Category: Black Holes

An international team of astronomers have discovered a supermassive black hole at the very edge of the observable Universe, located 13 billion light-years away. Since the Universe is 13.7 billion years old, we’re seeing this object when the Universe was only 700 million years old. Wow.

Active galactic nuclei, or quasars, occur when a supermassive black hole is feasting on infalling material. Material piles up faster than the black hole can feed, and it starts to glow so brightly that astronomers can see it clear across the Universe. This object, CFHQS J2329-0301, was discovered as part of a new distant quasar survey performed with the MegaCam imager on the Canada-France-Hawaii Telescope (CFHT).

The black hole powering the quasar is thought to have 500 million times the mass of the Sun – that makes it hungry and bright. And because the quasar is so bright, astronomers can use it as a background object to examine the gas in front. And with follow up observations, they can get more details about what kind of galaxy it formed inside.

Original Source: Canada-France-Hawaii Telescope News Release

You know the saying: nothing, not even light can escape a black hole. That makes them invisible. Amazingly, researchers from the University of Maryland have determined how fast a supermassive black hole is spinning. You won’t be surprised to know it’s spinning insanely fast, at the limits predicted by relativity.

The researchers used ESA’s XMM-Newton X-Ray telescope to examine the quantity of iron in an accretion disk around a supermassive black hole at the centre of galaxy MCG-06-30-15. Because the disk is spinning so rapidly, the light from the disk is warped relativistically. According to their calculation, the black hole must be spinning at least 98.7% of the maximum spin rate allowable by Einstein’s Theory of General Relativity.

This result helps astronomers understand how black holes grow over time. If supermassive black holes formed by slowly pulling in surrounding matter, they would be expected to spin faster and faster, until they reach this relativistic limit. If the supermassive black holes were instead formed by colliding smaller black holes, they’d be spinning much more slowly.

Original Source: UM News Release

Supermassive black holes lurk at the heart of galaxies, containing the mass of millions of stars. Stellar mass black holes can contain the mass of a few suns. But astronomers have been perplexed why they haven’t been able to turn up intermediate mass black holes, containing merely hundreds or thousands of times the mass of our Sun.

Well, now they have. Astronomers using the NSF’s Very Large Array (VLA) radio telescope have turned up a globular cluster in the Andromdeda Galaxy (M31) that seems to contain a black hole with the mass of 20,000 times the mass of the Sun; one of these long-sought intermediate black holes.

Researchers originally detected X-rays emitted from this globular cluster, and then did follow up observations in the radio spectrum to confirm that a high mass, compact object is inside the cluster. Although the best explanation is a black hole, it could also be a cluster of compact objects, like neutron stars and black holes. The quantity of radio emissions coming from the object fits the curve perfectly between stellar and supermassive black holes.

Original source: NRAO News Release

The huge majestic spiral galaxy we live in today was built up over billions of years through mergers with other galaxies. And in 5-10 billion years from now, we’ll merge together with the Andromeda Galaxy. Since both galaxies are thought to have a supermassive black hole at their centre, what will happen when they merge together? One possibility is that one black hole will get ejected from the combining galactic core at a tremendous velocity.

Astronomers have suspected this kind of interaction might happen. The velocities and gravitational forces are so great during a black hole merger, that one of the objects could be flung out like a slingshot. It was believed that the black hole would be stripped of its accretion disk as it’s flung out into the galaxy, so it would be impossible to detect.

But new calculations by Avi Loeb, a researcher with the Harvard-Smithsonian Center for Astrophysics, indicate that an ejected black hole might be able to bring its accretion disk along for the ride. And the radiation pouring out of this disk might be detectable here on Earth.

If the calculations are correct, the two merging black holes will be releasing torrents of gravitational radiation in the direction they’re orbiting. The momentum from this radiation will give one black hole a kick in the opposite direction, ejecting it at 16 million km/hour (10 million mph). At this speed, a black hole would traverse its galaxy in just 10 million years.

According to Loeb, as long as the gas within the disk was orbiting at a speed far great than the black hole ejection speed, it would follow the black hole on its journey. It could last a few million years, consuming this disk of material, and blazing brightly enough that powerful telescopes could detect it. The host galaxy would seem to have a double quasar.

Original Source: CfA News Release

Astronomers have located an ongoing galactic merger, pinpointing the exact location of each galaxy’s supermassive black hole. These twin monsters are swirling around each other, and in several million years, they’ll merge together, releasing a powerful blast of gravitational radiation.

The twin galaxies are collectively known as NGC 6240, located about 300 million light years away, and they were recently imaged by the powerful adaptive optics system of the W.M. Keck Observatory in Hawaii. Under Keck’s vision, NGC 6240 was revealed to have two rotating disks of stars, each of which had its own supermassive black hole.

