In the quest to understand the nature and origins of the universe, scientists have made the first detection of both gravitational waves and light arriving from a single cosmic event, the collision of neutron stars some 130 million light-years from Earth.
“Our ability to both see and hear these distant cosmic events can tell us a lot about the universe,” says Professor of Physics Steven Penn, an integral member of the global research team behind the discovery. “This is a significant development that gives us a richer understanding of stellar evolution and the opportunity to chart more precisely where these major events took place.”
The discovery opens unprecedented opportunities in the field of astronomy – including a new era of “multi-messenger” astronomy, while helping to resolve certain postulations about the universe. For example, thanks to the detection, new observations reveal that heavy elements like platinum and gold are produced from the colliding neutron stars, which are the smallest and densest stars known to exist.
The new scientific breakthrough was made using the U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO), of which Penn is a longstanding contributor; the Europe-based Virgo detector; and some 70 ground- and space-based observatories. The U.S. Gemini Observatory, the European Very Large Telescope and NASA’s Hubble Space Telescope helped to verify where heavy metals originate.
Scientists unveiled the discovery on Oct. 16 during a National Science Foundation (NSF) press conference. Penn hosted a public event coinciding with the announcement at HWS during which President Gregory J. Vincent ’83 and Senior Dean of the Faculty and Professor of Geoscience Nan Crystal Arens both shared remarks. The discovery also made international headlines, including coverage in The New York Times, The Wall Street Journal and on NPR.
A full announcement about the discovery and its implications is available on the NSF website.
“It’s the quality of research and our faculty’s commitment to research that reaffirms what many of us know, that many of our best professors are also our best researchers,” said Vincent during the HWS event. “That combination of teaching and research taking place here is truly outstanding. At HWS, you’re going to be exposed to some of the best scholars and researchers in the world.”
Arens noted: “One of the things that we do astonishingly well is allow our undergraduate students from their very first and second semesters, if they choose, to become involved in the kind of research that changes the fundamental way we understand the universe.”
The LIGO-Virgo results of the colliding neutron stars detection have been published in the journal Physical Review Letters.
The gravitational signal from the collision, named GW170817, was first detected on Aug. 17, 2017 by LIGO detectors, located in Hanford, Wash., and Livingston, La., and a Virgo detector in Italy. At nearly the same time on Aug. 17, the Gamma-ray Burst Monitor on NASA’s Fermi space telescope had detected a burst of gamma rays. LIGO-Virgo analysis software put the signals together.
Neutron stars are formed when massive stars explode in supernovas. The colliding neutron stars that were observed on Aug. 17 had spiraled together, emitted gravitational waves that were detectable for about 100 seconds. When they collided, a flash of light in the form of gamma rays was emitted and seen on Earth about two seconds after the gravitational waves. In the days and weeks following the smashup, other forms of light, or electromagnetic radiation (including X-ray, ultraviolet, optical, infrared and radio waves) were detected.
“It is tremendously exciting to experience a rare event that transforms our understanding of the workings of the universe,” says NSF Director France A. Córdova. “This discovery realizes a long-standing goal many of us have had, that is, to simultaneously observe rare cosmic events using both traditional as well as gravitational-wave observatories.”
Through his work, Penn has made significant contributions to the LIGO detectors which scientists used to observe gravitational waves for the first time in 2015, as well as subsequent detections. The first discovery confirmed a major prediction of Albert Einstein’s general theory of relativity.
In September, the LSC and the Virgo collaboration, which have been sharing data and coordinating their analyses, reported their first joint discovery of gravitational waves. Earlier this month, the Nobel Prize in Physics was awarded to Rainer Weiss of Massachusetts Institute of Technology, and Barry Barish and Kip Thorne of California Institute of Technology for the historic discovery of gravitational waves.