Exoplanets, which are planets located beyond our solar system, are undergoing a fascinating phenomenon – they are losing their atmospheres and consequently getting smaller. This intriguing discovery has shed light on a new process called “core-powered mass loss” that is responsible for this transformation. Unlike the commonly believed theory that harsh winds from their stars blow away the atmospheres of exoplanets, it is now believed that the radiation emitted by the hot cores of these sub-Neptune planets is causing their atmospheres to be pushed away.
Scientists have long wondered why there is a scarcity of exoplanets with sizes between super-Earths and sub-Neptunes. The explanation lies in the process of core-powered mass loss. This phenomenon causes sub-Neptune planets to shrink, eventually transforming into rocky super-Earths. This new understanding challenges the previously proposed theory of photoevaporation, in which a star’s radiation blasts away a planet’s atmosphere.
To unravel this mystery, a group of researchers analyzed data collected by NASA’s Kepler 2 mission, focusing on stars in the Praesepe and Hyades star clusters. They found that stars in the older age range, over 800 million years old, had a lower percentage of orbiting sub-Neptunes. This discovery provided strong evidence that core-powered mass loss is the likely cause of atmospheric escape on these planets.
The underlying reason behind the shrinking of exoplanets lies in their insufficient mass. Due to their low mass, they are unable to retain their atmospheres, leading to a gradual reduction in size. This finding provides valuable insight into the fundamental processes shaping the formation and evolution of exoplanets.
The implications of this research are far-reaching and have significant implications for our understanding of planets beyond our solar system. By delving into the mechanisms behind atmospheric loss and planet size reduction, scientists are making great strides in unraveling the mysteries of the universe. Further research in this field may open up new possibilities for the discovery and exploration of exoplanets, ultimately expanding our knowledge of the cosmos and our place within it.
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