Black holes are cosmic drains, gravitational funnels that pull in matter from their surroundings. This process, called accretion, doesn't always go smoothly: some of the infalling gas can be ejected back as narrow relativistic jets — jets. For supermassive black holes at the centers of galaxies, accretion typically drags on for millions of years, so an observer doesn't get to see the switch between regimes — for instance, the transition from quiet swallowing to a phase of powerful outflows. But nature has provided us with a time-lapse: when an ordinary failed star (possibly a brown dwarf or a planet) ventures too close to a black hole, tidal forces stretch it into a thin thread — a process called "spaghettification." The star's matter quickly forms an accretion disk, and the whole "gulp-and-spit" cycle plays out over weeks or months, letting astronomers track its stages in detail.

Using photometry, measuring brightness in different bands, scientists noticed a striking pattern: the decisive shift from a state where the disk's own radiation pressure can puff up the infalling gas (supercritical accretion) to a calmer outflow occurs at the same relative brightness level. The threshold is about 2% of the peak luminosity — the maximum at which radiation could "blow away" the accreting gas, like a strong wind sweeping leaves off a path. This critical threshold turned out to be identical for black holes weighing just a few solar masses and for giants of billions of solar masses. The analogy is apt, though it simplifies the physics: imagine a kitchen sink and a giant ocean whirlpool changing their splashes and foam at the same water pressure — meaning the transition is set not by absolute size but by a fundamental balance of forces.

This discovery helps explain the mysterious delays in jet appearance after a tidal disruption event begins, and it makes a compelling case: the physics of matter "draining" into black holes is universal. The scale may differ by billions of times, but the laws governing accretion and jet birth remain the same across the Universe.