What's so cool about the neutron star kilonova astronomers discovered, in 500 words

Gravitational waves — ripples in space and time — have changed the world, again. On Monday, a huge team of scientists working in collaboration with LIGO, the US-based gravitational wave observatory, and VIRGO, an observatory based in Italy, announced they had for the first time used gravitational waves to locate an object in the sky. Specifically, they found two neutron stars that had crashed into one another 130 million light-years away.

The discovery means we’re truly in a new age of astronomy: one in which scientists can listen for ripples in spacetime and figure out where to look in the universe to see amazing phenomena unfold in real time.

Here’s a brief rundown of why today’s announcement was so damn cool

For the first time, scientists have detected the gravitational waves that formed during the collision of two neutron stars.

At the same time the gravitational waves were detected, a space-based observatory recorded a gamma-ray burst. These are high-intensity beams of radiation that periodically blast through the universe like a strobe laser light. This confirms that binary neutron star collisions can create gamma-ray bursts, and that gamma rays and gravitational waves travel at the same speed, the speed of light — something Einstein correctly predicted 100 years ago.

The neutron stars collided 130 million years ago. But scientists were able, in a sense, to study the entirety of the event: from when the neutron stars were orbiting one another to the moment they crashed to the burning aftermath. (LIGO-VIRGO recorded 100 seconds of gravitational waves from the collision. Previous recordings of black holes only lasted a few seconds.)

When neutron stars collide, they produce an explosion called a kilonova, and astronomers have never witnessed one before. The kilonova produced the gamma-ray burst, but it also contained the right ingredients and energy needed to create heavy elements like gold, platinum, and uranium.

Now that there are three gravitational wave observatories up and running across the world (one in Louisiana, one in Washington state, and one in Italy), scientists can zero in on where in the sky the gravitational waves are coming from. They used this data to create a map of where to look for the kilonova and sent it to a worldwide network of astronomers. (All of this occurred within a 12-hour window.)

Astronomers found the kilonova that very night! And then they sent the exact coordinates to our biggest, baddest telescopes (Hubble, Chandra, and others).

Observations from those telescopes studied the light from the kilonova and how it evolved over the course of a few weeks. By reading the color of light from the kilonova, scientists figured out which elements it produced.

And lo and behold, it produced gold and platinum. That means all the gold on Earth was likely produced in a kilonova. With these observations, scientists were able to peek at a tiny slice of creation.

Also cool: Astronomers have now observed this kilonova in every wavelength of electromagnetic radiation, and in gravitational waves. No other event has been recorded so thoroughly.

And, all of this took the work of thousands of scientists (one of the papers published Monday has 4,500 co-authors!), working collaboratively, world over.

NASA and ESA. Acknowledgment: N. Tanvir (U. Leicester), A. Levan (U. Warwick), and A. Fruchter and O. Fox (STSc)

Further reading:

• Gravitational waves just led us to the incredible origin of gold in the universe. How LIGO kick-started a worldwide treasure hunt for a kilonova.
• Gravitational waves, explained. Why gravitational waves exist, how LIGO works, and why the effort to detect them won a Nobel Prize.

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