A large enough mass in a compact volume inevitably forms a black hole.
In 1964, we observationally detected our first one: Cygnus X-1.
Black holes emit no light, but numerous physical processes can still reveal them.
Matter infalling into a black hole’s vicinity forms accretion disks.
MORE FOR YOU
Once sufficiently heated, that matter emits X-ray light.
These “X-ray binaries” revealed humanity’s first black holes.
Supermassive black holes also produce X-rays.
NASA’s Chandra discovered thousands in its ultra-deep images.
Energetic black hole outflows create positrons: the electron’s antimatter counterpart.
These ejecta generate “Fermi bubbles” around galactic centers, including our own.
Additionally, gravitational waves reveal inspiraling and merging black holes.
But radio studies uncover black holes most abundantly.
Infalling matter around black holes commonly produces radio waves.
This explains the origin of quasars: QUAsi-StellAr Radio Sources.
Supermassive, active black holes emit tremendously powerful radio signals.
The 52-station LOFAR array just synthesized an unprecedented set of radio data.
Spanning 740 square degrees, they found 25,247 supermassive black holes.
LOFAR will eventually survey the entire northern hemisphere, expecting ~600,000+ identifiable black holes.
Observationally abundant, black holes aren’t purely theoretical anymore.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.