Summer Research Fellowship Programme of India's Science Academies

Trajectory of photon near black holes

Aditi Bagra

Department of Physics, Mody University, Ashiana Utsav, Kalwar road, near Govindpura, Jaipur, Rajasthan, 302012

Dr. Rathin Adhikari

Centre for Theoretical physics, Jamia Millia Islamia, Jamia Nagar, Okhla, New Delhi- 110025


When we look around us, we wonder so many things and try to seek answers to them to feed our curiosity. Black holes have been sucking up scientific attention from the every beginning. They were hinted at as early as the 1780s. Albert Einstein predicted Black Holes in his General Theory of Relativity. Recently after NASA released the first ever image of black hole, a lot of research initiatives have been taken. Black holes are basically celestial objects with enormous density (as all its mass is concentrated in a very small space) and hence their gravitational pull is enormous. Nothing can escape a black hole: anything (information for example) which crosses the boundary, known as the Event Horizon, is trapped inside it and gets completely lost. One may argue that if they do not emit any radiation, it is impossible to detect them? This is indeed true for isolated black holes, but luckily there are black holes that swallow gas, modify the trajectories of light near it (which is what this paper is about) and the nearby stars or have a stable life close to a companion star. Observations from earth and from space are performed at every wavelength: from radio to gamma rays. The concept of an object so massive that nothing can escape its fatal grip was first proposed at the end of the 18th century, extrapolated from the Newton's law of gravity however the true black hole revolution came with Einstein's General Theory of Relativity 1915. This thoery states that mass curves the fabric of space-time. The denser the mass, the greater the curvature. According to him, mass and energy are equivalent and hence even massless entity, such as light, is affected by gravity. In this project work, we will deal it with newtonian concept and then Schwarzschild equations given in the GTR to find out about the equation for the trajectory of light, or photon, under the influence of a black hole.

Keywords: event horizon, space-time, Schwarzschild equations, gravitational pull, General Theory of Relativity, radiation

Written, reviewed, revised, proofed and published with