Ground- and Space-Based Telescopes Join Forces To Tell the Tale of What Happens When Neutron Stars Collide

Two neutron stars collided 130 million years ago and the result was — gold.  That was the news today from an international team of scientists who presented their findings and the story of how it all unfolded from observations by ground- and space-based observatories around the world — a fusion called “multi-messenger astronomy.”

Scientists on Earth have now observed the gravitational waves and electromagnetic radiation resulting from the crash of two neutron stars 130 million years ago.  It not only was another discovery of gravitational waves, whose existence was proved not even two years ago, but a prime example of multi-messenger astronomy involving many fields of astrophysics, an international collaboration of scientists, and data from more than 70 ground- and space-based observatories.

The American Astronomical Society provided a succinct explanation of multi-messenger astronomy that signals just what a big deal today’s announcement is because of the many wavelengths — light and sound — in which it was observed and the number of observatories and scientists around the world involved:

Multi-messenger astronomy:
✅ seen AND heard
✅ US AND international partners
✅ from the ground AND in space
✅ observations AND theory https://t.co/sxWzkdfTka

— AAS Public Policy (@AAS_Policy) October 16, 2017

Scientists at the U.S. Laser Interferometer Gravitational Observatory (LIGO) tweeted a “flag” illustrating the number of countries involved in the discoveries.

pic.twitter.com/XFqdZUsflZ

— LIGO (@LIGO) October 16, 2017

And astrophysicist Katie Mack tweeted a chart showing all the wavelengths in which it was observed.

Love this figure showing the detection in ALL THE WAVELENGTHS pic.twitter.com/LKajlqMuiG

— Katie Mack (@AstroKatie) October 16, 2017

As recounted by Nadia Drake in her layperson-friendly story for the National Geographic, the excitement started on August 17 when detectors at LIGO, which was used for the first detection of gravitational waves in early 2016, recorded a new event. LIGO is composed of two detectors spaced hundreds of miles apart in Livingston, Louisiana and Hanford, Washington. They since have been joined by a European detector, VIRGO, in Italy.

Unlike the first discovery, these waves were from the collision of neutron stars, not the merging of black holes.  Two seconds later, NASA’s Fermi space telescope, which observes in the gamma ray portion (band) of the electromagnetic spectrum, the highest energy form of light, picked up something, too.  Scientists at other observatories around the world that study the universe in other bands of the spectrum began looking as well, resulting in the treasure trove of data released today.

In addition to Fermi, space-based telescopes involved in the discoveries were NASA’s Swift, Hubble, Chandra, and Spitzer, and the European Space Agency’s INTEGRAL.  NASA’s Paul Hertz, director of the astrophysics division at NASA headquarters in Washington, DC, said “the multiplier effect of study with many observatories is incredible.”

It is difficult to grasp the cosmological significance of the findings, and they are well beyond the scope of this website anyway, but they do demonstrate the advantage of combining ground- and space-based astronomy and a broad international scientific community in trying to make sense of our universe.

As for the gold, scientists have long wondered where heavy elements like gold originated.  As Drake explains in her article, lighter elements (hydrogen and helium) formed from the Big Bang, but what about the heavy elements like gold, silver and platinum?  Now it is known that they form from the collisions of neutron stars.

Here is the sound picked up by LIGO that started the cascade of astrophysical investigations that culminated in today’s announcement.

The chirp detected by @LIGO was almost 100 sec long! Get your headphones on for #GW170817 (it’s quiet at first…) https://t.co/SBvsZs7WTb

— LIGO (@LIGO) October 16, 2017

Three U.S. physicists — Rainer Weiss, Barry Barish and Kip Thorne — won the Nobel Prize in Physics earlier this month for their discovery of gravitational waves in 2016, proving a theory put forward by Albert Einstein.