---
name: Cygnus X-1
constellation: Cyg
created_by: 8mag
created_date: 2022-01-21 17:00:00
updated_by: skybber
updated_date: 2022-01-27 17:54:42.177288
---
a binary near η Cygni. It is a variable X-ray source. One component is visible, the other is invisible, but X-rays are emitted from its vicinity. The visible star is a luminous supergiant, the invisible component is probably a collapsed old star with a large mass - a black hole with a radius of only 10 km, which is siphoning off huge amounts of gas from the luminous supergiant (radius 10 million km) and emitting extremely intense X-rays before it reaches its boundary.