An extrasolar world covered in water?

Using instruments designed in part in Canada, a team of astronomers from the University of Montreal have discovered an exoplanet that may be entirely covered in water, a target they hope to observe soon with the Webb telescope.

Artist’s rendering of exoplanet TOI-1452 b, a small planet that may be completely covered by deep ocean. Credit: Benoit Gougeon, University of Montreal.

Charles Cadieux, the doctoral student who led the discovery of exoplanet TOI-1452 b. Photo courtesy of Cadieux.

An international team of researchers led by Charles Cadieux, a Ph.D. student at the University of Montreal and member of the Institute for Research on Exoplanets (iREx)announced the discovery of an exoplanet orbiting TOI-1452, one of two small stars in a binary system located in the constellation Draco about 100 light-years from Earth.

The exoplanet, known as TOI-1452 b, is slightly larger in size and mass than Earth and is located at a distance from its star where its temperature would be neither too hot nor too cold for light. liquid water exists on its surface. Astronomers believe it could be an ‘ocean planet’, a planet completely covered in a thick layer of water, similar to some of Jupiter’s and Saturn’s moons.

In an article published on August 12 in The Astronomical JournalCadieux and his team describe the observations that elucidated the nature and characteristics of this unique exoplanet.

“I am extremely proud of this discovery as it shows the high caliber of our researchers and our instrumentation,” said Rene Doyonprofessor at the University of Montreal and director of the iREx and Mont-Mégantic Observatory (OMM). “It is thanks to the OMM, a special instrument designed in our laboratories called SPI or and an innovative analytical method developed by our research team that we were able to detect this one-of-a-kind exoplanet.

Key role of the Mont-Mégantic Observatory

The Mont-Mégantic Observatory located in the Eastern Townships of Quebec houses a 1.6 m telescope that helped confirm this discovery. Credit: Emir Chouchane, University of Montreal.

It was NASA’s TESS space telescope, which scans the sky for planetary systems similar to our own, that put researchers on the trail of TOI-1452 b. Based on the TESS signal, which showed a slight dip in brightness every 11 days, astronomers predicted a planet that is about 70% larger in diameter than Earth.

Charles Cadieux belongs to a group of astronomers who perform ground-tracking observations of candidates identified by TESS to confirm their planet type and characteristics. He uses PESTOa camera installed on the OMM telescope which was developed by the professor from the University of Montreal David Lafreniere and his doctorate. student François-René Lachapelle.

“WMO played a crucial role in confirming the nature of this signal and in estimating the radius of the planet,” explains Cadieux. “It was not a routine check. We had to make sure that the signal detected by TESS was indeed caused by an exoplanet circling TOI-1452, the larger of the two stars in this binary system.

The host star TOI-1452 is much smaller than our Sun and is one of two stars of similar size in a binary system. The two stars revolve around each other and are separated by such a small distance – 97 astronomical units, or about two and a half times the distance between the Sun and Pluto – that the TESS telescope considers them a single bright spot. . But PESTO’s resolution is high enough to distinguish the two objects, and the images showed the exoplanet orbiting TOI-1452, which was confirmed by subsequent observations by a Japanese team.

Quebec ingenuity at work

The SPIRou instrument, partly designed by a Canadian team, made it possible to determine the mass of the exoplanet, and therefore to clarify its nature. Credit: S. Chastanet – CNRS/OMP.

To determine the mass of the planet, the researchers then observed the system with SPIRou, an instrument installed on the Canada-France-Hawaii Telescope in Hawaii. Designed largely in Canada, SPIRou is ideal for studying low-mass stars like TOI-1452 because it operates in the infrared spectrum, where these stars are brightest. Even then, it took more than 50 hours of observation to estimate the mass of the planet, which would be almost five times that of Earth.

Researchers Etienne Artigau and Neil Cook, also at the iREx of the University of Montreal, played a key role in the data analysis. They have developed a powerful analysis method capable of detecting the planet in the data collected with SPIRou. “The LBL method [for line-by-line] ]allows to clean the data obtained with SPIRou from many parasitic signals and to reveal the weak signature of planets like the one discovered by our team”, explains Artigau.

