Title: Study Using Kepler Telescope Data Reveals New Insights Into Shrinking Exoplanets
Researchers using the Kepler Space Telescope have discovered new evidence that some exoplanets are shrinking due to the loss of their atmospheres, a phenomenon likely caused by core radiation. This discovery provides insight into the observed size gap in exoplanets and suggests a significant atmospheric loss process different from the previously theorized photoevaporation.
The study, published in The Astronomical Journal, has the potential to explain the ‘missing’ exoplanets between super-Earths and sub-Neptunes. Data from NASA’s retired Kepler Space Telescope indicates that the cores of certain exoplanets are pushing their atmospheres away from the inside out, causing them to shrink.
Exoplanets come in a variety of sizes, but there is a noticeable absence of planets in the 1.5 to 2 times the size of Earth range, known as the “size gap.” Lead author of the study, Jessie Christiansen, explained that there’s something going on that impedes planets from reaching and/or staying at this size.
The study supports the theory that certain sub-Neptunes are losing their atmospheres over time due to insufficient mass and gravitational force to retain them. Core-powered mass loss, caused by radiation emitted from a planet’s hot core, is believed to be the leading explanation for this phenomenon.
By analyzing data from the star clusters Praesepe and Hyades with NASA’s K2, the researchers found that nearly 100% of stars in these clusters still have a sub-Neptune planet or planet candidate in their orbit, suggesting that they have retained their atmospheres. This differs from older stars, where only 25% have orbiting sub-Neptunes. The observations indicate that photoevaporation could not have taken place in Praesepe and Hyades, leaving core-powered mass loss as the leading explanation.
While the research is ongoing, the findings shed new light on the atmospheric loss process of exoplanets and suggest that the current understanding of photoevaporation and core-powered mass loss could evolve with future studies. The discovery was made possible using the NASA Exoplanet Archive, operated by Caltech under contract with NASA, and is a testament to the groundbreaking legacy of the Kepler mission.
Kepler, which concluded its mission on October 30, 2018, discovered more than 2,600 confirmed planets around other stars and provided valuable data for studies such as this. The mission was managed by NASA’s Ames Research Center and was instrumental in revolutionizing our understanding of exoplanets.