Cosmology; magnetic fields may pay a role in planets birth (Introduction)

by David Turell , Friday, July 23, 2021, 00:00 (1220 days ago) @ David Turell

A new study offers support:

http://abstractions.nautil.us/article/702/astronomers-find-secret-planet-making-ingredi...

"For some time now, scientists have suspected that magnetism may also play a role. What, specifically, magnetic fields do has remained unclear, partly because of the difficulty in including magnetic fields alongside gravity in the computer models used to investigate planet formation. In astronomy, said Meredith MacGregor, an astronomer at the University of Colorado, Boulder, there’s a common refrain: “We don’t bring up magnetic fields, because they’re difficult.”

"And yet magnetic fields are commonplace around planetesimals and protoplanets, coming either from the star itself or from the movement of starlight-washed gas and dust. In general terms, astronomers know that magnetic fields may be able to protect nascent planets from a star’s wind, or perhaps stir up the disk and move planet-making material about. “We’ve known for a long time that magnetic fields can be used as a shield and be used to disrupt things,” said Zoë Leinhardt, a planetary scientist at the University of Bristol who was not involved with the work. But details have been lacking, and the physics of magnetic fields at this scale are poorly understood.

“'It’s hard enough to model the gravity of these disks in high enough resolution and to understand what’s going on,” said Ravit Helled, a planetary scientist at the University of Zurich. Adding magnetic fields is a significantly larger challenge.

"In the new work, Helled, used the fastest [computer] in Europe, to run extremely high-resolution simulations that incorporated magnetic fields alongside gravity.

"Magnetism seems to have three key effects. First, magnetic fields shield certain clumps of gas—those that may grow up to be smaller planets—from the destructive influence of stellar radiation. In addition, those magnetic cocoons also slow down the growth of what would have become supermassive planets. The magnetic pressure pushing out into space “stops the infalling of new matter,” said Mayer, “maybe not completely, but it reduces it a lot.”

"The third apparent effect is both destructive and creative. Magnetic fields can stir gas up. In some cases, this influence disintegrates protoplanetary clumps. In others, it pushes gas closer together, which encourages clumping.

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"At this stage, we can’t be totally sure what is happening with magnetic fields on a protoplanetary scale. “This is more a proof of concept, that they can do this, they can marry the gravity and the magnetic fields to do something very interesting that I haven’t seen before.'”

Comment: the activities in the universe are so complex, we still have much to discover.