A redefinition of planets throughout the universe is required. This is what a group of astronomers from UCLA claims * The researchers will present the new definition at the General Assembly of the International Astronomical Union in August
Planetary scientists are pushing for a redefinition of planets that would extend beyond our solar system, with an emphasis on mass and orbital characteristics rather than proximity to the Sun. The proposal aims to address the outdated and heliocentric aspects of the current IAU definition.
The International Astronomical Union (IAU) defines a planet as a celestial body that orbits the Sun, is massive enough for gravity to shape it into a sphere, and has cleared its orbit of other bodies. However, scientists today recognize the existence of thousands of planets, but the IAU definition only applies to those within our solar system. The proposed new definition states that the body can orbit stars, brown dwarfs, or stellar remnants and sets mass limits that would apply to planets everywhere.
The scientists propose a new definition for a planet that would also fit celestial bodies that orbit stars outside our solar system. The forthcoming article in the Planetary Science Journal argues for this definition and provides quantitative criteria for further clarification of the definition.
Jean-Luc Margot, lead author of the paper and professor of Earth, Planetary and Space Sciences, and Physics and Astronomy at UCLA, will present the new definition at the August 2024 IAU General Assembly.
The International Astronomical Union (IAU) is a world organization founded in 1919 to promote and protect the science of astronomy through international cooperation. Based in Paris, France, its mission includes coordinating astronomical research, establishing a standard astronomical nomenclature, and disseminating scientific information. He is known for his role in defining planetary classifications and naming celestial bodies and features. The IAU includes over 12,000 members from more than 90 countries and hosts general meetings every three years, where major astronomical discoveries and developments are discussed.
In the current definition, a planet is a celestial body that orbits the Sun, is massive enough for gravity to shape it into a sphere, and has cleared its orbit of other bodies. "The current definition specifically refers to the orbit of our sun. "We recognize the existence of thousands of planets, but the IAU definition only applies to those in our solar system," Margo said. "We propose a new definition that will fit bodies orbiting any star, stellar remnant, or brown dwarf."
In the new definition, a planet is a celestial body that orbits one or more stars, brown dwarfs or stellar remnants, is more massive than 10^23 kg and less massive than 13 Jupiter masses (2.5 X 10^28 kg).
Margo and colleagues Brett Gladman of the University of British Columbia and Tony Young, a student at Chaparral High School in Temecula, California, used a mathematical algorithm on the properties of objects in our solar system to see which objects cluster together. The analysis revealed sets of distinct features shared by planets in our solar system that could serve as a starting point for creating a general taxonomy for planets.
The dynamic dominance requirement provides a lower bound for the mass. However, potential planets could also be too large to fit the new definition. Some of the gas giants, for example, are so large that thermonuclear fusion of deuterium occurs, and the object becomes a sub-star called a brown dwarf and is therefore not a planet. This limit is determined to be 13 Jupiter masses or higher.
The good news is that in the solar system, celestial bodies larger than 10^21 kg appear round. So all the bodies that meet the proposed lower limit of mass of 10^23 kg are expected to be spherical.
A formal change to the definition of a planet by the IAU is expected to take several years, but Margot and his colleagues hope their work will start a conversation that will lead to an improved definition. The last notable change of the definition of planets was at the IAU meeting in 2006, when it was decided to reduce the definition of planets and open a new definition of dwarf planets into which was introduced Former planet Pluto.
More of the topic in Hayadan:
