Is mystery of shrinking exoplanets solved? Data from NASA reveals new details

A recent study utilising data from NASA's retired Kepler Space Telescope has provided insights into the enigma of disappearing atmospheres and shrinking sizes of certain exoplanets. Researchers believe they may have identified a potential explanation for the "missing" planets falling between the size range of super-Earths and sub-Neptunes.

Exoplanets exist outside our solar system and exhibit diverse sizes, ranging from rocky planets to gas giants. In between, there are rocky super-Earths and sub-Neptunes. But there also exists a noticeable void, a "size gap."

NASA'sJet Propulsion Laboratory said that there is a "conspicuous absence" or a “size gap” of planets that are 1.5 to 2 times Earth's size. This has left scientists puzzled.

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However, the leadauthor of the new study in The Astronomical Journal and Caltech/IPAC research scientist Jessie Christiansen said that “scientists have now confirmed the detection of over 5,000 exoplanets, but there are fewer planets than expected with a diameter between 1.5 and 2 times that of Earth."

“Exoplanet scientists have enough data now to say that this gap is not a fluke. There’s something going on that impedes planets from reaching and/or staying at this size," Christiansen added.

Scientists have dedicated efforts to unravel the mysteries surrounding this absence and gain a deeper understanding of the planetary system.

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So what is behind the shrinking of exoplanets?

The study proposed that some sub-Neptunes lose their atmospheres, causing them to shrink. The leading explanations for this atmospheric loss are core-powered mass loss and photoevaporation. The researchers have uncovered new evidence supporting the theory of core-powered mass loss as a potential mechanism behind the shrinking of these planets.

Core-powered mass loss involves radiation from a planet's hot core gradually pushing its atmosphere away over time, eventually shrinking it. In contrast, photoevaporation occurs when a planet's atmosphere is eroded by the intense radiation from its host star.

The study suggested that core-powered mass loss occurs later in a planet's life, around 1 billion years, while photoevaporation is more likely to happen within the first 100 million years.

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Observations of star clusters

The researchers focused on star clusters Praesepe and Hyades, aged between 600 million and 800 million years.

By analysing these clusters, the team concluded intheir findings that core-powered mass loss is a more plausible reasoning for these "missing" exoplanets.

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While the study provides valuable insights, the researchers said that the understanding of photoevaporation and core-powered mass loss is an evolving field.

(With inputs from agencies)