tidal disruption event
A tidal disruption event (TDE) is an astrophysical transient that occurs when a star passes too close to a supermassive black hole. When the tidal radius (the distance where the star's self-gravity balances the tidal force) becomes smaller than the pericenter (closest orbital point), the star is disrupted. About half of the mass falls onto the black hole, forming an accretion disk with a characteristic fallback rate ∝ t^{−5/3}. The disk emits in soft X-rays and ultraviolet, reaching a peak luminosity of ~10⁴⁴ erg/s, then fading over months to years.
History
First described in detail by astrophysicist Martin Rees in 1988. The first candidates were discovered in the 1990s by X-ray telescopes.
How it works
When a star approaches closer than the Roche limit (the minimum distance at which it can hold itself by gravity), the black hole's powerful gravity starts stretching it. Half of the material is flung away, and half is pulled in, forming an accretion disk (a whirlpool of gas). Friction in the disk heats the gas, and it emits in X-rays and ultraviolet.
💡 One of the brightest recorded TDE flares, ASASSN-15lh, was initially thought to be a record supernova, but later turned out to be a star torn apart by a rapidly spinning black hole.