MONTREAL — Astronomers have identified a distant world that could rewrite understanding of planetary composition: an exoplanet potentially made up of as much as 30 percent water by mass, a staggering fraction that dwarfs Earth's meager water content and suggests a globe-spanning ocean hundreds of kilometers deep with no continents in sight.

The candidate, known as TOI-1452 b, orbits a small red dwarf star about 100 light-years away in the constellation Draco. Discovered by a team led by researchers at the Université de Montréal, the super-Earth is roughly 70 percent larger than our planet and nearly five times as massive. Its density, however, points to something extraordinary: a water-rich interior far beyond anything found in our solar system.

Ocean Planet 30% Water by Mass? 'Can't Even Compare to
Ocean Planet 30% Water by Mass? 'Can't Even Compare to Earth'—What Is TOI-1452 b?

Charles Cadieux, the lead researcher, described it as "one of the best candidates for an ocean planet that we have found to date." Interior modeling by experts at the University of Toronto suggests water could account for 22 to 30 percent of the planet's total mass, depending on assumptions about its rocky core composition. By contrast, Earth's oceans, despite covering 70 percent of the surface, represent less than 0.1 percent — often cited as roughly 0.02 percent — of the planet's mass.

"That's why we say it can't even compare to Earth," one astronomer noted in recent discussions of the find. "This isn't a planet with some water on it. This could be a true water world."

Discovery and key measurements

The planet was first flagged by NASA's Transiting Exoplanet Survey Satellite (TESS), which detected periodic dips in the host star's brightness as TOI-1452 b passed in front. Follow-up observations with ground-based telescopes and high-precision radial velocity measurements from instruments like SPIRou at the Canada-France-Hawaii Telescope helped pin down its mass and radius.

Those numbers — a radius of about 1.67 times Earth's and a mass of roughly 4.82 Earth masses — yield a density consistent with a substantial water component. Pure rock would be too dense; a thick hydrogen-helium atmosphere alone would make it puffier. A water-rich world fits the data best.

The planet orbits its cool M-dwarf star every 11 days at a distance that places it in the habitable zone, receiving about 1.8 times the stellar radiation Earth gets from the Sun. Equilibrium temperature calculations suggest a blackbody value around 326 Kelvin (about 53 degrees Celsius or 127 degrees Fahrenheit), warm enough for liquid water but dependent on the thickness and composition of any atmosphere.

What would a 30% water planet look like?

Imagine a world with no landmasses whatsoever — just a global ocean stretching pole to pole. On TOI-1452 b, that ocean could be hundreds of kilometers deep. At such pressures, water near the bottom would transition into exotic high-pressure ice phases, even while the surface remains liquid. A thick water-vapor or hydrogen-rich atmosphere might shroud the planet, potentially creating a steamy greenhouse effect.

Unlike Earth's thin veneer of oceans sitting atop a rocky crust and mantle, this planet's water would be a fundamental building block of its bulk composition. Some models allow for a small rocky core surrounded by a vast water mantle, while others suggest a more homogeneous mix. In either case, the sheer volume of water sets it apart dramatically from terrestrial planets.

Recent studies have tempered enthusiasm for so-called "Hycean" worlds — hydrogen-rich atmospheres over deep oceans — suggesting that chemical interactions between magma oceans and atmospheres may limit surface water to just a few percent in many cases. Yet TOI-1452 b remains a standout candidate because its measured density aligns so well with high water content without requiring extreme atmospheric assumptions.

Implications for habitability and planet formation

Liquid water is considered essential for life as we know it, making ocean planets intriguing targets in the search for extraterrestrial biology. A global ocean could provide vast chemical mixing grounds, though challenges abound: lack of exposed rock for mineral nutrients, potential high-pressure ice barriers isolating the seafloor, and uncertain atmospheric chemistry.

The James Webb Space Telescope (JWST) has already been pointed at similar candidates, and TOI-1452 b ranks high on observing lists for atmospheric characterization. Future spectra could reveal water vapor, oxygen, or biosignature gases, though distinguishing between a steamy atmosphere and a true surface ocean remains technically demanding.

The discovery also informs how planets form. Water-rich worlds likely accrete icy material beyond the snow line in their protoplanetary disks before migrating inward. Red dwarf systems, abundant in the galaxy, may be particularly prone to producing such planets due to their long lifetimes and compact habitable zones.

Some researchers caution that true 30-percent water worlds may be rarer than once thought, with recent modeling showing that interior-atmosphere interactions can destroy much of the accreted water. Still, TOI-1452 b stands as compelling evidence that diverse compositions exist beyond the rocky-gas dichotomy familiar from our solar system.

Comparison to other ocean world candidates

TOI-1452 b joins a short but growing list of potential water worlds. Kepler-138 c and d, observed with Hubble, also show low densities suggestive of water. K2-18 b, a sub-Neptune 124 light-years away, has drawn attention for possible water vapor and even controversial hints of dimethyl sulfide, a potential biosignature, though its classification as a true ocean planet or mini-Neptune remains debated.

What makes TOI-1452 b special is its position: small enough to be rocky or watery rather than gaseous, yet with density pointing strongly toward water, and close enough at 100 light-years for detailed follow-up.

Broader context in exoplanet science

As of 2026, thousands of exoplanets have been confirmed, with TESS and JWST accelerating discoveries. The "radius valley" — a gap in planet sizes between super-Earths and mini-Neptunes — may partly result from water worlds losing atmospheres or retaining thick water layers. Understanding TOI-1452 b could help solve such puzzles.

The find underscores how alien many exoplanets are. While science fiction often depicts Earth-like worlds with blue oceans and green continents, reality may favor endless water globes, lava worlds, or diamond rain planets. Each new candidate expands the imagination of what habitable environments might look like.

For now, TOI-1452 b remains a strong but unconfirmed ocean planet. Definitive proof would require atmospheric data showing liquid water signatures or refined interior models. Astronomers worldwide are eager for JWST time to probe its secrets.

As one scientist put it, "We thought we knew what planets look like. Then we found worlds that are basically giant water drops floating in space. The universe keeps surprising us."

The quest continues, with TOI-1452 b serving as a beacon for the next generation of exoplanet hunters. Whether it hosts exotic life beneath its waves or simply teaches us about planetary diversity, this distant ocean world reminds us how little we still know about the cosmos — and how much more there is to discover.

Key Facts About TOI-1452 b

  • Distance: ~100 light-years
  • Size: ~1.67 Earth radii
  • Mass: ~4.82 Earth masses
  • Water content estimate: Up to 30% by mass
  • Orbital period: 11.06 days
  • Host star: Cool red dwarf (M4 type)
  • Status: Prime candidate for deep global ocean; JWST observations pending

With ongoing observations and improving models, answers about this enigmatic water world may arrive within the next few years, potentially reshaping our view of habitable planets across the galaxy.