Are planets mysteriously shrinking? Scientists may have found the reason

In a recent study, astronomers used data from NASA’s Kepler Space Telescope. Explaining why so many giant exoplanets are shrinking and turning into rocky super-EarthsTheir mass is greater than that of our planet, but smaller than the gas giants Neptune and Jupiter.

Research published in The Astronomical Journal suggests: Atmospheric mass loss is responsible for the contraction process. But these atmospheres are not taken over by stellar winds or any external factors, but rather are expelled by internal processes: The cores of these planets attract layers of gas.

The process of air loss occurs normally on all planets. For example, in the case of Earth, Every day we lose approximately 90 tonnes of air from the protective covering of life on the planet. This is because our atmosphere is heated by the Sun. However, this loss occurs at a very slow pace that, according to scientists, will ensure our survival for at least 15 billion years.

Studying outer planets

The lead author of the new study, Jessie Christiansen, scientific leader of the NASA Exoplanet Archive, confirmed in a statement using data from the Kepler 2 probe, which ended its operations in 2018, that more than 5,000 exoplanets had been detected. researcher, “There are fewer planets than expected and are between 1.5 and 2 times the diameter of Earth.”

What prevented planets from reaching and/or remaining these sizes was what motivated the study. However, “exoplanet scientists now have enough data to say that this gap is not accidental,” Christiansen says.

Solving the mystery of exoplanet shrinkage

Core-induced mass loss hypothesis emerges radiation from the hot core of a planet “It’s pushing the atmosphere down“, explains Christiansen, will move away from the celestial body over time. In the other scenario, namely photoevaporation, “high-energy radiation from the star” [hospedeira] It acts like a hair dryer on an ice cube,” explains the astronomer.

To test their hypothesis, the team looked for sub-Neptunian stars in two star clusters: Praesepe, or Beehive, and the Hyades, which are 600 million and 800 million years old, respectively. Nearly all stars in this age group were sub-Neptunian stars with atmospheres in their orbits; This shows that no photoevaporation occurs, in which case they would all be devoid of the atmospheric layer.

But things changed when planets orbiting stars more than 800 million years old were examined in the K2 database. Here only 25% had sub-Neptunes. Since the oldest age of these stars is one billion years, sufficient time for core-induced mass loss to occur, the study concluded that this mechanism is responsible for atmospheric escape and the resulting shrinkage of the planets.

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