Brown Dwarf

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Brown dwarfs are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most massive gas giant planets and the least massive stars, approximately 13 to 80 times that of Jupiter (MJ). However, they can fuse deuterium (2H), and the most massive ones (> 65 MJ) can fuse lithium (7Li). Astronomers classify self-luminous objects by spectral class, a distinction intimately tied to the surface temperature, and brown dwarfs occupy types M, L, T, and Y. As brown dwarfs do not undergo stable hydrogen fusion, they cool down over time, progressively passing through later spectral types as they age. Despite their name, to the naked eye, brown dwarfs would appear in different colors depending on their temperature. The warmest ones are possibly orange or red, while cooler brown dwarfs would likely appear magenta to the human eye. Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth. — Wikipedia

Brown Dwarf (Encyclopædia Britannica)

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Innovation

Science

SciShow Space (YouTube Channel)

WISE (NASA Jet Propulsion Laboratory, YouTube Playlist)

What is a Brown Dwarf? (JPL/NASA)

Brown Dwarf (Wolfram Alpha)

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Preservation

History

The objects now called “brown dwarfs” were theorized by Shiv S. Kumar in the 1960s to exist 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. However, (a) the term black dwarf was already in use to refer to a cold white dwarf; (b) red dwarfs fuse hydrogen; and (c) these objects may be luminous at visible wavelengths early in their lives. Because of this, alternative names for these objects were proposed, including planetar and substar. In 1975, Jill Tarter suggested the term “brown dwarf”, using “brown” as an approximate color. — Wikipedia

Library

WorldCat, Library of Congress, UPenn Online Books, Open Library

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Participation

NOIRLabAstro (YouTube Channel)

This three-dimensional rendering highlights the trove of cold, nearby brown dwarfs discovered by citizen scientists participating in the Backyard Worlds: Planet 9 project. The Sun is at the center, and each brown dwarf appears as a colorful orb at its current location in space. Redder colors correspond to colder temperatures, with the innermost shell of deep red (extremely cold) discoveries representing the hundred newly published worlds. The green grid is aligned with the plane of the Milky Way, with squares spaced at intervals of 5 parsecs (roughly 15 light years). Over the course of many millions of years, these objects found near the Sun will disperse throughout the Milky Way. — Division of Physical Sciences, UC San Diego

Division of Physical Sciences, UC San Diego (YouTube Channel)

Citizen Scientists Discover Dozens of New Cosmic Neighbors in NASA Data (JPL/NASA)
Two Bizarre Brown Dwarfs Found With Citizen Scientists’ Help (JPL/NASA)

Backyard Worlds: Planet 9 is a NASA-funded citizen science project which is part of the Zooniverse web portal. It aims to discover new brown dwarfs, faint objects that are less massive than stars, some of which might be among the nearest neighbors of the Solar System, and might conceivably detect the hypothesized Planet Nine. The project’s principal investigator is Marc Kuchner, an astrophysicist at NASA’s Goddard Space Flight Center. — Wikipedia

Backyard Worlds: Planet 9 (Zooniverse)