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Old 17-02-2011, 10:34 AM
CraigS's Avatar

CraigS is offline
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Star Formation

Ok .. so the Drake Equation is here. The first term in it is 'R*', which is the average rate of star formation per year in our galaxy.

So then I find in today's news, this article which, whilst having a Dark Matter 'spin' to it, is really about our current state of knowledge when it comes to star formation in a galaxy.

Analysis of the brightness of the patches in the SPIRE images has shown that the star-formation rate in the distant infrared galaxies is 3-5 times higher than previously inferred from visible-wavelength observations of similar, very young galaxies by the Hubble Space Telescope and other telescopes.
.. and this is only because they used a different telescope. Ie: other variables in the model also have uncertainties associated with them.
Further analysis and simulations have shown that this smaller mass for the galaxies is a sweet spot for star formation. Less massive galaxies find it hard to form more than a first generation of stars before fizzling out. At the other end of the scale, more massive galaxies struggle because their gas cools rather slowly, preventing it from collapsing down to the high densities needed to ignite star formation.
.. ok .. so the smaller mass 'sweet spot' sets a new lower limit on the star formation rate within a Universe having lots of galaxies of different masses ...
But at this newly identified 'just-right' mass of a few hundred billion solar masses, galaxies can make stars at prodigious rates and thus grow rapidly.
"This is the first direct observation of the preferred mass scale for igniting a starburst," says Dr Cooray.
Also, the 'prodigious rate' in this lower mass set of galaxies, can result in more stars (of different masses, etc, etc) ..

Good to see progress on calculating the rate of star formation, for a given mass scale and that the rate has gone up by 3 to 5 times, when compared with the previously accepted figure.

However .. (from the report)

The underlying astrophysics needed to explain the numerical value we find are still missing in galaxy formation theories, since existing semi- analytical models predict a mass scale for faint sub-millimetre galaxies, that are roughly ten times larger.
Also good to note is that this information doesn't tell us anything about the statistical significance of this finding on the potential numbers of stars having habitable planets orbiting them.

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Old 17-02-2011, 10:41 AM
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renormalised (Carl)
No More Infinities

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This is for young galaxies....if you want to find the rate of star formation in the mature galaxies (and hence a much better determination of the values within the Drake equation), you need to study those areas of star formation within these galaxies. From doing so, astronomers have determined that the Milky Way produces 3-5 solar masses on new stars per year. It turns out to about one star of a solar mass per year...most of the others are smaller stars.

Interestingly, Andromeda produces 1 solar mass of stars per year.
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