Planets may emerge from stellar duo gathering icy dust

Gas freezing onto grains could form comets or larger worlds

ring of carbon monoxide gas around a star

CONSTRUCTION AHEAD  A ring of carbon monoxide gas (blue) and dust (red) roughly 300 times as wide as Earth’s orbit encircles the binary star HD 142527 (not visible) in this composite image. The dust concentration might be a region where planetary building blocks are forming. 

A. Isella/Rice Univ., B. Saxton/NRAO/AUI and NSF, ALMA/NRAO, ESO, NAOJ

WASHINGTON — A pair of stars is setting up an icy planetary construction zone, new data suggest. Carbon monoxide gas is freezing onto tiny dust grains orbiting the stellar duo. The frozen particles might eventually give rise to a population of comets or even a new planet.

A belt of gas and dust encircles the binary star HD 142527, about 450 light-years away in the constellation Lupus. Observations with the Atacama Large Millimeter/submillimeter Array in Chile reveal a region of the belt where there is very little carbon monoxide compared with dust. The gas is probably condensing onto dust grains and building a reservoir of ice-encrusted particles, astrophysicist Andrea Isella reported February 13 at the annual meeting of the American Association for the Advancement of Science.

“It’s the perfect recipe if you want to form planets or planetesimals,” said Isella, of Rice University in Houston. “Icy grains collide and stick together well.”

Gravitational interactions among the two stars and the belt trap dust grains in this zone, providing lots of surfaces on which the gas can condense. Without knowing the mass of the corralled dust, Isella can’t yet say if a family of comets or a full-fledged planet will eventually form. Something similar might have happened in our solar system 4.6 billion years ago, he says. Jupiter and the sun could have worked together to herd dust grains that collected ice and went on to form comets or even dwarf planets such as Pluto. 

Christopher Crockett is a freelance science writer and editor based in Arlington, Va. He has a Ph.D. in astronomy from the University of California, Los Angeles.

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