Gravity's growing role in 'The Starry Night'

By recombining the slices, which give a sense of depth to the graphical representation of the cloud, they could tease out information about how matter in the cloud was clumped in three dimensions.

The approach is yielding insights into a particular patch of the star-formation time line, when a slowly compressing hunk of a molecular cloud is somewhere between 3.3 and 0.33 light years across. The question: Is the impetus for a buildup of clumps into self-gravitating objects, well, gravity? Or do the self-gravitating clumps form initially because of turbulence within the molecular cloud?

Everybody knows that gravity is present on all size scales, Goodman explains. But models -- include some she acknowledges using -- don't take gravity into account. It's thought to be too weak on those distance scales given the distribution of dense clumps seen in two dimensions. So models only consider turbulence as a clumping agent.

But she adds, unclumped gas itself exerts gravity. So do stars that already have formed in the cloud, but may still be hidden from view. Add the third dimension, however, and more clumps, including those masking stars, appear than meets the 2D eye. This boosts the likelihood that gravity is playing a significant role as well.

And inside those cocoons?

This has implications for what these clumps do on the road to stardom, notes Ralph Pudritz, an astrophysicist at McMaster University in Hamilton, Ontario.

Two scenarios are competing for favor. Both assume the collapse continues.

But one holds that as a clump collapses, its gravity can suck up additional gas from its surroundings. In effect, when the star finally ignites, its mass will combine the mass of the original clump, plus any additional gas it's been able to snag. Estimates suggest this growth can result in a star with 10 to 100 times more mass than its original clump had.

The other holds that the clump has all the gas it's ever going to get. It may break into smaller clumps and form binary or other multi-star systems. Tatooine's dual suns come to mind. But gravity is insufficient to play any further role in the stars' final heft.

Neither is fully supported by available observations, Dr. Pudritz notes in an email. "That is why I am personally optimistic" about the Goodman team's approach.

As for Goodman, she says her results suggest that gravity could well be at work on and among these clumps.

"Our paper says that if some of those blobs are gravitationally bound to each other, then over their lifetimes they will gravitationally interact. They won't interact a lot in the particular region we studied," she says. But the results suggest that, as often happens, the truth will embrace elements of each camp's ideas.

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