When a piano falls into an abyss, we think about the abyss. We don't think about the piano's cover. In much the same way, astrophysicists have for decades studied extreme close encounters between small bodies and massive black holes. They focused on the black hole itself and what orbits it. But what the 'bullet'—the small object heading toward doom — is wearing, almost no one asked.
New work changes the perspective. A small object, be it a star or even a small black hole, can have its own entourage: a cloud of gas, a clump of dark matter (the invisible substance that reveals itself only through gravity). When such a 'dressed' object begins to fall toward a supermassive black hole, its entourage doesn't stay with it forever. Tidal forces (the same ones that raise ocean tides on Earth, but far more powerful) start stripping off its outer layers. Like a piano falling into an abyss, the wind tears off its cover piece by piece.
This process alters gravitational waves — the ripples in spacetime that detectors like the future LISA will catch. As the object loses its 'coat,' its mass decreases, and the wave's frequency starts changing differently than templates for constant mass predict. On the residual phase plot, the difference between the real signal and the template, a characteristic kink appears. It's like a car on a wet road suddenly losing its roof load: the motion changes immediately.
Astronomers gain a tool to peer into the immediate surroundings of objects that are otherwise impossible to see. Instead of treating mass loss as an annoying nuisance, it can be used as a probe. Just as the flutter of a coat in the wind tells you not only about the piano but also about the air it's falling through.
Tidal forces can strip material off an object at a distance that is tens of times smaller than the distance from Earth to the Sun, and this happens over years while the signal crawls through the detector's frequency band.
In Peter Watts's novel Blindsight, alien ships disguise themselves as ordinary asteroids, but their true nature is betrayed by anomalous gravitational interaction — much like a 'stripped' object gives itself away by a kink in the wave.