A Quantitative Criterion for Defining Planets

Since the late 1980s, scientists have discovered nearly 5,000 planetary bodies orbiting stars other than the sun. But astronomers are still working on what exactly we should call them.

Today at an American Astronomical Society meeting, UCLA professor Jean-Luc Margot described a simple test that can be used to clearly separate planets from other bodies like dwarf planets and minor planets.

The current official definition of a planet, which was issued by the International Astronomical Union in 2006, applies only to bodies in our solar system, which Margot said has created a “definitional limbo” for the newly discovered bodies.

The new approach would require only estimates of the star’s mass and the planet’s mass and orbital period — all of which can be easily obtained with Earth- or space-based telescopes. According to Margot’s criteria, all eight planets in our solar system and all classifiable exoplanets — the large bodies that orbit stars other than our sun — would be confirmed as planets.

Margot, a professor of planetary astronomy, wanted to ensure that the new system would be easy to follow. “One should not need a teleportation device to decide whether a newly discovered object is a planet.”





Arxiv - A Quantitative Criterion for Defining Planets

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