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Planets,Astronomy
Beyond Pluto: A new 9th planet?
It would just be way bigger, way further out and still waiting to be seen
By Christopher Crockett 2:17pm, January 21, 2016
A mystery planet may orbit the sun from the far reaches of the Kuiper Belt.
View the video
An unseen planet may be hiding in the outskirts of our solar system. Planetary scientists have
just projected its existence based on oddities in the orbits of some far-flung icy bodies. Those
tiny objects reside in the distant Kuiper (KY-pur) belt — a vast expanse of space beyond the
orbit of Neptune.
Konstantin Batygin and Michael Brown work at Caltech in Pasadena, Calif. Their new
calculations suggest this new mystery world would be roughly 10 times as massive as Earth.
And if it exists, it must travel a highly elongated orbit.
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Astronomers refer to Earth’s average distance from the sun as one “astronomical unit,” or
AU. The scientists are not sure how far away this new ninth planet would be. But their
calculations indicate it should be somewhere between 400 to 1,500 AU. For those keeping
score, that’s about 60 trillion to 220 trillion kilometers (37.3 trillion to 136.7 trillion miles) from
the sun.
Batygin and Brown described how they
came to that assessment in a paper
published early online, January 20,
in Astronomical Journal.
PLANET x Planetary scientists Konstantin Batygin
and Michael Brown discuss the latest evidence of
a hidden ninth planet orbiting along the outskirts
of our solar system.
They are not the first to suspect there
might be a true ninth planet. In March
CALTECH AMT
2014, two other researchers noticed that
a dozen objects, all far beyond Neptune, crossed the plane of the solar system at roughly the
same point in their orbits. It was as they were making their closest approach to the sun.
That plane is an imaginary surface going through the sun and the orbits of the major planets.
Over billions of years, interactions with the known giant planets — Jupiter, Saturn and Uranus
— should have randomized where in those orbits the rocky objects crossed that plane. The
probability of them all crossing the plane at this same point in their orbits by chance is just
0.007 percent, the Caltech team now reports.
But, they add, a planet patrolling the borderlands of the solar system could shepherd all of
those rocky bodies to cross the plane at the same point in their orbits. Indeed, that’s a major
argument that Batygin and Brown now offer for the existence of a giant mystery planet.
The new Caltech study seems to “make this super-Earth sized planet a much more real
possibility,” says Scott Sheppard. He’s a planetary scientist at the Carnegie Institution for
Science in Washington, D.C. He also co-authored the 2014 paper that had suggested a ninth
planet might exist.
Such a remote super-Earth probably started out much closer to the sun. It likely got kicked out
by the other giant planets during the solar system’s formative years, Batygin and Brown now
suspect.
Ironically, it was Brown’s 2005 discovery of larger-than-Pluto objects in the Kuiper belt that
kicked off the discussions about whether Pluto was actually a planet. In the end, Pluto was
demoted. It is now considered a somewhat different object: a “dwarf planet.”
Brown noted that his daughter was very young when Pluto got demoted and blamed her dad.
“[S]he suggested a few years ago that she'd forgive me if I found a new planet,” he told
the Washington Post. "So I guess I've been working on this for her.”
Power Words
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(for more about Power Words, click here)
astronomical unit A unit of distance in space that is roughly equal to the average distance
of Earth from the sun.
Kuiper belt An area of the solar system beyond the orbit of Neptune. It is a vast area
containing leftovers from the formation of the solar system that continue to orbit the sun. Many
objects in the Kuiper belt are made of ice, rock, frozen methane and ammonia.
orbit The curved path of a celestial object or spacecraft around a star, planet or moon. One
complete circuit around a celestial body.
orbital eccentricity The degree to which a planet’s orbit deviates from a perfect circle.
plane (in geometry and space) A flat surface (like a sheet or piece of paper) that extends in
all directions, infinitely, without end. It has no height (or depth), much the way a line also has
just two dimensions.
planet A celestial object that orbits a star, is big enough for gravity to have squashed it into a
roundish ball and it must have cleared other objects out of the way in its orbital
neighborhood. To accomplish the third feat, it must be big enough to pull neighboring objects
into the planet itself or to sling-shot them around the planet and off into outer space.
Astronomers of the International Astronomical Union (IAU) created this three-part scientific
definition of a planet in August 2006 to determine Pluto’s status. Based on that definition, IAU
ruled that Pluto did not qualify. The solar system now includes eight planets: Mercury, Venus,
Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Pluto A dwarf planet that is located in the Kuiper Belt, just beyond Neptune. Pluto is the
tenth largest object orbiting the sun.
solar system The eight major planets and their moons in orbit around the sun, together with
smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets
Further Reading
R. Feltman. “Q&A: The ‘Pluto Killer’ who thinks he’s found the true ninth planet.” Washington
Post. January 20, 2016.
C. Crockett. “Pluto hosts ice mountains, data suggest.” Science News for Students. July 16,
2015.
C. Crockett. “Picture this: Pluto hearts us.” Science News for Students. July 16, 2015.
C. Crockett. “Visiting Pluto.” Science News for Students. July 10, 2015.
C. Crockett. “Students sent instrument to Pluto.” Science News for Students. July 30, 2015.
A. Yeager. “Dwarf planet has water.” Science News for Students. January 30, 2014.
B. Brookshire. “Sizing up the Kuiper belt.” Eureka! Lab blog. January 21, 2014.
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Beyond Pluto: A new 9th planet? | Science News f...
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J. Cutraro. “The trouble with Pluto.” Science News for Students. October 8, 2008.
J. Cutraro. “Explainer: What is a planet?” Science News for Students. October 8, 2008.
E. Sohn. “Strange Neptune.” Science News for Students. January 9, 2007.
C. Gramling. “Dwarf planet discord.” Science News for Students. October 6, 2006.
ORIGINAL JOURNAL SOURCE: K. Batygin and M.E. Brown. Evidence for a distant giant
planet in the solar system. The Astronomical Journal. Vol. 151, February 2016, p. 22.
doi:10.3847/0004-6256/151/2/22.
ORIGINAL JOURNAL SOURCE: C.A. Trujillo and S.S. Sheppard. A Sedna-like body with a
perihelion of 80 astronomical units. Nature. Vol. 507, March 27, 2014, p. 471. doi:
10.1038/nature13156.
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