Oddball Star System Throws Planet Formation Theories Into Question

Star system GJ 3512, made up of a red dwarf star and a gas giant. (Guillem Anglada-Escude / IEEC / Science Wave / spaceengine.org)

(CN) – The origin story behind a massive, newly discovered exoplanet and the small red dwarf star it orbits is difficult to explain using the standard theories on how the cosmos was formed billions of years ago, astronomers said in a study released Thursday.

NASA has confirmed the discovery of nearly 4,000 exoplanets – also called “extrasolar” planets because they lie outside of our solar system – and trillions more are believed to be currently out of sight.

Astronomers have found exoplanets orbiting red dwarfs – relatively cool stars with low mass found in large numbers in the Milky Way – but this dynamic is rare.

Only about 10% of known exoplanets, including some close in size to Earth and Neptune, orbit these small stars, called M-dwarfs.

But the newly discovered gas giant, designated by scientists as GJ 3512b, is enormous – containing nearly half the mass of Jupiter, the largest planet in our solar system.

The exoplanet’s relationship to its small host star, which has a tenth of the mass of the sun, chips away at the foundation of “core accretion” planet formation theories, scientists said in a study published in Science.

Surveys of exoplanets have found that gas giants close in size to Jupiter are extremely scarce in red dwarf systems.

How gas giants are able to form in those systems remains a mystery, but scientists said in the study that “alternative disc instability theories” may play a larger role in planet formation than previously believed.

Yale University scientist Greg Laughlin said in a statement that “fresh” discoveries of exoplanets in the cosmos are not often seen as remarkable.

“But one that challenges current theories of planet forma­tion can animate astronomers,” Laughlin said.

Lead author Juan Carlos Morales of the Institute of Space Sciences and his team of researchers studied the red dwarf, designated as GJ 3512, by tracking its movements using optical and near-infrared radial velocity instruments.

Astronomers were astounded by the discovery of the gas giant around GJ 3512, which it orbits in 204 days.

Researchers believe the observed red dwarf system initially formed with three planets. At some point, one planet was ejected from the system, leaving GJ 3512b – with its elongated 7-month orbit – and another surviving planet.

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