Scientists theorize black hole mergers could create light

Anyone with a passing familiarity with black holes knows that they are said to have such high levels of gravity that even light can't escape. A new theory suggests that a black hole merger could produce light. Astronomers from the American Museum of Natural History describe what may be the first light ever detected from a black hole merger.Scientists say that when a pair of black holes spiral around each other and ultimately collide, they send out ripples in space and time called gravitational waves. The team says that because black holes do not give off light, the events are not expected to shine with any light waves or electromagnetic radiation. However, the theory developed by museum researchers in the department of astrophysics, along with professors from other institutions, describes a way that black holes might explode with light.

The researchers made observations using Caltech's Zwicky Transient Facility (ZTF), the Laser Interferometer Gravitational-wave Observatory (LIGO), and the European Virgo detector to back up their theoretical simulations. In theory, the team says that a supermassive black hole at the center of the galaxy is surrounded by a "swarm of stars and dead stars, including black holes." Scientists say that the swirling black holes can briefly find gravitational partners and pair up but usually lose the partners quickly.

In a supermassive black hole's disk, the flowing gas organizes the black holes so they can pair up. When the smaller black holes merge, the resulting larger black hole experiences a kick that sends it off in a random direction, and it plows through the gas in the disk. When the new black hole speeds to the disk of gas, it creates a blight flare that is visible with telescopes. The team says that flare is predicted to begin days to weeks after the initial splash of gravitational waves produced during the merger.

The scientists then went back and looked through archival data to find gravitational waves from colliding black holes flagged by LIGO and Virgo in May 2019. The team then looked back at archival ZTF images and found the signal that started days after the gravitational-wave event. The researchers say they will have another opportunity to observe the phenomenon in the next few years as the newly formed black hole should cause another flare.