An enormous alien planet
— one that is 11 times more massive than Jupiter — was discovered in the most
distant orbit yet found around a single parent star.
The existence of such a massive and distantly orbiting planet
raises new questions about how these bizarre worlds are formed, the researchers
said.
"This system is especially fascinating because no model of
either planet or star formation fully explains what we see," study lead
researcher Vanessa Bailey, a fifth-year graduate student in the University of
Arizona's department of astronomy, said in a statement.
In the most commonly accepted theories of planet
formation, it is thought that planets that orbit close to their parent star,
such as Earth, began as small, asteroid-type bodies that clumped together in
the primordial disk of gas and dust around the burgeoning star. Yet, this
process operates too slowly to explain how gaient planets form far awayfrom their stars.
Bailey said.
"A Binary star system can be formed when two adjacent clumps of gas collapse more or
less independently to form stars, and these stars are close enough to each
other to exert a mutual gravitation attraction and bind them together in an
orbit," she explained.
The star and planet may have collapsed independently,
but the materials that clumped together to form the planet were insufficient
for it to grow large enough to ignite into a new star.
But, there are still problems with this scenario. For one,
difference between the masses of two stars in a binary system is typically no
more than a ratio of 10 to 1.
"In our case, the mass ratio is more than 100-to-1,"
"This extreme mass ratio is not predicted from binary star
formation theories — just like planet formation theory predicts that we cannot
form planets so far from the host star."
Researchers are also keen to study the new planet, because
leftover material from when the planet and star formed can still be detected.
"Systems like this one, where we have additional
information about the environment in which the planet resides, have the
potential to help us disentangle the various formation models," Bailey
said. "Future observations of the planet's orbital motion and the primary
star's debris -disk may help answer that question."
The planet HD 106906 b is only 13 million years old, and is
still glowing from the residual heat from its formation," the researchers
said. By comparison, Earth formed 4.5 billion years ago, which makes it roughly
350 times older than the newfound exoplanet.
The planet was found using a thermal infrared camera mounted on
the Magellan telescope in the Atacama Desert in Chile. The researchers used
data from the hubble space pe to confirm their discovery.
The study, which has been accepted for publication in a future
issue of The Astrophysical Journal Letters, could lead to a better
understanding of distantly orbiting exoplanets.
"Every new directly detected planet pushes our
understanding of how and where planets can form,"
study co-investigator
Tiffany Meshkat, a graduate student at Leiden Observatory in the Netherlands,
said in a statement.
"Discoveries like HD 106906 b provide us with a
deeper understanding of the diversity of other planetary systems."
