[unravel two]In a Major First, Scientists Detect Two Massive Mergers of Black Holes With Neutron Stars
An artistic image inspired by a black hole-neutron star merger event. (Carl Knox, OzGrav/Swinburne)
Black holes are the cosmic monsters of the universe as nothing can escape their pull, not even light. Now, for the first time, astronomers have spotted black holes gobbling the corpse of massive stars in two separate events.
The two cosmic monsters lurking at the centre of distinct galaxies swallowed up their respective cosmic neighbours, the neutron stars. Neutron stars are the collapsed core of massive supergiant stars. As these gigantic celestial entities collided, both the volatile events triggered ripples across the universe, and some were felt by our planet as well. These ensuing ripples in the space-time fabric are known as the gravitational waves.
This is the first such account where astronomers have documented the collision of black holes with their neutron stars—a remnant of the star noted to be 10 to 30 times more massive than our Sun.
”Gravitational waves have allowed us to detect collisions of pairs of black holes and pairs of neutron stars, but the mixed collision of a black hole with a neutron star has been the elusive missing piece of the family picture of compact object mergers,” said Chase Kimball, a Northwestern graduate student who co-authored the study.
The team proved that the gravitational waves that hit Earth originated from two different events. The study was carried out with the help of the detectors—the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US and Virgo in Italy.
The detectors noted two new gravitational waves in a gap of 10 days. The first one has been dubbed as GW200105, detected on January 5, 2020. The second, originating from a different merger, is named GW200115 and was caught on January 15, 2020.
The first wave GW200105 came from the collision of a black hole of 9-solar mass with a neutron star of 1.9-solar mass. This cataclysmic cosmic explosion is estimated to be about 900 million light-years from Earth. The waves covered 17% of the entire sky—equivalent to the area occupied by as many as 34,000 full moons.
The second wave (GW200115), on the other hand, was a result of a massive merger between a black hole of at least 6-solar mass and a companion neutron star of nearly 1.5-solar mass—roughly 1 billion light-years from Earth. As per the study, waves were tracked from the patch of the sky which is comparable to the total area of 2,900 full moons.
The scientists state that this is the first confident observation, which can further help to decode the frequency of such massive collisions in the universe. The team has also estimated that there are chances of at least one such massive merger happening every month and that too within a distance of just one billion light-years from Earth.
Furthermore, the study could also unravel how collisions like that of the black hole-neutron star influence the expansion and shrinking of space-time fabric. An international team of astrophysicists, including Northwestern University, conducted the study.
The study was published in the Astrophysical Journal Letters earlier this week and can be accessed here.