2024-07-27 05:34:14
Currently, the International Astronomical Union (IAU) defines a planet as a celestial body with three characteristics: it orbits the Sun, it is large enough for gravity to shape it into a round shape, and all smaller objects except moons and other moons have been dispersed from its orbit.
“The problem was that we had the word ‘planet’ before, but we didn’t have a quantitative definition of it,” says Brett Gladman, an astronomer at the University of British Columbia who proposed the new definition with his colleagues.
The proposal was made on July 17. žurnale „The Planetary Science Journal“ in a published paper scheduled to be presented at the IAU General Assembly in August.
According to B. Gladman, the current definition has many shortcomings. First of all, the criteria are vague: it is unclear how large these bodies must be or “how empty” their orbits must be to be considered planets. For example, asteroids regularly cross the orbits of Earth and Jupiter, raising the question of whether the planets’ orbits are indeed empty. The current definition also excludes objects that orbit stars other than the Sun — such as the more than 5,500 exoplanets discovered outside our Solar System.
“However, the roundness criterion is the most problematic,” says Jean-Luc Margot, an astronomer at the University of California, USA, and lead author of the paper. – Roundness is simply impossible to determine. We don’t have that technology and we won’t have it in the near future.”
Instead of focusing on the roundness of the planets and the trajectories of their orbits, the new definition emphasizes a measurable quantity, the object’s mass.
To ensure that their classification system was logical and unbiased, the researchers used a machine learning technique called unsupervised learning, an algorithm that groups similar objects into groups. This method also successfully grouped the eight planets of the Solar System.
“No matter how much you criticize the current IAU definition, you can at least be satisfied that the result – eight planets – is a reasonable classification,” says the researcher.
Astronomers say that a planet’s ability to “clear” its orbital path can be determined by the planet’s mass. Only objects of sufficient mass, including the eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), can do this
It also sets a lower mass limit at which an object can be considered a planet. But Pluto, which has a mass of only 1.31 x 1022 kg, will still not be considered a planet under the new definition.
As for the roundness of a celestial object with a mass greater than 1021 kg, the shape is usually spherical due to gravitational attraction. In this way, the new definition does not actually contradict the current definition, but rather refines it, says JL Margot.
However, there is always the possibility that there could be resistance to the new definition, according to the researchers. JL Margot will present the proposal to the IAU General Assembly in August – but he does not expect consensus to be reached immediately. Instead, he hopes that during the presentation, the team will find people who are interested in the idea and continue the discussion, according to Live Science.
2024-07-27 05:34:14