Category: Black Holes

Supermassive black holes are thought to lurk at the heart of most galaxies. Scientists have long believed that only the galaxies with thick central bulges could pull together enough mass for a supermassive black hole to form. But NASA’s Spitzer Space Telescope has turned up evidence that even skinny galaxies, with no central bulge, can still form these galactic monsters.

Astronomers used the Spitzer Space Telescope to survey 32 flat and bulgeless galaxies, and still turned up supermassive black holes in their central cores. This means that galaxy bulges aren’t necessary to build up these black holes; instead, the mysterious and invisible dark matter might be necessary to bring them together.

“This finding challenges the current paradigm. The fact that galaxies without bulges have black holes means that the bulges cannot be the determining factor, said Shobita Satyapal of George Mason University, presenting her research at the American Astronomical Society’s Winter meeting in Austin. “It’s possible that the dark matter that fills the halos around galaxies plays an important role in the early development of supermassive black holes.”

Seen from edge on, our own Milky Way’s bulge would be clearly visible, with the thin spiral arms trailing away to the sides. And researchers know we have a supermassive black hole. Researchers used to think there was a direct connection between the size of the bulge, and the mass of the black hole.

But in 2003, astronomers discovered a relatively lightweight black hole in a galaxy without a bulge. And then earlier this year, Satyapal and her team found another example of this bulgeless black hole.

Since bulges don’t seem to matter, Satyapal suggests that a galaxy’s dark matter halo is the deciding factor to determine how massive a black hole can get.

“Maybe the bulge was just serving as a proxy for the dark matter mass – the real determining factor behind the existence and mass of a black hole in a galaxy’s center,” said Satyapal.

Original Source: Spitzer News Release

Greedy black holes can only consume so much material. The leftover matter backs up into an accretion disk surrounding the black hole. The pull of the black hole is so strong that flashes of radiation emitted from this accretion disk might need to make several orbits around the black hole before it can actually escape the gravitational pull. And these echoes might serve as a probe, allowing astronomers to understand the nature of the black hole itself.

Keigo Fukumura and Demosthenes Kazanas from NASA’s Goddard Space Flight Center revealed their theoretical research at the Winter meeting of the American Astronomical Society.

“The light echoes come about because of the severe warping of spacetime predicted by Einstein,” said Fukumura. “If the black hole is spinning fast, it can literally drag the surrounding space, and this can produce some wild special effects.”

Black holes are surrounded by a disk of searing hot gas rotating at close to the speed of light. A black hole can only consume material so quickly, so any additional matter backs up into this accretion disk. The material in these disks can form hot spots which emit random bursts of X-rays.

When the researchers accounted for the predictions made by Einstein’s general theory of relativity, they realized that the severe warp of spacetime can actually change the path X-rays take as they escape the grasp of the black hole. The X-rays can actually be delayed, depending on the position of the black hole, the position of the flare, and Earth.

If the black hole is rotating at the most extreme speeds, photons can actually make several orbits around the black hole before escaping.

“For each X-ray burst from a hot spot, the observer will receive two or more flashes separated by a constant interval, so even a signal made up from a totally random collection of bursts from hot spots at different positions will contain an echo of itself,” says Kazanas.

Astronomers watching these flashes will have a powerful observational tool they can use to probe the nature of the black hole. The frequency of the flashes would provide astronomers with an accurate way to measure the mass of the black hole.

Original Source: NASA News Release

The supermassive black holes that lurk at the hearts of the most massive galaxies might be spinning faster than astronomers ever thought. In fact, they might be spinning at the very limits predicted by Einstein’s theory of relativity. Perhaps it’s this extreme rotational speed that generates the energetic jets that blast out of the most massive and active galaxies.

Astronomers used NASA’s Chandra X-Ray Observatory to study 9 giant galaxies that seem to contain rapidly spinning supermassive black holes. These galaxies have large disturbances in their gaseous atmosphere, so the researchers calculated that these black holes must be spinning at near their maximum rates.

