Department of Physics and Astronomy
Stony Brook University
7:30 pm; ESS Building, Room 001
Friday, December 01, 2017

When Neutron Stars Collide: The Story of GW170817

Prof. Jim Lattimer

The recent LIGO/VIRGO observation of gravitational waves from the merger of two neutron stars, and follow-up observations in gamma ray, X-rays, ultraviolet, optical, infrared, millimeter and radio radiation was the most intensively studied astronomical event of all time. These observations revealed that two approximately 1.4 solar mass neutron stars merged after being born in supernova explosions and orbiting each other for around 11 billion years, and in the process, created a short gamma-ray burst and ejected about 20,000 Earth masses of heavy elements into space. The merger occurred in a galaxy far, far, away, about 130 million light years distant. It seems likely that the remnant collapsed into a black hole within a second. The optical and infrared radiation observed for over a week following the merger likely originates from the radioactive decay of nuclei formed from ejected neutron star matter, which apparently solves the century-old mystery of the origin of half of elements heavier than iron, the so-called r-process elements, which include gold and platinum. This event also confirmed the association between short gamma-ray bursts and mergers.

Jim Lattimer has been on the astronomy faculty at Stony Brook University for nearly 40 years, mostly studying supernovae, neutron stars, and the dense matter equation of state. He and his thesis advisor, David Schramm, first predicted 43 years ago that merger-ejected neutron star matter would synthesize r-process elements. But until recently, this idea was met with skepticism and it was widely believed that supernovae were responsible for the creation of these elements. This talk will not only discuss the observations of GW170817, but will also present a first-hand history of the debate concerning the origin of r-process elements.