Black holes are like cosmic drains. As they pull in matter, they sometimes spew out jets. For giants at the centers of galaxies, this process drags on for millions of years, hiding any regime changes. But when a hapless star gets too close and gets turned into 'spaghetti', everything speeds up. Observations showed: the key transition occurs at the same level of brightness — when it drops to 2% of the maximum, beyond which light itself would have blown away the infalling gas. This threshold works for both black holes weighing a few Suns and monsters billions of Suns. It's as if a kitchen sink and a giant ocean whirlpool changed their splash pattern at the same water pressure. This explains the puzzling delays in jet appearances and proves that the physics of cosmic drainage is universal.
The brightness limit beyond which light blows away matter, for a 10-million-solar-mass black hole, is comparable to the radiance of hundreds of billions of suns. Just 2% of that value is still a dazzling blaze, and exactly at that level the hole switches its ejection mode.
In 'Interstellar,' the black hole Gargantua tears apart a star — similar real-life catastrophes led to the discovery of a unified law for black holes.