DARK MATTER

DARK MATTER

TOPIC: Science & Tech

Context- Astronomical observations suggest that a significant part of the universe is made up of dark matter which interacts with the rest of the universe only through the gravitational pull.

Concept-

Primordial black holes:

• One hypothesis is that dark matter comprises a large number of compact objects such as primordial black holes.
• When the universe was very young, hot and dense – soon after the Big Bang, it must have had quantum fluctuations of its density.
• This, in turn, would have caused some regions to become extremely dense, and therefore, to collapse under their own gravity to form the primordial black holes.

Gravitational lensing:

• When light travels through space and passes near a massive or compact body – a star, a galaxy or a black hole, for example, the intense gravity of that body may attract the light towards it, bending it from its rectilinear (straight line) path.
• This phenomenon is known as gravitational lensing and was first observed by Arthur Eddington in 1919.
• Massive objects like galaxies can bend light significantly, producing multiple images, this is called strong lensing.
• Lighter objects like stars or black holes bend light less, and this is called microlensing.
• A similar lensing can happen to gravitational waves travelling towards the Earth, and this would leave signatures in the detected gravitational waves. This can be used to detect the presence, or the existence, of primordial black holes.