Contrary to what most experts believe, neutron stars colliding with each other produce a jet of material streaming from the merger at ultra-high speeds.
This has been confirmed by recent observations on the neutron star merger observed in August 2017 more than a hundred days after the merged object came out from its hiding place behind the sun.
Early models predicted that the merger of two neutron stars would generate a broad cocoon of star material around the resulting object. The latest findings, however, upend the prevailing theory about what happens in the aftermath of a neutron star merger.
Jet Of Light Streaming From A Neutron Star Merger
A team of astrophysicists at the University of Warwick used the low-orbit Hubble Space Telescope to detect a powerful beam of light streaming from the neutron star merger. The beam was slightly off-center but was directed toward Earth.
The neutron star merger GW170817 was first detected by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) on Aug. 17, 2017. It was spotted 130 million light-years from Earth in the galaxy NGC 4993. This was the first neutron star merger observed by mankind and the fifth known instance of gravitational waves, a phenomenon predicted by Albert Einstein more than a century ago.
Experts studying the phenomenon have early on spotted visible light caused by the radioactive decay of heavy elements. Since then, however, the glow has faded and has been replaced by a jet of material traveling at a slight angle toward Earth at almost the speed of light.
"This is quite different than some people have suggested, that the material wouldn't come out in a jet, but in all directions," says lead author and physicist Joe Lyman of the University of Warwick.
The researchers propose that neutron star mergers create short gamma-ray bursts that come out in a jet that can only be seen on Earth when the stream of material flows in this direction. However, experts rarely detect these jets because not many of them are directed toward Earth.
"If we'd looked straight down this beam we'd have seen a really powerful burst of gamma-ray," says Andrew Levan, another lead author also from the University of Warwick.
Details of the study can be seen in a paper published in the journal Nature Astronomy.
Scientists studying GW170817 detected gravitational waves coming off from the merger of the two neutron stars. This was followed shortly by gamma-ray bursts spotted by the Fermi Gama-Ray Space Telescope.
Twelve hours later, they saw a bright signal of light, believed to be stellar material ejected from the merger at half the speed of light. Experts say the radioactive decay of heavy elements caused a glow that could be seen from Earth.
The merger continued to emit electromagnetic signals weeks after the event. Using the Karl G. Jansky Very Large Array (VLA) Telescope in New Mexico, researchers confirmed the existence of radio waves, the nature of which allowed them to predict the events following the merger.
When two neutron stars merge, they collapse in on themselves to form a body that is most likely a black hole. This super-dense body is quite small, never bigger than a city on Earth, but it is filled with mass and energy that is several times that of the sun.
As the black hole spins, its strong gravitational pull sucks in the surrounding material. This movement forms a rapidly spinning disk that ejects two jets of star material from its poles.
Scientists previously believed that, as the radio signals become stronger, the jets of material lose the ability to make their way out of the sphere of debris surrounding the merger. Earlier observations showed steadily gaining radio emissions, leading experts to think that the super-fast jets formed a glowing cocoon around the merger instead.