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Des astronomes québécois découvrent une probable exoplanète océanique

Quebec astronomers discover a possible oceanic exoplanet

Clara Deskernings, The Canadian Press

MONTREAL – An international team of researchers, led by the University of Montreal, has discovered what could be a rare oceanic exoplanet.

There are only a few candidates for this title and none have been confirmed yet, according to astrophysics doctoral student Charles Cadiux, who led the research. “We’ve already discovered water elsewhere,” he recalls, “whether in the form of steam, or in ice on certain moons of our solar system.” But aquatic worlds currently only exist in theory.

TOI-1452 b, as it is called, is located 100 light-years from Earth, in a two star system in the constellation Dragon.

If it is thought of as an oceanic planet, it is because with a radius 70% larger than Earth’s, a mass five times greater and a similar density, only a few scenarios could explain these scales.

In fact, it is not impossible for the planet to be completely rocky, but that is unlikely according to Mr. Kedio. “It wouldn’t be compatible with what we find on its star,” he explains. TOI-1452 b could also have a thin atmosphere composed of very light elements, such as hydrogen and helium.

But the ocean world hypothesis, “It’s the most likely scenario at the moment,” notes Mr. Cadio. In this case, “up to 30% of the mass” of the planet will be liquid water. By comparison, the mass of the Earth, this blue planet, contains less than 1% of water.

Most doubts can be dispelled with the new and modern James Webb Telescope. “When a planet passes in front of its star, light passes through that planet’s atmosphere,” explains Mr. Cudio. One can then detect the atmosphere or even “see the water signature” the way light rays are affected.

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However, Cadiux cautions that while scientists can apply for James-Webb’s use time, the process is “highly competitive” and acceptance of his submission is not guaranteed.

starlight

Unlike stars, planets do not produce their own light. Thus most of them are hidden from our eyes. But in a tiny fraction of the solar systems, the shadow sometimes passes in front of a star, revealing the presence of a celestial body.

“You have to be lucky to notice it” in the vastness of space, stresses Mr. Cudio. For example, if this passage, called a transit, always occurs in front of the luminous face of the Earth, then it is impossible to determine it from the ground.

This is why NASA launched the Transiting Exoplanet Reconnaissance Satellite (TESS) in 2018. This was the first thing that alerted the scientific community about TOI-1452b.

The team at the Institute for Research on Exoplanets, to which Mr. Cadio belongs, used the Mont-Mégantic observatory to confirm that it was indeed a planet and to find out its radius.

Then the researchers visited the telescope of Canada, France and Hawaii, which has an instrument capable of determining the mass.

The study “TOI-1452 b: SPIRou and TESS Reveal a Super-Earth in a moderate orbit passing through the M4 Dwarf” was published August 12 in the scientific journal The Astronomical Journal. The article was co-signed by about fifty researchers from North and South America, Europe and Asia.