THE FOUR TYPES OF BLACK HOLE

PRIMORDIAL

(A RANGE OF DIFFERENT MASSES)

These are as-yet-unconfirmed relics from the formation of the Universe in the Big Bang. So far we’ve been able to rule out their existence in certain mass ranges, but the door is still open to the possibility that the Universe is littered with tiny black holes. Together, they could explain the dark matter mystery – the fact that there appears to be an invisible glue binding galaxies together.

STELLAR MASS

(5 TO 100 SOLAR MASSES)

These are your so-called ‘ordinary’ black holes. When the most massive stars die – those more than 30 times the mass of the Sun – they explode into a supernova. The star’s core collapses into an infinitely small, dense point called a singularity. The gravity is so strong that anything venturing within a certain distance of the singularity – a region called the event horizon – cannot escape its clutches.

INTERMEDIATE

(100 TO 1,000,000 SOLAR MASSES)

For decades, astronomers puzzled over the fact that there are stellar mass black holes and supermassive ones, but seemingly very little in the middle. This was odd because big black holes are thought to be constructed through mergers of smaller ones. There was a missing link in this construction chain. But in March 2020 a 50,000 solar mass black hole may have been spotted by the Hubble Space Telescope.

SUPERMASSIVE

(GREATER THAN 1,000,000 SOLAR MASSES)

These leviathans are found in centres of major galaxies and are the seeds around which the galaxies are constructed. The one at the heart of our own Milky Way is called Sagittarius A* (pronounced ‘A star’) and tips the scales at around four million times the mass of the Sun. That pales in comparison to the supermassive black hole in the galaxy M87, which weighs in at a whopping seven billion solar masses.