‘Ocean planet’ discovered by Canadian research team

An international team of researchers has announced the discovery of TOI-1452 b, an exoplanet orbiting one of two small stars in a binary system located in the Draco constellation about 100 light-years from Earth.

The exoplanet is slightly greater 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 liquid water to exist on its surface. The astronomers believe it could be an “ocean planet” completely covered by a thick layer of water, similar to some of Jupiter’s and Saturn’s moons.

René Doyon, Université de Montréal Professor and Director of the Institute for Research on Exoplanets (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.

“It is thanks to the OMM, a special instrument designed in our labs called SPIRou, and an innovative analytic method developed by our research team, that we were able to detect this one-of-a-kind exoplanet.”

It was NASA’s space telescope TESS, which surveys the entire sky in search of planetary systems close to our own that put the researchers on the trail of this exoplanet. Based on the TESS signal, which showed a slight decrease in brightness every 11 days, astronomers predicted a planet about 70% larger than Earth.

Lead researcher Charles Cadieux, a PhD student at the Université de Montréal and member of iREx, 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 really caused by an exoplanet circling TOI-1452, the largest of the two stars in that binary system.”

The host star TOI-1452 is much smaller than our Sun and is one of two stars of similar size in the binary system. The two stars orbit 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 sees them as a single point of light. But 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.

The exoplanet TOI-1452 b is probably rocky like Earth, but its radius, mass, and density suggest a world that is very different. Earth is essentially a very dry planet because although about 70% of its surface is covered by ocean, water actually only makes up a negligible fraction of its mass — less than 1%.

But water may be much more abundant on some exoplanets. In recent years, astronomers have identified and determined the radius and mass of many exoplanets with a size between that of Earth and Neptune (about 3.8 times larger than Earth). Some of these planets have a density that can only be explained if a large fraction of their mass is made up of lighter materials than those that make up the internal structure of the Earth such as water. These hypothetical worlds have been dubbed “ocean planets.”

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