Astronomers discovered an exoplanet that could be covered entirely in water

An extrasolar world covered in water?

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An international team of researchers led by Charles Cadieux, a Ph.D. student at the Université de Montréal and member of the Institute for Research on Exoplanets (iREx), has discovered an exoplanet called TOI-1452 b, that is believed to be an ocean planet. The exoplanet is slightly greater in size and mass than Earth.

Located in the Draco constellation, about 100 light-years from Earth, the exoplanet orbits its star called TOI-1452. The distance between the star and planet is such that its temperature would be neither too hot nor too cold for liquid water to exist on its surface. According to astronomers, TOI-1452 b is a planet completely covered by a thick layer of water, like those of Jupiter’s and Saturn’s moons.

René Doyon, Université de Montréal Professor and Director of iREx and of the Observatoire du Mont-Mégantic (OMM) said, “I’m extremely proud of this discovery because it shows the high calibre of our researchers and instrumentation. Thanks to the OMM, a special instrument designed in our labs called SPIRou, and an innovative analytic method developed by our research team, we were able to detect this one-of-a-kind exoplanet.”

The host star TOI-1452 is much smaller than our Sun and is one of two similar size stars in a binary system. The two stars orbit each other and are separated by such a small distance — 97 astronomical units.

NASA’s TESS detected the exoplanet. Based on the TESS signal, which showed a slight decrease in brightness every 11 days, astronomers predicted a planet with a diameter about 70% larger than Earth’s.

For follow-up observations, astronomers used PESTO, a camera installed on the OMM’s telescope.

Cadieux said, “The OMM played a crucial role in confirming the nature of this signal and estimating the planet’s radius. This was no routine check. We had to make sure the signal detected by TESS was caused by an exoplanet circling TOI-1452, the largest of the two stars in that binary system.”

“PESTO’s resolution is high enough to distinguish the two objects, and the images showed that the exoplanet does orbit TOI-1452, which was confirmed through subsequent observations by a Japanese team.”

Astronomers later used SPIRou, an instrument installed on the Canada-France-Hawaii Telescope in Hawai’i, to determine the planet’s mass. After more than 50 hours of observation, it was estimated that the planet has nearly five times the mass of Earth.

The exoplanet TOI-1452 b is believed to be a rocky world like Earth, but its radius, mass, and density suggest it differs from ours.

Researchers Étienne Artigau and Neil Cook, also with iREx at the Université de Montréal, played a crucial role in analyzing the data. They developed a powerful analytic method capable of detecting the planet in the data collected with SPIRou.

Artigau said“The LBL method [for line-by-line] ] allows us to clean the data obtained with SPIRou of many parasite signals and to reveal the weak signature of planets such as the one discovered by our team.”

Cadieux said, “TOI-1452 b is one of the best candidates for an ocean planet we have found. Its radius and mass suggest a much lower density than expected for a planet made up of metal and rock, like Earth.”

The University of Toronto’s Mykhaylo Plotnykov and Diana Valencia are specialists in exoplanet interior modeling. Their analysis of TOI-1452 b shows that water may make up as much as 30% of its mass.

Journal Reference:

  1. Charles Cadieux, René Doyon et al. TOI-1452 b: SPIRou and TESS Reveal a Super-Earth in a Temperate Orbit Transiting an M4 Dwarf. The Astronomical Journal 164 96. DOI: 10.3847/1538-3881/ac7cea

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