Article by: Andacs Robert Eugen, on 03 September 2022, at 10:26 am Los Angeles time

An exoplanet just 100 light-years from Earth appears to be the best candidate yet for a world completely covered in water. It was named TOI-1452b by the researchers, and measurements of its size and mass suggest a density profile consistent with a surface-wide liquid ocean. 

Scientists believe that such worlds are possible, but have yet to find one to prove it. It is quite easy to understand why TOI-1452b has not been detected until now, despite its relative proximity to the Solar System.

The exoplanet was discovered in the orbit of one of the close binary pairs of small and faint red dwarfs, separated by a distance of only 97 astronomical units. So little that the two stars appear to be one. 

However, the TESS telescope is sensitive enough to regularly detect faint variations in starlight that indicate that an object regularly passes between us and the host star. Observations have shown that there is indeed an exoplanet orbiting one of the stars in the TOI-1452 binary. 

By observing how much light the star emits and how much it darkens when the exoplanet passes in front of it, the researchers were able to determine that the exoplanet is relatively small, 1.672 times the size of Earth - what we call a "super-Earth". 

It is in an orbit that appears extremely close to us, with our relatively "lazy" 365-day orbit. However, because the star is so cold and faint compared to the Sun, the exoplanet is in the middle of the star's temperate zone. It is not so far from the star that the liquid water on its surface freezes, nor so close that the water evaporates under the star's heat.

Once they had the size and mass of an object, astronomers could deduce its average density. For TOI-1452b, this density is 5.6 grams per cubic centimeter, which is very close to Earth's density of 5.5 grams per cubic centimeter. 

But an Earth-like density for an object that has more mass indicates that the object is composed of lighter material, the researchers said. They determined that up to 30% of its mass could be water. For comparison, water makes up less than 1 percent of Earth's mass. 

However, with only the measurement tools we have, it is impossible to determine the exact composition of TOI-1452b. If, however, TOI-1452b is a water-covered world, the James Webb Telescope is the best chance to find it. 

"Our observations with the Webb telescope will be critical to better understanding TOI-1452b," says astronomer René Doyon of the University of Montreal. "As soon as we can, we will use Webb to observe this strange and wonderful world."