When Dead Stars Collide: Dartmouth Physicist Explains Breakthrough 'Kilonova' Observation

It was a violent collision hundreds of millions of light years away, the likes of which forged the gold found in our jewelry and the uranium in our stockpile of nuclear bombs. Scientists around the globe announced Monday groundbreaking observations of two neutron stars crashing together at nearly the speed of light. A Dartmouth physicist asserts it's the beginning of a new field of scientific discovery.

"This is opening up a new branch of astronomy, gravitational wave astronomy," said Robert Caldwell, a theoretical physicist studying cosmology at Dartmouth College.

Using gravitational waves to learn about the universe is possible thanks to LIGO, the Laser Interferometer Gravitation-Wave Observatory. The scientists behind the cutting-edge detector won a Nobel Prize in Physics this month for the first-ever direct observation of gravitational waves in Feb. 2016.

Caldwell said LIGO's detection of gravitational waves made it possible for observers to train their telescopes on the neutron star collision, called a kilonova, back in August. What they saw was a massive explosion when the two stars, each just over 12 miles wide but weighing more than our sun, smashed together. They released their findings in a flurry of papers and conferences this week.

"This is the first time that light has been seen from a gravitational wave event," he said. "This gives us a new way to measure the size and rate of expansion of the universe."

That has big implications for understanding why the expansion of the universe is accelerating, and not slowing doing. "The Big Bang is not running out of gas," Caldwell said. "It's picking up steam."

Caldwell hopes to use more gravitational wave observations in his own research to glimpse what he calls the gravitational wave background of the universe, "a faint hum of gravitational waves coming from all directions." That hum, he said, is potentially a remnant of the earliest fraction of a second of the universe after the Big Bang.

"If we could detect this, we might be able to learn something about where the Big Bang came from," he said. "The birth of the Big Bang."