GW250114 was the most powerful gravitational-wave signal measured to date. Early this year, it was detected simultaneously at the Laser Interferometer Gravitational-Wave Observatory (LIGO) facilities in Washington and Louisiana. Analysis found that the wave was generated when two black holes, each about 33 times the mass of the sun, merged to form a black hole larger than 63 times the mass of the sun.
In the general theory of relativity published in 1916, Einstein predicted that when celestial bodies act violently, the surrounding spacetime twists and gravitational waves occur, much like a bowling ball dropped on a sheet makes a dent. Even though the event that produced these gravitational waves happened about 1 billion light-years (光年; one light-year is the distance light travels in one year, about 9.46 trillion km) away, the signal was so strong that researchers could precisely determine the spin speeds of all the black holes and even the initial ringing of the final black hole.
As predicted, it was confirmed that the area of the "event horizon" of the final black hole is larger than the sum of the areas of the two black holes. The event horizon is the boundary between the material orbiting around a black hole and the black hole itself. If matter crosses this boundary and falls into the black hole, it can never return. The illustration depicts the view from near one black hole just before the collision.