什么是Binary Black Hole？

The final merger is the most violent event in the universe since the Big Bang, and almost nobody would notice it. When GW150914's two black holes — 36 and 29 solar masses — combined, the remnant weighed 62 solar masses. Three entire suns had been converted into pure gravitational radiation in a fifth of a second, briefly radiating more power than every star in the observable universe put together. No light was emitted at all. The only thing that reached Earth, 1.3 billion years later, was a change in the distance between mirrors of about one part in 10^21 — a thousandth of the width of a proton across a 4 km arm.

Drawing this honestly requires changing the marcher itself. Everywhere else in this section light falls toward a single centre with a conserved angular momentum; here it is pulled by two, and the sum of two black hole solutions is not itself a solution of Einstein's equations. What the shader does instead is superpose the two pulls, each measured against its own hole — exact for one hole, accurate while the pair is well separated, and honestly labelled as an approximation for the last few orbits, where only full numerical relativity will do.

What that buys is a picture nothing else produces. The two shadows are not two black holes composited together: each bends the light of the other, so their facing edges are visibly flattened and each carries a thin crescent secondary image of itself on its outer flank, lensed around its partner. Beyond them the circumbinary disc is held off at roughly twice the separation — the pair torques anything closer straight out — and feeds each hole through streams crossing the cavity. The background starfield is sheared by the pair's own gravitational waves, exaggerated by some twenty orders of magnitude so that it is visible at all.