The astronomers planetA similar change from the previous PlutoThe new definition adds measurable criteria, such as taking into account the planet’s mass, but still leaves Pluto as a dwarf planet.
Currently, the International Astronomical Union (IAU) Define a planet It is a celestial body with three distinct characteristics: it orbits the Sun, is large enough to be molded into a round shape by gravity, and excludes all smaller objects in its orbit other than the Moon and other moons.
“The problem in the past was that although we had the word ‘planet,’ we didn’t have a quantitative definition of it.” Brett Gladman“The idea is that the Sun is a star that is moving in a direction that is different from the Sun,” said David S. Wilson, an astronomer at the University of British Columbia who, along with his colleagues, proposed the new definition, outlined in a paper posted to a preprint server on July 10, told Live Science. arXiv and, IAU General Assembly In August.
Without a quantitative standard, the current definition runs into a lot of problems, Gladman said. Specifically, the criteria are vague and it’s unclear how big these objects have to be or “how distinct” their orbits have to be to be considered planets. For example, Earth and Jupiter are asteroid that Cross their path regularlyThe question arises as to whether planets really have well-defined orbits, as the current definition doesn’t even take into account objects orbiting stars other than the Sun, such as those orbiting more than 5,500 stars. Exoplanets Detected beyond our reach Solar System.
But “the biggest problem is the roundness standard.” Jean-Luc Margot“Roundness is simply not observable. We don’t have the technology, and we don’t see it coming anytime soon,” UCLA astronomer and lead author of the paper told Live Science.
Instead of focusing on a planet’s roundness or orbit, the new definition emphasizes a measurable quantity: the mass of an object. The new definition defines a planet as a celestial body that meets the following criteria:
To ensure their classification framework was logical and unbiased, the scientists used a technique called unsupervised clustering, an algorithm that groups similar objects together. This technique: Solar System.
“Whatever criticisms one may have of the current IAU definition, we can at least be persuaded that the resulting classification of eight planets is valid,” he said.
Astronomers are looking at the ability to clear orbits, the so-called Dynamic Advantagecan be determined by the mass of the planet. For example, the mass of each of the eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) is at least three orders of magnitude greater than the mass of the dwarf planets, which are not dynamically dominant.
Dynamic advantage also Mass Lower Limit Regarding planetary qualifications: However, Pluto, with a mass of just 2.88 x 10^22 pounds (1.31 x 10^22 kg), still does not qualify as a planet under the new definition.
Regarding sphericity, the mass of an object larger than 10^21 kg is Typically spherical It’s because of gravity. So, Margot says, the new definition doesn’t contradict the current definition, but rather adds specificity to it.
“Humans are so tied to language and names and classifications because that’s how we think about the world,” Gladman added. “It’s how we organize the complexity of the world. We want to name things and classify them, and scientists want to do that too. We want to do that accurately.”
There’s always the possibility of opposition: Margot plans to present the proposal at the IAU General Assembly in August, but he doesn’t expect there to be consensus. Rather, he hopes that through the presentation, the team will identify people who are interested in the idea and that the discussion will continue.
The proposal was written out of “a conviction that we can do better as a community,” Margot said, and “we owe it to ourselves and the public to come up with better definitions for these important astrophysical terms.”
