Nine years ago, the International Astronomical Union (IAU) established new criteria for determining what can be classified as a “planet” and what is not. This was a controversial move that deprived Pluto of the status of the ninth planet of the solar system. But now how to classify planets located outside the solar system, the number of which is approaching 5,000.
On Tuesday, astronomer Jean-Luc Margot of the University of California, Los Angeles presented his view of what is called “Test for the Planet.”
MAS says: “Planet” is a heavenly body that:
- revolves around the sun;
- has enough mass to become almost round;
- cannot clear its orbital path.
It was the last criterion that prevented Pluto from becoming a planet. Astronomers ranked Pluto to a new category of “dwarf planets”, which also includes Ceres, located in the main Asteroid Belt, as well as the dwarf planets Eris, Haumea and Makemake, which are located in the Kuiper Belt.
The ability of the planet to clear its orbital path is the main criterion that Margo uses in the development of a classification system for planets outside the solar system. His test can determine whether a body can clear a certain area around its orbit during a certain time scale, for example, during the lifetime of the parent star. The test is simple to implement and allows you to immediately classify 99 percent of all known exoplanets.
The proposed criterion requires only an estimate of the stellar mass, the mass of the planet, and the orbital period, all of which can be easily obtained from Earth or based on data from space telescopes.
When applying this test to the Solar System, Pluto still cannot be defined as a planet.
"The gap between planets and non-planets is striking," said Margo in a statement. "The dramatic difference suggests that there is a fundamental difference in how these objects were formed."
Planetary scientist Alan Stern, who heads the New Horizons mission team, says that this is a very narrow view of things.
"I think that among planetary scientists there is a clear understanding that Pluto is much more like the planets of the solar system than anything else," he added.