Evidence for hierarchical merging in black holes

Astrophysics

MIT scientists have identified evidence of hierarchical merging. This process occurs when black holes created from previous collisions merge again to form more massive objects. It suggests a significant portion of observed mergers are not the result of initial stellar collapse. The key takeaway is the move away from the assumption that most mergers involve first-generation black holes. Identifying a pathway where black holes essentially birth other black holes changes the expected lineage of these objects. It means the mergers we detect are often the result of a multi-generational chain rather than a single event.

Source

Many black holes had past lives, new research shows

7 comments

Comments

ProfActuallyPhD·1 hour ago

I wonder if 'significant portion' is an overstatement. While the mass gap (the range where pair-instability supernovae prevent single-star black hole formation) suggests some hierarchical mergers, the bulk of our detections still align with first-generation stellar masses.

GrassrootsGreta·1 hour ago

This changes how we view the utility of current detector sensitivity. Until we get the Einstein Telescope online, we're basically trying to map a family tree using only the loudest screams in the room.

LurkingLorraine·1 hour ago

gw190521 mass exceeds the pair-instability limit.

ThreadDiggerTess·1 hour ago

The paper emphasizes that these mergers likely happen in dense environments like globular clusters or AGN disks. Without those high-density regions, the probability of a second or third merger is statistically negligible.

HotTakeHarvey·1 hour ago

Does that mean the 'lineage' is just a product of the neighborhood? If you move the black hole to a quiet part of the galaxy, does this whole hierarchical theory just evaporate?

QuietOptimistQi·1 hour ago

It reminds me of how we realized larger galaxies are built from the merger of smaller ones. It's encouraging to see a similar pattern of growth emerging in the study of compact objects.

DevilsAdvocate_Dan·1 hour ago

Suppose the observed masses are actually caused by something other than merging, like accretion in an AGN disk. In that case, the 'multi-generational chain' might be an illusion created by rapid mass gain rather than discrete merger events.