BLACK HOLE

Subject : Science and tech

Context: Nobel Prize in Physics for the year 2020 was awarded to three astrophysicists Roger Penrose from the UK, Reinhard Genzel from Germany, and Andrea Ghez from the USA.

Concept:

Discovery

Black hole formation is a robust prediction of the general theory of relativity

• Black holes were one of the first and most extreme predictions of Einstein’s General Theory of Relativity which came in 1915.
• The theory explains gravity, as objects try to follow a straight line through a universe whose geometry is warped by matter and energy. As a result, planets, as well as light beams, follow curving paths.
• He proved that if too much mass accumulated in too small a place, collapse into a black hole was inevitable. At the boundary of a black hole, called the event horizon, one would have to go faster than the speed of light to escape it, which is impossible. At the centre of a black hole, where the density became infinite, the laws of physics, would no longer apply.

Discovery of a super massive black hole at the centre of the Milky way galaxy, now known to be the Sagittarius A*

• It has a mass four million times that of the Sun and is confined to an area roughly the size of our Solar System.
• In 2019, scientists got the first optical image of a black hole which is at the centre of the Messier 87 galaxy.
• Sagittarius A* is the second black hole whose photographs have been captured by the Event Horizon Telescope project. It is yet to be released.

Black Hole

• A black hole is formed when stars collapse and can be defined as a space in the universe with an escape velocity so strong that even light cannot escape it.
• Escape velocity is the speed at which an object must travel to override a planet or an object’s gravitational force.
• Since light cannot get out, black holes are invisible and can only be tracked with the help of a space telescope or other special tools.
• And the reason light cannot escape is mainly that the gravity inside a black hole is very strong as a result of a lot of matter being squeezed into a small space.
• It acts like an ideal black body reflecting no light. It continues to grow, by absorbing mass from its surroundings.