The rate of star formation

Nov 26, 2010
An optical image of the California Nebula, a giant cloud of gas and dust whose total mass is nearly 100,000 solar-masses. Despite its huge size, this nebula is among the least efficient in making stars. A new paper explains the paradoxically low number of new stars as due to the lack of dense material in this object. Credit: Caltech, Palomar Observatory, Digitized Sky Survey

(PhysOrg.com) -- New stars continue to appear in the night sky, as the gas and dust in giant interstellar clouds gradually coalesces under the influence of gravity until nuclear burning begins.

Precisely how all this happens is an active area of current astronomical research, one which also holds the key to understanding how planets form, how the brightest galaxies shine, and how the produced the essential for life. Among the outstanding puzzles: what physical parameters determine the *rate at which stars form?

SAO astronomer Charlie Lada, together with two colleagues, offers important new insights into this question in a paper this month in The . The scientists examined in eleven relatively nearby regions actively producing stars. The regions are quite different from one another in overall mass, with values ranging from about 800 solar-masses to 100,000 solar-masses.

The star formation rates in these regions, based on infrared observations of very young stars, also differ - from a few stars every million years to nearly a thousand stars every million years. But curiously the more massive clouds do not necessarily produce at a faster rate - in fact, the new study finds that the most massive cloud, the California Nebula, actually had a very low rate, and was the least efficient. The most efficient region, by comparison, was among the least massive.

The astronomers found that the key predictor of the star formation rate was the density of the material in the cloud above a critical value. They estimated the density by examining the extinction of optical and near infrared light passing through the clouds, since the opacity is the result of dense dust in the cloud. Over the years numerous other predictors have been hypothesized (for example, the total cloud mass), but these new results provide solid evidence for the importance of density.

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User comments : 14

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omatumr
1.4 / 5 (11) Nov 26, 2010
No, stars form on the collapsed cores of previous stars.

Just as the Sun did 5 Gyr ago:
http://www.youtub...e_Qk-q7M

With kind regards,
Oliver K. Manuel
Skepticus_Rex
3.9 / 5 (7) Nov 27, 2010
There wouldn't be enough star cores to go around in such a scenario. Observations show multiple stars forming in regions that were created by a single supernova or by fewer supernovae than newly formed stars. And then there are star formation regions occuring in colliding galaxies as well as in regions where black holes are believed to exist.

This hypothesis does not fit all the available evidence.
jdaviqwert
5 / 5 (4) Nov 27, 2010
No, stars form on the collapsed cores of previous stars.

Just as the Sun did 5 Gyr ago:
http://www.youtub...e_Qk-q7M

With kind regards,
Oliver K. Manuel


Creationist theories are based on belief in special interpretation of ancient texts. These ideas are not even wrong. Just crank ravings.
omatumr
1.4 / 5 (10) Nov 27, 2010
There wouldn't be enough star cores to go around in such a scenario. Observations show multiple stars forming in regions that were created by a single supernova or by fewer supernovae than newly formed stars.

This hypothesis does not fit all the available evidence.


Do you assume that each cosmic explosion creates a single neutron star?

Or does neutron repulsion cause massive objects, for example at the centers of galaxies, to fragment into multiple neutron stars on which new stars form?

Please take the time to read the papers on neutron repulsion. You can start with this simple video summary, but eventually you will need to read the papers and look at the nuclear rest mass data for yourself.

http://www.youtub...yLYSiPO0

"Attraction repulsion of nucleons: Sources of stellar energy"
J. Fusion Energy 19 (2001) 93-98.

"Earth's heat source - The Sun"
Energy & Environment 20 (2009) 131-144.

