When stars larger than our Sun run out of fuel, they collapse inward and then explode in some of the highest energy events in the universe.
Scientists think that these explosions are the sources of cosmic rays — extremely high-energy fragments of atomic nuclei hurtling through the galaxy at the speed of light.
Earth is pummeled by cosmic rays every single day. Our magnetic field protects us from the radiation damage these rays bring, but some particles do get through.
And a team of scientists just found some in the Indian Ocean.
William Attard McCarthy - McCarthy's PhotoWorks/Moment/Getty Images
In sediment cores from 1,300-2,300 feet deep under the ocean’s surface, scientists found traces of an isotope of iron called 60Fe.
This isotope is only found in cosmic rays.
They calculated the isotopes were about 33,000 years old and possibly originated from the Local Interstellar Cloud — a 30-lightyear-wide “bubble” of gas and dust through which our own Milky Way solar system is currently drifting.
The supernova from which the cosmic iron originated could have been a million years old, the researchers say, but more research needs to be done to pinpoint when exactly the iron fragments made it to Earth.