Physical Size

A scroll-driven journey through the scale of the universe, from subatomic structures to the largest known cosmic systems.

Cygnus X-1Stellar black hole·120 km

NGC 4395 Black HoleIntermediate-mass black hole·59,000 km

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Black holes

Cygnus X-1

Cygnus X-1 was the first cosmic object widely accepted as a black hole. It blazes in X-rays because the black hole is stripping hot gas from a massive blue supergiant companion and funneling it into a compact accretion flow.

Scale fact120 kmevent horizon diameter

Object class: Stellar black hole
Mass: ~21 solar masses
Estimated age: ~5 million years
Host: Cygnus X-1 binary system

Black holes

NGC 4395 Black Hole

The black hole in NGC 4395 powers an active galactic nucleus inside a small bulgeless galaxy. Its existence helped show that a galaxy does not need a large central bulge to host a feeding central black hole.

Scale fact59,000 kmevent horizon diameter

Object class: Intermediate-mass black hole
Host: NGC 4395
Mass: ~10,000 solar masses