Category: Black Holes

Astronomers now believe there are supermassive black holes at the heart of every galaxy. When these black holes are actively feeding on material, they blaze with radiation, visible across the Universe. These active galaxies are known as quasars, and they were thought to be very common in the early Universe. But astronomers were having trouble finding almost any of them. It turns out, they were just hiding.

Supermassive black holes live at the very centre of galaxies, regions that can be thick with gas and dust. As the supermassive black hole goes into its actively feeding stage, the torrents of radiation that pour out collide with the dust. Instead of shining across the Universe, the radiation is smothered by dust.

These black holes are hidden, but they’re not entirely undetectable. Astronomers used NASA’s Spitzer Space Telescope to study 1,000 dusty, massive galaxies known to be furiously making stars. With all this gas and dust tearing around, you would think the supermassive black holes would be actively feeding, and blazing as quasars. But no quasars were seen.

Spitzer’s infrared view, however, allowed astronomers to pierce through the dusty veil surrounding the supermassive black hole, and see that 200 of the galaxies were producing an unusual amount of infrared light. The quasars heat up the dust in the surrounding doughnut cloud, and this cloud gives off the radiation detected by Spitzer.

These quasars are between 9 and 11 billion light-years away. In other words, we see the light they gave off when they were only 2.5 – 4.5 billion years old. Before now, only the rare, extremely energetic quasar was visible – after they had cleared away the surrounding gas and dust. This expanded population gives astronomers a much better understanding of galaxy evolution in the early Universe.

This discovery also downplays the role that galaxy collisions might have had in the early Universe, “theorists thought that mergers between galaxies were required to initiate this quasar activity, but we now see that quasars can be active in unharassed galaxies,” said co-author David Alexander of Durham University, United Kingdom.

The observations were made as part of the Great Observatories Origins Deep Survey, the most sensitive survey to date of the distant universe at multiple wavelengths.

Original Source: NASA News Release

Black holes come in two varieties: supermassive and stellar. The supermassive variety can have millions of times
the mass of a star, while the stellar varieties are usually just a few times the mass of a single sun. Using the Chandra X-Ray Observatory, astronomers have turned up the most massive stellar mass black hole ever seen, weighing in at 15.7 times the mass of the Sun, lurking in a nearby galaxy.

M33 is a relatively nearby galaxy, located only 3 million light years from Earth. This newly discovered black hole has been designated as M33 X-7.

Astronomers using NASA’s Chandra X-Ray Observatory and the Gemini telescope on Mauna Kea were able to precisely determine the black hole’s mass because it’s actually in a binary system. Its binary partner is unusual too; a star with 70 times the mass of the Sun.

M33 X-7 orbits its companion star every 3.5 days, briefly passing behind it. This blocks the torrent of X-rays streaming from the environment around the black hole, so that astronomers were able to calculate its orbit. Once they could calculate the orbits of the two binary objects, it’s relatively straightforward to calculate their respective masses.

The fate of the companion star will eventually match its partner. “This is a huge star that is partnered with a huge black hole,” said coauthor Jeffrey McClintock of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “Eventually, the companion will also go supernova and then we’ll have a pair of black holes.”

Although the black hole has less mass today, it must have started out with more. With more mass in the original star, it would have consumed its fuel more quickly, and detonated as a supernova earlier.

Here’s a puzzle, though. Before the black hole formed, the two stars wouldn’t have been able to orbit so closely. In fact, they would have been orbiting inside each other. This means that they were once further apart, and the process of sharing their outer atmospheres brought their orbits closer together.

Original Source: Chandra News Release

Carl Sagan noted that we’re all made of starstuff; the elements fused together in stars and detonating supernovae. But maybe we’re made of something else too, outflowing dust from actively feeding supermassive black holes – known as quasars – that populated the early Universe. New observations made by NASA’s Spitzer Space Telescope has found evidence of dust pouring out of distant quasars. Dust that might have gone on to form more complex molecules, and even life. We’re all made of quasarstuff?

