Another First: LIGO Detects Gravitational Waves Produced by Neutron Star Collision

In a dramatic demonstration of how astrophysics is being transformed by the newfound ability to detect gravitational waves (ripples in the fabric of space-time that are created when massive objects spin around each other and collide), scientists have, for the first time, caught two neutron stars in the act of colliding. In doing so, they may have revealed that these collisions are the source of heavy elements such as gold and platinum - solving a long-standing mystery about the origin of these heavy elements. This marks the first time that a cosmic event has been viewed in both gravitational waves and light. The discovery was a group effort - made using the U.S.-based Laser Interferometer Gravitational-wave Observatory (LIGO), the Europe-based Virgo detector, along with 70 other ground- and space-based observatories. The gravitational signal, named GW170817, was first detected on August 17, 2017, by the two identical LIGO detectors (operated by Caltech  and MIT). In the days following, other forms of light, or electromagnetic radiation - including X-ray, ultraviolet, optical, infrared, and radio waves - were detected.To learn more, read a Tech Briefs Q&A with Brad Cenko , Research Astrophysicist at the NASA Goddard Space Flight Center.

Transcript

00:00:01 [Music] for the first time astronomers have detected a single cosmic Cataclysm in both gravitational waves ripples in space-time itself and electromagnetic waves what we typically call light this hugely collaborative effort includes the LIGO and Virgo gravitational wave Observatory z' along with a multitude of telescopes in space and on earth that

00:00:25 together collectively monitor the full spectrum of light the spectacular event was produced by the collision and merger of two neutron stars these objects are the burnt-out remains of giant stars that have exploded as supernovae they leave behind cores of exotic matter composed primarily of neutrons crushed together under the intense pull of gravity more mass than our Sun is

00:00:48 compressed into a sphere that is about the size of a city astronomers have long known that neutron stars are found in pairs orbiting one another the theory of relativity predicts that the motions of these incredibly massive objects should generate gravitational waves these waves would drain energy from the orbiting bodies causing them to slowly spiral together and eventually collide with

00:01:10 each other in a spectacular explosion on August 17th 2017 a gravitational wave chirp was recorded by the National Science foundation-funded LIGO observatories and less than two seconds later a short burst of gamma rays a high-energy form of light was detected by NASA's Fermi telescope researchers quickly realize these two fundamentally different types of ways could have come

00:01:33 from a single neutron star merger if so it was critical to identify exactly where this had taken place in the sky and if the explosion could be seen by other telescopes the Fermi data indicated the bursts came somewhere from a patch of sky covering about 1200 square degrees an area equivalent to six thousand four moons adding information from an independent

00:01:54 gamma-ray detection from the integral satellite the search area was further reduced the LIGO observatories place the source somewhere in long narrow strips of the sky one of which overlapped with a target patch the Virgo gravitational wave Observatory in Italy working in conjunction with LIGO should easily have been able to detect the signal of the

00:02:14 strength but saw almost nothing this was an important piece of the puzzle since any gravitational wave observatory has a small number of blind spots where it cannot detect the incoming signal restricting the source location of virgos blind spots further narrow in the search area down to approximately twenty eight square degrees or 144 moons around 50 candidate galaxies were identified in

00:02:38 this area for follow-up observations using optical telescopes less than 11 hours after the first detection z' astronomers using the carnegie Swope telescope identified a previously unseen blip of light in the outer reaches of the galaxy named NGC for 993 several independent confirmations will report it from other telescopes over the next hour the first-ever optical counterpart to a

00:03:02 gravitational wave event had been found knowing exactly where to look astronomers began an unprecedented campaign of follow-up observations using more than 70 telescopes around the world in the space during the course of the next two weeks a neutron star merger was detected across the entire electromagnetic spectrum the gravitational wave data have for the

00:03:25 first time provided a direct measurement for the masses and orbits of a neutron star pair before their collision and merging the data also enabled ongoing follow-up observations across the electromagnetic spectrum characterizing the explosion and revealing how such unimaginable events have played a formative role in shaping the world around us these results for the first

00:03:46 time confirm that neutron star mergers create precious elements like gold and platinum as well as a host of other heavy elements all across the periodic table explosions like these through our cosmic history have seeded the universe with the materials that later will form new stars new planets and beings like ourselves who look up and wonder

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