LOOKING TO THE HEAVENS FOR GOLD.

• Author: Svitil, Kathy
• Position: SCIENCE & TECHNOLOGY

SCIENTISTS for the first time have detected both the ripples in space and time known as gravitational waves as well as light produced and emitted during the same cosmic event: the spectacular collision of two neutron stars. Neutron stars, formed when massive stars explode in supernovas, are the smallest, densest stars known to exist, with a teaspoon of neutron star material having a mass of about 1,000,000,000 tons.

The light-based detections in the seconds, hours, days, and weeks that followed--which included California Institute of Technology-led observations in the infrared, X-ray, ultraviolet, and radio waves--show that the collision of the neutron stars released newly synthesized heavy elements into the surrounding universe, providing the first concrete proof that such smashups are the birthplace of half of the universe's elements heavier than iron, including gold and platinum.

Using the flood of data from across the electromagnetic (EM) spectrum obtained in the aftermath of the merger, Caltech astronomers have developed a new concordant picture of the dynamics of neutron star mergers and their evolution.

The gravitational-wave discovery was made Aug. 17, 2017, with the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors. As the pair of neutron stars spiraled closer and closer together, they began to emit gravitational waves that were measurable for tens of seconds by LIGO's instruments before the inevitable cataclysm, starting at 8:41 a.m. Eastern Daylight Time. About two seconds after the gravitational waves ended, a bright flash of light--in the form of gamma rays--was detected by NASA's Fermi space telescope.

"We quickly established that the two stars were each less than around twice the mass of the sun, putting them in the typical mass range of neutron stars," says Alan J. Weinstein professor of physics and head of Caltech's astrophysical data analysis group for LIGO. Although black holes can, in theory, have masses as low as calculated for the merging objects, the coincident gamma-ray burst suggested that the stars had to have been made of matter--and matter, unlike black holes, emits light.

Later studies by the LIGO Scientific Collaboration (LSC), a group of more than 1,200 scientists worldwide, found some evidence that the material in each of the stars might have been torn apart by the gravity of its companion in a way that black holes could not. "The detection of gravitational waves from a binary neutron...