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University Of Arizona Scientists Spot Planets In Dust Rings Around A Dozen Stars

KJZZ | By Nicholas Gerbis

Published December 10, 2018 at 5:00 AM MST

The Taurus Molecular Cloud is a star-forming region about 450 light-years away. The image covers roughly 14x16 light-years and shows the glow of cosmic dust, dotted with a few compact, bright cores — the seeds of future stars.

An international team of scientists has found evidence of protoplanets forming in the dust rings around 12 young stars in the constellation Taurus.

The paper appears in "The Astrophysical Journal."

University of Arizona astrophysicist Paula Pinilla, who led the research with Feng Long of Peking University, was excited to discover the data matched patterns predicted by the recently-retired Kepler Space Telescope, data from which grouped all planets smaller than Jupiter-scale giants into two groups: super-Earths and mini-Neptunes.

"This is very cool because it goes in agreement with the exoplanet characteristics that show that this is the most typical kind of planet that we have found so far," she said.

Protoplanets are large masses of matter in the process of clumping together to form planets.

When Pinilla and her colleagues observed a sampling of 32 stars of various brightnesses and masses in the Taurus molecular cloud — the Earth's nearest star-forming region — they expected to see smooth, featureless disks of dust revolving around them.

protoplanetary disks are more like doughnuts with holes, but even more often appear as a series of rings. — Until recently, protoplanetary disks were believed to be smooth, pancake-like objects. This study shows some disks to be like doughnuts with holes or, more often, a series of rings, likely carved by planets that are otherwise invisible to us.

Instead, data from Chile's Atacama Large Millimeter/submillimeter Array (ALMA) showed almost 40 percent of the disks were grooved with gaps plowed by burgeoning planets.

By looking at the patterns of gap locations and widths, the contrast between rings and gaps, and the separations between rings and gaps, they concluded that most gaps must contain low-mass planets: super-Earths and Neptunes.

The researchers were also able to eliminate alternative explanations for the patterns of rings and grooves — ice lines made from nitrogen and carbon monoxide, and magnetic field effects — neither of which fit the patterns in the data.

ALMA is a group of 66 radio telescopes located at about 16,000-feet elevation in the dry air of Chile's Atacama Desert. The 40-foot diameter instruments work together to form the equivalent of a single 46,000-foot-wide dish.

Because the instrument uses wavelengths of electromagnetic energy that fall between radio and microwave, scientists can use them to peer into areas visible light cannot penetrate, such as the cores of gas clouds.