An ocean exoplanet 100 light years from Earth

TOI-1452 b is an exoplanet located 100 light-years from Earth in the constellation Dragon. Initially spotted by NASA’s Transiting Exoplanet Survey Satellite (TESS) telescope, it was later observed using some of the most advanced instruments on the ground. It appears from these new observations that the planet could be an “ocean world”, that is to say an object whose surface is covered almost entirely by a vast and deep layer of water. Its identification makes it a target of choice for the James Webb Space Telescope, whose first results far exceed the expectations of astronomers.

A planet in a binary system

It is therefore the TESS space telescope, which regularly observes the entire celestial vault, in search of planetary systems close to ours, which put researchers on the trail of this exoplanet. It is indeed designed to observe the tiny drops in luminosity caused by the passage of a planet in front of its star, a transit in astronomical terms. That of TOI-1452 takes place every 11 days and corresponds to an exoplanet about 70% larger than Earth. For TESS, the star TOI-1452 appears as a single light source: it is actually a binary whose two members are stars smaller than the Sun which are separated by 97 astronomical units, or about two and a half times the distance between the Sun and Pluto.

This is the PESTO instrument, installed on theMont-Mégantic Observatory, in Quebec, which resolved the two stars and confirmed the presence of the exoplanet, orbiting the larger of the two. Observations later confirmed by a Japanese team.

SPIRou and PESTO to the rescue

To determine the mass of the planet, the researchers then observed the system with SPIRou, an instrument installed on the Canada-France-Hawaii telescope. It is an infrared spectropolarimeter which measures, by Doppler effect, the minute variations in the speed of stars induced by the planets which revolve around them. After fifty hours of observation, the team led by Charles Cadieux, from the University of Montreal, succeeded in establishing a measurement. TOI-1452 b would have a mass about 5 times that of Earth. Other parameters, listed in an article published in The Astronomical Journalindicate that it is a rocky planet but “its radius and mass suggest a much lower density than one would expect for a planet composed mostly of metal and rock, like Earth“explains the astronomer, in a press release.

Although Earth is called the “Blue Planet”, it actually harbors very little water: less than 1% of its mass. Other stars contain much more, including in the solar system such as the satellites of Jupiter (Ganymede and Callisto) or Saturn (Titan and Enceladus). The precious liquid would constitute there up to 30% of the mass and would also be the case of TOI-1452 b. Let us add that the exoplanet is located in the habitable zone of its star, that is to say that its surface temperature allows the presence of liquid water: it could therefore be an ocean planet, a star which would be completely covered by a deep body of water.

Artistic representation of the surface of TOI-1452 b. Credits: Benoît Gougeon, University of Montreal.

To date, several other candidate planets are likely to possess the same supposed characteristics as TOI-1452 b. But the latter has other advantages that designate it for future complementary studies: it is relatively close to the Sun (100 ly) and above all its position in the sky means that it can be observed optimally by the James Webb telescope. The NASA machine is powerful enough to be able to carry out analyzes of its atmosphere, which will make it possible to confirm the oceanic character of the star. However, its observation is not yet scheduled, the slots for using the telescope being very difficult to obtain…

Leave a Comment