The Hills mechanism is a phenomenon that occurs when a

binary star system A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

is disrupted by a supermassive

black hole A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...

Tidal force The tidal force is a gravitational effect that stretches a body along the line towards the center of mass of another body due to a gradient (difference in strength) in gravitational field from the other body; it is responsible for diverse phenomen ...

s from the black hole cause one of the stars to be captured by it, and fall into an orbit around it. The other star is thrown away from the black hole at very high speeds. The phenomenon was proposed by astronomer

Jack Hills The Jack Hills are a range of hills in Mid West Western Australia. They are best known as the source of the oldest material of terrestrial origin found to date: Hadean zircons that formed around 4.39 billion years ago. These zircons have enable ...

in 1988 and confirmed in 2019, when an example of such a jettisoned star was observed. This ejected star, namely

S5-HVS1 S5-HVS1 is an A-type main-sequence star notable as the fastest one detected as of November 2019, and has been determined to be traveling at . The star is in the Grus (or Crane) constellation in the southern sky, and about 29,000 light-years f ...

, an

A-type main-sequence star An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...

, notable as the fastest star detected as of November 2019, has been determined to be traveling at nearly four million miles an hour (more specifically, , almost 0.6% of the speed of light) away from the galactic core of the Milky Way.

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See also