"We have
convincing evidence that the census of the solar system is incomplete.”
A huge planet might be sitting at the edge of our solar
system without ever being seen.
The world — which could be about ten times as massive as
Earth — would be large enough to become the ninth planet of our solar system.
The planet has not yet been seen by scientists. Instead,
they have found it by watching the way that dwarf planets and other objects in
the outer solar system move — their orbits seem to be disturbed by something
huge but hidden sitting out there.
“If there’s going to be another planet in the solar
system, I think this is it,” Greg Laughlin of the University of California,
Santa Cruz told National Geographic. “It would be quite extraordinary if we had
one. Fingers crossed. It would be amazing.”
If the planet exists, it is thought to be about ten times
as massive or three times as large as Earth. That sort of sized planet occurs
throughout the universe — but has been an obvious omission from our own.
"This would be a real ninth planet," says
Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy.
"There have only been two true planets discovered since ancient times, and
this would be a third. It's a pretty substantial chunk of our solar system
that's still out there to be found, which is pretty exciting."
It would be around 200 to 300 times as far away from the
sun is when it gets closest to the star, scientists say. It will spend some of
its time as much as four times as far away as that, and an entire orbit of the
sun probably takes about 20,000 years.
The planet might have made its way out to the edge of the
universe when it was thrown out there by the gravity of Jupiter or Saturn, the
scientists suggest.
At such distances, the planet could be impossible to spot
— even with the two huge telescopes that are currently looking for it. So
little light is sent back from that far away, that it might never make it back
for us to see.
It is surrounded by much brighter lights — even the
distant Pluto could be about 10,000 times brighter — and so scientists have to
be sure that they point telescopes at exactly the right point and pick out an
already very unlikely speck of light.
That is why the scientists have spotted the potential
planet by seeing the disturbances that it is causing in the gravitational field
of the far star system. There appears to be a “great perturber” upsetting the
movement of other objects in that far away region, and the new paper — authored
by Michael Brown and Konstantin Batygin and published in the Astronomical
Journal — claims that is being caused by a mysterious, unknown world.
The solar system does not often change. The only recent
addition was Pluto, which was found in 1930 and spent most of the 21st century
as its most distant and smallest planet — until it was controversially
downgraded to being just a dwarf planet, and the solar system went back to
having eight members.
If the new planet is real, then it will definitely be a
planet, scientists say. Since it dominates a bigger region than any of the
other planets, it would "the most planet-y of the planets in the whole
solar system", Brown said.
The downgrading of Pluto was partly the result of work by
astronomer Michael Brown, who co-wrote the new paper. He had found that Pluto
was surrounded by a huge number of similarly sized planets, and the
International Astronomical Union decided that Pluto would be excluded from a
new definition.
The two astronomers found the new potential planet while
they were looking at those small rocks. They seemed to fly around on orbits
that could not be happening by chance, and instead were best explained by a big
ninth planet sitting out there with them.
A ninth planet has long been hypothesized — and become
the basis of some conspiracy theories — originally going under the name Planet
X. It was first talked about more than a century ago, and looking for that
planet was what brought astronomers to find Pluto.
The name of the planet will be crowd-sourced too, if the
researchers get their way — as opposed to being proposed by the discoverer and
then approved by the International Astronomical Union (IAU), which is the usual
way of doing things. Brown’s and Batygin’s personal name preference is
“George,” a hat-tip to British astronomer William Herschel, who discovered
Uranus and wanted to name it Georgium Sidus (the Georgian Planet) after King
George III. That might be a hard sell to the IAU—to say nothing of nearly all
other stargazers, who tend to like a little more lyricism in their cosmos. “We
actually call it Fatty when we’re just talking to each other,” Brown admitted.
Whatever the planet is eventually called, its very
existence will do more than simply add to the population of the solar system.
It will also add to its mystery. Even in our tiny corner of the universe, it
seems, there can still be big surprises lurking.
Brown acknowledged that the history of astronomy is
riddled with false hopes. Urbain Le Verrier, the French mathematician who
correctly predicted the existence of Neptune, in 1846, also predicted the
existence of a planet orbiting between the sun and Mercury. He called it
Vulcan, and it turned out not to exist. Every few years, someone announces the
discovery of Planet X, some large object that Galileo and four centuries of his
descendants missed, only to retract it. “If somebody proposed this—if I picked
up a newspaper and read a headline—my first reaction would be, Oh my God, these
guys are crazy,” Brown said of his and Batygin’s finding. “But if somebody then
looked at the evidence, they’d have a hard time disagreeing that the evidence
is there.”
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