Did a Star Explode and Strike Earth 10 Million Years Ago?

Approximately 10 million years ago, a volatile star might have unleashed cosmic rays toward Earth, and astronomers are currently narrowing down the potential culprits behind this cosmic event.

Earlier this year, Dominique Koll of Helmholtz Zentrum Dresden-Rossendorf and his colleagues in Germany discovered a spike in radioactive beryllium trapped in five kilometers of sediment in the Pacific Ocean, dating back over 10 million years. This form of beryllium is generated exclusively when cosmic rays collide with the Earth’s atmosphere, leading Koll and his team to hypothesize that a supernova explosion might be the origin of this event.

Nonetheless, alternative explanations cannot be dismissed. These include the Sun’s magnetic influence on Earth at that time and the possibility of ocean currents from Earth’s poles contributing to beryllium deposition, areas where cosmic rays and beryllium production are typically more intense.

Now, Efrem Maconi from the University of Vienna and his team have pinpointed two likely supernova candidates using data obtained from the Gaia space telescope.

By examining the trajectories of roughly 2,700 stars near our Sun over the past 20 million years and assessing their potential to produce supernovae, Macconi and his colleagues determined that there is a 70% probability of such events occurring among these star clusters.

Researchers have identified two possible progenitors for the explosion. The most probable one, located about 200 light years away, is a relatively young cluster named ASCC 20, while the cluster OCSN 61, situated further away, is also a potential source.

Additional support for the supernova theory is that 10 million years ago, our solar system was engulfed in a bustling region of the galaxy, surrounded by extensive clouds of gas, dust, and stars known as the Radcliffe waves.

“This is a promising indication that warrants further investigation,” says Koll. “If [Maconi] were to claim we could fully eliminate this possibility, I would happily accept that as a solid conclusion. However, in this instance, it certainly remains intriguing.”

Further modeling of stellar movements will be necessary to ascertain whether these stars indeed played a role, yet this hypothesis aligns well with other findings in Earth’s geological history. Unlike cosmic rays that travel close to the speed of light, dust moves much slower, making it plausible that beryllium spikes resulted from cosmic rays from a supernova initially impacting Earth.

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