Black Holes Collision in Space

Context

Scientists detect signals of violent collision between two Black Holes.

Background

On May 21, 2019, a short gravitational wave signal came from two gigantic black holes weighing at least 85 and 66 times the mass of the sun. On September 2, 2020, the astronomers declared it the biggest collision ever detected that led to the formation of a black hole 150 times the mass of the sun.

The collision was observed by the National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO), the world’s largest gravitational wave observatory, and the European-based Virgo detector and VIRGO Scientific Collaboration.

In Detail

Seven million years ago, two Black Holes crashed into each other and merged into one enormous Black Hole with the mass of 142 Suns. The collision reverberated through space and time, and these ripples a phenomenon called gravitational waves first predicted by Albert Einstein.
These ripples traveled 16.5 billion light-years through the universe, reaching Earth in May 2019.

For one-tenth of a second, the waves stretched the mile-long arms of two enormous physics observatories - LIGO and VIRGO.

It was a signal from a gravitational wave, a relatively new field of discovery. Gravitational waves are invisible ripples that form when a star explodes in a supernova or when two big stars orbit each other and when two black holes merge. Travelling at the speed of light, gravitational waves squeeze and stretch anything in their path.

Black Holes and Their Merger

A black hole is a region of space-time where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform space-time to form a black hole.

There are two main ways in which black hole mergers are thought to form. The first is known as a common envelope process, where two neighboring stars, after billions of years, explode to form two neighboring black holes that eventually share a common envelope, or disk of gas. After another few billion years, the black holes spiral in and merge.

The other common path by which black hole mergers occurs is via dynamical interactions. Imagine, in place of a monogamous environment, a galactic rave, where thousands of black holes are crammed into a small, dense region of the universe. When two black holes start to partner up, a third may knock the couple apart in a dynamical interaction that can repeat many times over, before a pair of black holes finally merges.

In both the common envelope process and the dynamical interaction scenario, the merging black holes should have roughly the same mass and also should have relatively no spin.

If one black hole was a product of a previous pairing of two parent black holes of similar mass, it would itself be more massive than either parent, and later significantly overshadow its first-generation partner, creating a high mass ratio in the final merger.

A hierarchical process could also generate a merger with a high spin: The parent black holes, in their chaotic merging, would spin up the resulting black hole, which would then carry this spin into its own ultimate collision.

In the present case, the two merged to create a new black hole of about 142 solar masses. Energy equivalent to eight solar masses was released in the form of gravitational waves, leading to the strongest ever wave detected by scientists so far.

Conclusion

Space is a source of immense surprises at every moment, every observation we make of two black holes colliding gives us new and surprising information about the lives of black holes throughout the space. As LIGO and Virgo continue to make new detections, we can use these discoveries to learn new things about the universe.

Connecting the Article

Question for Prelims

When two Black Holes merge, then which of the following events is likely to take place ?

(a) Release of immense energy
(b) Sucking of immense energy
(c) Formation of new galaxy
(d) None of the above

Question for Mains

Discuss the current research of Space Science done in India and also mention the contribution of at least one Indian scientist in the field of Space Science.