Did a star blow up and hit Earth 10 million years ago?

An exploding star may have sent cosmic shrapnel toward Earth 10 million years ago, and astronomers have now narrowed down the most likely culprits for this interstellar incident.

Earlier this year Dominic Coll at the Helmholtz Center Dresden-Rossendorf in Germany and his colleagues. discovered a thorn radioactive beryllium buried in metallic rocks 5 kilometers below the Pacific Ocean, which they estimate to be just over 10 million years old. This form of beryllium only forms when cosmic rays crash into the Earth's atmosphere, so Call and his team theorized that one possible cause could be a supernova explosion that occurred many years ago.

However, there were other possible explanations that they could not rule out, such as the magnetic shielding of the Earth by the Sun was weaker at the time, or the beryllium being deposited there by stronger ocean currents from the Earth's poles, where cosmic rays are stronger and produce more beryllium.

Now, Efrem Makoni from the University of Vienna in Austria and his colleagues discovered two possible sources of supernovae using data from the Gaia space telescope, which mapped the current positions of billions of stars in the Milky Way and their movements.

By tracing the orbits of about 2,700 star clusters relative to the Sun over the past 20 million years, and calculating how likely it was that each of those clusters could have produced a supernova during that time, Makoni and his team found that there was a 70 percent chance that the star exploded about 300 light-years from Earth during a beryllium outburst, 10 million years ago, and a 30 percent chance the likelihood that this did not happen. supernova.

Researchers point to two possible sources of the explosion, if it did occur. The most likely source, within about 200 light-years, is a relatively young group called ASCC 20, but a cluster of stars called OCSN 61 is likely responsible for it.

Another hint that a supernova is responsible is that 10 million years ago our solar system was in much busier part a galaxy engulfed by a huge wave of gas, dust and stars called a Radcliffe wave.

“This is a good sign that this should be investigated further,” Call says. “If [Maconi] I would say that we can completely exclude this and there are no candidates [supernovae]then I'd say, “Okay, okay, that's a big claim and we can take that explanation off the list, but in this case it's definitely intriguing.”

We'll need more modeling of the stars' movements to figure out whether the star actually did the deed, Call says, but it fits well with other evidence from Earth's geological record, which reveals a burst of radioactive isotopes deposited from cosmic dust about 7.5 million years ago. Dust travels much more slowly than cosmic rays, which approach the speed of light, so it's possible that a burst of beryllium occurred when supernova cosmic rays first touched Earth, and the dust it produced reached our planet a couple of million years later, although Call admits that would be very difficult to test.

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