Detailed images of disks swirling around young stars show the details of how solar systems come to be.
Quanta Magazine said:Over the past two and half centuries, scientists envisioning the origin of planetary systems (including our own) have focused on a specific scene: a spinning disk around a newborn star, sculpting planets out of gas and dust like clay on a potter’s wheel.
But as for testing the idea, by actually spotting an exoplanet coalesce from swirling matter? No luck yet. “Nowadays, everybody says planets form in protoplanetary disks,” said Ruobing Dong, an astrophysicist at the University of Arizona.“This sentence is, technically, a theoretical statement.”
Advances over the past few years suggest it won’t stay theoretical for long. Using second-generation instruments mounted on giant ground-based telescopes, several teams have finally resolved the inner regions of a few protoplanetary disks, uncovering unexpected, enigmatic patterns.
The latest views came on April 11, when the European Southern Observatory released eight images of disks around young, sunlike stars, perhaps illustrating what our own solar system looked like in its infancy.
The images don’t show clear, unambiguous points of lights from planets. But these and other systems do contain tantalizing — albeit indirect — hints that infant planets may be hiding within. Some disks are like a vinyl record, with rings and gaps that could have been carved out by young worlds. In others, starlight illuminates both a top and bottom surface of the disk, forming a structure that resembles a yo-yo.
If astronomers could find an embryonic planet in a place like this, the payoff would be far-reaching. Beyond just proving one of astronomy’s deepest-held ideas, the quantitative measurement of where a planet is forming, and at what size, would immediately help differentiate between battling theories of how planets are born.
One account of planet formation, called core accretion, holds that planets form slowly, coalescing around rocky cores, and in a region close to their stars. Another theory appeals to gravitational instabilities in the disk, suggesting giant planets can coalesce quickly, far away from their stars. Currently, these ideas can be tested against the distribution of current planets in our solar system and extrasolar systems. But they’ve never been studied with the process still under way, before planets have a chance to migrate and rearrange themselves.
That gives astronomers who study these systems a unifying, unfinished quest. Look at dim, distant, untidy disks. Hunt down baby planets. And at long last, after centuries of anticipation, begin to unravel the fundamental processes that shape countless worlds across the universe.
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