What stage of a star’s life do planets start forming? This is what a recent study published in Nature Communications hopes to address as a pair of researchers from the Southwest Research Institute (SwRI) investigated the processes responsible for forming exoplanetary systems with multiple planets that exhibit smaller orbits than our solar system. This study has the potential to help scientists better understand the formation and evolution of small and compact solar systems and what this could mean for finding life beyond Earth.
“Compact systems are one of the great mysteries of exoplanet science,” said Dr. Raluca Rufu, who is a Postdoctoral Research at SwRI and lead author of the study. “They contain multiple rocky planets of similar size, like peas-in-a-pod, and a common mass ratio that is very different than that of our solar system’s planets.”
For the study, the researchers used a series of computer models to simulate how these small and compact exoplanetary systems form and evolve despite their architecture. The goal was to ascertain how and when planets start forming during a star’s formation process, specifically when gas and dust begins to fall towards the star, known as infall, as gravity begins taking over during the final stages of the star’s formation. It is during this stage that astronomers have long hypothesized when planets begin to form, but the simulations produced by this study tell a different story.
“We find that planets that accrete during infall can survive until the gas disk disperses and orbital migration ends,” said Dr. Robin Canup, who is a planetary scientist at SwRI and co-author of the study. “Importantly, across a broad range of conditions, the mass of surviving systems is proportional to the mass of the host star, providing the first explanation for the similar mass ratios of observed multi-planet compact systems.”
A new model proposed by the researchers tat could explain the formation and evolution of compact exoplanetary systems. (Credit: Southwest Research Institute)
Essentially, this could explain how small and compact exoplanetary systems form and evolve, with one system of interest for astronomers being the TRAPPIST-1 system that boasts seven worlds all within the orbit of Mercury with orbital periods ranging from approximately 1.5 to 19 days. For context, Mercury takes 88 days to orbit the Sun.
What new discoveries about exoplanetary system formation and evolution will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
Sources: Nature Communications, EurekAlert!, Southwest Research Institute