When Pluto was officially bumped out of the solar system’s planet “club” in 2006, many people were outraged.
Not only was everything we had come to believe about the solar system thrown into question, but our books and 3D models became immediately obsolete.
Nearly two decades later there is a push by some influential scientists to reset the definition of a planet, which was originally established in a different time and space, so to speak.
The current definition, established in 2006 by the International Astronomical Union (IAU), specifies that, to qualify for the planet club, a celestial body must orbit the sun within our solar system.
However, it is well established that celestial bodies orbiting stars outside our solar system are common.
Based on this, UCLA professor of earth, planetary and space sciences and of physics and astronomy Jean-Luc Margot will present a proposed new definition at the IAU General Assembly next month.
“Under the current definition, a planet is a celestial body that orbits the sun, is massive enough that gravity has forced it into a spherical shape and has cleared away other objects near its orbit around the sun,” Professor Margot said in an article published by UCLA.
“The current definition specifically mentions orbiting our sun. We now know about the existence of thousands of planets, but the IAU definition applies only to the ones in our solar system.
“We propose a new definition that can be applied to celestial bodies that orbit any star, stellar remnant or brown dwarf.”
Specifically, the new definition would include require a planet to:
- Orbit one or more stars, brown dwarfs or stellar remnants
- Be larger than 10 to the power of 23 kg
- Be less massive than 13 Jupiter masses
“All the planets in our solar system are dynamically dominant, but other objects – including dwarf planets like Pluto, which is not a true planet, and asteroids – are not,” Professor Margot said. “So this property can be included in the definition of planet.”
“The current requirement to be spherical, on the other hand, is more problematic.
“Distant planets can rarely be observed in enough detail to ascertain their shape with certainty. The authors argue that the shape requirement is so difficult to implement that it is effectively useless for definitional purposes, even though planets are generally round.”
The full report is on the UCLA website.
