How Cosmic Rays Might Make Earth-Like Planets More Common

Scientists have long thought that Earth-like planets need a rare cosmic event to form. They believed a nearby supernova explosion provided essential radioactive materials, like aluminum-26, to create planets like Earth. These materials heated early planetary building blocks, causing them to lose water and other volatile substances.

The Flaw in the Theory

However, this idea had a big flaw. It required the supernova to explode at just the right distance—close enough to deliver materials but not so close that it would destroy the forming solar system. This seemed too lucky to be common.

A New Perspective

A researcher studying supernovae and cosmic rays thought this explanation wasn't complete. Supernovae are powerful particle accelerators, sending out high-energy cosmic rays far into space. What if these cosmic rays played a bigger role in planet formation than previously thought?

The researcher and their team explored this idea using computer simulations. They found that cosmic rays could trigger nuclear reactions in the early solar system, creating the necessary radioactive materials.

The Cosmic-Ray Bath

This process, called a "cosmic-ray bath," works at typical distances from a supernova, about one parsec. At this distance, the forming solar system remains intact. Many sun-like stars form in clusters with massive stars that later explode as supernovae. If cosmic-ray baths are common in these environments, then the conditions that shaped Earth might be widespread.

Implications for Planet Formation

This discovery suggests that Earth-like planets might not be as rare as once thought. If cosmic-ray immersion is a common process, then many sun-like stars could have planets with similar thermal histories to Earth. Of course, other factors still matter, like the lifetime of the planetary disk and the structure of the star cluster. But this research shows that Earth's formation might not have depended on an extremely lucky event.

Interconnected Astrophysics

This study highlights how interconnected different areas of astrophysics are. A process usually studied in high-energy astrophysics—cosmic-ray acceleration—turns out to be crucial for understanding planetary science and habitability. Sometimes, the key to understanding our origins lies in noticing what we've been overlooking.