What type of black hole may have formed from density fluctuations in the early universe?

A primordial black hole may have formed from density fluctuations in the early universe.

Unlike stellar black holes, primordial black holes would not require the collapse of a star. In some early-universe scenarios, unusually dense regions could have collapsed under their own gravity soon after the Big Bang. Their possible masses depend on the conditions and time of formation.

The idea was developed in modern form during the 1960s, including work by Yakov Zel’dovich and Igor Novikov. Primordial black holes remain hypothetical: no observation has conclusively established that they exist.

They have been proposed as possible dark-matter candidates and as seeds for larger black holes, but observations place strong limits on how many could exist in different mass ranges. They are also discussed in connection with gravitational waves and early-universe cosmology. Their status differs from stellar black holes, which are supported by observations of binary systems, stellar motion, and gravitational-wave events.