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posted by janrinok on Wednesday October 02 2019, @09:37PM   Printer-friendly
from the where-did-you-come-from? dept.

Arthur T Knackerbracket has found the following story:

A gas giant orbiting a tiny red dwarf star thirty light years away has left astronomers baffled because it's not supposed to exist, according to a study published in Science on Thursday.

Under the standard model of planet formation, the object known as GJ 3512 b should have never been born as it’s considered almost impossible for low-mass stars like GJ 3512 to harbour massive gas planets. The protoplanetary disk, a rotating jumble of gas and dust around a young star, simply doesn’t contain enough matter to form hefty gaseous planets when the star is small.

Current theories suggest that planets are grown from smaller bits of debris known as planetesimals glomming together in protoplanetary disks. In order to create a gas giant, a sufficient amount of these planetesimals have to stick together to form a solid core. The rocky centre accumulates gas from the surrounding disk by its gravitational pull, Markus Nielbock, a spokesperson at the Max Planck Institute of Astronomy, who was not explicitly involved in the research, explained to The Register.

“If the disk isn't heavy enough, however, there is not sufficient solid material around that can form those planetesimals quickly enough before they migrate through the disk into the inner regions and eventually fall into the star.”

So how did all that material go into forming gas giants like GJ 3512 b? The global team of researchers believe that the protoplanetary disk must have directly collapsed under its own gravity instead.

In this scenario, GJ 3512 b sprung from material gathered near the outer regions of the disk - beyond 10 astronomical units, or ten times the distance between the Sun and Earth. The temperatures here are very cold, about 10 kelvin (-263 °C), and the outward thermal pressure of the disk cannot counteract the inward gravitational compression. The disk, therefore, collapses under its own weight.

The surrounding material forms a solid core massive enough to accrue gas in the disk so that a planet like GJ 3512 b is possible. These types of disks are described as gravitationally unstable disks. But even this idea doesn’t completely explain the strange system.

[...] There is evidence, however, that the system once contained a third planet alongside the GJ 3512 b and the second planet GJ 3512 c, speculated by the researchers. A series of gravitational instabilities led to the ejection of the third planet and brought GJ 3512 b’s orbit closer to it star and more eccentric. It currently completes an orbit in 204 days.

The exoplanet isn’t really that remarkable on its own. But when the researchers consider it alongside its star, they’re flummoxed.

Related: When Dwarfs Give Birth To Giants

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  • (Score: 1, Informative) by Anonymous Coward on Thursday October 03 2019, @02:06AM (1 child)

    by Anonymous Coward on Thursday October 03 2019, @02:06AM (#902131)

    Will be fixed in the next release of Universe (tm)

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  • (Score: 3, Funny) by KritonK on Thursday October 03 2019, @08:39AM

    by KritonK (465) on Thursday October 03 2019, @08:39AM (#902202)

    We apologize for the inconvenience.
            —God's Final Message to His Creation.