Scientists have detected ripples in the fabric of space and time from a neutron star collision. They call those ripples gravitational waves.

Two neutron stars, each small as a city but heavier than the sun, collided, thus forming a black hole. This powerful event in space threw gravitational waves and light toward our planet. Scientists detected these gravitational waves for the first time since Albert Einstein first predicted them.

This event occurred some 130 million light-years away and the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) detected it.

LIGO’s pair of ultrasensitive detectors in Louisiana and Washington state made history two years ago by recording the gravitational waves coming from the collision of two black holes — a discovery that earned the experiment’s architects the Nobel Prize in Physics this month. Three more signals from black hole collisions followed the initial discovery.

Making any observations of these faraway cataclysms beyond the gravitational waves themselves was unlikely. That’s because black holes don’t give off light.

Astronomers had never seen such a show before, but now LIGO was telling them where to look. More than 70 telescopes turned toward the same location in the sky.

All the previous gravitational-wave detections since the first in September 2015 had been the result of two merging black holes which have left only gravitational waves as fleeting clues of their merger.

“The evidence that these new gravitational waves are from merging neutron stars has been captured, for the first time, by observatories on Earth and in orbit that detect electromagnetic radiation, including visible light and other wavelengths,” said Chad Hanna, assistant professor of physics and of astronomy & astrophysics and Freed Early Career Professor at Penn State.

An artist’s impression of gravitational waves generated by binary neutron stars. Credits: R. Hurt/Caltech-JPL

So, in 1916, Albert Einstein was the first one to predict the gravitational waves. Einstein’s theory of general relativity suggests that gravity results from how mass warps the fabric of space and time. When an object with mass moves, it generates gravitational waves that travel at the speed of light, thus stretching and squeezing space-time along the way. These gravitational waves travel just like the waves on water. They are extremely difficult to detect because they are very weak.

A century after Einstein’s prediction, in 2016, researchers successfully detected the first direct evidence of gravitational waves. They have achieved this using the Laser Interferometer Gravitational-Wave Observatory (LIGO). So, thanks to this work, three scientists won the 2017 Nobel Prize in physics in October.

Neutron stars are remnants of stars, just like black holes, that died in catastrophic explosions known as supernovas. When a star dies in a supernova, their core collapses. Thus, the protons and electrons essentially melt into each other to form neutrons.

So, a massive enough core may form a black hole, which has such a powerful gravitational pull. In the other side, a less massive core will form a neutron star.

Thumbnail image credit: Dana Berry, SkyWorks Digital, Inc./Harvard-Smithsonian Center for Astrophysics