How a Cataclysmic Neutron Star Merger Gave Us Heavy Elements Like Strontium
Scientists discovered a vein of heavy elements in the wreckage left behind a cataclysmic neutron star merger and finally revealing how the heavy elements in our universe are formed, according to Space.Com. These results were just published in the latest issue of the peer-reviewed journal Nature.
Astronomers have long puzzled over how these heavier elements formed in the first place: we know that lighter elements on the periodic table (like hydrogen) formed just after the Big Bang. Mid-weight elements including iron quite literally didn't exist for the first few billion years, and we actually didn't know how heavier elements were even formed in the first place. "This is the final stage of a decades-long chase to pin down the origin of the elements," Darach Watson, the lead author of the study, told CNN.
Neutron stars are the bones left behind after a supernova explosion; they are incredibly small and impossibly dense. This is how they came to be called "neutron" stars in the first place – their extreme density exerts a gravitational pull that is powerful enough to compress protons and electrons together until they warp into neutrons.
In 2017 astronomers witnessed the first known neutron star collision that was powerful enough to send gravitational waves rippling across the universe, and it was this data that our scientists were analyzing. Specifically, they were looking for spectral lines, or signature wavelengths of light that correspond to particular elements. In this case, they found high levels of strontium lingering in the aftermath of the explosion, which is a heavy element found in soil and minerals on Earth.
Scientists suspect that "in order to create a relatively light heavy element like strontium, you need to destroy some neutrons first – you need to bombard them with neutrinos, enough to make them decay more quickly into protons and electrons," explained Watson. In other words, you need conditions that match the perfect storm of a neutron star merger. Watson added, "Everything we've found points to elements that formed only in the presence of lots of neutrons."
Cover image: ESO/L. Calçada/M. Kornmesser CC BY 4.0