Quirks and Quarks

The behind the scenes hunt for the neutron star collision

Astronomers raced against time to hunt for the source of the neutron star collision.
This illustration shows the hot, dense, expanding cloud of debris stripped from the neutron stars just before they collided. This cloud produces the kilonova's visible and infrared light. Within this neutron-rich debris, large quantities of some of the universe's heaviest elements were forged, including hundreds of Earth masses of gold and platinum. (NASA's Goddard Space Flight Center/CI Lab)

The initial discovery

At 8:41 a.m. ET on August 17th, 2017, gravitational wave detectors picked up an unusual signal - a ripple in space time. And at that same moment, NASA's Fermi space telescope with its eye in orbit around the Earth also detected something unusual. It picked up an intense burst of high-energy light known as a gamma ray burst coming from deep space.

Astronomers almost immediately suspected these signals came from a cataclysmic collision between two neutron stars - the densest stars in our universe. They sent an alert out to astronomers around the world to begin the hunt for this stellar explosion. 

The hunt for the collision source

By combining data from the gravitational wave detectors and the gamma ray burst, astronomers had a general idea of where to look for the source of this neutron star collision. Dr. Maria Drout, a Hubble and Carnegie-Dunlap Fellow at the University of Toronto's Dunlap Institute and the Observatories of the Carnegie Institution for Science, was working remotely out of Pasadena, California that day with her colleagues at three observatories in Chile.

They knew they only had one hour to search for the neutron star merger as soon as the sun set. As they waited for the sun to set, Dr. Drout and her colleagues narrowed down the potential galaxies in the target region to fully optimize their search. It only took them 10-15 minutes to discover the source of the cataclysmic collision. As they continued to observe the fallout from the explosion over the next few weeks, they discovered that many of the heavier elements in our universe, including gold and platinum, likely formed in a neutron star collision just like the one they were observing. 
An image (r.) taken on August 17th with the Swope Telescope at the Las Campanas Observatory in Chile shows SSS17a (arrow) in the galaxy NGC 4993. An image (l.) taken on April 28th with the Hubble Space Telescope; the neutron star merger has not occurred and SSS17a is not visible. (D.A. Coulter, et al.)

Why this is the dawn of a new era in astronomy

"It's being called the dawn of a new era because this is the first time that we have for the same system both gravitation wave detections and detections of light - across the entire electromagnetic spectrum. This is incredibly valuable because each of them give you new and different, complementary pieces of information," says Dr. Drout.