Counting up the Active Black Holes with Chandra

agns.thumbnail.jpg

The newest image released from NASA’s Chandra X-Ray Observatory is helping astronomers build up a census of the number of actively feeding supermassive black holes across the Universe. Scientists are hoping to build up a comprehensive picture of where (and thus when), these black holes were blasting out radiation.

It’s now thought that almost every galaxy in the Universe seems to contain a supermassive black hole at its centre. Perhaps the black holes came first and the rest of the galaxy formed around it, or maybe things evolved the other way around. Whatever the case, most of these black holes are in a quiescent state; apart from their gravitational influence on nearby stars, they’re all but invisible.

From time to time, however, the space surrounding these black holes flares up. Material falling into the black hole chokes up, and spreads out into a rapidly rotating accretion disk. Although the black hole itself is invisible, it’s this blocked up matter waiting to be consumed that shines hotly in the most energetic wavelengths.

This latest survey, gathered by NASA’s Chandra X-Ray Observatory seems to indicate that younger, more distant galaxy clusters contained many more active nuclei than the ones we see closer to us (and thus, closer to our current time). The more distant sample contains galaxies seen when the Universe was only 58% of its current age, while the closer sample shows galaxies at 82% of the galaxy’s current age. The more distant sample had 20x the number of active nuclei over the closer sample.

The research seems to point that the early Universe was much more likely to contain active galactic nuclei. This makes sense, since there was much more gas and dust in galaxies back then. This material was able to fuel the supermassive black holes. The research also points to a time in the future when there’ll be much less material to feed the black holes. It will become rarer and rarer to see these events.

Original Source: Chandra News Release

Black Holes are Key to the Evolution of the Universe

Slicer.thumbnail.jpg

A supercomputer simulation has retraced the evolution of the Universe, giving astronomers new clues on where they should point their telescopes. And it seems that one of the most important ingredients to this cosmic recipe is black holes.

The simulation is called BHCosmo, and it was performed on the Cray XT3 system at the Pittsburgh Supercomputing Center. The researchers tied up the whole system – 2,000 processors – for 4 weeks to run the simulation.

They started with initial conditions that matched the cosmic microwave background radiation. Next they seeded the area with 250 million particles of matter, and surrounded that with the gravitational force of dark matter. The researchers watched how the particles of matter collapsed to form galaxies and black holes.

One of the most important findings of the simulation was the impact of black holes. Galaxies look the way they do because of the supermassive black holes at their centres.

Eventually they hope to model the entire Universe with a resolution that matches the Sloan Digital Sky Survey, but that will take more computer power.

Original Source: Carnegie Mellon

Neutron Stars Have Jets Too

Chandra.thumbnail.jpg

One time, astronomers thought that only black holes had jets of material pouring out of them. Something to do with the event horizon, and a lack of a solid surface. Well, step aside black holes, neutron stars seem to have them too.

This is according to new images captured by NASA’s Chandra X-Ray Observatory, which imaged a system called Circinus X-1. This is actually a binary system, consisting of a massive star with several times the mass of our Sun, and a neutron star. The neutron star is feeding on material from the star, and has gathered together an accretion disk around itself. It’s consuming so much material from the star that it backs up into this disk, which glows hot in the X-Ray spectrum.

And just like with a black hole, the centre of the accretion disk acts like an engine, firing material out into space along these jets. But the power from this engine comes from the neutron star.

In the Chandra image in the upper left, you can see what looks like cones on the two sides of the neutron star. This neutron star could be wobbling like a top, with the jets tracking out these larger arcs.

Original Source: Chandra News Release

Are Microscopic Black Holes Buzzing Inside the Earth?

2007-0619blackhole.thumbnail.jpg

There’s a book by Larry Niven called “Hole Man”, where a group of explorers on Mars come across an alien communications device. One of the scientists thinks there’s a microscopic black hole inside, which powers the device, and to prove it, he turns off the containment field. The black hole falls into Mars, consuming the planet from within, and threatening the entire solar system.

Just science fiction? Maybe not. According to B.E. Zhilyaev, a researcher at the Main Astronomical Observatory in Ukraine, in the research paper Singular Sources of Energy in Stars and Planets, the Universe could be buzzing with these microscopic blackholes. They might even be inside stars and planets.

This isn’t a new concept. Physicists have been theorizing about the possibility of microscopic, primordial black holes for years, and used them to explain everything from dark matter to gamma ray bursts.

