REPORT: Colliding Neutron Stars Create Most of the Universe’s Heavy Metals

For the first time, two neutron stars were directly observed colliding with one another and collapsing into a black hole. For astronomers, this discovery is a huge deal, because it hints at where most of the heavy metals in our Universe, such as silver, uranium, platinum and gold, come from.

We are made of star stuff. With the exception of hydrogen and some helium, all the elements that we know and are made of were forged in the hot cores of giant stars billions of years ago. This includes carbon, nitrogen, oxygen and iron. Now, scientists are learning how most of the Universe’s heavy metals, like silver, gold, platinum and uranium, are generated. Without metals, life (as we know it) can not exist.

For the first time, in August 2017, two neutron stars were directly observed colliding with one another and collapsing into a black hole. The event occurred 130 million light years away. Astronomers at the Laser Interferometer Gravitational-Wave Observatories (LIGO) in the United States and the Virgo Interferometer in Italy detected gravitational waves, ripples in the fabric of spacetime caused by the birth of a black hole, emitting from a pair of merging neutron stars.

The resulting explosion is called a kilonova; the electromagnetic counterpart of gravitational waves. Albert Einstein predicted the existence of gravitational waves nearly a century ago, and recent detection of them confirms that empty space is, incredibly, not empty. Instead, it’s referred to as the fabric of spacetime, and it contains everything in the Universe.

The biggest astronomical discovery of 2017

For astronomers, this discovery is a huge deal, because it hints at where most of the heavy metals in our Universe, such as silver, uranium, platinum and gold, come from. The project involved 4,500 astrophysicists from around the world; in other words, most of them. Also, for the first time, gravitational waves were detected from such an event. It’s also the first time that a neutron star merger has been directly observed, although computer models predict that a kilonova should occur when neutron stars collide. Lighter metals like iron, barium, lead and tungsten are created when giant stars go supernova, blasting their guts into space in their final death throes.

neutron stars, gravitational waves, neutron star collision, nuclear fusion, what happens when neutron stars collide
Georgia Tech’s Center for Relativistic Astrophysics

When neutron stars merge and collapse into a black hole, they generate a powerful blast of electromagnetic radiation called a gamma-ray burst. GRBs are the most extreme explosions in the universe. Because they occur as focused jets of energy, GRBs need to be facing Earth to be seen. GRBs are so energetic that one occurring in our stellar neighborhood could easily sterilize the surface of our planet. In fact, some scientists believe that a GRB could have been responsible for the Great Dying, a mass extinction event that wiped out 95 percent of all life on Earth 250 million years ago.

What are neutron stars?

Neutron stars are arguably the wildest objects in the Universe. Neutron stars are created when massive stars with cores of 1-3 solar masses go supernova. The stars’ cores collapse under their own gravity once the star begins to fuse iron. Neutron stars are only 10-12 miles across, but have the mass of roughly 1.4 suns. This makes them almost unimaginably dense; just a teaspoon full of neutron star material would weigh billions of tons. For scale, this would be like shrinking all of Earth’s mass into a volume the size of a golf ball.

Neutron stars are so dense that their protons and electrons are forced together by gravity, forming a hot sphere of neutrons. It’s understandably difficult to form a visual of this. Their gravity is so strong that NASA compares their impact to “a marshmallow impacting the star’s surface [hitting] with the force of a thousand hydrogen bombs.”

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