Scientists have discovered that there may be many more planets that have atmospheres and hydrospheres and are similar in size to Earth than previously thought. At least, this conclusion has led them to study super-Earths and mini-Neptunes.
New model of planetary formation
A new study by Rice University researchers Sho Shibata and Andre Izidoro presents a compelling new model for the formation of super-Earths and mini-Neptunes – planets that are 1-4 times larger than Earth and among the most common in our galaxy. Using advanced simulations, the researchers hypothesize that these planets arise from separate rings of planetesimals, providing new insights into the evolution of planets beyond our Solar System. The results of the study were recently published in The Astrophysical Journal Letters.
For decades, scientists have debated how super-Earths and mini-Neptunes form. Traditional models suggest that planetesimals, the tiny building blocks of planets, form in broad regions of a young star’s disk. But Shibata and Izidoro propose another theory: These materials probably combine to form tight rings at specific locations on the disk, making planet formation more organized than previously thought.
“This work is particularly important because it models the formation of super-Earths and mini-Neptunes, which are considered the most common types of planets in the galaxy,” said Shibata, a postdoctoral fellow in Earth, Environmental and Planetary Sciences. “One of our key findings is that the formation paths of the Solar System and exoplanet systems may have fundamental similarities.”
Predicting Earth-like exoplanets
The study also provides insight into the size homogeneity observed in multi-planet systems. Many exoplanetary systems have a “pea-in-a-pod” appearance, where planets within the same system are strikingly similar in size. The ring model naturally creates this homogeneity by controlling how planets form and grow in their respective rings.
Shibata and Izidoro’s modeling is also consistent with the observed distribution of planetary orbits, reinforcing the idea that planets originate in specific locations rather than being randomly scattered across the disk.
In addition to explaining these observations, the model also provides a predictive analysis of planet formation and even hints at the possibility of other Earth-like planets. Izidoro says that while it would be rare, rocky planets in the habitable zone could form from late-stage giant collisions, similar to how Earth and its moon were formed.
Significance for future research
“Our predictions suggest that about 1% of super-Earth and mini-Neptune systems may contain Earth-like planets within the habitable zone of their stars,” Izidoro says. “While this fraction is relatively small, given how common super-Earths and mini-Neptunes are, it means that there is approximately one Earth-like planet for every 300 Sun-like stars.”
Looking ahead, these findings could have profound implications for future exoplanet research.
“These predictions will be tested with future telescopes, giving us important information about the formation of planets and their suitability for life,” Shibata said. “If future observations confirm our predictions, it could completely change our understanding of how planets form — not just in our galaxy, but throughout the Universe.”
According to phys.org
