Discovery of a new category of planets

Our solar system consists of two large classes of planets: rocky terrestrial planets like Earth or Mars and giant planets formed of gases like Neptune or Saturn. Thus, the other planets located outside our system, the exoplanets, have long been categorized in these two classes, until today.

An international team led by an astronomer from the Université de Montréal (UdeM) has succeeded in drawing a clearer picture of what could be a third class of planets that are not found in our solar system.

The latter, called sub-Neptunians or super-Terres, were known before, but nobody could identify them. The most amazing thing is that they represent no less than 80% of the planets in our galaxy!

To get there, the team led by Björn Benneke, a professor of astronomy at UdeM, compiled many datasets from NASA’s Hubble and Spitzer space telescopes for five years.

The team focused mainly on a planet named GJ 3470 b. It is 12.6 times more massive than the Earth, but less massive than Neptune (an intermediate between the rocky and gaseous planets of the solar system).

Also, 80% of the planets that make up our galaxy are of a more or less similar mass and size. For a long time, scientists were aware of their size and shape, but nobody had been able to determine their chemical composition.

Thanks to this discovery, we can now establish the majority of the planets of our universe. Mr. Benneke mentions that before, scientists looked at the wrong sample of planets (those of our solar system) and therefore could not conduct a complete analysis of the universe.

The sub-Neptunian planets, or super-Earths, could even shelter life, as the astronomer of UdeM says:

Now, scientists will continue to observe GJ 3470b in more detail with NASA’s James Webb Space Telescope to better understand these new planets and be able, who knows, to find a way of life on a similar sub-Neptunian.

The study us published in Nature Astronomy.

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