This illustration shows the unusual orbit of planet
Kepler-413b around a close pair of orange and red dwarf stars. The planet's
66-day orbit is tilted 2.5 degrees with respect to the plane of the binary
star's orbit. The orbit of the planet wobbles around the central stars over 11
years, an effect called precession. This planet is also very unusual in that it
can potentially precess wildly on its spin axis, much like a child's
top.
Image Credit: NASA, ESA, and A. Feild (STScI)
Imagine living on a planet with seasons so erratic you would hardly know
whether to wear Bermuda shorts or a heavy overcoat. That is the situation on a
weird, wobbly world found by NASA's planet-hunting Kepler space telescope.
The planet, designated Kepler-413b, precesses, or wobbles, wildly on its spin
axis, much like a child's top. The tilt of the planet's spin axis can vary by as
much as 30 degrees over 11 years, leading to rapid and erratic changes in
seasons. In contrast, Earth's rotational precession is 23.5 degrees over 26,000
years. Researchers are amazed that this far-off planet is precessing on a human
timescale.
Kepler 413-b is located 2,300 light-years away in the constellation Cygnus.
It circles a close pair of orange and red dwarf stars every 66 days. The
planet's orbit around the binary stars appears to wobble, too, because the plane
of its orbit is tilted 2.5 degrees with respect to the plane of the star pair's
orbit. As seen from Earth, the wobbling orbit moves up and down
continuously.
Kepler finds planets by noticing the dimming of a star or stars when a planet
transits, or travels in front of them. Normally, planets transit like clockwork.
Astronomers using Kepler discovered the wobbling when they found an unusual
pattern of transiting for Kepler-413b.
"Looking at the Kepler data over the course of 1,500 days, we saw three
transits in the first 180 days -- one transit every 66 days -- then we had 800
days with no transits at all. After that, we saw five more transits in a row,"
said Veselin Kostov, the principal investigator on the observation. Kostov is
affiliated with the Space Telescope Science Institute and Johns Hopkins
University in Baltimore, Md. The next transit visible from Earth's point of view
is not predicted to occur until 2020. This is because the orbit moves up and
down, a result of the wobbling, in such a great degree that it sometimes does
not transit the stars as viewed from Earth.
Astronomers are still trying to explain why this planet is out of alignment
with its stars. There could be other planetary bodies in the system that tilted
the orbit. Or, it could be that a third star nearby that is a visual companion
may actually be gravitationally bound to the system and exerting an
influence.
"Presumably there are planets out there like this one that we're not seeing
because we're in the unfavorable period," said Peter McCullough, a team member
with the Space Telescope Science Institute and Johns Hopkins University. "And
that's one of the things that Veselin is researching: Is there a silent majority
of things that we're not seeing?"
Even with its changing seasons, Kepler-413b is too warm for life as we know
it. Because it orbits so close to the stars, its temperatures are too high for
liquid water to exist, making it inhabitable. It also is a super Neptune -- a
giant gas planet with a mass about 65 times that of Earth -- so there is no
surface on which to stand.
NASA's Ames Research Center at Moffett Field, Calif., is responsible for the
Kepler mission concept, ground system development, mission operations and
science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif.,
managed Kepler mission development. Ball Aerospace & Technologies Corp. in
Boulder, Colo., developed the Kepler flight system and supports mission
operations with the Laboratory for Atmospheric and Space Physics at the
University of Colorado in Boulder. The Space Telescope Science Institute in
Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's
10th Discovery mission and was funded by the agency's Science Mission
Directorate.
For images and more information about Kepler-413b, visit:
For more information about the Kepler space telescope, visit:
NASA
Guillermo Gonzalo Sánchez Achutegui
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