How can this be called a planet?

Leading astronomers around the world are debating the criteria to be able to call a celestial body a planet, comparing Pluto Pluto and a newly discovered asteroid, Sedna.

Some astronomers make suggestions that should eliminate bias on signs related to the position of celestial bodies in the Solar System.

The International Astronomical Society IAU - responsible for setting standards, has gathered special working groups to consider whether Sedna is a planet in the Solar System, and even Pluto has must be a planet yet?

The asteroid Sedna was discovered in July 2005, in the Kuiper rock belt, outside of Neptune. The discoverers attributed it to the tenth planet, because it was larger than the 9th planet, Pluto Pluto.

The Solar System is considered to have 9 planets, from inside to outside, including: Mecury Glass, Venus Venus, Earth, Mars Mars, Jupiter Jupiter, Saturn Saturn, Uranus Uranus, Neptune Neptune, and Pluton Pluto.

In it the largest Jupiter with a mass of 2.5 times the total mass of other planets combined (by 318 times the mass of Earth), 142,800 km in diameter.

Pluto is the smallest and furthest planet, 4000 km in diameter, 6 billion km from the Sun.

Between Mars and Jupiter there is a belt of asteroids and asteroids, the origin of comets that roam the Solar System.

Outside Neptune, in the space of Pluto is the Kuiper belt of asteroids with flattened orbits that lie on the outskirts of the Solar System.

The debate became fierce when the groups could not reach agreement. There are two opinions given, based on completely different criteria.

The group's proposal comes from Southwest Research Institute, Southwest Research Institute in Boulder, USA, simply based on the size of the object. That means Sedna is also a planet, and even the number of planets in the Solar System may increase if found in the Kuiper belt of bodies of similar size to Pluto.

But the second suggestion, given by the team from IAU's Minor Planet center in Cambridge, is that setting the size threshold to determine whether the criterion is planetary is entirely arbitrary.

"There is no scientific value when confirming that there are 9 planets, including Pluto - so there are many similar small bodies, could it be considered as planets?" - Team leader, Brian Marsden asked.

Thus, if based on the second proposal, the number of planets in the Solar System will be reduced, ie, Pluto is not yet considered a planet. In this view, a celestial body will be considered a planet when it is an outstanding individual than the surrounding celestial bodies, both in size and orbital dynamics.

Other sub-species in the outer ring of Mars are not considered planets because they have so many similar individuals in a narrow space. And Pluto Pluto is not included because it is closer to the more massive planet - Neptune.

In the debate there was a third proposal given by the team from London, but very far from the original topic. This idea only classifies planets, based on its characteristics such as the position, composition or level of civilization that exists on the planet. According to this classification, the Earth will be "planet earth with life", and Pluto Pluto will be a planet "recorded in historic planet."

Brian Marsden liked this third idea, because it allowed the public to explain Pluto as a special thing. Alan Stern, a member of Southwest Research Institute, is vehemently opposed to the idea, because he is out of topic. "People will ask why a doctor cannot say when a celestial body is a planet, while ordinary people can speak."

The groups will vote on ideas in the coming time, but the debate may still continue without knowing .