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New planet identified in Solar System
July 29, 2005
Special to World Science
Astronomers say they have found a new planet in our Solar System, the first one bigger than Pluto since that object was discovered in 1930.
The planet is also further away than Pluto, the furthest known planet, the researchers said.
It’s “the first object bigger than Pluto ever found in the outer solar system,”
said Michael E. Brown of the California Institute of Technology
in Pasadena, Calif., one of the discoverers.
The planet, temporarily named 2003UB313, was found in an ongoing survey at Palomar Observatory’s Samuel Oschin telescope, he added.
The observatory is on the Palomar Mountain near San Diego, Calif.
Brown said he made the finding with Chad Trujillo of the Gemini Observatory in Chile and Hawaii, and David Rabinowitz of Yale University in New Haven,
Conn.
The group has proposed a name for the new planet to the International Astornomical Union, the organization in charge of nomenclature of celestial
objects, Brown added.
A few other planet-like Solar System objects have been discovered since Pluto was identified, but none are bigger than Pluto, and astronomers don’t agree on whether to call them planets. They’re
thought to be something between planets and
asteroids.
No precise definition of
planet exists, actually. Scientists are debating what such a definition would
be; there are a wide variety of Solar System objects, and few clear divisions
between the different types.
Pluto itself, while
historically considered a planet, is more correctly termed a “Kuiper
Belt Object,” Brown maintains. The Kuiper Belt is an area of the solar system outside
Neptune’s orbit, and which is believed to contain asteroids, comets, and icy bodies.
One possible definition of “planet”
that some astronomers have discussed includes any newfound Solar System object
larger than Pluto. So by this definition, the object that Smith and colleagues
say they found might be considered a planet.
If so, and if Pluto is also
a considered planet, this makes the newfound body the 10th known planet.
Currently about 97 times further from the sun than the Earth,
it is also the farthest-known object in the solar system, and the third brightest Kuiper
Belt Object, Brown said.
“It will be visible with a telescope over the next six months and is currently almost directly overhead in the early-morning eastern sky, in the constellation Cetus,” said Brown.
Brown, Trujillo and Rabinowitz said they first photographed the new planet on
October 31, 2003. But it so far away that its motion was not detected until they reanalyzed the data
last January. Since then, the scientists said, they have been studying the planet to better estimate its size and its motions.
Scientists can infer the size of a solar system object by its brightness, just as one can infer the size of a faraway light bulb if one knows its
power. The reflectance of the planet is unknown. Scientists can not yet tell how much light from the sun is reflected away, but the amount
of light the planet reflects puts a lower limit on its size.
“Even if it reflected 100 percent of the light reaching it, it would still be as big as Pluto,” said Brown. “I’d
say it’s probably one and a half times the size of Pluto.”
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