Astrophysicists find Jupiter likely bumped giant planet from solar system

This is Jupiter's Great Red Spot in 2000 as seen by NASA's Cassini orbiter. Credit: NASA/JPL/Space Science Institute

It's like something out of an interplanetary chess game. Astrophysicists at the University of Toronto have found that a close encounter with Jupiter about four billion years ago may have resulted in another planet's ejection from the Solar System altogether.

The existence of a fifth giant gas planet at the time of the Solar System's formation - in addition to Jupiter, Saturn, Uranus and Neptune that we know of today - was first proposed in 2011. But if it did exist, how did it get pushed out?

For years, scientists have suspected the ouster was either Saturn or Jupiter.

"Our evidence points to Jupiter," said Ryan Cloutier, a PhD candidate in U of T's Department of Astronomy & Astrophysics and lead author of a new study published in The Astrophysical Journal.

Planet ejections occur as a result of a close planetary encounter in which one of the objects accelerates so much that it breaks free from the massive gravitational pull of the Sun. However, earlier studies which proposed that giant planets could possibly eject one another did not consider the effect such violent encounters would have on minor bodies, such as the known moons of the giant , and their orbits.

So Cloutier and his colleagues turned their attention to moons and orbits, developing computer simulations based on the modern-day trajectories of Callisto and lapetus, the regular moons orbiting around Jupiter and Saturn respectively. They then measured the likelihood of each one producing its current orbit in the event that its host planet was responsible for ejecting the hypothetical planet, an incident which would have caused significant disturbance to each moon's original orbit.

"Ultimately, we found that Jupiter is capable of ejecting the fifth giant planet while retaining a moon with the orbit of Callisto," said Cloutier, who is also a graduate fellow at the Centre for Planetary Sciences at the University of Toronto at Scarborough. "On the other hand, it would have been very difficult for Saturn to do so because Iapetus would have been excessively unsettled, resulting in an orbit that is difficult to reconcile with its current trajectory."

The findings are reported in a paper titled "Could Jupiter or Saturn have ejected a fifth giant planet?" published in the November 1 issue of The Astrophysical Journal.

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Journal information: Astrophysical Journal

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Oct 29, 2015
Imagine if it were not expelled all the way but was on a very long 26 million year orbit. It be the cause for mass extinctions: http://astronomyn...nctions/

Oct 29, 2015
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Oct 29, 2015
Please don't go there. Look at the thread on that article: There isn't any periodicity in mass extinctions, and the statistics of comets impacting Earth is marginal re any putative periodicity. There isn't any useful hypothesis to fish out there despite 30 years of (mostly bad) research.

Re the ejected 5th gas giant, it was leaving the system - that is what ejection means.

Oct 29, 2015
I'm assuming that after four billion years of travel there's no hope of spotting the planet even if we could calculate exactly where to look?

Nov 02, 2015
Qitana, the early solar system was a brutal swirl of material forming lumps, colliding, interacting, accreting etc etc. There were some big winners, but a lot of small stuff was ejected to the Kuiper Belt and Oort Cloud. The degree of gravitational tugging and resonances available suggested even something Neptune size *could* be kicked about by Jupiter & Co.

IIRC, there's an odd, soft-edged gap within asteroid belt that is considered proof that Jupiter did migrate some-what. And the orbits of Uranus & Neptune don't fit with their composition, suggesting they've had a grav-assist from Jupiter & Saturn.

Nice to see the gas giants' moons' dynamics do set a limit on how much Jupiter could 'throw its weight about' due action & reaction etc etc.

Check out 'Late Heavy Bombardment', then look at our Moon to see how nasty things got in the *inner* solar system...

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