Brown Dwarfs: Crash Course Astronomy #28

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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 as well called brown dwarfs. Brown dwarfs, have a mass that places them between giant planets and small stars. They were only recently discovered in the 1990’s, 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.

Table of Contents
Intermediate in Mass 1:22
Thousands Are Known 4:48
Cannot Fuse Hydrogen Like “Normal” Stars 8:46

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The sun in extreme ultraviolet [credit: NASA, ESA / Wikimedia Commons]
Jupiter [credit: NASA, ESA, and A. Simon (Goddard Space Flight Center)]
Forming a Planetary Gap [credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)]
Exoplanet [credit: NASA/JPL-Caltech]
A Trio of Brown Dwarfs (L/T/Y) [credit: NASA/JPL-Caltech]
Artist’s concept of a T-type brown dwarf [credit: NASA/JPL-Caltech]
Brown Dwarf Gliese 229B [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 T-dwarf [credit: R. Hurt/NASA – R. Hurt/NASA, Wikimedia Commons]
First Ultra-Cool WISE Brown Dwarf [credit: NASA/JPL-Caltech/WISE Team]
Brown Dwarf Comparison [credit: NASA/JPL-Caltech/UCB]
Storms Expected on Brown Dwarfs [credit: NASA/JPL-Caltech/T. Pyle (IPAC)]
Stars and brown dwarfs closest to the Sun [credit: NASA/Penn State University]


PhamNet says:

Is it just me or do the significant phases of a star's life cycle (Fusion, Supernova, Neutron Star, Black Hole) involves an event where the star can violate one of the forces. For example, A star being born involves nuclear fusion, so has become immune to the weak nuclear force? Then after a supernova, if the star becomes a neutron star, then it has become immune to the strong nuclear force? Then when it becomes a black hole, then its become immune to gravity? So what about electromagnetism?

PhamNet says:

Are there any amateur cosmologists or scientists that make discoveries or write u fluential papers anymore? Just curious if theres hope for me yet.

Lorie Marinas says:


azi maynard says:

lol 0:45 those are all minecraft blocks lol

Toughen Up, Fluffy says:

They prefer to be called brown little people.

Stevie Wu says:

Why you add minecraft .-.

Adel Skkr says:

what!? mc blocks!?!!

ociv delos says:

the magenta dwarf looks scary

Jess Golden says:

How can elements fuse in these brown dwarfs (lithium, deuterium) if no fusion is actually going on(like in a main sequence star)?

Baby Vegeta says:

very interesting

Victor Garcia says:

I dont actually know if brown dwarfs can be 2 times the mass of Jupiter, at that point the object is still a planet.

Victor Garcia says:

Phil, this isnt right! L-dwarf spectral type does correspond to objects that are brown dwarfs and dont fuse hydrogen!

Edward Troth says:


FloreSpace says:

Oh Boy A Feral Giraffe Killed My Little Transparent Yeti

Go K says:

8:05 The sun is way too small in that picture when compared to the size of jupiter. Please get images from better sources.
Properly scaled image is below.

FirstRisingSouI says:

Oh Boy, A Feral Giraffe Killed My Little Transparent Yeti.
I'll never forget star classification again.

Parikshit Hegde says:

whats DFTBA

kurama says:

dafuq happened to vsauce?

Seth Sumner says:


acebulf says:

Brown Dwarfs of mass between 13 and 60 Jupiter masses can fuse hydrogen via Lithium, H-1 + Li-7 => 2(He-4)

Cycling in Edmonton from the Eyes of a Teen says:

How about dividing brown dwarfs and planets by whether the object is orbiting anything other than a galactic core or is part of a star cluster? Planets orbit something neighbourly close.

Ishmael Zivan says:

Oh look we can put Minecraft blocks into Jupiter since the Minecraft world is larger than Earth

Dan Dubs says:

Stars are born in Birkeland currents, not because of gravity. Planets are born in brown dwarf stars (Saturn, Jupiter, Neptune, Uranus) that I think are the flyers when the star goes supernova.

IIGrayfoxII says:

I am surprised that I cant find a mention to nibiru star

just4fun607 says:

caught myself in the weird part on the internet

Reletr, Master of the Realms says:

Why are there MC blocks?

Green Blaze says:

Fascinating, these lil' fuckers. Great episode.

tokyOgoomba says:

I always liked reading about the planets and stars when I was a child and this channel is resparking my interest in astronomy. Loving the videos, keep making them!

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