While Jupiter is nowhere near massive enough to initiate fusion in its core, there are even more massive objects out there that fall just short of that achievement called brown dwarfs. Brown dwarfs have a mass between giant planets and small stars. They were only recently discovered in the 1990s, but thousands are now known. More massive ones can fuse deuterium, and even lithium, but not hydrogen, distinguishing them from “normal” stars. Sort of.

Correction: In the illustration at 9:30, the numbers listed after the star names are the year of discovery, not distance.

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Chapters:
Introduction: Brown Dwarfs 00:00
L Stars & The Lithium Test 2:50
Discovering the First Brown Dwarfs 4:14
What Color Are Brown Dwarfs? 6:24
Physical Characteristics of Brown Dwarfs 7:30
Small Stars vs. Big Planets 8:11
Review 10:17


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PHOTOS/VIDEOS
The sun in extreme ultraviolet https://en.wikipedia.org/wiki/File:Th... [credit: NASA, ESA / Wikimedia Commons]
Jupiter http://www.spacetelescope.org/static/... [credit: NASA, ESA, and A. Simon (Goddard Space Flight Center)]
Forming a Planetary Gap http://www.spitzer.caltech.edu/video... [credit: NASA/JPLCaltech/R. Hurt (SSC/Caltech)]
Exoplanet http://uanews.org/sites/default/files... [credit: NASA/JPLCaltech]
A Trio of Brown Dwarfs (L/T/Y) http://www.nasa.gov/mission_pages/WIS... [credit: NASA/JPLCaltech]
Artist's concept of a Ttype brown dwarf https://en.wikipedia.org/wiki/Brown_d... [credit: NASA/JPLCaltech]
Brown Dwarf Gliese 229B https://en.wikipedia.org/wiki/File:Br... [credit: NASA / Wikimedia Commons]
Gliese 229B Spectrum image provided by Phil Plait [credit: NASA/ESA/Hubble/Al Schultz et al]
Artist's vision of a Tdwarf https://en.wikipedia.org/wiki/Brown_d... [credit: R. Hurt/NASA R. Hurt/NASA, Wikimedia Commons]
First UltraCool WISE Brown Dwarf http://wise.ssl.berkeley.edu/gallery_... [credit: NASA/JPLCaltech/WISE Team]
Brown Dwarf Comparison http://www.nasa.gov/mission_pages/WIS... [credit: NASA/JPLCaltech/UCB]
Storms Expected on Brown Dwarfs http://www.spitzer.caltech.edu/images... [credit: NASA/JPLCaltech/T. Pyle (IPAC)]
Stars and brown dwarfs closest to the Sun https://en.wikipedia.org/wiki/Luhman_... [credit: NASA/Penn State University]