Small Galaxy With A Big, Dark Heart

Supermassive black holes, weighing millions to billions of times more than our Sun, are thought to dwell in the hearts of most–if not all–galaxies in the Universe. Such beasts are characterized by their extremely heavy masses, insatiable hunger, and messy table manners. These gravitational monstrosities are mysterious and puzzling. But, the mystery grew even more perplexing when a supermassive monster–weighing in at an unbelievable 17 billion Suns–was caught dwelling in the heart of a bizarre small galaxy that is almost entirely black hole!

“This is totally not what I was looking for. I was expecting to find really big black holes in really big galaxies,” Dr. Remco van den Bosch, an astronomer at the Max Planck Institute in Heidelberg, Germany, said in the November 26, 2012 Science Now. Dr. Van den Bosch is lead author of the paper describing this incredible gravitational monstrosity.

In 1915, Albert Einstein’s Theory of General Relativity predicted the presence of objects that possessed such strong gravitational fields that anything that unfortunately traveled too close to their gaping mouths would be devoured. However, the concept of the real existence of such gravitational monstrosities seemed so remote that Einstein himself rejected the concept–but scientists now know that such beasts can and do exist.

Black holes of stellar-mass form when a very massive star collapses violently in the brilliant fireworks display of a supernova explosion, heralding the end of its life as a main-sequence (hydrogen-burning) star. After a hole of stellar-mass has been born, it can continue to gain weight by feeding on its surroundings. It is believed that a supermassive hole is born when one of stellar-mass gains weight by devouring stars and gas–as well as by merging with other black holes.

Astronomers have known for about a decade that perhaps every large galaxy in the Universe hosts a ravenous supermassive monster in its heart, sequestered there in sinister secret. Supermassive beasts can be at least as large as our entire Solar System. Our Milky Way Galaxy’s black hole is named Sagittarius A* (pronounced Sagittarius-a-star), and it is a calm old beast, except when it goes on an occasional feeding frenzy, and devours a hearty portion of gas or star-stuff that has unluckily floated too close to its maw. Sagittarius A* weighs in at approximately 4 million times as much as our Sun.

It is widely thought that supermassive black holes are subject to a standard correlation. That is, the heavier the galaxy’s central bulge of glittering stars, the more massive the resident sinister beast. This basically indicates that the weight of a galaxy’s star-blazing bulge is approximately a thousand times that of its central supermassive hole.

However, the little compact galaxy, NGC 1277, apparently marches to the beat of a different drum. The little galaxy, which is located approximately 250 million light-years from our planet, possesses a supermassive monster in its heart that makes up a whopping 14% of its entire mass. Most other galaxies are thought to obediently follow the beat of the “standard correlation”, and host black holes that amount to a comparatively trifling 0.1% of their total mass.

“This is a really oddball galaxy. It’s almost all black hole. This could be the first object in a new class of galaxy-black hole systems,” study team member Dr. Karl Gebbardt said in a statement published in the November 28, 2012 Gebbardt is at the University of Texas at Austin.

The study, published in the November 29, 2012 issue of the journal Nature, found that if this monster of a supermassive black hole was situated at the center of our own Solar System, it would swallow up all eight major planets and extend about 10 times further than the dwarf planet Pluto and its icy kind where they tumble around in the frigid, remote blackness of the Kuiper Belt.

NGC 1277 is a relatively small member of a cluster of galaxies located in the constellation Perseus. It also represents a type of galaxy commonly found to inhabit clusters. This little galaxy with a big, dark heart is a so-called lenticular galaxy, meaning that it is a bewitching cross between a spiral and an elliptical galaxy. Spirals are gigantic star-blazing pin-wheels, like our own Milky Way, and they contain stellar populations of all ages. Ellipticals are shaped like huge footballs, and they primarily host old, red stars. Like an elliptical, NGC 1277 no longer produces star-bursts of fiery baby stars, and primarily hosts only elderly stars. The most youthful stars in the little galaxy are 8 billion years old–meaning that they are twice the age of our middle-aged Sun, which is approximately 4.56 billion years old. However, like a lovely, pin-wheel-shaped spiral, NGC 1277 sports a disk that is brightly glittering with a multitude of incandescent stars.

“Maybe this thing is a relic from way back when,” Dr. Van den Bosch continued to speculate in the November 28, 2012 Science Now. He went on to explain that supermassive holes ignited by fiery quasars–which are especially active galactic nuclei (AGN) that inhabited the early Universe–haunted Space soon after the Big Bang. Perhaps, he went on to suggest, NGC 1277 represents a case of arrested development, and it began its galactic childhood as an immense black hole, but never managed to ensnare a host of fiery stars. In other words, like Peter Pan, NGC 1277 “never grew up”! Its sister-galaxies, swarming along with it in the Perseus cluster, may have selfishly taken for themselves the stars that would have enabled poor little NGC 1277 to reach star-struck galactic adulthood.

NGC 1277’s supermassive monster could be considerably more massive than the currently identified second-runner-up, which is calculated (though not confirmed) to weigh-in at approximately 6 billion to 37 billion solar-masses. This beast dwells within the dark heart of the galaxy NGC 4486B, and it hogs up approximately 11% of that galaxy’s central bulge.

Dr. Van den Bosch said in the November 28, 2012 that his team discovered the monster black hole during a survey it was conducting to hunt down “the biggest black holes we could find.”

The astronomers carefully analyzed the light emanating from 700 galaxies, using the huge light-gathering telescope, the Hobby-Eberly Telescope, at the University of Texas at Austin’s McDonald Observatory. The team discovered that six of the galaxies under scrutiny had stars and other objects flying around inside of them at breathtaking average speeds of over 218 miles a second! The galaxies, like NGC 1277, were also petite–a mere 9,784 light-years across, or less. The team suspected that black holes were responsible for these measurements, and used archival data of NGC 1277 from the venerable Hubble Space Telescope. This was how they spotted NGC 1277’s big, dark heart.

Dr. Van den Bosch is curious about whether or not these supermassive black holes only formed in the early Universe, or if some formed later in its history.”It could just be this thing has been sitting around since the Big Bang and not done much since then. It might be a relic of what star formation and galactic formation looked like at that time,” he commented in the November 28, 2012

The team is trying to find out whether NGC 1277 is one-of-a-kind. However, as astronomer Dr. Chung-Pei Ma of the University of California at Berkeley noted in the November 28, 2012 Science Now: “When you just have one very strange system, then you can almost always cook up some theories. But if these galaxies form a class of their own, then that would be quite exciting.”