TOI-1452b, an ocean planet near the planet Miller in the movie Interstellar
This oceanic planet seems to come out of the film Interstellar, an American science fiction film by director Christopher Nolan, released in November 2014: in 2067 the planet Earth is exhausted and humanity has 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 an Earth-like habitable planet there. The crew travels through a wormhole and ends up in another galaxy where they visit several planets, including Miller, an oceanic planet. The proximity of a black hole causes a lengthening of space-time so that on this planet one hour represents seven years.
The exoplanet TOI-1452b is not located near a black hole, but orbits a star of a binary system located in the constellation of the Dragon about one hundred light years from Earth. This planet is slightly larger in mass and size than the Earth. The temperature that reigns on its surface keeps the water in a liquid state and astronomers are convinced that it is completely covered with it.
The star around which the oceanic planet TOI-1452b orbits is much smaller than our Sun. The binary system consists of two similar stars that orbit each other, being separated by a small distance, on an astronomical scale, estimated at 97 astronomical units, or 14.5 billion kilometers.
The researchers managed to “get their hands on” this ocean planet using an instrument called PESTO which is located at the Mont-Mégantic Observatory in Canada.
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PESTO, a unique camera for searching for exoplanets
Astronomers at the institute for exoplanet research were helped by NASA’s TESS telescope, a small spacecraft launched in 2018 and dedicated to the search for exoplanets. This telescope, which operates according to the transit detection method, scans space continuously for periods of 27 days. In the case of TOI-1452b, TESS showed a drop in brightness every 11 days suggesting an exoplanet 70% larger than Earth.
PESTO is a camera attached to the 1.6m telescope of the Mont-Mégantic Observatory. It confirmed the nature of the signal sent by TESS. This camera is used to time the transits of exoplanets with great precision. It works in the visible red spectrum and works with a quick-reading charge transfer detector. The very high sampling rate of the PESTO signal, the zero reading noise and the absence of dead times between images allow timestamps down to the millisecond. The photometric accuracy of PESTO is such that no other camera of this quality exists anywhere else.
While the TESS telescope observes the two TOI-1452 stars as a single bright spot, the resolution of the PESTO camera is high enough to perfectly distinguish the two stars of this stellar pair. PESTO was then able to confirm that the oceanic planet TOI-1452b actually orbits the larger of the two stars, although their sizes are close.
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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 for the measurement of radial velocities on relatively low-mass stars. This device can also detect exoplanets orbiting low-mass stars.
After more than fifty hours of observation and analysis, SPIRou determined that the mass of TOI-1452b was about five times that of the Earth. This planet is probably a rocky planet, but due to its radius, mass and density, it is very different from our own 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 may be much richer in water. Furthermore, the low density of some 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 internal structure of the Earth.
A model of the internal structure of this oceanic exoplanet showed that water could represent up to 30% of its mass, i.e. an identical proportion to those that exist for some 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 of 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.
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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 Temperate Orbit Transit of a dwarf M4 “, The astrophysical diarypublished on 12 August 2022, https://iopscience.iop.org/article/10.3847/1538-3881/ac7cea