Our Sun formed in a region of the Milky Way enriched by the deaths of massive stars. As these monsters detonated as supernovae, they created the heavier elements and spread them far and wide around the region. But what about the early Universe, before generations of massive stars had a chance to live and then die as supernovae? Where did all the raw materials come from?

Researchers from the University of Manchester in the U.K. have written a new research article describing how they have discovered dust pouring out of supermassive black holes in the early Universe. Known as quasars, and bright enough to be seen clear across the Universe, these actively feeding black holes are actually quite messy. They eject more material out in polar jets than they’re actually able to consume.

And according to Spitzer, the material they’re ejecting contains plenty of complex dust. In one example, a quasar 8 billion light-years away is spewing out a mix of ingredients that make up glass, sand, marble and even precious gems like rubies and sapphires.

This is quite surprising, since the main ingredient of sand, crystalline silicate, can’t last long in space. The radiation from stars should be blasting the molecules back to a glass-like state. If there’s crystalline silicate, there must be a source replenishing it faster than the radiation can break it down. That source seems to be quasars.

It now appears that both supernovae and quasars work together to seed galaxies with heavier elements and complex molecules. So, we might not only be starstuff, we could also be quasarstuff.

Original Source: NASA/JPL/Spitzer News Release

You just know this is going to take some serious computer horsepower. Rochester Institute of Technology’s Center for Computational Relativity and Gravitation was recently awarded $330,000 from the National Science Foundation to simulate collisions between black holes. Dubbed “newHorizons”, this will be a cluster of 85 dual core processors acting like a single large computer. 1.4 terabytes of memory; 36 terabytes of storage. Yowza.

Sorry to geek out there, I’m getting little tired of the computer sitting on my desk right now. But any upgrade I might buy won’t hold a candle to this new supercomputer from the Rochester Institute of Technology.

The project is headed up by Manuela Campanelli, who led her team to solve the 10 equations in Einstein’s theory of general relativity for strong field gravity. She joined forces with physics professor David Merritt, who built the 32-node gravitySimulator, which calculations the gravitational interaction between objects, such as dark matter and galaxies.

As I mentioned in the intro, this new machine will consist of 85 nodes – individual computers with their own memory, processor – which are connected together. The latency, or delay, in communication between the individual computers is so low, that they can act like a single, large supercomputer – but built at a fraction of the cost.

Once newHorizons is built, the development team is expecting it’ll be running 24 hours a day for 5 or 6 years, simulating black hole collisions and mergers. The extra horsepower will allow physicists to simulate more complex interactions with additional variables that would overwhelm other computers.

Original Source: RIT News Release

Astronomers now believe there’s a supermassive black hole at the centre of almost every galaxy in the Universe. These black holes can have millions, or even hundreds of millions of times the mass of the Sun. Unlike stellar mass black holes, the supermassive versions might have formed differently, going from a cloud of gas directly to a black hole – skipping the star stage entirely.

Since their discovery, astronomers still don’t really know how supermassive black holes got going. But there they are, inside most galaxies. In fact, quasar observations show that supermassive black holes were present in the early Universe. Quasars are some of the brightest objects in the Universe, blazing from the radiation emitted by supermassive black holes actively consuming material.

One possibility is that these monsters had humble beginnings, starting out as a massive star, going supernova, and then becoming a black hole. It’s a process astronomers understand fairly well. The problem with this theory is that these early supermassive black holes must have been growing constantly right from the beginning, at the maximum rate predicted by physics. And as we see today, galaxies go through active and quiescent stages depending on when their black hole is consuming material.

But a second possibility is that these black holes formed directly, pulling together so much material that they bypassed the stellar stage entirely.