Millions of years ago, these would have been two separate galaxies that got to close to one another, and began merging. This process of galactic evolution is similar to the process that built up our own Milky Way, over billions of years. Astronomers are starting to understand the connection between the black holes and the total mass of the galaxy that surrounds them. As galaxies grow, the mass of their supermassive black holes grows too.

The twin supermassive black holes are slowly falling in to a common centre of gravity. In the next 10 to 100 million years, they’ll spiral into each other and merge into a single black hole. This collision will release waves of gravitational radiation.

Original Source: UCSC News Release

It might sound surprising, but one of the most difficult tasks astronomers have is determining the mass of objects. It takes a binary system, where two stars or orbiting one another, to be able to make an accurate mass calculation. And determining the mass of black holes is even more difficult because they’re invisible.

But the clever astronomers have figured out a way, by measuring the location of the swirling accretion disk of material waiting to be consumed around a black hole. Since material can pile up faster than the black hole can consume it, it compresses together, heats up, and emits radiation that astronomers can detect. Researchers have discovered that there is a direct relationship between a black hole and the size of its surrounding accretion disk. Astronomers have calculated that this hot gas piles up in a location that scales up with the mass of the black hole. The more massive the black hole, the farther out the congestion occurs.

This technique has helped astronomers identify likely intermediate black holes, which contain thousand of times the mass of the Sun. Much more than a stellar mass black hole, but much less than the hundreds of millions of suns worth of mass in supermassive black holes.

Original Source: ESA News Release

Here’s a scenario that will face many of us in the far future. You’re hurtling through the cosmos at nearly the speed of light in your spaceship when you take a wrong turn and pass into the event horizon of a black hole. Uh oh, you’re dead – not yet, but it’s inevitable. Since nothing, not even light can escape the pull from a black hole once it passes into the event horizon, what can you do to maximize your existence before you join the singularity as a smear of particles?

Physicists used to think that blackholes were sort of like quicksand in this situation. Once you cross the event horizon, or Schwarzschild radius, your date with the singularity is certain. It will occur at some point in the future, in a finite amount of proper time. The more you try to struggle, the faster your demise will come. It was thought that your best strategy was to do nothing at all and just freefall to your doom.

Fortunately, Geraint F. Lewis and Juliana Kwan from the School of Physics at the University of Sydney, have got some suggestions that fly in the face of this stuggle = quick death hypothesis. Their paper is called No Way Back: Maximizing survival time below the Schwarzschild event horizon, and it was recently accepted for publication in the Proceedings of the Astronomical Society of Australia.

When an unlucky victim falls into the event horizon of a black hole, they will survive for a finite amount of time. If you fall straight down into a stellar black hole, you’ll last a fraction of a second. For a supermassive black hole, you might last a few hours.

Due to the tremendous tidal forces, an unlucky victim will suffer spaghettification, where differences in gravity from your head to your feet stretch you out. But let’s not worry about that for now. You’re trying to maximize survival time.

Since you’ve got a spaceship capable of zipping around from star to star, you’ve got a powerful engine, capable of affecting your rate of descent. Point down towards the singularity and you’ll fall faster, point away and you’ll fall more slowly. Keep in mind that you’re inside a black hole, flying a spaceship capable of traveling near the speed of light, so Einstein’s theories of relativity come into play.

And it’s how you use your acceleration that defines how much personal time you’ll have left.

In a moment of panic, you may point your rocket outwards and fire it at full thrust, keeping the engine running until you arrive at the central singularity. However, Lewis and Kwan have demonstrated that in the convoluted space-time within the event horizon, such a strategy actually hastens your demise, and you’ll actually end up experiencing less time overall. So, what are you to do? Lewis and Kwan have the solution, identifying an acceleration “sweet-spot” that gives you the maximal survival time. All you have to do, once across the event horizon, is fire your rocket for a fixed amount of time, and then turn it off and enjoy the rest of the fall.

But how long should you fire your rocket for? Lewis and Kwan show this is a simple calculation involving the mass of the black hole, how powerful your rocket is, and how fast you crossed the event horizon, easily doable on a desktop computer.

Here’s another analogy from Lewis:

“Consider a race to the centre between a free faller and a rocketeer. Suppose they cross the event horizon together holding hands. As they cross, they start identical stop watches. One falls inwards, while the other accelerates towards the centre for a little, then swings their rocket round and decelerates such that the free faller and the rocketeer meet and clasp hands again just before hitting the singularity. A check on their stop watches would reveal that the free faller would experience the most personal time in the trip. This is related to one of the basic results of relativity – people in freefall experience the maximum proper time.”

So now you know. Even after you’ve fallen into the black hole’s event horizon, there are things you can do to lengthen your harrowing journey so that you get to experience more time.

Time to you can use to deal with your spaghettification problem.

Original Source: Arxiv research paper