Black holes: A Journey from Death to Birth

The first image of Black Hole at the centre of Galaxy M87 using Event Horizon Telescope

Blackhole is like a giant cosmic vacuum cleaner in space that sucks out the matter from the fabric of space-time. Okay, that’s only an analogy, the true definition goes like this, a region in space-time where gravity is so massive that nothing can escape from it, not even light.

Birth of black holes are the perfect example of a life cycle, a big star fall upon in itself, collapsing under the force of its own gravity. This gravitational collapse occurs when the internal pressure of the body is unable to counteract on its own gravity and results in a supernova. Supernovae are spectacular explosion leaving the whole galaxy to brighten for 1–2 years. In the explosion the outer layers of the star are blown off, leaving a contracting core of the star. It’s the gravitational potential energy that is released upon sudden collapse.

SN 1994D (bright spot on the lower left), a Type Ia supernova within its host galaxy, NGC 4526

What happens to the star after supernova depends on the initial size of the star. If the star had enough matter then the core will shrink down to black hole otherwise the core will shrink down to a neutron star. Stars between 10-29 solar masses collapse in a neutron star. The remnants of supernovae can provoke the formation of new stars. Supernovae might also be the other source of gravitational waves, which are experimentally found by LIGO in 2015 when two colliding black holes merged.

A black hole is an important topic to study. Our own Milkyway galaxy has a supermassive black hole at its rotational centre. Black holes give us the understanding of gravity which is required for the interstellar travel. Observation of black hole has boosted in proving postulates of the general theory of relativity.

An absorption image of a sonic black hole created in the lab. Image Credit: Oren Lahav, et al. ©2010 The American Physical Society

On a more interesting note, the idea of black hole intrigued scientists so much that they created a sonic black hole, or dumb hole, which is analogous to the gravitational black hole. Physicists are interested in this because they show many properties similar to a gravitational black hole. In a sonic black hole, sound perturbations are unable to escape from the fluid which is flowing more quickly than the speed of sound. Bose-Einstein Condensate is being used as fluids in this experiment. The border of a sonic black hole, at which the flow speed changes from being greater than the speed of sound to less than the speed of sound, is called the event horizon. In their experiments, they could maintain the black hole event horizon for at least 20 milliseconds before it became unstable.

A misconception relating event horizons, especially black hole event horizons, is that they represent an inflexible surface that destroys objects that approach them. This is an information loss paradox that opens up whole new possibilities of virtual particles, heat, and hawking radiation. The temperature of black holes is connected to this whole concept of Hawking Radiation. The idea that over vast periods of time, black holes will generate virtual particles right at the edge of their event horizons. The most common kind of particles is photons, aka light, aka heat.

In practice, all event horizons appear to be some distance away from any observer, and objects sent towards an event horizon never appear to cross it from the sending observer’s point of view. Any object that approaches the horizon from the observer’s side appears to slow down and never quite crosses the horizon. It’s because of the time dilation due to the immense gravity of the black hole.

This image highlights and explains various aspects of the black hole visualization. Credits: NASA’s Goddard Space Flight Center/Jeremy Schnittman

Understanding the underlying quantum mechanics rules of black holes will assist us in the advancement of quantum technologies here on the earth, like quantum computing, quantum information, and transportation of qubits which is a very small step towards the development of teleportation.

All these observations and experiments help our understanding of gravity, virtual particles generated at event horizon that are the basic requirements for the wormholes and all these are the keys to make efficient interstellar travel, warp drives which we have seen in star trek and other science fictions. The development of efficient space travel is more important than terraforming other planet or locating another habitable planet.

Today’s science fiction tomorrow’s reality

Student at IIT Madras and Hansraj College LinkedIn -

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