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Thursday, February 4, 1999 Published at 00:40 GMT


Pluto stays a planet

Pluto and its tiny moon Charon

By BBC News Online Science Editor Dr David Whitehouse

After several weeks of debate, astronomy's governing body, the International Astronomical Union (IAU) has said that tiny Pluto will not be demoted from its planetary status.

The argument began when a group of astronomers suggested that Pluto be assigned a number as well as a name.

[ image: The best map we have of Pluto]
The best map we have of Pluto
This is because many scientists regard Pluto as being the leading member of a family of smaller objects orbiting the Sun in deep space.

One group wanted to call Pluto Minor Planet number 10,001. Others said leave Pluto alone.

Since its discovery in 1930 it has been clear that tiny Pluto, which is smaller than our Moon, is something of an oddity in the outer solar system.

It looked even more out of place among the solar system's larger planets following the recent discovery of swarms of smaller bodies orbiting the Sun even further away which may be related to Pluto.

But the IAU has said that it has "decided against assigning any minor planet number to Pluto."

The decision will be welcomed by most astronomers. The American Astronomical Society had said that any "dual citizenship" for Pluto would have diminished its standing.

"There are a lot of people with an emotional attachment to Pluto," said Michael A'Hearn of the IAU.

Brian Marsden of the Harvard-Smithsonian Centre for Astrophysics said "we are leaving Pluto untouched, I promise."

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