Studying and Gathering Evidence for the Existence of Black Holes

Identifying Black Holes

Black holes are extremely compact celestial objects with immense gravitational pull.
They are so dense that they draw in everything around them, including light, hence why they appear ‘black’.
There is no direct way to observe black holes because they do not emit light, but they can be studied by examining their gravitational influence on surrounding objects.

Evidence of Black Holes from Surrounding Matter

One indicator of a black hole is the observation of accretion discs, rings of gas and dust spiralling into the invisible centre, heated by gravitational friction causing it to emit X-rays.
The speed of material in these discs can indicate the mass of the central object; if it is concentrated within a small radius and doesn’t emit light, a black hole is a probable culprit.
This evidence was used to identify the black hole at the centre of our galaxy, Sagittarius A.

Evidence of Black Holes from Star Movement

Another way of detecting black holes is by observing the movement of stars.
If a star is observed to orbit an invisible object with a significant mass, it could be a black hole.
This method was used to detect black holes in binary star systems, where a visible star orbits an unseen companion.

Stellar Evolution and Black Holes

The existence and understanding of black holes is directly tied to the science of stellar evolution.
Stars more than about 25 times the mass of our Sun end their lives in massive explosions known as supernovae, leaving behind either a dense neutron star or a black hole.
Thus, the study of stellar evolution and life cycles contributes to our detection and understanding of black holes.

Gravitational Waves and Black Holes

The detection of gravitational waves has provided a new way to study black holes.
These waves are ripples in the fabric of spacetime caused by violent cosmic events, such as the collision of two black holes.
The first detection of gravitational waves by LIGO (Laser Interferometer Gravitational-Wave Observatory) in 2015 confirmed the predictions of Einstein’s theory of general relativity and opened up a new era in astronomy.