Context
Recently, Scientists from the Event Horizon Telescope (EHT) facility, revealed the first image of the black hole named Sagittarius A* at the centre of our galaxy - the Milky Way.
What is Sagittarius A*?
- Pronounced Sagittarius ‘A’ star, it refers to the believed location of the supermassive black hole in the centre of our galaxy.
- About 50 years ago, astronomers identified an area within the constellation of Sagittarius that was the strongest region of radio emission – thus making it the likely centre of the Milky Way.
- It possesses 4 million times the mass of our sun and is located about 26,000 light-years—the distance light travels in a year, 5.9 trillion miles (9.5 trillion km)—from Earth.
- It strengthens Einstein’s general theory of relativity that a point in space where matter is so compressed as to create a gravity field from which even light cannot escape.
- The researchers said that imaging Sagittarius A*The black hole at the centre of the Milky Way was much more difficult than imaging M87.
- In 2019, the Event Horizon Telescope made history by releasing the first ever image of a black holeMessier 87 (M87) – the black hole at the centre of a galaxy M87, which is a supergiant elliptical galaxy.
What is a black hole?
- The concept was given by Albert Einstein in 1915 but the term ‘black hole’ was coined in the 1960s by American physicist John Archibald Wheeler.
- Black holes are extremely dense points in space that create deep gravity sinks from which even light cannot escape.
- It can be formed by the death of a massive star. A black hole takes up zero space but does have mass, that used to be a star. And black holes get more massive as they consume matter near them.
- The bigger they are, the larger a zone of “no return” they have, where anything entering their territory is irrevocably lost to the black hole. This point of no return is called the event horizon.
- When a massive star (more than 8 times bigger than Sun) runs out of its thermonuclear fuel in its core- signifies the end of its life and the core becomes unstable. Then its gravity caused the core to collapse upon itself.
- This huge weight of its constituent matter falling in compresses the dying star to a point of zero volume and infinite density- called the singularity.
- In April 2019, the scientists at the Event Horizon Telescope Project released the first-ever image of a Black Hole (more precisely, of its shadow).
What is an event horizon?
- Black holes are extraordinarily dense objects with gravity so strong that not even light can escape, making viewing them extremely challenging.
- A black hole’s event horizon is the point of no return beyond which anything—stars, planets, gas, dust and all forms of electromagnetic radiation—gets dragged into oblivion.
- The closer someone came to a black hole, the greater the speed they would need to escape that massive gravity.
- The event horizon is the threshold around the black hole where the escape velocity surpasses the speed of light.
