For a planet, this would be like a day at the spa. After years of growing old, a massive planet could, in theory, brighten up with a radiant, youthful glow. Rejuvenated planets, as they are nicknamed, are only hypothetical. But new research from NASA's Spitzer Space Telescope has identified one such candidate, seemingly looking billions of years younger than its actual age.
"When planets are young, they still glow with infrared light from
their formation," said Michael Jura of UCLA, coauthor of a new paper on
the results in the June 10 issue of the Astrophysical Journal Letters.
"But as they get older and cooler, you can't see them anymore.
Rejuvenated planets would be visible again."
How might a planet reclaim the essence of its youth? Years ago,
astronomers predicted that some massive, Jupiter-like planets might
accumulate mass from their dying stars. As stars like our sun age, they
puff up into red giants and then gradually lose about half or more of
their mass, shrinking into skeletons of stars, called white dwarfs. The
dying stars blow winds of material outward that could fall onto giant
planets that might be orbiting in the outer reaches of the star system.
Thus, a giant planet might swell in mass, and heat up due to friction
felt by the falling material. This older planet, having cooled off over
billions of years, would once again radiate a warm, infrared glow.
The new study describes a dead star, or white dwarf, called PG
0010+280. An undergraduate student on the project, Blake Pantoja, then
at UCLA, serendipitously discovered unexpected infrared light around
this star while searching through data from NASA's Wide-field Infrared
Survey Explorer, or WISE. Follow-up research led them to Spitzer
observations of the star, taken back in 2006, which also showed the
excess of infrared light.
At first, the team thought the extra infrared light was probably
coming from a disk of material around the white dwarf. In the last
decade or so, more and more disks around these dead stars have been
discovered -- around 40 so far. The disks are thought to have formed
when asteroids wandered too close to the white dwarfs, becoming chewed
up by the white dwarfs' intense, shearing gravitational forces.
Other evidence for white dwarfs shredding asteroids comes from
observations of the elements in white dwarfs. White dwarfs should
contain only hydrogen and helium in their atmospheres, but researchers
have found signs of heavier elements -- such as oxygen, magnesium,
silicon and iron -- in about 100 systems to date. The elements are
thought to be leftover bits of crushed asteroids, polluting the white
dwarf atmospheres.
But the Spitzer data for the white dwarf PG 0010+280 did not fit well
with models for asteroid disks, leading the team to look at other
possibilities. Perhaps the infrared light is coming from a companion
small "failed" star, called a brown dwarf -- or more intriguingly, from a
rejuvenated planet.
"I find the most exciting part of this research is that this infrared
excess could potentially come from a giant planet, though we need more
work to prove it," said Siyi Xu of UCLA and the European Southern
Observatory in Germany. "If confirmed, it would directly tell us that
some planets can survive the red giant stage of stars and be present
around white dwarfs."
In the future, NASA's upcoming James Webb Space Telescope could
possibly help distinguish between a glowing disk or a planet around the
dead star, solving the mystery. But for now, the search for rejuvenated
planets -- much like humanity's own quest for a fountain of youth --
endures.
JPL manages the Spitzer Space Telescope mission for NASA's Science
Mission Directorate, Washington. Science operations are conducted at the
Spitzer Science Center at the California Institute of Technology in
Pasadena. Spacecraft operations are based at Lockheed Martin Space
Systems Company, Littleton, Colorado. Data are archived at the Infrared
Science Archive housed at the Infrared Processing and Analysis Center at
Caltech. Caltech manages JPL for NASA.
For more information on Spitzer, visit: http://spitzer.caltech.edu - http://www.nasa.gov/spitzer
Media Contact
Whitney Clavin
Jet Propulsion Laboratory, Pasadena, California
818-354-4673
Email: whitney.clavin@jpl.nasa.gov
Source: JPL-Caltech/News
