First-seen neutron star collision creates light, gravitational waves and gold

ATLANTA — For the first time, two neutron stars in a nearby galaxy have been observed engaging in a spiral death dance around one another until they collided.

What resulted from that collision is being called an “unprecedented” discovery that is ushering in a new era of astronomy, scientists announced Monday.

“We can now fill in a few more tiles in the jigsaw puzzle that is the story of our universe,” said Laura Cadonati, deputy spokeswoman for the LIGO Scientific Collaboration and professor in the school of physics at Georgia Tech.

The collision created the first observed instance of a single source emitting ripples in space time, known as gravitational waves, as well as light, which was released in the form of a two-second gamma ray burst.

The collision also created heavy elements such as gold, platinum and lead, scattering them across the universe in a kilonova — similar to a supernova — after the initial fireball.

It is being hailed as the first known instance of multimessenger astrophysics: One source in the universe emitting two kinds of waves, gravitational and electromagnetic.

News conferences were held around the world and a multitude of research papers were published Monday to detail the discovery, which was captured by space and Earth-based telescopes on Aug. 17.

These papers and conferences include representatives for the thousands of scientists, 70 observatories and gravitational wave detectors LIGO and Virgo that participated in one of the most-observed and -studied astronomical events of our time.

One paper includes thousands of authors making up 35 percent of the global astronomy community.

Gravitational waves were first directly detected two years ago, proving Albert Einstein’s theory of general relativity, and recently, three scientists were awarded the Nobel Prize in physics for their work on that first detection.

Those gravitational waves were the result of two black holes colliding, and the signal lasted for only a fraction of a second. Because black holes don’t emit light, these waves were invisible and only “heard” as thumps.

This discovery of two neutron stars colliding to create the same type of waves, in addition to light, allowed astronomers to study gravitational waves in a new way.

The signal lasted for 100 seconds, providing them with even more data and insight. It revealed that light and gravitational waves travel at the same speed.

“Now, we can use this type of event to measure the rate of expansion of the universe,” said Marcelle Soares-Santos, assistant professor at Brandeis University and research associate at the Fermilab Center for Particle Astrophysics.

Vicky Kalogera, leading astrophysicist for the LIGO Scientific Collaboration, compared previous detections of gravitational waves to experiencing a thunderstorm in a room with no windows — only hearing the thunder.

This detection was like experiencing a storm in a room with windows, changing everything scientists thought they knew.

Kalogera is also co-founder and the current director of CIERA, the Center for Interdisciplinary Exploration and Research in Astrophysics, an endowed research center at Northwestern University.

“The impact for astrophysics is equivalent to the transition from watching a set of still pictures in black and white to sitting in a 3-D-IMAX movie theater: It is a multisensory experience of the universe,” Cadonati said.

Theories and mysteries were tested and revealed in this rare observation.

Events such as this happen less than 100 times per million years in a galaxy. But the LIGO and Virgo detectors will become more sensitive in the future to look for similar events in tens of millions of galaxies.

“This was the culmination of a number of different areas in astronomy and physics, coming together in one amazing event,” said Tony Piro, the George Ellery Hale Distinguished Scholar in Theoretical Astrophysics at the Carnegie Observatories.

In a collaboration with UC Santa Cruz, Carnegie Observatories were the first in the world to discover this event. They were able to collect early data just before, during and after the collision and study it in more detail.

The discovery confirms that gamma-ray bursts can result from the collision of neutron stars, as well as that heavy elements are created as a result of violent collisions between stars.

It confirms what these neutron stars look like when they collide. And it confirms that gravitational waves and light can happen together.

“This singular event finally solves all these problems, bringing together all these mysteries at once,” Piro said.

Neutron stars are the smallest in the universe, with a diameter comparable to the size of a city such as Chicago or Atlanta.

They are the leftover remnants of supernovae. But they are incredibly dense, with masses bigger than that of our sun.

So think of the sun, compressed into a major city. Now, think of two of them violently crashing into each other.

“This is more energy than has been released by the sun during its entire life, and this was released during just tens of seconds as the neutron stars (spiraled) together,” Piro said.

Science is a team sport, Kalogera said.

When Virgo and LIGO, working together for the first time in a collaboration of scientists across the world, detected the signal of the gravitational waves in August, an alert was sent out to observatories across the world.

They embarked on a quest to pinpoint where in the sky the signal was coming from so they could observe it in detail, especially when they realized it was accompanied by a gamma-ray burst.

They saw the bright blue explosion, which faded to a deep red.

Astronomers, physicists, engineers and other scientists using multiple space and Earth-based instruments made this possible, from detection to follow-up observations.

And although the collision itself happened 130 million years ago, because of its distance in light-years, it was witnessed it from Earth on Aug. 17.

Any scientist involved in the seconds, days and weeks after this detection will admit they’ve slept little since. To them, it is a once-in-a-lifetime discovery.

The observation also came days before the total solar eclipse, so it’s been hard for them to keep quiet about the discovery. Expect papers and more findings to be released in the weeks, months and years ahead.