I’ve always been interested in astronomy, and at a young age I learned all about red giants, white dwarves, and black holes. I spent a lot of nights during the second semester of my freshman year in college at the telescope in the science center while I was taking a course called Astronomy 14.
Yesterday I went with my younger son to the Hayden Planetarium and saw their current show, Journey to the Stars. And I learned about a class of stars I’d never heard of before: the brown dwarf.
Actually, the brown dwarf isn’t really a star. It’s a sub-stellar body that isn’t massive enough to maintain nuclear fusion at its core. Brown dwarfs (yes, that’s the way the plural is spelled) are more massive than giant gas planets like Jupiter but less massive than the smallest stars. They usually have masses between 15 and 75 times the mass of Jupiter. The Planetarium show refers to the first confirmed brown dwarf, which was discovered in 1995 in the Pleiades star cluster.
Some astronomers think that the universe may be full of brown dwarfs and that they may provide the answer to the famous problem of the universe’s “missing mass.”
If you find all of this as fascinating as I do, you may enjoy the trailer for Journey to the Stars below.
And this page from CalTech’s Cool Cosmos website has some cool renditions of brown dwarfs.
Unfortunately, currently the common belief is that brown dwarfs can’t really solve the “missing mass” problem – at least not in its entirely. One reason is because the “missing mass” appears to have a different distribution than normal stars, while brown dwarfs should have rough the same distribution in galaxies as normal stars. The second is that brown dwarfs are made of normal matter. From studying the Cosmic Microwave Background, we can estimate the total amount of normal matter in the universe and their doesn’t appear to be enough to explain all the mass. Brown dwarfs could explain where some of the missing normal matter is, though most of it is likely in very low density (diffuse) clouds of gas that stretch between galaxies and galaxy clusters.
And I thought that I was writing a post that had nothing to do with NYU Abu Dhabi. Thanks for setting us straight about the brown dwarfs.
[Joseph is Assistant Professor of Physics, NYU Abu Dhabi. His scholarly focus is core collapse supernovae — the cosmic explosions believed to mark the death of the most massive stars, in particular the neutron stars and pulsar wind nebulae formed in these events. More broadly, he studies radio and X-ray active galactic nuclei, high redshift radio galaxies, the acceleration and propagation of cosmic rays, and the evolution of massive stars.]