A theory that claims neutron star mergers produce short gamma-ray bursts has recently been proven by the GROWTH team, comprised by astronomers from around the world.
Short GRBs refer to energetic explosions emitting a wave of gamma rays, with a duration of fewer than two seconds. Since 2005, only a few of such astronomical events were successfully detected throughout the galaxy. Their origin has also remained a mystery until the discovery of a gamma ray-emitting GRB in 2014.
A compact merger generated GRB 130603B lasting 0.2 light-seconds and followed by an afterglow of X-rays. Scientists then observed a jet of small-sized particles, which they identified to be similar to primary objects of a neutron star. This led them to conclude that collision of neutron stars are potential sources of short GRBs.
A report published by journal Nature on Dec. 20 supports such conclusion. Scientists from various institutions, such as the University of Sydney, Caltech, and CSIRO, observed a neutron star merger detected in August 2017.
After three months of investigation, their radio telescopes picked up a wide-angled emission of gamma waves from the wreckage lying 130 million light years away from Earth.
Astronomers Fail To Find Jet In Neutron Star Merger Site
A gamma-ray curve dubbed GW170817 was produced by the neutron star collision. It was emitted at a distance of 40 megaparsecs without an identifiable jet associated with GRBs. This led scientists to formulate two conclusions.
One conclusion states that a jet was produced but was only directed away from the line of sight, while another proposes that GW170817 could be the tail of a cocoon, a neutron-rich material ejected in the collision. The cocoon model explains the wide-angled curve of GW170817 and is the most consistent with the team's observations.
Based on their discovery, neutron star mergers may not be the direct sources of short GRBs but they expel cocoons, which could be potential sources of transient electromagnetic waves occurring around the Universe.
Recently, neutron stars have been associated with habitable planets. A study by Leiden University's Alessandro Patruno and Mihkel Kama suggests that such planets exist in zones around neutron stars despite harsh conditions.
Discovery Of Cocoons Opens More Investigations
Now that the team has discovered the existence of cocoons, its member Dr. Adam Deller from the Swinburne University of Technology says they will conduct investigations to look for more of the neutron-rich material. He also forecasted a bright future for gravitational-wave astronomy.
A collision of two stars has been predicted for 2022. The event is expected to produce a red nova, which will be visible from Earth.