In a groundbreaking discovery, scientists believe they have identified a new exoplanet that may be entirely covered in water. While some of the moons belonging to Jupiter and Saturn are thought to be water-based, no such planets have yet been confirmed. This new planet is one of the most likely candidates to date.

Scientists have discovered more than 5,000 exoplanets, according to NASA, each one novel in its own way. An exoplanet is any planet that does not orbit the Sun. It can be challenging to discover exoplanets from Earth, as the light of these planets’ own stars can block them out. In an effort to locate more such planets, NASA and MIT collaborated to launch the Transiting Exoplanet Survey Satellite (TESS) in 2018, which was specifically designed to identify new planets for study.

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It was a signal from TESS that first alerted astronomers to the presence of the new potential water world, dubbed TOI-1452 b. The planet orbits a solar system with two stars, which is a relatively near neighbor at only about 100 light-years from Earth in the Draco constellation. Charles Cadieux, a Ph.D. student at the Université de Montréal and member of the Institute for Research on Exoplanets (iREx), belongs to a group of astronomers that follows up on potential planets identified by TESS. In an article published in The Astronomical Journal, Cadieux and his team revealed that the planet is roughly 70 percent larger than Earth. Most excitingly, it is what’s known as a “Goldilocks” planet, meaning it is the ideal distance from its star to be habitable and to contain water in liquid form.

The Universal Search For Water

Artistic representation of the surface of TOI-1452 b, which could be an “ocean planet”, i.e. a planet entirely covered by a thick layer of liquid water.
Artistic representation credit: Benoit Gougeon, Université de Montréal.

TOI-1452 b was discovered because its stars dimmed, slightly, every eleven days. While a dimming star can suggest a massive explosion, this blip suggested a satellite of some sort in a regular orbit, obscuring the star’s light in rhythm. Such observations can reveal the existence of a planet, but alone they offer little insight into its makeup. To learn that the new exoplanet may be a water world, scientists had to estimate its mass through exhaustive observation. Rocky, metallic planets like Earth are extremely dense, but some planets are significantly less so. The only explanation is that such planets are made up of lighter materials, such as water.

While 70 percent of Earth’s surface is covered by water, our planet is nevertheless considered “dry.” Despite the surface area, water only makes up 1 percent of the planet’s mass, whereas an ocean planet would more closely resemble the one famously depicted by Interstellar. In a conversation with the Insitut de Recherche Sur Les Exoplanètes, Cadieux noted that TOI-1452 b is so likely to be an ocean planet because "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."

The next step is to attempt to take direct images of the new exoplanet to confirm its composition. As a rare planet, situated in the temperate zone and likely made of water, it’s of great interest to astronomers worldwide. The discovery team intends to book time to observe the TOI-1452 b exoplanet with the James Webb Space Telescope as soon as possible, to hopefully reveal a watery world not so distant from our own.

Source: The Astronomical Journal, iREx