In the past few decades, it has become part of astronomical lore, if not quite a law, that at the center of every luminous city of light, called a galaxy, lurks something like a hungry Beelzebub, a giant black hole into which the equivalent of millions or even billions of suns have disappeared.

The bigger the galaxy, the more massive the black hole at its center.

So it was a surprise a decade ago when Marc Postman, of the Space Telescope Science Institute, using the Hubble Space Telescope to survey clusters of galaxies, found a supergiant galaxy with no sign of a black hole in its center.

Normally, the galaxy’s core would have a kink of extra light in its center, a kind of sparkling cloak, produced by stars that had been gathered there by the gravity of a giant black hole.

In the years since, the two researchers and their colleagues have been ransacking the galaxy, looking for X-rays or radio waves from the missing black hole.

Using the standard rule of thumb, the black hole missing from the center of the 2261 galaxy should be 10 billion solar masses or more, comparable to the mightiest of these monsters known to astronomers?

“What happens when you eject a supermassive black hole from a galaxy?” Dr.

The discovery in the 1960s of quasars in the centers of galaxies first led astronomers to consider that supermassive black holes were responsible for such fireworks.

By the turn of the century, astronomers had come to the conclusion that every galaxy harbored a supermassive black hole, millions to billions of times more massive than the sun, in its bosom.

Where they came from — whether they grew from smaller black holes that had formed from the collapse of stars, or formed through some other process early in the universe — nobody is sure?

When two galaxies collided and merged — an especially common event in the earlier universe — their central black holes would meet and form a binary system, two black holes circling each other.

Begelman and his colleagues argued that these two massive black holes, swinging around, would interact with the sea of stars they were immersed in.

Every once in a while, one of these stars would have a close encounter with the binary, and gravitational forces would push the star out of the center, leaving the black holes even more tightly bound.

But instead of a peak at the center of the core, there was a dip, as if the supermassive black hole and its attendant stars had simply been taken away.

Spectroscopic measurements by the Hubble could tell how fast the stars in the knots were jiggling around, and thus whether some massive object — a black hole — was needed to keep them all together.

“Either any black hole at the center is very faint, or it isn’t there,” he wrote in an email.

Postman’s team, has published a detailed analysis of how the merger of two supermassive black holes could reform the galaxy into what the astronomers have found.

Having lost its supermassive anchor, the cloud of stars around the black hole binary spreads out, becoming more diffuse.

That telescope will be able to examine all four knots at the same time and determine whether any of them are a cloaked, supermassive black hole!