Collision Between Two Massive Neutron Stars Seen for First Time

For the first time in history, astronomers have come up with direct detection of gravitational waves as well as light from a single cosmic event—a collision of two huge neutron stars.

The observation occurred on August 17, 2017 and has been reported in back to back press conferences in Europe and the United States on October 16, 2017.

“This is the first-ever discovery of a merger of two neutron stars, a cataclysmic event that has been predicted to be the origin of short gamma-ray bursts,” stated Matthew Baring, professor of physics and astronomy at Rice University and a member of the Fermi-Large Area Telescope (LAT) Collaboration that has observed this transient event.

“I have worked on the enigmatic gamma-ray bursts since my Ph.D. thesis,” stated Baring. “They have demonstrated the richness and beauty of Einstein’s special theory of relativity again and again, and in this signature result, they offer a stunning display of his general theory of relativity in action.”

The findings were made by means of the US-based Laser Interferometer Gravitational-Wave Observatory (LIGO), the Europe-based gravitational wave detector called as Virgo, and also nearly 70 ground- and space-based observatories. The foremost of this vast international effort was the Fermi Gamma-Ray Burst Monitor (GBM) detector, which discovered the electromagnetic counterpart nearly 2 seconds following the gravitational signal.

Neutron stars are the densest and smallest stars existing in the universe. Within a sphere of size less than half the diameter of Harris County, their mass is more than that of the sun, and they are sometimes discovered in pairs orbiting each other. The August 17, 2017 observation was the outcome of a pair smashing together, which is a very rare happening. The collision resulted in ripples in space-time that were observed by LIGO and Virgo, and discharged energy across the electromagnetic spectrum, including X-rays, visible light, and radio waves.

According to Baring, the observation of both electromagnetic and gravitational radiation from the same event introduces a new age of astronomy where researchers can have in-depth knowledge of the composition of neutron stars, the processes leading to the development of heavy elements in the periodic table, and the evolution of compact stellar objects in the universe.

“As astrophysicists worldwide had hoped, in anticipation of the LIGO era, this watershed discovery transitions gravitational-wave science into a much broader, richer ‘multi-messenger’ forum, where many astronomical disciplines participate and learn about the exotic constituents of the cosmos,” stated Baring.

Baring stated that the August 17, 2017 observation assisted in answering various questions: how can be heavy elements (e.g. gold and platinum) formed? Do gravity waves travel at the speed of light? It may also offer in-depth knowledge into research questions that Baring has analyzed for nearly 20 years.

For instance, the neutron star collisions are considered to produce huge jets of gamma-ray bursts emitted outward in dense columns. The speed of the outflowing jets has been the core interest of Baring’s study. He stated that the Fermi-LAT and Fermi-GBM observations of the collision might offer new hints.

According to Baring, early interpretations of the gamma-ray data indicate that the relativistic outflow might not be very fast as anticipated by many astronomers or that astrophysicists might be observing the cataclysm from outer side of the column. “The hope is that the Fermi-GBM data may inform the structure and internal constitution of the progenitor neutron stars. That is a focus of my present research on X-ray signatures from their surfaces and magnetospheres,” stated Baring.