Scientists have discovered that even relatively small black holes can be surprisingly inefficient at swallowing matter.

Using Japan’s XRISM X-ray observatory, astronomers studied the binary system 4U 1630-472, about 26,000 light-years away. It consists of a stellar-mass black hole and a sun-like companion star.

The black hole pulls matter from its companion, forming a spinning accretion disk rather than falling straight in. Friction and gravity heat this gas to about 10 million degrees Celsius, producing bright X-ray radiation.

The system’s brightness varies dramatically. During quiet periods, it shines like the Sun, but roughly every two years, it erupts—growing 10,000 times brighter in just seven days.

XRISM observed 4U 1630-472 in February 2024 during a fading flare. Even as X-ray emission dropped, the black hole continued ejecting gas at 32 million kilometers per hour—around 3% of the speed of light, 15,000 times faster than an F-16 fighter jet.

John Miller, project lead from the University of Michigan, explained that studying small black holes lets scientists observe gas flows in real time—a process that would take hundreds of millions of years for supermassive black holes in galactic centers.

Surprisingly, the gas doesn’t settle into an orderly flow. Instead, the black hole “spills” matter, ejecting it rather than swallowing it directly.

Future observations with XRISM could reveal more, but NASA budget cuts may threaten this research. Understanding these small black holes is crucial for learning how massive black holes evolve over cosmic time.