Ripples in space-time caused by the collision of two neutron stars 130 million years ago reveal the cosmic origins of precious metals like gold and silver.
Colliding neutron stars [Image by NSF LIGO Sonoma State University/A. Simonnet]
Astronomers announced on October 16, 2017 that they have detected gravitational waves that came off the merging of two neutron stars. This is the fifth time in two years that astronomers have detected these ripples in space-time, the existence of which Albert Einstein predicted way back in 1916.
These gravitational waves may be the fifth to be detected, but something sets them apart from the other gravitational waves that have also been discovered. In the previous four discoveries, the gravitational waves came from colliding black holes. These latest waves were the first to have been detected to have come from colliding neutron stars instead. Neutron stars, unlike black holes, produce metallic radioactive debris when they collide. This debris is visible, but only if you know where to point your telescope.
Colliding neutron stars and their gravitational waves. [Image by R. Hurt/Caltech-JPL]
A neutron star is the dense remaining core of a large dead star. When the supernova explodes, the neutron star is what remains. It has a gravitational field that’s strong enough to compress matter equivalent to the sun’s into an orb the size of a city. Thus, calling it a “star” is kind of a stretch, but “atomic nucleus” doesn’t really slide off the tongue just as easily.
"This is the first time that we hear the death spiral of two neutron stars, and we also see the fireworks that came from the final merger," said Northwestern University’s Vicky Kalogera at a press conference.
The Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves that indicated that they didn’t come from colliding black holes, but from colliding neutron stars instead. NASA’s Fermi Gamma-ray Space Telescope caught a short burst of gamma rays, which is another known indicator of colliding neutron stars. Research teams from across the globe began observing the collision as well as soon as LIGO and NASA raised the alarm.
For weeks after the initial discovery, observatories around the world were fixated on one spot near the galaxy NGC 4993. With these observations came a resolution to an enduring debate on the origins of our precious metals.
Have scientists struck a goldmine upon discovering the cosmic origins of gold?
Scientists have long thought that our precious metals originated from the depths of exploding supernovae. However, more recent findings showed that supernovae don’t eject as much as the expected amount of these metals. This is because forming these metals would require an excessive amount of neutrons, which can be found in the nuclei of stars. As you may expect, the collision of neutron stars has the ability to release a sufficient amount of neutrons to form precious metals.
The debris released by the observed collision, according to the findings, released enough precious metals to fill at least 10 thousand Earths. This amount is enough to account for the known amount of these metals present in the universe.
While these observations have answered many questions, there are still many others left unanswered. Research teams around the world have released several papers simultaneously in a number of journals to create a pool of findings. It’s highly likely that we’ll see more studies on gravitational waves in the coming months and years.
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