Astronomers are losing Pluto

Discovery of the one more planet in the Solar System made astronomers think again about the classification for planets.
Working group of International Astronomic Union (IAU) intends to decide if this space object called Sedna is a planet or not.

IAU considers minimum size of the planet as the key criterion. The outcome of applying this criterion may be depriving the Pluto of the status of planet. Some astronomers have always considered the Pluto too small to have this status.

"If we start using this classification, the Pluto will not be considered a planet any more”, said Professor Evan Williams. “However, our cultural tradition for about a century has been naming the Pluto planet. IAU established working group to find the solution to this problem".

The discovered space object has been called Sedna (not official name yet) after the Eskimo Goddess of sea. The discovery was made on the Samuel Oschin Telescope at the Palomar Observatory east of San Diego on 14 November 2003. It is the last of the series of the celestial bodies discovered in the outer borders of the Solar System recently. The size of these celestial bodies can be compared with that of the Pluto. The Sedna is estimated to be one fourth of the Pluto in size.

Many astronomers, including Michael Brown from Californian Institute of Technology say that the Sedna is not a planet, but planetoid (something between planet and asteroid). However, the Sedna and the other celestial bodies discovered recently in the Koiper Zone (the area of space debris outside the Solar System) are much bigger than the typical asteroid. Some scholars believe that new celestial body much bigger that the Pluto can be discovered in the Koiper Zone soon. 

One of the solutions for the “Pluto problem” is making the Pluto exception and agreeing to continue considering the Pluto planet.  After the Pluto was discovered in 1930, it was considered bigger in size than it really is, and scholar had no doubts about calling it planet. Today astronomers are not ready to reconcile themselves with the idea that the Pluto is not planet. In 1999 the offer to change the status for the Pluto was rejected with indignation, BBC reports.

Source: Information agencies