With kind regards,
Oliver K. Manuel
KwasniczJ
1 / 5 (10) Nov 27, 2010
..new paper explains the paradoxically low number of new stars as due to the lack of dense material in this object..
This is apparently tautological explanation: the missing dense objects inside of gas is caused with the lack of dense material. It violates the contemporary cosmological model, in which all stars were formed from such clouds free of dense material originally.
Parsec
5 / 5 (5) Nov 27, 2010
..new paper explains the paradoxically low number of new stars as due to the lack of dense material in this object..
This is apparently tautological explanation: the missing dense objects inside of gas is caused with the lack of dense material. It violates the contemporary cosmological model, in which all stars were formed from such clouds free of dense material originally.

Nope. Learn the model before you quote from it. The first stars were almost completely free of dust and metals, which made them huge and take a while to form, but the clouds they formed from had to be dense enough to collapse.
yyz
4.3 / 5 (6) Nov 27, 2010
"The first stars were almost completely free of dust and metals, which made them huge and take a while to form, but the clouds they formed from had to be dense enough to collapse."

While the CW surrounding Pop III stars is that they were formed as supermassive beasts(>100 solar masses), some models have been put forward that allow for less massive Pop III stars. One popular model holds that so-called secondary Pop III stars may have formed in the immediate vicinity of massive Pop III stars. Violent stellar winds from the primary star would induce collapse of gas nearby, forming low mass (
yyz
not rated yet Nov 27, 2010
Oops, ate some of my post. Try from...

Violent stellar winds from the primary star would induce collapse of gas nearby, forming low mass secondary Pop III stars
KwasniczJ
1.9 / 5 (9) Nov 27, 2010
The first stars were almost completely free of dust and metals, which made them huge and take a while to form, but the clouds they formed from had to be dense enough to collapse.
Did they? IMO the universe has been expanded into existing size due the inflation with all matter divided into sparse plasma clouds by existing models. From such state it would be impossible to collapse for elementary particles of matter - we can just see example of it.
yyz
4.3 / 5 (6) Nov 27, 2010
con't.

The secondary stars would have masses of under 20 Msun and could be quite numerous. This mode of formation could have major implications for the construction of the first galaxies.

Some models predict that primordial low mass Pop III stars may still exist today! Of course this is all speculation given that no unambiguous examples of any Pop III stars have been found.

Here's a recent paper on the formation of secondary Pop III stars: http://arxiv.org/...69v1.pdf
kevinrtrs
1.5 / 5 (8) Nov 29, 2010
New stars continue to appear in the night sky, as the gas and dust in giant interstellar clouds gradually coalesces under the influence of gravity until nuclear burning begins

One has to question the researcher's premise about "star formation". Are they documenting the appearance of stars and hence assuming that they also represent the birth of those stars? If stars take so many millions of years to form, when exactly do they become visible to the observer as a new-born star?
The interesting paradox is that those highly visible nebula are visible precisely because they're HOT. If they're hot, the gas molecules will be moving at far too high a speed to settle down into any kind of high density that would precipitate into a star.
This means that really no one should be able to SEE any dust where stars are forming, hence no one should be able to see when stars actually get born - according to the big bang model.
Stars were created by an outside force, one necessary to start fusion.
lengould100
5 / 5 (1) Nov 29, 2010
I thought this whole question was settled as "And then someone said 'Let there be light'"? LOL
barakn
4.2 / 5 (5) Nov 29, 2010
I see kevinrtrs unwittingly made the same argument that the paper's authors did - the California Nebula isn't dense enough to support a high star formation rate. He then goes on to make some moronic statements, like claiming visible nebula are visible only because they are hot (hint: there's a difference between emission and reflection nebula).
Ethelred
5 / 5 (3) Dec 04, 2010
This means that really no one should be able to SEE any dust where stars are forming, hence no one should be able to see when stars actually get born - according to the big bang model.
We see the dust that the stars form from. Those nebula are dark and we can see dark nebula. However the nebula where stars have already begun to form stop being dark because they are heated by the early forming stars. Those stars not only light up the nebula they blow out the dust around them and collapse the remaining cold zones of the nebula.

Kevin, the world and Universe won't beome 6000 years old just because you don't want to accept the truth.

Ethelred
Physorg should do themselves and us a favor and Stop the Ranking Insanity.

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