Stories tagged Charon

Aug
16
2006

The 12 planets: In this artist's impression the planets are drawn to scale, but without correct relative distances.  Image courtesy the International Astronomical Union/Martin Kornmesser.
The 12 planets: In this artist's impression the planets are drawn to scale, but without correct relative distances. Image courtesy the International Astronomical Union/Martin Kornmesser.

The international panel that was formed to establish a scientific definition of a planet will make a recommendation to the International Astronomical Union (IAU) General Assembly that will increase the number of objects in out solar system that are defined as planets from nine to twelve.

The panel was originally formed to discuss the issue of Pluto’s status as a planet. Not only does the panel recommend retaining Pluto’s planetary status, but also promoting Ceres, Charon and "Xena" to planets. The new definition of a planet is that it has to orbit a star, not be a star itself, not a satellite of another planet, and massive enough that its gravitational forces compress it into a roughly round shape. This opens the door for many more objects in our solar system to be called planets, notably Vesta, Pallas and Hygiea. In fact, there may be more than 53 objects that meet the new criteria to be called a planet, and probably many more yet to be discovered.

The proposal is not final, and will be discussed on August 23 at the International Astronomical Union General Assembly meeting in Prague.

Watch a fly by of the new solar system here.

UPDATE: Turns out they changed the rules, and we now have only eight planets. Pluto doesn't qualify under the new definitions a planet. To be a “planet” it must:

1. Orbit a sun.
2. Have sufficient mass so that it assumes a nearly round shape.
3. And have sufficient mass to have "cleared the neighborhood around its orbit".

Pluto has not cleared the neighborhood of its orbit of Kuiper Belt Objects, so it is no longer considered a planet.