“We think these monster black holes are spinning close to the limit set by Einstein’s theory of relatively, which means that they can drag material around them at close to the speed of light,” said Rodrigo Nemmen, a visiting graduate student at Penn State University.

According to Einstein, when a black hole rotates at extreme speeds, it can actually catch up the surrounding space time and make that rotate as well. This effect, linked with the inflowing streams of gas can produce rotating, tightly wound towers of powerful magnetic fields. These fields channel the energy and inflowing gas into powerful jets which blast away from the black hole at nearly the speed of light.

It’s believed that black holes can acquire these extreme rotational speeds when galaxies merge. Fresh material falling onto the black hole just boosts its speed higher and higher until it reaches the hard limits allowed by relativity.

And it’s this extreme rate of spin that forms the power source for the jets. With the number of powerful jets seen pouring out of many galaxies, it might be that most supermassive black holes are spinning at extreme rates; we just haven’t detected them yet.

Supermassive black holes can be very disruptive to their local environments. The jets pump enormous amounts of energy into their surroundings, heating up gas. Since stars can only form when there are large clouds of cold gas, these process of heating can stall star formation in the host galaxy.

Astronomers want to work out the relationship between supermassive black holes and the rates of star formation in the most massive galaxies in the Universe.

Original Source: Chandra News Release

Uh oh, this doesn’t sound good. It turns out there could be hundreds of rogue black holes, each weighing thousands of times the mass of the Sun, hurtling though the Milky Way. Oh, and they’d be almost impossible to spot.

Vanderbilt astronomer Kelly Holley-Bockelmann presented the results of a supercomputer simulation at the Winter meeting of the American Astronomical Society.

The research focused on modeling the controversial “intermediate mass” black holes. These are the theorized black holes that should form within globular star clusters, containing a few thousand times the mass of the Sun; much heavier than the stellar mass black holes, but a fraction the mass of the supermassive variety. Astronomers have been looking for them for years, and even after all that searching, they’ve only come up with a couple of tentative candidates. So maybe these black holes are all around us, kicked out of their globular clusters, free to wander the galaxy.

Scientists have been hard at work modeling what might happen as two black holes merge. This is the realm where Einstein’s theory of relativity comes into play because of the tremendous forces and masses involved.

The simulations predict that as two black holes come together to form a new, even more massive black hole, it should receive a tremendous “kick” because of the conservation of momentum. The newly formed black hole should actually get kicked right out of the globular cluster in a random direction as fast as 4,000 kilometres a second.

Since the escape velocity of a globular cluster is only about 100 km/s, that black hole won’t ever come back to its home.

Now, if this research is true, the roughly 200 globular clusters in the Milky Way might have spawned intermediate-sized black holes, and then ejected them in random directions into the galaxy. There are probably several hundred black holes wandering invisibly through our galaxy.

Now don’t get too scared, “these rogue black holes are extremely unlikely to do any damage to us in the lifetime of the Universe,” soothed Holly-Bockelmann. “Their danger zone, the Schwarzschild radius, is really tiny, only a few hundred kilometers. There are far more dangerous things in our neighborhood.”

Original Source: Vanderbilt News Release

You know that big list of unsolved mysteries in astronomy? Well, you can remove, “what causes the highest energy cosmic rays?” Thanks to new research using the Pierre Auger Cosmic Ray Observatory in South America, the answer appears to be: supermassive black holes.

High energy cosmic rays are actually particles – protons mostly – accelerated to tremendous velocities. When they crash into the Earth’s atmosphere, they explode in a spray of energy and sub-particles that can be detected here on the surface. Fortunately our atmosphere protects us from damage, but out in space, they’re a real threat.

Just a single particle can have the same energy as fast moving tennis ball.

Astronomers have been wondering for years how particles can get boosted to such high energy levels. A massive team of 370 researchers from 17 countries have been working on the answer using the newly developed Pierre Auger Cosmic Ray Observatory, nestled in the mountains of South America.

