Not only around the Sun. Scientists have proposed to expand the concept of "planet"

Scientists at the University of California, Los Angeles, have proposed expanding the definition of a "planet" beyond the solar system. According to scientists, it is very vague.

A team of experts led by planetary scientist Jean-Luc Margaux argues that the current definition, adopted by the International Astronomical Union (IAU) in 2006, is too "Sun-centric." Therefore, they propose a more accurate alternative, Earth.com writes.

Currently, the definition of a planet is a celestial body that orbits the Sun, has enough mass to become spherical under the influence of gravity, and "pushes" other objects out of its orbit. But it only refers to celestial bodies in our solar system and has nothing to say about exoplanets, of which there are more than 6,000.

"The current definition specifically mentions orbiting our sun. This only applies to planets in our solar system. Our team's proposal will be applicable to celestial bodies that orbit any star, star remnant, or brown dwarf," said lead author Professor Jean-Luc Margaux.

The International Astronomical Union's criteria also require that the body have a shape close to spherical due to its own gravity, and that it be the only body of similar size in its orbit, except for its satellites. These points, according to scientists, are not formulated precisely enough, which makes them difficult to verify.

Therefore, scientists propose a new definition, which states that a planet is a body in orbit around one or more stars, brown dwarfs, or stellar remnants with a mass of more than 10²³ kilograms, i.e., a mass less than 13 Jupiter masses (2.5 X 10²⁸ kilograms).

To come up with these constraints, experts analyzed solar system objects to determine what common features distinguish planets from other objects. They replaced the old requirement of a body's predominance in its orbit. After all, the researchers noticed that it is with a mass of about 10²³ kg that planets begin to "absorb" small objects on their way.

Scientists also sought to separate planets from nascent stars. It is known that thermonuclear reactions begin in the interior of too massive gas giants, turning the planet into a brown dwarf star.

They also decided to abandon the old requirement of a spherical shape, since it is almost impossible to determine their shape when observing distant exoplanets. However, the authors of the paper argue that this also falls under the mass limit, meaning that all solar system objects heavier than 10²¹ kg are spherical. Therefore, the mass of a space body is not difficult to determine.

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