The team also includes Quebec researchers Farbod Jahandar and Thomas Vandal, two doctorates. students from the University of Montreal. Jahandar analyzed the composition of the host star, useful for constraining the internal structure of the planet, while Vandal helped analyze data collected with SPIRou.

An aquatic world

TOI-1452 b is probably rocky like Earth, but its radius, mass, and density suggest a world very different from ours. Earth is essentially a very dry planet; even though we sometimes call it the blue planet because about 70% of its surface is covered by ocean, water actually makes up only a negligible fraction of its mass — less than 1%.

Water can be much more abundant on some exoplanets. In recent years, astronomers have identified and determined the radius and mass of numerous exoplanets between the size of Earth and Neptune (about 3.8 times larger than Earth). Some of these planets have a density that can only be explained if much of their mass is made up of volatiles like water. These hypothetical worlds have been dubbed “ocean planets”.

“TOI-1452 b is one of the best candidates for an ocean planet we’ve found to date,” Cadieux said. “Its radius and mass suggest a much lower density than would be expected for a planet composed mostly of metal and rock, like Earth.”

Artistic representation of the surface of TOI-1452 b, which could be an “ocean planet”, i.e. a planet completely covered in a thick layer of liquid water. Credit: Benoit Gougeon, University of Montreal.

Mykhaylo Plotnykov and Diana Valencia of the University of Toronto are specialists in modeling the interiors of exoplanets. Their analysis of TOI-1452b shows that up to 30% of its mass can be water, a proportion similar to that of some natural satellites in our solar system, such as Jupiter’s moons Ganymede and Callisto, and the moons of Saturn Titan and Enceladus. .

To be continued…

An exoplanet such as TOI-1452 b is a perfect candidate for closer observation with the James Webb Space Telescope, or Webb for short. It is one of the few known temperate planets that exhibit characteristics consistent with an oceanic planet. It is close enough to Earth for researchers to hope to study its atmosphere and test this hypothesis. And, fortunately, it is in a region of the sky that the telescope can observe all year round.

“Our observations with the Webb Telescope will be essential to better understand TOI-1452 b,” said Doyon, who is also the principal investigator of NIRISS, one of the four science instruments of the James Webb Space Telescope. “As soon as we can, we will set aside time on the Webb to observe this weird and wonderful world.”

To learn more

The article “TOI-1452 b: SPIRou and TESS reveal a super-Earth in temperate orbit passing through an M4 dwarf” was published in The Astronomical Journal on August 12. In addition to Charles Cadieux, René Doyon, Étienne Artigau, Neil Cook, Farbod Jahandar and Thomas Vandal from iREx at the University of Montreal and Mykhaylo Plotnykov and Diana Valencia from the University of Toronto, the research team includes Nicolas B. Cowan (iREx, MSI, McGill, Canada); Björn Benneke, Stefan Pelletier and Antoine Darveau-Bernier (iREx, UdeM, Canada); Ryan Cloutier, former member of iREx (Harvard, USA); and 43 co-authors from Ontario, France, Brazil, United States, Japan, Spain, Switzerland, Portugal, Hungary, Germany and Crimea.

Media contacts

Marie-Eve Naud
Education and Public Awareness Coordinator
Institute for research on exoplanets
Montreal university
514-279-3222, marie-eve.naud@umontreal.ca

Nathalie Ouellette
Coordinator
Institute for research on exoplanets
Montreal university
nathalie.ouellette.2@umontreal.ca

Scientific contacts

Charles Cadieux
PhD student
Montreal university
514-503-0176, charles.cadieux.1@umontreal.ca

Rene Doyon
Professor, University of Montreal
Director, Institute for Research on Exoplanets
Director, Mont-Mégantic Observatory
514-349-5779, rene.doyon@umontreal.ca

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