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Frigid Brown Dwarf Found Only 7.2 Light-Years Away
An anonymous reader writes "Astronomer Kevin Luhman just found the 7th closest star to the sun. It's a mere 7.2 light-years away, discovered using NASA's Spitzer and WISE telescopes. How could it exist so close for so long without us knowing? It's a brown dwarf — barely a star at all. 'Brown dwarfs are star-like objects that are more massive than planets, but not quite massive enough to ignite sustained fusion in their cores. Hydrogen fusion is what powers the Sun, and makes it hot; it's the mighty pressure of the Sun's core that makes that happen. Brown dwarfs don't have the oomph needed to keep that going.' This small almost-star is downright chilly at around 225-260 Kelvin. That's -48 to -13 C (or -54 to 9 F). As Phil Plait points out, that's not much different from the temperature in the freezer in your kitchen. He adds, 'It implies this object is very old, too, because it would've been a few thousands degrees when it formed, and would take at least a billion years to cool down to its current chilly temperature. It's hard to determine how old it actually is, but it's most likely 1-10 billion years old. It has a very low mass, too, probably between 3 and 10 times the mass of Jupiter. That's pretty lightweight even for a brown dwarf. And here's another amazing thing about it: It might be a planet. What I mean is, it may have formed around a star like a planet does, then got ejected by gravitational interactions with other planets.'"
That would make it a rogue planet.
That's part of the MACHO hypothesis regarding dark matter. We could explain away dark matter with trillions of brown dwarfs but that doesn't seem satisfactory for astronomers and cosmologists. For some reason (big bang and cosmic background calculations etc.) we know think that baryonic (regular matter) is only about 4% of the universe's amount of mass-energy and about 25% of non-baryonic dark matter is needed to make it all fit. Not enough baryonic matter to have enough brown dwarfs playing the role of dark matter in/around galaxies.
The Wikipedia article on dark matter discusses this in depth. Although I'm no astrophysicist and can't vouch for the article's accuracy, it does outline some of the reasons why those studying it believe that objects like this cannot account for the amount of dark matter required to explain how galaxies behave.
How can we continue to believe in a just universe and freedom to eat crackers if we have no ale?
Your question is whether Dark Matter could be real and observed MACHOs.
The other main option is that Dark Matter could be hypothetical WIMPs
Numerous experiments have ruled out MACHOS as making up the bulk of Dark Matter. The missing mass problem is not solved by MACHOs.
At the moment the WIMPS are beating the MACHOS.
See also History of the search for Dark Matter
Google that without SafeSearch. ewwww.
Two elements of TFA caught my eye:
micrometers
Together, these figures are within the range for a type I (or, maybe even a type II) Dyson sphere.
And, it is only 7.2 light years away?
Yes, it is very probably the Brown Dwarf that the astronomers think it is.
But, imagine. It could be a Dyson sphere; our first evidence of advanced life beyond the earth.
"values of beta will give rise to dom!"