The International Astronomical Union (IAU) on Thursday adopted a resolution on planet definition, according to which Pluto had been stripped of the planetary status. (Xinhua Photo) Photo Gallery >>>

    LOS ANGELES, Aug. 24 (Xinhua)-- The new planet definition passed by the International Astronomical Union (IAU) is "scientifically right" and is a great step forward, an astronomer who spotted a celestial body larger than Pluto said on Thursday.

    Mike Brown, a professor of planetary science at the California Institute of Technology, should have become the discoverer of a new planet but for the IAU's new definition passed in Prague, Czech Republic earlier this day.

    Brown announced last year the discovery of celestial body 2003UB313, also informally named "Xena." Somewhat larger than Pluto, the body should be qualified as the tenth planet of the solar system, Brown claimed at that time.

    But now Brown said the new definition, which regulates that only eight planets revolve Sun and that Xena should be classified as "dwarf planet" as well as Pluto, is acceptable.

    "I'm of course disappointed that Xena will not be the tenth planet, but I definitely support the IAU in this difficult and courageous decision," said Brown. "It is scientifically the right thing to do, and is a great step forward in astronomy."

    "Pluto would never be considered a planet if it were discovered today, and I think the fact that we've now found one Kuiper-belt object bigger than Pluto underscores its shaky status," he said.

    Pluto was discovered in 1930. Because of its size and distance from Earth, astronomers had no idea of its composition or other characteristics at the time.

    But having no reason to think that many other similar bodies would eventually be found in the outer reaches of the solar system-- or that a new type of body even existed in the region -- they assumed that designating the new discovery as the ninth planet was a scientifically accurate decision.

    About two decades later, U.S. astronomer Gerard Kuiper postulated that a region in the outer solar system could house a gigantic number of comet-like objects too faint to be seen with the telescopes of the day. The Kuiper belt, as it is called now, was demonstrated to exist in the 1990s, and astronomers have been finding objects of various size in the region ever since.

    Few astronomers had previously called for the Kuiper-belt objects to be called planets, because most were significantly smaller than Pluto. But Brown's discovery of Xena's has actually raised a new need for a more precise definition of which objects are planets and which are not.

    Brown expected the new definition to pose a difficulty for a public that has been accustomed to thinking for the last 75 years that the solar system has nine planets. But people would at last accept it, he noted.

    "It's going to be a difficult thing to accept at first, but we will accept it eventually, and that's the right scientific and cultural thing to do," he said. Enditem