It takes a star several times the mass of our Sun to form a black hole naturally when it dies, so there probably isn’t a process that can make them any more. But during the first few moments after the Big Bang, the entire Universe was compressed into a microscopic singularity. These primordial black holes could have been generated right at the beginning, and have been with us ever since.

It’s also theorized that the new Large Hadron Collider might be capable of creating microscopic black holes through the collision of particles at relativistic velocities.

Before you can wrap your head around this research, consider how big a black hole has to be. For a stellar mass black hole, the event horizon – the point at which nothing can escape – is only a few kilometres from its centre. A black hole with the mass of the Earth? It would be less than 2 cm across. A black hole with the mass of a mountain? Smaller than a hydrogen atom.

Even though a microscopic black hole might contain the mass of a mountain, it would experience almost no friction as it passed through regular matter. It would fall through regular material as if it wasn’t there.

In most encounters with stars, these black holes would pass right through. But in a three-body interaction, between a star and a planet for example, the black hole could be trapped inside the star. The black hole would then orbit inside the star for billions of years until it comes to rest at the centre. They could form with the stars and planets from a protostellar cloud of gas and dust, or be captured and incorporated later.

So how do you know if you’ve got a black hole in your star? As the black hole grows over time, it starts to change the amount of heat generated by the star. A large enough black hole could cause the star to expand in size, and even undergo a supernova prematurely. According to Zhilyaev the interactions between stars and microscopic black holes could be detectable through bursts of gamma rays.

And if a black hole gets inside your planet? You get additional heat. This might account for unusual temperatures seen on Saturn and Jupiter, which are hotter than they should be from solar heating alone. A black hole inside the Earth might actually raise temperatures on the surface enough to sustain animal life long after the Sun dies out.

A power source that would last for eons, providing the most efficient possible conversion of matter to energy. Just don’t think about the monster consuming the ground beneath your feet as it keeps you warm.

How Supermassive Black Holes Come Together

2007-0608merger.thumbnail.jpg

Galaxies get bigger and bigger through galactic mergers. Two small galaxies come together, merge their stars, and you get a bigger galaxy. But astronomers have always wondered, what happens with the two supermassive black holes that seem to always lurk at the heart of galaxies. What happens when two compact objects with millions of times the mass of our sun collide? Good question.

An international team of physicists have developed a computer simulation designed to answer this very question. And in a recent article in Science Express, they published the results of the simulation.

It turns out the interaction depends a lot on the amount of hot gas surrounding each black hole. As they start to interact, this gas exerts a frictional force on the black holes, slowing down their spin rate. Once they get within the width of our solar system, they should start emitting gravitational waves, which continues to extract energy from the system. This causes them to continue coming together, and eventually merge.

This simulation is good news for experiments designed to search for gravitational waves. The mergers should be so energetic, they’ll generate gravitational waves detectable across space.

Original Source: Stanford News Release

Most Distant Black Hole Discovered

2007-0607blackhole.thumbnail.jpg

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

Spitzer Locates a Binary Pair of Black Holes

2007-0531spitzer.thumbnail.jpg

A clever trick has enabled NASA’s Spitzer Space Telescope to calculate the distance to a distant object, confirming that it’s part of our Milky Way. An even more intriguing finding is that the object is probably a binary pair of black holes, orbiting one another – an extremely rare thing to see.

The Spitzer Space Telescope is the only space telescope that orbits the Sun behind the Earth. It’s already 70 million km (40 million miles), and it’s drifting further away every year. This distance between Spitzer and the Earth allows astronomers to look at an object from two different perspectives. Just like our two eyes give us depth perception, two telescopes can measure the distance to an object.

Astronomers noticed that something was causing a star to brighten. The speed and intensity of this brightening matched a gravitational lensing event, where a foreground object’s gravity focuses the light from a more distant star. They imaged the lensing event from here on Earth, but they also called Spitzer into duty to watch as well. Data from the two sources were combined together to determine that the lensing object is inside our galactic halo, and therefore part of its mass.

The light curve of the gravitational lens has led the researchers to believe that they’re looking at two compact objects orbiting one another, quite possibly a binary pair of black holes. It’s also possible that it’s just a pair of regular stars in a neighbouring, satellite galaxy.

Original Source: Spitzer News Release

Supermassive Black Holes Spin at the Limits of Relativity

2007-0529smb.thumbnail.jpg

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

Medium-Sized Black Hole Lurks in a Star Cluster

2007-0528vla.thumbnail.jpg

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

Ejected Black Holes May Take Their Fuel With Them

2007-0523blackholes.thumbnail.jpg

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