Stories tagged Ceres

Sep
21
2006

Artist's concept of Eris.: Image courtsey NASA/JPL-Caltech.
Artist's concept of Eris.: Image courtsey NASA/JPL-Caltech.

The “Tenth Planet” that caused Pluto to lose its planetary status has been classified and named, and to the dismay of many, it was not named Xena. The International Astronomical Union has classified it as a dwarf planet and named it Eris, after the Greek goddess of Chaos, which is appropriate for the chaos it cause in the astronomical community over what should be defined a planet and what should not.

The debate centered around the argument that if Pluto was considered a planet, then 2003 UB313, as it was known at the time, should be a planet as well as it was larger than Pluto. The debate culminated at the International Astronomical Union meeting last month where Pluto was stripped of the title “planet” and relegated to “dwarf planet” along with Eris and the former asteroid Ceres.

Eris' moon was also given a formal name: Dysnomia. In Greek mythology Dysnomia was the daughter of Eris.

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.