AUSTIN, Texas — The most massive black hole in the universe tips the cosmic scales at 18 billion times more massive than the sun, astronomers suggest today at a meeting of the American Astronomical Society.

Even though researchers suggested black holes up to this mass might exist in quasars, this is the first direct confirmation of such a behemoth.

The hefty gravity well is six times more massive than the previous record and is orbited by a smaller black hole, which allowed the measurement of the giant's mass.

Black holes can't be seen, but astronomers detect them by noting how other objects are affected by the tremendous gravity created in tremendously small sphere of space.

The binary black hole system powers a quasar known as OJ 287, which is located 3.5 billion light-years from us in the constellation Cancer. The quasar — an overwhelming beacon of light associated with a developing galaxy — has been studied in greater detail than most quasars.

Quasars are thought to be powered by gas falling into giant black holes boasting millions or billions of solar masses. Though smaller than the solar system, a quasar can outshine an entire galaxy.

This particular quasar has a regularly pulsing light signal with two major pulses every 12 years. The first two pulses were observed in the year 1994-1995, and the first one of the next set in 2005. The observations helped astronomers refine their computer models, predicting the next pulse would come on Sept. 13, 2007.

Mauri Valtonen of the Tuorla Observatory in Finland, who presented the study, says there is a simple physical explanation for the 12-year pulsing. "In addition to the primary back hole in the [accretion] disk, we have a secondary black hole that crosses the disk twice during the orbital period," Valtonen said. "And that's what gives us the two pulses."

An international network of astronomers operating telescopes across the globe took part in monitoring the quasar in September and October. The largest telescopes involved were the German Calar Alto telescope and the Nordic optical telescope.

Sure enough, right on schedule OJ 287 sent out a light pulse on that date. No other pulses of that kind showed up during September or October, indicating, the astronomers say, the binary black-hole model was correct.

The next pulse is due in January 2016.