Every major galaxy has a black hole for a heart.

And these celestial Hoovers run a very tight ship, allowing nothing — not even a particle of light — to escape their dominion.

That’s why, when scientists look to the center of a galaxy, they typically don’t see a lot of stars being born. You can’t really have something with an insatiable appetite for stars hanging around the nursery. It’s a fox-hen house thing.

Besides, most black holes pump out too much powerful gamma radiation — a kind of sustained post-meal belch — and keep their surroundings too hot for stars to form.

That is, most black holes. At the heart of some galaxy clusters — where hundreds of galaxies are tightly embedded in hot gas and that mystery sauce known as dark matter — there may be a kind of black hole that nurtures baby stars.

And NASA scientists think they may have found one about 5.8 billion years from Earth, at the heart of the Phoenix galaxy cluster. The region appears to be undergoing a celestial baby boom, with new stars flickering to life at a furious pace.

Leveraging data from NASA space telescopes and a National Science Foundation radio observatory, new research describes a kind of black hole that doesn’t put a damper on star fertility. Instead, this black hole encourages it.

A softer, kinder black hole, you say? Scientists suspect it’s more like an underdeveloped black hole — one that’s too weak to work at its normal job as a destroyer of all things. And, inadvertently, it has become a creator of things.

The energetic belches it issues into the cosmos are less intense. The region surrounding it a lot less hot. It all adds up to ideal conditions for a star nursery.

“This is a phenomenon that astronomers had been trying to find for a long time,” Michael McDonald, the astronomer at MIT who led the study notes in a NASA release. “This cluster demonstrates that, in some instances, the energetic output from a black hole can actually enhance cooling, leading to dramatic consequences.”

Indeed, the supermassive black hole at the heart of the Phoenix galaxy cluster is positively popping with star babies.

Still a black hole

black holeA black hole seen doing its proper black hole duties — and devouring a star. (Photo: NASA)

After analyzing data from the Chandra X-Ray Observatory, the researchers noted that hot gas in the heart of this cluster is cooling rapidly. And the super-slacker black hole that’s supposed to be keeping things too hot for star formation appears to have taken the day off.

Hubble data fills in the picture: The cluster boasts a birth rate of about 500 stars per year. By comparison, our Milky Way pops out just one baby star per year.

“Imagine running an air-conditioner in your house on a hot day, but then starting a wood fire. Your living room can’t properly cool down until you put out the fire,” study co-author Brian McNamara of Canada's University of Waterloo explains in the release. “Similarly, when a black hole’s heating ability is turned off in a galaxy cluster, the gas can then cool.”

But before we get too excited for all those twinkling star babies in the Phoenix cluster, keep in mind that a black hole is still going to be a black hole. This one will eventually get stronger — and hungrier.

“These results show that the black hole has temporarily been assisting in the formation of stars,” notes study co-author Mark Voit of Michigan State University, in the NASA release. “But when it strengthens its effects will start to mimic those of black holes in other clusters, stifling more star birth.”

Even an undersized or undeveloped black hole will eventually get strong enough to go back to work — and start snuffing out stars, like candles on a birthday cake.

Turn out the lights. Black hole’s back. And this party’s over.

This black hole nurtures baby stars instead of eating them
There's a supermassive black hole behind the 'baby boom' in the Phoenix galaxy cluster.