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."

Comments

Um... yay?

[Capt'n Hector]

This is a simple math/physics problem. I'm not quite sure what the grand point of it is though (kinda like the pluto(!)=planet debate). Maybe you can graph the distribution of star masses, and then see how much "dark matter" there is on the tail end of brown dwarfs.

Re:Um... yay?

[Artifakt]

It's not quite simple. It's admittedly very simple in the abstract, for a model star where you're only looking at what combinations of temperature and core density allow standard stellar fusion at a break even rate (All normal stars run at break even, in the short enough run, in the sense that the total energy produced is equal to the light pressure keeping interior layers from collapsing, plus the light emmitted to space). Physicists such as Hoyle and Gamow pretty much wrote the math for this at least forty years ago, and much of this was known well before the US designed the "Super" in 1949-50, where it turned out to be applicable (although some of it was so classified then that even the best professional Astrophysicists couldn't assume they had seen nearly all the relevant literature).

        Here's just some of what makes it more complex for the real world though, and I'm probably missing plenty of other complexifying factors:
        Spinning Star? What range of rotation rates occurs in low-mass stars, How much pressure does it relieve at the core at a minimum? (Is there any real occurance of a low mass star with absolutely no rotation?)
        Which Population (I or II). Low mass stars can be very old, as they burn their fuel so slowly. This affects how much of the heavier elements are found in their cores. Just where newer generation stars formed makes a big difference in how much of what heavier elements are in them, but there's not much of a difference theoretically possible for the first generation. Are their faint stars can we observe, but not get enough of a spectrum on to be confident of their composition?
          Are there any convection currents in low mass stars? Do such, as yet unproved, currents include the full range of modalities found in a star the size of our Sun, or fewer? (or maybe even something truly novel, completely different than in bigger stars?). We're not even real sure how typical current patterns within our Sun are for stars of its general type, last I looked.
          Can having a large, close companion star significantly reduce the minimum mass threshold, or would any such received radiation effects be trivial?

Re:For those who are wondering...

[Anonymous Coward]

I believe that 2010 should still be feasable. It's been a few years, but as I recall it the monoliths descended into Jupiter and used some exotic forces to compact it down to a scale where it was finally dense enough to ignite fusion. This article only speaks to how massive something must be for gravity to compact it that far; theoretically all you really need for a self-sustaining reaction is the proper density and pressure, however those might be achieved.

Re:Finally a Definitive Answer!

[Lave]

Sorry to be pedantitc but FTFA:

Although the telescope would have been able to detect fainter stars, none could be found- so it appears that they simply don't exist. "We checked the instruments over and over again" said Professor Richer "but we don't see any stars fainter than this".

So they could have detected much dimmer stars but didn't - so assuming a big enough sample, they discovered the minimum mass to initiate fusion. Pretty impressive.

So finally a Definitive Answer! Until someone bothers to look at a larger sample set,, finds dimmer stars, and they have to lower the minimum again.

For a little perspective...

[damburger]

8% of the Suns mass is still about 100 times the mass of Jupiter. So all that crap about turning Jupiter into a star in "2010" was a load of bollocks. Like, well, pretty much everything in that shite film.