Planet Nine is a
hypothetical planet in the outer region of the Solar System. Its gravitational
effects could explain the unusual clustering of orbits for a group of extreme
trans-Neptunian objects (ETNOs), bodies beyond Neptune that orbit the Sun at
distances averaging more than 250 times that of the Earth. These eTNOs tend to
make their closest approaches to the Sun in one sector, and their orbits are
similarly tilted. These alignments suggest that an undiscovered planet may be
shepherding the orbits of the most distant known Solar System objects.
Nonetheless, some astronomers question the idea that the hypothetical planet
exists and instead assert that the clustering of the eTNOs orbits is due to
observing biases, resulting from the difficulty of discovering and tracking
these objects during much of the year.
In Depth
In January 2015, Caltech astronomers "Konstantin
Batygin" and "Mike Brown" announced new research that provides
evidence of a giant planet tracing an unusual, elongated orbit in the outer solar
system. The prediction is based on detailed mathematical modeling and computer
simulations, not direct observation.
This large object could explain the unique orbits of at least five
smaller objects discovered in the distant Kuiper Belt.
"The possibility of a new planet is certainly an exciting one
for me as a planetary scientist and for all of us," said Jim Green,
director of NASA's Planetary Science Division. "This is not, however, the
detection or discovery of a new planet. It's too early to say with certainty
there's a so-called Planet X. What we're seeing is an early prediction based on
modeling from limited observations. It's the start of a process that could lead
to an exciting result."
The Caltech scientists believe Planet X may have has a mass about
10 times that of Earth and be similar in size to Uranus or Neptune. The
predicted orbit is about 20 times farther from our Sun on average than Neptune
(which orbits the Sun at an average distance of 2.8 billion miles). It would
take this new planet between 10,000 and 20,000 years to make just one full
orbit around the Sun (where Neptune completes an orbit roughly every 165
years).
Artist's concept of a hypothetical planet orbiting far from the Sun. Credit: Caltech/R. Hurt (IPAC)
Overview
Caltech
researchers have found mathematical evidence suggesting there may be a
"Planet X" deep in the solar system. This hypothetical Neptune-sized
planet orbits our Sun in a highly elongated orbit far beyond Pluto. The object,
which the researchers have nicknamed "Planet Nine," could have a mass
about 10 times that of Earth and orbit about 20 times farther from the Sun on
average than Neptune. It may take between 10,000 and 20,000 Earth years to make
one full orbit around the Sun.
In January 2015, Caltech astronomers
Konstantin Batygin and Mike Brown announced new research that provides evidence
of a giant planet tracing an unusual, elongated orbit in the outer solar
system. The prediction is based on detailed mathematical modeling and computer
simulations, not direct observation. The announcement does not mean there is a
new planet in our solar system. The existence of this distant world is only
theoretical at this point and no direct observation of the object nicknamed
"Planet 9" has been made. The mathematical prediction of a planet
could explain the unique orbits of some smaller objects in the Kuiper Belt, a
distant region of icy debris that extends far beyond the orbit of Neptune.
Astronomers are now searching for the predicted planet.
In Depth
This large object could explain the unique orbits of at least
five smaller objects discovered in the distant Kuiper Belt.
"The possibility of a new planet is certainly an exciting
one for me as a planetary scientist and for all of us," said Jim Green,
director of NASA's Planetary Science Division. "This is not, however, the
detection or discovery of a new planet. It's too early to say with certainty
there's a so-called Planet X. What we're seeing is an early prediction based on
modeling from limited observations. It's the start of a process that could lead
to an exciting result."
The Caltech scientists believe Planet X may have has a mass
about 10 times that of Earth and be similar in size to Uranus or Neptune. The
predicted orbit is about 20 times farther from our Sun on average than Neptune
(which orbits the Sun at an average distance of 2.8 billion miles). It would
take this new planet between 10,000 and 20,000 years to make just one full
orbit around the Sun (where Neptune completes an orbit roughly every 165 years).
When
was it discovered?
Planet X has not yet been
discovered, and there is debate in the scientific community about whether it
exists. The prediction in the Jan. 20 issue of the Astronomical Journal is
based on mathematical modeling.
What is its Name?
Batygin and Brown nicknamed their predicted object "Planet
Nine," but the actual naming rights of an object go to the person who
actually discovers it. The name used during previous hunts for the long
suspected giant, undiscovered object beyond Neptune is "Planet X."
If the predicted world is found, the name must be
approved by the International Astronomical Union. Planets are traditionally
named for mythological Roman gods.
Sources
Fesenmaier, Kimm, "Caltech Researchers Find Evidence of a Real Ninth Planet,"
press release, last modified January 20, 2015
Konstantin Batygin and Michael E. Brown, "Evidence for a Distant Giant Planet in the Solar System,"
The Astronomical Journal
Green, James, "A New Planet in our Solar System? NASA Takes a Look,"
video statement, last modified January 20, 2015
