Stories
Slash Boxes
Comments

SoylentNews is people

posted by martyb on Monday April 16 2018, @04:44PM   Printer-friendly
from the our-biggest-rockets-can't-move-the-earth...-and-here-planets-get...-ejected?!! dept.

Circumbinary castaways: Short-period binary systems can eject orbiting worlds

When eclipsing binaries orbit each other closely, within about 10 days or less, Fleming and co-authors wondered, do tides — the gravitational forces each exerts on the other — have "dynamical consequences" to the star system?

"That's actually what we found" using computer simulations, Fleming said. "Tidal forces transport angular momentum [3m18s video] from the stellar rotations to the orbits. They slow down the stellar rotations, expanding the orbital period."

[...] The expanding stellar orbit "engulfs planets that were originally safe, and then they are no longer safe — and they get thrown out of the system," said Rory Barnes, UW assistant professor of astronomy and a co-author on the paper. And the ejection of one planet in this way can perturb the orbits of other orbiting worlds in a sort of cascading effect, ultimately sending them out of the system as well.

Making things even more difficult for circumbinary planets is what astronomers call a "region of instability" created by the competing gravitational pulls of the two stars.

"There's a region that you just can't cross — if you go in there, you get ejected from the system," Fleming said. "We've confirmed this in simulations, and many others have studied the region as well."

This is called the "dynamical stability limit." It moves outward as the stellar orbit increases, enveloping planets and making their orbits unstable, and ultimately tossing them from the system.

On The Lack of Circumbinary Planets Orbiting Isolated Binary Stars (arXiv:1804.03676)


Original Submission

 
This discussion has been archived. No new comments can be posted.
Display Options Threshold/Breakthrough Mark All as Read Mark All as Unread
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
  • (Score: 2) by JoeMerchant on Monday April 16 2018, @08:24PM

    by JoeMerchant (3937) on Monday April 16 2018, @08:24PM (#667785)

    I think these guys mostly herd undergrads for a living, but also publish simulations and other stuff as PR work for their institution.

    It's a very cliquish club, I lived in a University town for quite a while and considered getting a job with the big brick monument, but without a PhD they'll barely let you mop the floors, and even with a PhD you've got to suck up to the existing old guard to their satisfaction long enough for them to die off before any hope of advancement to a spot where you might get to call some shots on the sucking up yourself.

    My father played the "bounce from institution to institution" advancement game for about 20 years across 6 states until he turned about 64. He's settled down now at the last place for almost 10 years now - tried advancing to department chair when the opportunity came around, but decided that mid-level politics wasn't worth the potential payoff to higher level politics. Now he just hangs around doing whatever he feels like, daring them to fire him because he's ready to go anyway.

    --
    🌻🌻 [google.com]
    Starting Score:    1  point
    Karma-Bonus Modifier   +1  

    Total Score:   2