Clara Descurninges, The Canadian Press
MONTREAL — An international team of researchers, led by the University of Montreal, have discovered what could be a rare oceanic exoplanet.
There are only a handful of candidates for this title and none have yet been confirmed, according to doctoral student in astrophysics Charles Cadieux, who piloted the research. “We have already discovered water elsewhere”, whether in the form of vapor, or in ice on certain moons of our solar system, he recalls. But the aquatic worlds currently only exist in theory.
TOI-1452 b, as it is called, lies 100 light-years from Earth, in a two-star system in the constellation Dragon.
If it is thought to be an ocean planet, it is because with a radius 70% larger than that of Earth, a mass five times greater and a similar density, only a few scenarios could explain these measures.
Indeed, it is not impossible that the planet is entirely rocky, but this is unlikely according to Mr. Cadieux. “It would not be compatible with what we find on its star,” he explains. It could also be that TOI-1452 b has a thin atmosphere composed of very light elements, such as hydrogen and helium.
But the hypothesis of the oceanic world, “it is the scenario which is most probable at the moment”, indicates Mr. Cadieux. In this case, “up to about 30% of the mass” of the planet would be liquid water. In comparison, the mass of the Earth, this blue planet, contains less than 1% water.
Most doubts could be dispelled using the brand new, state-of-the-art James-Webb Telescope. “When the planet passes in front of its star, the light passes through the atmosphere of that planet,” explains Mr. Cadieux. One could then discover an atmosphere or even “see the water signature” in the way the light rays are affected.
However, Cadieux cautions that while scientists can request James-Webb time, the process is “hypercompetitive” and his submission is not guaranteed to be accepted.
Starlight
Unlike stars, planets do not produce their own light. Most of them are thus concealed from our eyes. But in a tiny fraction of solar systems, a shadow sometimes passes in front of a star, revealing the presence of a celestial body.
“You have to be lucky to observe that” in the vastness of space, underlines Mr. Cadieux. For example, if this passage, called transit, always occurs in front of an illuminated face of the Earth, then it is impossible to spot it from the ground.
This is why NASA launched its Transiting Exoplanet Survey Satellite (TESS) in 2018. It was this one that first alerted the scientific community about TOI-1452 b.
The team from the Institute for Research on Exoplanets, of which Mr. Cadieux is a member, then used the Mont-Mégantic Observatory to confirm that it was indeed a planet and to find out its radius.
The researchers then visited the Canada-France-Hawaii Telescope, which has an instrument capable of determining mass.
The study “TOI-1452 b: SPIRou and TESS Reveal a Super-Earth in a Temperate Orbit Transiting an M4 Dwarf” was published on August 12 in the scientific journal The Astronomical Journal. About fifty researchers from North and South America, Europe and Asia co-signed the article.