Zhaohuan Zhu (Physics and Astronomy) with UNLV’s Nevada Center for Astrophysics is part of an international research team that recently published findings and images supporting the theory of gravitational instability in planet formation.

Zhu, a co-author on an article published July 25 in The Astrophysical Journal Letters, had published theoretical predictions about clumps formed by gravitational instability nearly a decade ago. He joined the current research team when they shared their preliminary findings which supported his past theories.

One common theory for planet formation is core accretion, which is how our solar system was formed. Heavier elements not able to be pulled in by the sun spiral together to make planets, with the heaviest elements like iron and zinc settling at their core.

Gravitational instability is a less common theory suggesting that gravity breaks the material around a star into massive clumps of gas and dust which eventually collapse to form planets. A recent image taken with a Spectro-Polarimetric High-contrast exoplanet REsearch (SPHERE) instrument by the European Southern Observatory through this project showed scientists images of material orbiting a star and extending in spiral arms over distances larger than our solar system.

These new images lend credibility to the gravitational instability theory as they have been able to identify forming clumps along these spiraling arms in sizes similar to large planets.

“We know that, in spiral galaxies, the spirals are the birthplace for stars,” says Zhu. “This observation reveals that a similar process may be occurring in circumstellar disks. The spirals in these much smaller disks could be the birthplace for planets.”