[ExI] Jupiter Brains

[Emlyn]

A solution to Fermi's Paradox?

http://seattletimes.nwsource.com/html/businesstechnology/2015084720_apussciwanderingplanets.html

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'Exciting' find: Possible planets without orbits

Are these planets without orbits? Astronomers have found 10 potential
planets as massive as Jupiter wandering through a slice of the Milky
Way galaxy, following either very wide orbits or no orbit at all. And
scientists think they are more common than the stars.

These mysterious bodies, apparently gaseous balls like the largest
planets in our solar system, may help scientists understand how
planets form.

"They're finding evidence for a lot of pretty big planets," said Alan
Boss of the Carnegie Institution of Washington, who wasn't involved in
the research.

If they orbit stars, their sheer number suggests every star in the
galaxy has one or two of them, "which is astounding" because that's
five or 10 times the number of stars scientists had thought harbored
such gas-giant planets, he said.

And if instead they are wandering free, that "would be really
stunning" because it's hard to explain how they formed, he said.

If that's the case, it would give a boost to some theories that say
planets can be thrown out of orbit during formation, said Lisa
Kaltenegger of the Harvard-Smithsonian Center for Astrophysics,
another outside expert.

Other scientists have reported free-wandering objects in star-forming
regions of the cosmos, but the newfound objects appear to be
different, said one author of the new study, physicist David Bennett
of the University of Notre Dame.

Bennett and colleagues from Japan, New Zealand and elsewhere report
the finding in Thursday's issue of the journal Nature. They didn't
observe the objects directly. Instead, they used the fact that massive
objects bend the light of distant stars with their gravity, just as a
lens does. So they looked extensively for such "microlensing" events.

They found 10, each caused by one of the newfound objects. They
calculated each object has about the mass of Jupiter, and estimated
how common such objects are. They also found no sign of a star near
these bodies, at least not within 10 times the distance from Earth to
the sun. (For comparison, within our solar system that would basically
rule out an orbit closer than Saturn's.)

So the newfound objects either orbit a star more distant than that, or
they don't orbit a star at all, the researchers concluded. They drew
on other data to determine most of the objects don't orbit a star.

Scientists believe planets are formed when disks of dust that orbit
stars form clumps, so that these clumps - the planets - remain in
orbit. Maybe the newfound objects started out that way, but then got
tossed out of orbit or into distant orbits by the gravitational tugs
of larger planets, the researchers suggest.

The work suggests that such a tossing-out process is quite common, Bennett said.

Boss said maybe the bodies formed around a pair of stars instead, one
of which supplied the gravitational tug. But even that would take some
explaining to produce an object without an orbit, he said. Or maybe
they somehow formed outside of any orbit. So the theoretical challenge
in explaining the existence of such bodies is "exciting," he said.

Boss said he suspects most of these are in a distant orbit, and that
maybe they even formed at that great distance rather than being tossed
outward from a closer orbit.

Kaltenegger also said the new results can't rule out the possibility
that these possible planets are in orbit, and that they may only have
the mass of Saturn, about a third of Jupiter's.

But if they aren't orbiting a star, she noted, they don't fit the
official definition of a planet - at least not the definition applied
to objects in our own solar system.

All in all, Boss said, the new work is "pretty exciting in telling
what is out there in the night sky... Lots of theories will grow in
this environment."

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Emlyn

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