified by sensitive wide-area radio surveys. The finding is reported in a paper published October 5 on arXiv.org.

  • Citizen scientists discover dozens of brown dwarfs
    on August 18, 2020 at 3:00 pm

    How complete is our census of the Sun's closest neighbors? Astronomers and a team of data-sleuthing volunteers participating in Backyard Worlds: Planet 9, a citizen science project, have discovered roughly 100 cool worlds near the Sun—objects more massive than planets but lighter than stars, known as brown dwarfs.

  • Record EOS measurement pressures shed light on...
    on August 6, 2020 at 12:21 pm

    Using the power of the National Ignition Facility (NIF), the world's highest-energy laser system, researchers at Lawrence Livermore National Laboratory (LLNL) and an international team of collaborators have developed an experimental capability for measuring the basic properties of matter, such as the equation of state (EOS), at the highest pressures thus far achieved in a controlled laboratory experiment.

  • Ground system for NASA's Roman Space Telescope...
    on July 25, 2020 at 6:36 am

    When it launches in the mid-2020s, NASA's Nancy Grace Roman Space Telescope will create enormous panoramic pictures of space in unprecedented detail. The mission's wide field of view will enable scientists to conduct sweeping cosmic surveys, yielding a wealth of new information about the universe.

  • First image of a multi-planet system around a...
    on July 22, 2020 at 1:00 pm

    The European Southern Observatory's Very Large Telescope (ESO's VLT) has taken the first ever image of a young, sun-like star accompanied by two giant exoplanets. Images of systems with multiple exoplanets are extremely rare, and—until now—astronomers had never directly observed more than one planet orbiting a star similar to the sun. The observations can help astronomers understand how planets formed and evolved around our own sun.