This newly discovered giant Earth may be an ocean planet shrouded in the deep sea

Scientists announced this week that the James Webb Space Telescope, which among its many talents can analyze the atmospheres of exoplanets, has just confirmed the presence of carbon dioxide in a world orbiting the sun 700 light-years away. It is the first observation of carbon dioxide in the planetary atmosphere outside our solar system.

But this discovery, made about a world very different from our own, is just the first taste of what Web tools may soon reveal. Astronomers are eager to focus the telescope on planets like Earth, where liquid water, an essential ingredient for life as we know it, is abundant. In the coming months and years, they will undoubtedly get their chance.

There are a number of promising Earth-like planets that Webb could study in the near future, but in a research paper recently published in Astronomical Journalscientists from the University of Montreal argue that they have discovered one of the best candidates to date.

The planet, which orbits a star in the binary system TOI-1452, is 100 light-years away. It’s about 70% larger than Earth – a type of exoplanet called a super-Earth – and orbits in a region scientists call the habitable zone where liquid water is possible. Even more exciting, however, is the fact that the density of the planet indicates the existence of a global ocean.

water world

Scientists first spied TOI-1452 b in data collected by the TESS space telescope. The team also confirmed the existence of the planet and identified key features through ground-based observations. By measuring how much a star orbiting a planet wobbles, researchers can estimate its mass, while analyzing how much light it blocks as it moves between its star and Earth gives estimates of its size.

TOI-1452 b orbits a red dwarf star that is smaller and lighter than our Sun. Therefore, while the planet is in a narrow orbit relative to the Earth – it completes a circle around its star every 11 days – it receives the same amount of solar radiation as Venus. This makes it smack in the middle of the habitable zone. If we consider its surprisingly low density, the leading theory is that TOI-1452 b is a water world.

One model in the study estimated that water could make up 30 percent of the planet’s mass. By comparison, water covers 70 percent of the Earth’s surface but only 1 percent of its mass. So if the model proves accurate, the entire surface of TOI-1452 b could be covered by a global ocean much deeper than any ocean on Earth.

“TOI-1452 b is one of the best candidates for an ocean planet we’ve discovered so far,” said Charles Kedio, an astronomer at the University of Montreal and lead author of the new research paper. “Its radius and mass indicate a much lower density than one might expect for a planet composed primarily of metal and rock, such as Earth.”

The keyword is filter. The data leaves plenty of room for uncertainty as to whether TOI-1452 is in fact an ocean planet. The paper also explores scenarios in which the world is rocky without an atmosphere or rocky with an extended atmosphere of light gases such as hydrogen and helium. The only way to be sure is to have a look.

Next blue marble

When light shines through the atmosphere of an exoplanet, the characteristic wavelengths are absorbed by different chemical components. The resulting spectrum is similar to a fingerprint of the chemical composition of the atmosphere, with the gaps announcing the presence of various elements such as hydrogen and helium or molecules such as water vapor. Until now, our ability to directly analyze the atmospheres of exoplanets, especially those around smaller planets, has been limited.

But with Webb, humanity has a new pair of glasses that are more than fit for the job. In addition to the physical properties of TOI-1452 b, the planet is relatively close to Earth, and its position in the sky is available for year-round observation. Scientists say they hope to book time on the telescope soon to directly confirm or reject their hypothesis.

Whether this particular planet is outside is somewhat off topic. Even more exciting is our new ability to peek into the atmospheres of a list of promising planets light-years away. It’s entirely possible that scientists will soon locate and confirm the location of an ocean world orbiting another star: the first blue marble outside our solar system.

From there, we might find more balls, and while Webb wasn’t explicitly designed to detect biosignatures – the chemical fingerprints of life itself – upcoming telescopes will. These include the Giant Earth-based Magellan Telescope, the Thirty Meter Telescope, and the European Very Large Telescope.

As the Rolodex of confirmed ocean planets grows, so does the list of promising targets for future telescopes to train their eyes on, and in what will undoubtedly be a world-shaking discovery, we may finally spy the first signs of life in loneliness. Empty.

Image Credit: Benoit Gougeon, University of Montreal

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