Astronomers discover an ocean planet completely covered in water

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

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

The exoplanet TOI-1452b is not located near a black hole, but instead orbits a star in a binary system that is located 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 that reigns on its surface keeps the water in a liquid state and astronomers are convinced that it is completely covered by it.

The star around which ocean planet TOI-1452b orbits is much smaller than our Sun. The binary system is made up of two similar stars that orbit around each other, being separated by a small distance, on an astronomical scale, estimated at 97 astronomical units, or 14.5 billion km.

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

(Also read: Two rocky planets the size of Earth discovered just 33 light years away)

PESTO, a unique camera for the search for exoplanets

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

Astronomers at the exoplanet research institute were helped by NASA’s TESS telescope, a small spacecraft launched in 2018 and dedicated to searching for exoplanets. This telescope, which operates according to the transit detection method, continuously scans space for periods of 27 days. For TOI-1452b, TESS showed a dip in brightness every 11 days, suggesting an exoplanet 70% larger than Earth.

PESTO is a camera attached to the 1.6m telescope at the Mont-Mégantic Observatory. He confirmed the nature of the signal sent by TESS. This camera is used to time exoplanet transits with great precision. It operates in the red visible spectrum and is powered by a fast-reading charge transfer detector. The very high sampling rate of the PESTO signal, the zero read noise and the absence of dead times between images allow timestamps of up to milliseconds. The photometric precision of PESTO is such that there is no other camera of this quality anywhere else.

While the TESS telescope observes the two stars TOI-1452 as a single bright point, the resolution of the PESTO camera is high enough to perfectly distinguish the two stars of this stellar pair. Thus, PESTO was able to confirm that ocean planet TOI-1452b orbits the larger of the two stars, even though their sizes are similar.

(Also read: They discover a super-earth in the habitable zone of their star)

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 the measurement of radial velocities in 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 around 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. In addition, 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, lighter than those that make up the internal structure of the Earth.

A model of the internal structure of this oceanic exoplanet has shown that water could represent up to 30% of its mass, that is, a proportion identical to that which exists 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 in-depth observation and analysis by the James Webb Telescope. It’s close enough for astronomers to study its atmosphere, and it’s in a region 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)

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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 Warm Orbit Transiting a M4 Midget”, the astrophysical journalpublished August 12, 2022, https://iopscience.iop.org/article/10.3847/1538-3881/ac7cea

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