When people say that we are made of star dust, they are in fact romanticizing. No, all of our composing atoms originated on Earth, even though the Earth is composed of two different planets – the original Earth and Theia. But the remnants of distant stars are far closer than you may even imagine.
While it’s true that any dying star that stops shining right now is too far away for its light to reach us within our lifetimes, that doesn’t mean that the stars we’re still seeing are still in existence. And it certainly doesn’t mean that there is nothing left of them even if they blew up.
Ancient star dust
As you might have surmised from the title, a team of researchers from the Washington University in Saint Louis managed to determine that Earth is pummeled by stardust from a dead supernova. This pummeling is done by specks of intergalactic dust propelled from the exploding star with speeds close to that of light.
The finding comes as a result of a team of researchers discovering tiny deposits of iron-60 isotopes in most of the world’s oceans. The specks of radioactive cosmic dust were very difficult to trace, primarily because of the many shifts in trajectory they suffered as they were slingshot by the gravity and magnetic fields of other celestial bodies.
Isotopes and dating
As for the iron-60 isotopes, the researchers realized that they didn’t come from Earth because iron-60 is only produced in dying stars. It is also with the help of isotopes that scientists were able to figure out that Earth as it is today, as well as the moon, resulted from the head-on collision with a forming planet that was part of our solar system.
Still, once they realized that the dust specks weren’t from Earth, as well that they were radioactive, the team used dating procedures to figure out exactly when the supernova that pushed dust with such force that it’s falling on Earth today exploded, as well as how close it was to our own floating space rock.
Seventeen years of data
By looking at seventeen years of cosmic ray data captured by spectrometers, satellites, and other very expensive imagers, the scientists managed to find fifteen atomic nuclei in the iron-60 or 60Fe particles. And it’s with their help that the team managed to pinpoint the time and place of the exploding supernova.
According to the findings, the supernova was actually pretty close to Earth, and it went up just a few million years ago. While it may seem like a lot, if we consider the distances and times in outer space, that’s quite recent. In fact, it is estimated that our Homo erectus ancestors probably witnessed the explosion in the sky, as it would have been close enough to see with the naked eye.
Image source: Wikimedia