Famous black holes and candidates

Cygnus X-1

Distance: 6,000 light years Solar masses: 21.2 A stellar-mass black hole orbiting a blue supergiant star, from which the black hole is stealing gas that forms an accretion disc. It occasionally outbursts in X-rays.

Sagittarius A*

Distance: 26,000 light years Solar masses: 4.1 million

The supermassive black hole at the centre of our Milky Way. It’s generally inactive, with only modest X-ray outbursts as it consumes small gas clouds.

Messier 87 black hole

Distance: 54 million light years

Solar masses: 6.5 billion The first black hole to be imaged right down to the event horizon, revealing the black hole’s ’shadow’ on the surrounding accretion disc.

GW150914 black hole

Distance: 1.4 billion light years

Solar masses: 62

The product of the first black hole merger to be detected by gravitational waves formed when a 35-solar-mass black hole collided with a 30-solarmass black hole. The extra three solar masses were converted into gravitation alwave energy.

3C 273

Distance: 2.4 billion light years Solar masses: 886 million The first quasar discovered, the black hole at its heart is hungrily guzzling gas, producing an incredibly bright accretion disc and a jet moving at almost the speed of light.