Dr. Mitchell C. Begelman, a professor in the Department of Astrophysical and Planetary Sciences at the University of Colorado, Boulder recently published a paper entitled Did supermassive black holes form by direct collapse? This paper sketches out this alternate theory of black hole formation in the early Universe.

After the Big Bang, the Universe cooled enough for the first stars to form out of the original hydrogen and helium. This was pure material, unpolluted by previous generations of stars. Astronomers have calculated that these first stars, called Population III, would have a maximum rate that they could gather material together to form a star.

But what if there was much more gas around? Way beyond the limits that could form a star.

With a regular star, material comes in relatively slowly, creating a central mass. With enough mass, the star ignites, and this creates and outward pressure that stops further material from compacting too tightly.

But Dr. Begelman has calculated that if the infall rate exceeds just a few tenths of a solar mass per year, the stellar core would be so tightly bound that the energy release of nuclear fusion wouldn’t be enough to stop the core from continuing to contract. You would never have a star, you would just go from a cloud of hydrogen to a tightly bound central mass. And then a black hole.

The question is, would it be possible to have material come together so quickly? It can, if something’s pushing it… like dark matter. According to Dr. Begelman, there could be several situations where an external force, like the gravity from a large halo of dark matter which could work to force gas into a central area. In fact, material has been calculated falling into a black hole this quickly, because that’s the rate it takes to power quasars. But the question is, will this work if the black hole isn’t there, or really small.

Once there are a few solar masses of accumulated gas, the core begins to shrink under the pull of its increasing mass. The object goes through a brief period of nuclear fusion when it reaches 100 solar masses, but it passes through this phase so rapidly that it doesn’t get a chance to expand again.

Eventually the object reaches several thousand solar masses, and its temperature has climbed to several hundred million degrees. At this point, gravity finally takes over, collapsing the core, and turning the object into a 10-20 solar mass black hole which then starts consuming all the mass around it.

From this point on, the black hole is able to draw in further material efficiently, growing at the maximum levels predicted by physics, eventually gathering up millions of times the mass of the Sun. If too much material falls in, the baby supermassive black hole might act like a mini-quasar – Dr. Begelman has dubbed this a “quasistar” – blazing with radiation as infalling material backs up in the black hole’s surroundings.

And there’s the good news: these quasistars might be detectable by powerful telescopes. However, they would have very short lifetimes, only lasting 100,000 years. They might be marginally detectable by the upcoming James Webb Space Telescope.

Original Source: Arxiv paper

New observations from the Spitzer Space Telescope indicate that supermassive black holes at the heart of elliptical galaxies might keep temperatures so high that gas can’t cool down. And without large clouds of cool gas, new stars can’t form. As long as the black hole is raging, star formation in the galaxy is put on hold.

Thanks to the Spitzer observations, astronomers have detected dust grains mingling with blazing hot gas at temperatures of 10 million degrees Celsius in an area surrounding the elliptical galaxy NGC 5044. Astronomers have seen this kind of situation before, where hot gas surrounding galaxies blaze hot in the X-ray spectrum.

There are many kinds of galaxies. Spiral galaxies like our own Milky Way have active regions of star formation. The older, larger, redder elliptical galaxies are different. They’re found at the centres of galaxy clusters, and have large quantities of hot gas that never seems to cool down enough to begin star formation.

Researchers from UC Santa Cruz think that this hot gas is being heated by the supermassive black holes through a process called feedback heating. They believe that material ejected by dying stars gravitates towards the centre of the galaxy. As it approaches the black hole, a large amount of energy is released, heating the gas up. This makes it buoyant, sort of like how smoke and embers float away from a fire. These plumes then mix with other, more distant gas, and heat it up as well. Each time the supermassive black hole feeds, it creates a feedback effect that travels outward, heating up gas across the galaxy.

And this is what kills star formation. Stars can only form when dust is cool enough to condense together, like water makes steam – you only get rain when it cools down. With all this heated gas, material never comes together to create stars.

Original Source: Spitzer News Release