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It doesn't take much to make a massive star. Just a lot of interstellar dust and gas, and perhaps – according to a new theory published this week – a lot of little stars nearby.
As carbon-based lifeforms, on a planet rich with relatively heavy atoms, we owe our existence to heavy stars. Yes, OK, to our little Sun too, since it gives us warmth and light. Details. But it was the explosion of other massive stars into supernovae in the extraordinarily distant past, scattering elements created at the star's heart, to which we owe many of our heavier atomic components.
Astrophysicists at Princeton and the University of California at Berkeley have now proposed a new theory of star formation, essentially arguing that huge supernova-prone stars like this may owe their own existence to smaller stars the size of our own Sun.
According to their computer models, they say, stars ranging from 10 to
150 times the mass of the Sun may in fact require some starter stars nearby in order to form. These massive bodies form out of huge clouds of interstellar gas and dust – but without small stars forming first, these huge clouds may fragment before forming the larger stars, the researchers say.
The smaller stars warm up the clouds of molecular hydrogen, preventing them from falling apart before they can birth a massive star. Not unlike a few space heaters warming up a cozy winter bedroom, where things can get hot and heavy... well, no, better leave that particular metaphor.
The research has implications for how astronomers have viewed the number of stars in distant galaxies. Our instruments allows us to see the brightest stars, but often don't pick up the light from relatively smaller bodies, forming in the outer reaches of galaxies where dust clouds aren't dense enough to form the large, bright stars. Thus, astronomers may have underestimated the level of star formation elsewhere and elsewhen in the universe, the researchers say.
"In fact, there may be many stars forming in the outer reaches of distant galaxies, just not the bright ones we can see," McKee said in a statement. "Star formation could be occurring that is essentially invisible.
The study was published as a letter in the current edition of Nature.
A minimum column density of 1 g cm-2 for massive star formation [Nature]
Small 'helper' stars needed for massive star formation [University of California, Berkeley press release]
(Image: Screen shot from a Princeton animation of the collapse of a proto-star core into a massive star. Credit: Mark Krumholz/Princeton)
