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Researchers Discover a Star's Minimum Possible Mass
paulmac84 writes "Stars that don't have enough mass never shine, dying billions of years before their bigger counterparts. But astronomers have never been able to measure the exact mass limit, because the lightest stars that do shine can be simply too faint to detect. Now, new images show for the first time how big a star must be to avoid impending doom. The long-awaited new images finally lay this question to rest, say the authors. The dimmest stars were measured as being 8.3% of the Sun's mass. All protostars that are smaller than this are headed for life as a brown dwarf."
... that's 87 Jupiters.
If there were dimmer stars present there, the Hubble's main camera would have been sensitive enough to have seen them...they're pretty sure of this because they were able to notice some very dim white dwarfs (a white dwarf is the remenant stellar core of a bigger star which went nova; they are very hot [initally] but also very tiny), which are dimmer than the smallest M-class stars still in the main sequence.
Basicly, this observation is in reasonably close accordance with the theories about stellar fusion; basicly, an potential star needs to have about ten or fifteen times Jupiter's mass before deuterium fusion is possible, and about 70 times Jupiter's mass before normal hydrogen fusion happens (according to the models).
Jupiter weighs 1.899 * 10^29kg; Sol weighs 1.989 * 10^32 kg (or about 1050 times what Jupiter weighs).
8.4% of Sol's mass is 1.65 * 10^30, or 87 times what Jupiter weighs.
"The human race's favorite method for being in control of the facts is to ignore them." -Celia Green
Didn't Karen Carpenter set the standard for the minimum mass of a star?
Brown Dwarf? That's "colored star of alternaive height" to you, mister!
Trust the Computer. The Computer is your friend.
Many years ago people believed that heavy things fell faster than light things. They didn't bother testing this theory because they knew it to be true. Then, one day, someone tested that theory and found it was false.
Perhaps it is a simple problem to answer mathematically. And now we've tested it. We have actual data. Does the data match up with the mathematical answer? Maybe, maybe not, I don't pretend to know. But I imagine people out there do - so either we've got another point of verification that our models are good, or it's time to figure out what's wrong with them.
Either way, this is what's called Science.
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True enough, but both back-of-the-envelope calculations and the best models give you an answer that's spot on, to within something less than a factor of two. It's not as though there's some great debate within the community about whether the minimum mass for pop-II stars is significantly different from
I'm a great fan of observational confirmations, and of giving Hubble time to people doing this sort of work, but it's hard to imagine why anyone who isn't a specialist in stellar modeling looking to test their code to within a few percent would care about this particular result.
It hardly seems like press release material. What's more, dressing up the article to make it seem like some great mystery has been solved is disingenuous.
But, I suppose, "this just in: astronomers have confirmed something that they've been rather confident is true for decades" doesn't sell papers.