How black holes are formed through the merging of neutron stars

In 2017, the Laser Interferometer Gravitational-Wave (LIGO) observatories recorded a signal which indicated that two massive and dense stellar bodies had merged to form a third body, likely a black hole. In the process they gave off vibrations that quite literally shook the universe and its very fabric of space-time.
The event, dubbed GW170817, is what’s called a binary neutron star merger.
- When the two neutron stars meet, their merger leads to the formation of either a more massive neutron star, or a black hole (depending on whether the mass of the remnant exceeds the Tolman–Oppenheimer–Volkoff limit).

From the Hubble data, it appeared the jets of matter were moving seven times faster than light.
The researchers explain the reason behind the discrepancy is due to something called superluminal motion. Since the jet of matter reaches Earth at the speed of light, the space agency explains, the light it emits at later points has a relatively shorter distance, making it appear faster than it actually is.
Hence, the observation of particles moving at seven times the speed of light is an illusion. This happens in cases where a source moves (towards us) with a velocity that is very close to light’s velocity.

We have learnt that neutron star mergers can result in material moving with speeds as high as 0.9997c, where “c” is the speed of light.
They have also measured more accurately a factor called the Lorenz factor which scales with the actual speed of the particles in the jet.
This resolves the earlier fuzziness about what the source was and puts the source clearly as massive neutron stars merging to give a black hole and throwing off relativistic jets of particles in the process.

Neutron stars are the collapsed cores of massive stars, left behind after a star has undergone a supernova explosion and reached the end of its lifetime.
They are extremely dense

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