Astronomers Discover ‘Water World’ Perfect for Observation With Webb Telescope

The James Webb Space Telescope has already offered some stunning images of galaxies and nebulae, but NASA also hopes to take a peek at exoplanets with Webb’s powerful optics. Astronomers from the Université de Montréal may have just found the perfect target. The newly discovered exoplanet is nearby in astronomical terms, and the team believes it may be an Earth-sized “water world” with a globe-spanning ocean — something that we might be able to confirm with future Webb observations.

The first hint of TOI-1452 b came from NASA’s Transiting Exoplanet Survey Satellite (TESS). This successor to the late, great Kepler Space Telescope watches the sky for evidence of exoplanet transits in front of distant stars. TESS identifies periodic dips in luminance that could be indicative of an exoplanet, and that’s what it saw in TOI-1452, a binary red dwarf system just 100 light years away.

TESS is geared toward observing lots of stars at once, so it doesn’t have enough resolution to confirm exoplanets on its own — to TESS, TOI-1452 is just a single point of light. The Université de Montréal team, led by Ph.D. student Charles Cadieux, turned to the Observatoire du Mont-Mégantic and a camera system called PESTO (extra-solar planets in transit and occultation, in French) to get a closer look at the solar system. They now report that TOI-1452 b is indeed an exoplanet orbiting the larger of the two binaries every 11 days. It’s close enough to the star, which is cooler than our own, for water to exist in liquid form.

After confirming the signal was an exoplanet, it was time to learn everything possible about its properties. Using the SPIRou spectrograph housed in Hawaii, Cadieux and his team spent 50 hours scanning TOI-1452 b and have determined that it’s probably about five times Earth’s mass, but its density appears to be lower than Earth’s. Whereas Earth is only about one percent water, TOI-1452 b could be one giant ocean accounting for 30 percent of its mass. “TOI-1452 b is one of the best candidates for an ocean planet that we have found to date,” said Cadieux. “Its radius and mass suggest a much lower density than what one would expect for a planet that is basically made up of metal and rock, like Earth.”

This is not a sure thing, though. It’s also possible that TOI-1452 b could be a Neptune-like gas giant with a diffuse, cloudy atmosphere. Only future observations will be able to answer that, and there’s good news on that front. Because this exoplanet is fairly close to Earth, it could be a prime candidate for observation with Webb. It orbits close to its parent star, and this could allow Webb to capture a spectrum of starlight shining through its atmosphere. In yet another stroke of luck, TOI-1452 b is in a part of the sky Webb can see year-round. Webb investigator René Doyon (also at the University of Montreal) says he plans to book time on the telescope to observe TOI-1452 b as soon as possible.

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