Primordial Black Hole क्या है?
A primordial black hole would have formed in the first fraction of a second after the Big Bang, when the universe was dense enough that ordinary density fluctuations could collapse directly into black holes — no star required. None has been confirmed, but they remain one of the most interesting open questions in cosmology.
Every other black hole has a mass floor set by stellar physics: you need at least a few solar masses of collapsed core. Primordial black holes have no such floor. Formed from the collapse of overdense regions in the early universe, they could in principle span an enormous range, from far below the mass of an asteroid up to thousands of solar masses, with a horizon anywhere from smaller than an atom to kilometres across.
That makes them a candidate for dark matter. A population of asteroid-mass primordial black holes would be invisible, gravitationally correct, and made of nothing exotic. Most of the possible mass range has been closed off by observation — microlensing surveys, the cosmic microwave background, the survival of star clusters — but a window around 10^17 to 10^22 kilograms remains stubbornly open.
They also come with a built-in clock. Stephen Hawking showed in 1974 that black holes radiate, with a temperature inversely proportional to their mass, so small ones evaporate. A black hole formed with about 10^12 kilograms would be finishing its evaporation right now, ending in a burst of gamma rays. Searches for exactly that signature have so far come up empty. The model shows what an object with no accretion disk looks like: pure geometry, visible only as a hole in the sky that bends the starlight around it.