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Rare exoplanet 245 light-years away could be a massive water world

An illustration of a distant exoplanet. Depositphotos.

Astronomers have discovered a rare exoplanet located 245 light-years away from us, and it could potentially be a massive water world.

TOI-733b, a rare exoplanet 245 light-years away, may hold the key to understanding the puzzling gap in exoplanet sizes between super-Earths and mini-Neptunes.

A Planetary Mystery: The Small Planet Radius Valley

A team of astronomers led by Iskra Georgieva from Chalmers University of Technology in Sweden believes that TOI-733b, an exoplanet with a radius just under twice that of Earth, could help solve a curious gap in the exoplanet record. This gap exists between the sizes of super-Earths, which have up to 1.5 Earth radii, and mini-Neptunes, which have over 2 Earth radii.

TOI-733b’s Characteristics and Potential for Atmospheric Loss

Orbiting a star slightly smaller than the Sun with a period of 4.9 days, TOI-733b’s measurements indicate that it may have lost its atmosphere or be an ocean-covered water world. The heat from its closely orbiting star might be evaporating the exoplanet’s atmosphere, possibly leading to its eventual transformation into a small, bare rock.

Shrinking Mini-Neptunes and the Role of Stars

Recent evidence suggests that shrinking mini-Neptunes may be the reason for the small planet radius valley. These worlds lose their atmospheres under their stars’ intense heat, becoming smaller, stripped cores. However, it remains unclear whether mass loss is driven by the star or an internal process resulting from heat escaping the exoplanet’s core.

Exploring Exoplanets within the Radius Valley

Exoplanets within the radius valley are essential for unlocking this mystery. By analyzing a significant number of worlds undergoing this process, planetary astronomers can better understand the strange gap in exoplanet sizes. Georgieva and her team used data from NASA’s TESS telescope and the HARPS spectrograph to measure TOI-733b’s characteristics.

TOI-733b’s Density and Possible Composition

With a density of 3.98 grams per cubic centimeter, TOI-733b’s composition remains uncertain. The team’s modeling suggests that if the exoplanet once had a Neptune-like atmosphere of hydrogen and helium, it has likely already lost it. It might have reformed a secondary atmosphere of heavier elements, or it could be an ocean world with an atmosphere rich in water vapor.

Awaiting the Next Generation of Telescopes

Unfortunately, TOI-733b is not ideal for probing its atmosphere using current technology. We will have to wait for the next generation of telescopes to unveil TOI-733b’s secrets. However, this research indicates that studying this rare exoplanet will be crucial for understanding planet formation and evolution.

It is worth mentioning that a 2019 study published in the Proceedings of the National Academy of Sciences strengthens the argument that water worlds are prevalent throughout the Milky Way. Harvard University astronomer Li Zeng and his team used computer simulations to reveal new findings, suggesting that sub-Neptune-sized planets, with radii two to four times Earth’s, are more likely to be water worlds rather than gas dwarfs enveloped by dense atmospheres, as previously thought.