Our knowledge about space is very limited which demands extensive exploration studies.
We live on the surface of the planet Earth and have no real clue of how vast our outer space really is! Scientists have successfully sent humans on the Moon and planning for Mars mission, however, these are very small steps to conquer the universe. Before going to office or any destination, we often check the travel distance, but, the space is totally different; its size is beyond our comprehension. For understanding and better exploration, in such a vast universe, scientists need a proper system to identify celestial objects and events. In this article, we will discuss about new definition system for planets to be implemented by astrophysicists.
The International Astronomical Union (IAU) is responsible for officially naming celestial objects. As per definition made by IAU in 2006: “A planet is a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and has cleared the neighbourhood around its orbit.”
Just like solar system, there are other systems across the whole universe. As the old definition was only focused on sun or solar system, there is a need to change the definition of planet.
Moreover, over the last couple of decades, scientists have discovered over 5,000 exoplanets, or worlds that are orbiting distant stars.
Jean-Luc Margot, lead author of the article and UCLA professor of Earth, planetary and space sciences and of physics and astronomy said: “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.”
According to the new definition proposed by scientists: “A planet is a celestial body that orbits one or more stars, brown dwarfs or stellar remnants and is more massive than 10^23 kg and; is less massive than 13 Jupiter masses (2.5*10^28 kg).
As per old system, a planet needs to be spherical, which is more problematic to understand and research purpose. It often becomes unclear even with powerful telescopes to decipher the shape and size of Planets that are located far away from us. Even, Jupiter and Saturn are not totally spherical in shape.
An astronaut closely working with the planet nomenclature said: “The good news is that, in the solar system, celestial bodies larger than 10^21 kg appear to be round. So all bodies that satisfy the proposed lower limit on mass of 10^23 kg are expected to be spherical.”
From planet status, Pluto was reclassified as dwarf planet in 2006. According to old definition, Pluto met all the criteria except one—it “has not cleared its neighboring region of other objects.” This led to a lot of uproar among scientific communities across the globe. While talking about the fate of Pluto, Margot said: “All the planets in our solar system are dynamically dominant, but other objects—including dwarf planets like Pluto and asteroids—are not. So this property can be included in the definition of planet.”
However, in the modern definition, Pluto doesn't qualify to “full planet status.”
The astronomers will come together for an election on the topic of new definition of a planet in August, 2024. After this, exoplanets and mass limits are expected to be updated.
