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A new study by scientists offers an alternative explanation for the formation of Earth-like planets: instead of a rare direct impact from a supernova explosion, cosmic rays could have played a key role, enriching the early Solar System with radioactive elements at a safe distance for the protoplanetary disk. This is reported by Phys Org, according to UNN.
Details
For many years, it was believed that the early Solar System received short-lived radioactive elements, particularly aluminum-26, directly from a nearby supernova explosion. The decay of these elements heated young planetesimals and contributed to the loss of water and volatiles, which was important for the formation of rocky, relatively dry planets like Earth.
However, such a scenario required very precise and, consequently, rare conditions. The supernova had to explode at a strictly defined distance, close enough to deliver material, but not so close as to destroy the protoplanetary disk. Also, a favorable geometry for efficient injection was needed. Because of this, the origin of Earth looks like the result of an extremely rare event.
“Cosmic Ray Bath”
In a new paper published in Science Advances, scientists proposed an alternative mechanism. Supernovae are not only sources of ejected matter but also powerful particle accelerators. Their shock waves create streams of cosmic rays that can propagate far beyond the explosion debris.
According to the researchers, numerical simulations showed that when cosmic rays from a supernova interact with the protosolar disk, they can trigger nuclear reactions that naturally form short-lived radioactive elements, including aluminum-26. The necessary amount of these elements can arise at distances of about one parsec from the supernova, typical for star clusters. At such a distance, the disk remains intact.
The authors called this process a “cosmic ray bath.” In this case, it was enough for the Solar System to simply form in the same star cluster with a massive star that later exploded as a supernova, without the rare direct impact of its ejecta.
What this means for Earth-like planets
Researchers note that many Sun-like stars are born in clusters where there are massive stars and, consequently, supernovae. If “cosmic ray baths” are a common phenomenon, then the thermal conditions that shaped Earth’s interior may be typical, not exceptional.
At the same time, scientists emphasize that a supernova does not guarantee the appearance of a habitable planet. Other factors remain important, including the lifetime of the disk and the dynamics of the star cluster.
Recall
The International Asteroid Warning Network (IAWN) is tracking interstellar comet 3I/ATLAS, which will approach Earth within 270 million kilometers. This observation is part of a campaign to improve the measurement of comet and asteroid trajectories.
