Astronomers discover a sea planet completely covered in water

TOI-1452b, an ocean planet close to the planet Miller in the movie Interstellar

This sea planet seems straight out of the movie Interstellar, an American science fiction film by director Christopher Nolan, released in November 2014: In 2067, the planet Earth is exhausted and humanity is plunged into a terrible food crisis. The Space Shuttle Ranger leaves Earth and docks with the Endurance spacecraft to explore a new solar system in hopes of finding a habitable Earth-like planet there. The crew traverses a wormhole and ends up in another galaxy, where they visit several planets, including Miller, a sea planet. The proximity of a black hole causes a stretching of space-time, so that one hour on this planet represents seven years.

The exoplanet TOI-1452b is not located near a black hole, but orbits a star in a binary system, which is in the constellation of the Dragon about a hundred light years from Earth. This planet is slightly larger in mass and size than Earth. The temperature prevailing at the surface keeps the water in a liquid state, and astronomers are convinced that it is completely covered by it.

The star that the ocean planet TOI-1452b orbits is much smaller than our sun. The binary system consists of two identical stars orbiting each other, separated by a small distance on an astronomical scale, estimated at 97 astronomical units or 14.5 billion kilometers.

Scientists have managed to “get their hands on” this ocean planet using an instrument called PESTO, which is located at the Mont-Mégantic Observatory in Canada.

(Also read: Two Earth-sized rocky planets discovered just 33 light years away)

PESTO, a unique camera for the search for exoplanets

NASA’s TESS telescope has provided the first information about the exoplanet TOI-1452b. Source: Dotted Yeti/Shutterstock

Astronomers at the Institute for Exoplanet Research were aided by NASA’s TESS telescope, a small spacecraft launched in 2018 dedicated to searching for exoplanets. This telescope, which operates according to the transit detection method, scans space continuously over periods of 27 days. In the case of TOI-1452b, TESS showed a decrease in brightness every 11 days, suggesting an exoplanet 70% larger than Earth.

PESTO is a camera mounted on the Mont-Mégantic Observatory’s 1.6m telescope. It confirmed the nature of the signal sent by TESS. This camera is used to time the transits of exoplanets with great precision. It operates in the red visible spectrum and works with a fast-reading charge transfer detector. The very high sampling rate of the PESTO signal, zero read noise and the absence of dead times between frames allow timestamps down to the millisecond. The photometric precision of PESTO is such that no other camera of this quality can be found anywhere else.

While the TESS telescope observes the two stars TOI-1452 as a single point of light, the resolution of the PESTO camera is high enough to perfectly distinguish the two stars from this star pair. PESTO was therefore able to confirm that the ocean planet TOI-1452b does indeed orbit the larger of the two stars, even though their sizes are close.

(Also read: A super-Earth discovered in its star’s habitable zone)

A rocky planet with a fairly low density

To determine the mass of this oceanic exoplanet, the researchers used SPIRou, a spectropolarimeter that operates in the infrared spectrum and allows measurements of radial velocities on relatively low-mass stars. This device can also detect exoplanets orbiting low-mass stars.

After more than fifty hours of observations and analysis, SPIRou determined that TOI-1452b’s mass was about five times that of Earth. This planet is probably a rocky planet, but due to its radius, mass and density, it is very different from our planet. On Earth, water covers about 70% of the globe’s surface, but this amount ultimately represents only 1% of its mass. According to astronomers, some exoplanets could be much richer in water. Moreover, the low density of certain exoplanets such as TOI-1452b can only be explained by the presence of a large amount of materials such as water, which are lighter than those that make up the inner structure of the Earth.

A model of the internal structure of this oceanic exoplanet has shown that water may represent up to 30% of its mass, i.e. a proportion identical to those found for certain natural satellites of Jupiter, such as Ganymede and Callisto or even Titan and Enceladus for Saturn.

This exoplanet is currently one of the best candidates for observation and in-depth analysis by the James Webb telescope. It’s close enough for astronomers to study its atmosphere, and it’s in an area of ​​the sky where it can be studied every day of the year.

(Also read: Binary star: the new target for the search for extraterrestrial life)

Source:

Charles Cadieux, René Doyon, Mykhaylo Plotnykov, Guillaume Hébrard, Farbod Jahandar, Étienne Artigau, Diana Valencia, Neil J. Cook, Eder Martioli, Thomas Vandal, “TOI-1452 b: SPIRou and TESS Reveal a Super-Earth in a Temperate Orbit Transit an M4 midget”, The Astrophysical Journalpublished 2022 August 12, https://iopscience.iop.org/article/10.3847/1538-3881/ac7cea

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