Dr. Djorgovski, one of the authors of a paper published in the journal Nature on Wednesday, will discuss the research at a meeting in Seattle. The lead author is Matthew Graham, a computational scientist at Caltech’s Center for Data-Driven Discovery.

The merging black holes manifested as a regular flicker in a quasar — a mass of light and energy — in a remote galaxy known as PG 1302-102. The most logical explanation, Dr. Graham and his colleagues wrote, is a pair of black holes circling each other less than a light-year apart.

“This is the most convincing evidence for a tight pair of black holes with a separation smaller than the solar system,” said Avi Loeb, a cosmologist at the Harvard-Smithsonian Center for Astrophysics who was not involved in the work, noting that other, less convincing systems have been suspected. He cautioned, moreover, that the evidence is not yet airtight; the apparent variation in the quasar light could be a statistical effect from not checking it frequently enough.

If it holds up under scrutiny, the system could be a bonanza for the young field of gravitational wave astronomy. It would also provide a preview of what will happen in our own Milky Way galaxy in a few billion years when it collides with the neighboring Andromeda galaxy, sending the black holes at the hearts of both galaxies into an “intimate (pre-arranged) companionship,” as Dr. Loeb put it in an email.

Black holes are the most extreme consequences of Einstein’s theory: maws so deep and dense that not even light can escape. There seems to be one weighing as much as millions or even billions of suns squatting like Dante’s Lucifer in the center of every galaxy. Normally they are dormant, but when they feed on stars and gas, burping energy into space, they can light up as quasars, beacons that far outshine the galaxies in which they live.