GSFC: NASA Study Shows Disk Patterns Can Self-Generate

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GSFC: NASA Study Shows Disk Patterns Can Self-Generate

Postby bystander » Sat Jan 13, 2018 5:08 pm

No Planets Needed: NASA Study Shows Disk Patterns Can Self-Generate
NASA | GSFC | 2018 Jan 11

Click to play embedded YouTube video.
Debris Disk Simulations Generate Spirals, Rings, and Arcs
Credit: NASA/GSFC/Scott Wiessenger
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When scientists searching for exoplanets — worlds located beyond our solar system — first spotted patterns in disks of dust and gas around young stars, they thought newly formed planets might be the cause. But a recent NASA study cautions that there may be another explanation — one that doesn’t involve planets at all.

Exoplanet hunters watch stars for a few telltale signs that there might be planets in orbit, like changes in the color and brightness of the starlight. For young stars, which are often surrounded by disks of dust and gas, scientists look for patterns in the debris — such as rings, arcs and spirals — that might be caused by an orbiting world. ...

When high-energy UV starlight hits dust grains, it strips away electrons. Those electrons collide with and heat nearby gas. As the gas warms, its pressure increases and it traps more dust, which in turn heats more gas. The resulting cycle, called the photoelectric instability (PeI), can work in tandem with other forces to create some of the features astronomers have previously associated with planets in debris disks. ...

The interplay between radiation pressure and the photoelectric instability in optically
thin disks of gas and dust
- Alexander J.W. Richert, Wladimir Lyra, Marc Kuchner
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