Tilted Forum Project Discussion Community - View Single Post - How many planets are in our solar system?

Redlemon · 11-04-2005, 01:31 PM

From the bottom of the link in the original post:

Quote:

What in the World is a Planet Anyway?

With the recent discoveries of Sedna and now 2003 UB 313 at distances from the Sun well beyond those of the “traditional” planets that we all learned in elementary school, the question: “What is a planet?” has taken on added significance.

There is a diverse range of objects populating our solar system, and many objects are clearly not planets. These include: comets, asteroids (sometimes called minor planets), satellites, dust grains, charged particles, planetesimals and of course the sun. But what is it that makes a planet a planet?

Some have argued that Pluto does not fit the bill as a planet given its small size and highly eccentric, greatly inclined orbit.. However, it is countered that Pluto has a satellite like other planets, it orbits the sun like other planets and it is made up of planet-like material. Therefore, it is a planet. So where does that leave objects like 2003 UB 313?

Many of the same arguments that have been used to “demote” Pluto from planet status are also being used on 2003 UB 313 (as well as Sedna and similar objects), even though these arguments have not made much progress and often just cloud the issue with semantics.

Many of the same arguments that have been used to “demote” Pluto from planet status are also being used on 2003 UB 313 (as well as Sedna and similar objects that now number four).

The main differences between 2003 UB 313 and Pluto are: it is probably a bit bigger than Pluto, it is located in the Kuiper Belt about 3-times further from the sun than Pluto, and the inclination of its orbit is about 44° with respect to the plane of the solar system. (Note: 44° is a very high inclination, the second highest is of Pluto at 17°. One of the reasons UB 313 has not been discovered until now is because it was not believed that Kuiper Belt objects could have such a large inclination to the ecliptic.)

Given the fact that there is not a consensus on Pluto’s status, it is unlikely that there will ever be agreement on 2003 UB 313 or other objects like it. Suffice it to say that we are learning a lot more about our solar system and there will probably be more surprises as we explore to even greater depths.