The observatory is actually an array of detectors spread out over a 3,000 km² area. As the cosmic rays collide with the atmosphere, the resulting spray of particles are caught by the detectors, which house large tanks of water. The detectors are so sensitive, they can detect a different in timing, which allow astronomers to triangulate the direction the cosmic ray came from. The particles are flung with such energy that they point back to their galaxies, like bullets coming from a gun.

Before the Pierre Auger observatory, cosmic ray detections were rare. Astronomers just didn’t have enough data to know where they were coming from. But over the last 3 years, the observatory has recorded a million cosmic rays, including 80 of the highest energy.

Astronomers now know that cosmic rays don’t come from all regions of the sky, but they’re shot out from actively feeding supermassive black holes.

The exact process that creates the cosmic rays isn’t fully understood, but astronomers think that the environment around an active supermassive black hole is ferocious, to say the least. Powerful magnetic fields are generated, which can act like natural particle accelerators, pushing protons to energy levels much higher than anything physicists could recreate with our technology.

Original Source: University of Chicago News Release

Astronomers are now understanding the connection between supermassive black holes and the galaxies they inhabit better and better. In fact, it now looks like the powerful winds that blow out of these monsters can have a significant effect on the galaxies they inhabit, helping determine their growth.

In a recent study, published in the journal Nature, a group of scientists from the Rochester Institute of Technology report on their study of the rotating winds the rise up above the accretion disks surrounding supermassive black holes in distant galaxies.

With millions of times the mass of the Sun, supermassive black holes pull strongly at the material in their host galaxy. Just like water going down a drain, this material backs up into a swirling accretion disk. The material heats up, and blazes with radiation visible clear across the Universe – this is a quasar.

Astronomers from RIT and the University of Hertfordshire in England studied one quasar, PG 1700+518, located about 3 billion light-years from Earth. They were able to detect winds of gas coming off the accretion disk for the first time, both moving vertically away from the disk, but also rotating at the same speed.

This helps solve the long-standing mystery of how the accretion disk rids itself of angular momentum. It turns out, this wind needs to happen. If gas wasn’t being removed this way, material would stop falling in, and the quasar would turn off as the supermassive black hole was starved for fuel.

This wind both helps manage the growth of the black hole, but it also regulates the evolution of the galaxy. As the wind moves out into more distant regions of the galaxy, it helps collapse pockets of cold hydrogen, leading to regions of star formation.

Original Source: RIT News Release

Wait, stop the internet! Remember when I said the most massive black hole had been discovered? Sorry, that record has been broken by an even more “most massive black hole”. 16 times the mass of the Sun? Please. This new one raises the bar with a mass of 24 to 33 times the mass of our Sun.

As with the previous black hole, located in the nearby galaxy M33, this newly announced black hole is in a binary system. It’s located in the nearby dwarf galaxy IC 10, 1.8 million light-years from Earth in the constellation Cassiopeia. Since it’s orbiting another star, astronomers were able to calculate its mass – 24-33 solar masses.

The discovering team, led by Andrea Prestwich of the Harvard-Smithsonian Center for Astrophysics used NASA’s Chandra X-ray Observatory to study IC 10. They observed that the galaxy’s brightest X-ray source, IC 10 X-1, varied in brightness. This led them to believe that a star was periodically passing in front of a black hole, briefly obscuring it from view.

Follow up observations with NASA’s Swift satellite confirmed that the black hole was being eclipsed by the companion star, and gathered enough data that astronomers could work out the orbital period, and thus the masses of both objects.

A black hole this massive is surprising. Astronomers calculate that massive stars should throw off most of their gas before detonating as supernovae. No black hole should be able to exceed 15 times the mass of the Sun.

In the case of IC 10 X-1; however, it’s blown past that theoretical limit. Of course, it could have detonated as its largest size, and then consumed material from its companion article. But according to their calculations, it could only have gained 1 or 2 solar masses over the years.

So how did it get so large?

It probably started life with about 60 times the mass of the Sun. Since its host galaxy is deficient in any heavier elements, it was probably composed largely of hydrogen and helium. The heavier elements are actually easier to blow away from the star on the solar wind, so it maintained most of its mass right up until the end.

Original Source: CfA News Release