'The nearest known planetary system to Earth sports two asteroid
belts, a new study suggests. The relatively young system could offer
clues about how solar systems form and might be the ideal place to
look for the faint glint of an Earth-like planet.
The belts were found in orbit around the nearby star Epsilon Eridani,
which sits just 10.5 light years from Earth. The star boasts a planet
that orbits once every 7 years and weighs about 60% the mass of
Jupiter. Astronomers have also previously detected a far-out ring of
icy material around the star, similar to our own Kuiper belt.
Now, two rocky asteroid belts have been found much closer to the star,
a new study suggests. Dana Backman of the SETI Institute in Mountain
View, California, and colleagues caught the warmer glow of the two
belts using NASA's Spitzer Space Telescope, which images objects at
infrared wavelengths.
Epsilon Eridani's inner belt is similar to the solar system's own
asteroid belt, which sits between Mars and Jupiter.
The ring of debris sits 3 astronomical units (where 1 AU is the Earth-
Sun distance) away from the star, and seems to be composed of silicon-
based minerals. The star's one known planet may orbit just beyond this
ring.
A second belt, which sits 20 AU from the star, holds 20 times more
material, weighing in at roughly the same mass as the Moon.
Pale blue dot
The previously known icy ring sits between 35 and 90 AU from Epsilon
Eridani. This cometary belt is roughly 100 times more massive than the
Kuiper belt that lies beyond Neptune's orbit in our own solar system.
Two other planets, between the size of Neptune and Jupiter, might also
orbit Epsilon Eridani beyond its outer asteroid belt. One might have
helped carve the outside edge of the outer asteroid belt, and the
other might orbit just inside the star's icy 'Kuiper' belt.
Smaller planets could also be lurking inside Epsilon Eridani's inner
asteroid belt. "I would put money on there being an Earth-like planet
in the space between the inner asteroid belt and the star," Backman
told New Scientist.
The star is close enough that an Earth-like planet might be directly
imaged with future telescopes, such as the Terrestrial Planet Finder
Interferometer, a proposed orbiting array of telescopes currently
being considered by NASA. The system might "be the first one where you
could point to a pale blue dot and say, 'There's the Earth,'" Backman
told New Scientist.
Epsilon Eridani is only 850 million years old, about 20% the age of
the Sun. As a result, it sheds light on what the solar system might
once have looked like, before most of its debris was swallowed by the
Sun or cast far away, says team member Massimo Marengo of the Harvard-
Smithsonian Center for Astrophysics in Cambridge, Massachusetts. Those
insights could help refine models of how solar systems form, he added.'
Taken from New Scientist at http://space.newscientist.com/article/dn15050-nearest-planetary-system-boasts-two-asteroid-belts.html?DCMP=ILC-hmts&nsref=news1_head_dn15050
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