Study reveals distinct evolutionary paths of super-Earths and mini-Neptunes

A group of researchers has found that super-Earths (SEs) and mini-Neptunes (MNs) followed distinct evolutionary paths after conducting an in-depth study based on a large set of observational data, according to the National Astronomical Observatories of the Chinese Academy of Sciences.

The findings were published in the journal Science, using observational data from China's Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), Europe's Gaia satellite and the Kepler space telescope.

In the solar system, the four rocky planets — Mercury, Venus, Earth and Mars — are located in the inner solar system, while the outer region is home to four gas and ice giants: Jupiter, Saturn, Uranus and Neptune.

Since the launch of the Kepler space telescope in 2009, astronomers have discovered thousands of exoplanets beyond our solar system, the vast majority of which have radii between those of Earth and Neptune.

These planets do not form a single uniform group but instead fall into two categories: super-Earths, which are slightly larger than Earth and composed mainly of rock and iron, and mini-Neptunes, which are larger and possess thick gaseous envelopes.

The researchers said SEs are like the "survivors" of exoplanetary systems. They may have experienced violent processes such as gravitational scattering and giant impacts, which pushed their orbits to relatively high eccentricities before tidal forces rapidly circularized them.

In contrast, MNs are like "natives" living in "quiet zones." Their evolution is dominated by gentle, long-term orbital changes, with eccentricity slowly transferred from the outer to the inner regions, and they rarely experience dramatic dynamical events.

"SEs and MNs may seem similar, but they have distinctly different 'personalities'," said Xie Jiwei, the corresponding author of the study. "Their orbital evolution history is crucial for understanding the formation and evolution of planetary systems."

Source(s): Xin Hua