What Would Happen if a Small Black Hole Hit the Earth?

We can all guess what would happen should a massive black hole drift into our solar system… there wouldn’t be much left once the intense gravitational pull consumes the planets and starts sucking away at our Sun. But what if the black hole is small, perhaps a left over remnant from the Big Bang, passing unnoticed through our neighborhood, having no observable impact on local space? What if this small singularity falls in the path of Earths orbit and hits our planet? This strange event has been pondered by theoretical physicists, understanding how a small black hole could be detected as it punches a neat hole though the Earth…

Primordial black holes (PBHs) are a predicted product of the Big Bang. Due to the massive energy generated at the beginning of our Universe, countless black holes are thought to have been created. However, small black holes are not expected to live very long. As black holes are theorized to radiate energy, they will also lose mass (according to Stephen Hawking’s theory, Hawking Radiation), small black holes will therefore fizz out of existence very rapidly. In a well known 1975 publication by Hawking, he estimates the minimum size a black hole must be to survive until present day. The PBH would have to be at least 1012kg (that’s 1,000,000,000,000 kg) in mass when it is created. 1012kg is actually quite small in cosmic standards – Earth has a mass of 6×1024kg – so we are talking about the size of a small mountain.

So, picture the scene. The Earth (any planet for that matter) is happily orbiting the Sun. A small primordial black hole just happens to be passing through our solar system, and across Earths orbit. We are all aware of how a rocky body such as a Near Earth Asteroid would affect the Earth if it hit us, but what would happen if a small Near Earth Black Hole hit us? Theoretical physicists from the Budker Institute of Nuclear Physics in Russia, and the INTEGRAL Science Data Center in Switzerland, have been pondering this same question, and in a new paper they calculate how we might observe the event should it happen (just in case we didn’t know we had hit something!).

PBHs falling into stars or planets have been thought of before. As previously reviewed in the Universe Today, some observations of the planets and stars could be attributed to small black holes getting trapped inside the gravitational well of the body. This might explain the unusual temperatures observed in Saturn and Jupiter, they are hotter than they should be, the extra heat might be produced by interactions with a PBH hiding inside. If trapped within a star, a PBH might take energy from the nuclear reactions in the core, perhaps bringing on a premature supernova. But what if the PBH is travelling very fast and hits the Earth? This is what this research focuses on.

I’d expect some catastrophic, energetic event as a primordial black hole hits the Earth. After all, it’s a black hole! But the results from this paper are a bit of an anti-climax, but cool all the same.

By calculating where the energy from the collision may come from, the researchers can estimate what effect the collision may have. The two main sources of energy will be from the PBH actually hitting Earth material (kinetic) and from black hole radiation. Assuming we have more likelihood of hitting a micro-black hole (i.e. much, much smaller than a black hole from a collapsed star) originating from the beginning of the Universe, it is going to be tiny. Using Hawking’s 1012kg black hole as an example, a black hole of this size will have a radius of 1.5×10-15 meters… that’s approximately the size of a proton!

This may be one tiny black hole, but it packs quite a punch. But is it measurable? PBHs are theorized to zip straight through matter as if it wasn’t there, but it will leave a mark. As the tiny entity flies through the Earth at a supersonic velocity, it will pump out radiation in the form of electrons and positrons. The total energy created by a PBH roughly equals the energy produced by the detonation of one tonne of TNT, but this energy is the total energy it deposits along its path through the Earths diameter, not the energy it produces on impact. So don’t expect a magnificent explosion, we’d be lucky to see a spark as it hits the ground.

Any hopes of detecting such a small black hole impact are slim, as the seismic waves generated would be negligible. In fact, the only evidence of a black hole of this size passing through the planet will be the radiation damage along the microscopic tunnel passing from one side of the Earth to the other. As boldly stated by the Russian/Swiss team:

It creates a long tube of heavily radiative damaged material, which should stay recognizable for geological time.” – Khriplovich, Pomeransky, Produit and Ruban, from the paper: “Can one detect passage of small black hole through the Earth?

As this research focuses on a tiny, primordial black hole, it would be interesting to investigate the effects of a larger black hole would have on impact – perhaps one with the mass of the Earth and the radius of a golf ball…?

Source paper: arXiv

Synthetic Black Hole Event Horizon Created in UK Laboratory

Researchers at St. Andrews University, Scotland, claim to have found a way to simulate an event horizon of a black hole – not through a new cosmic observation technique, and not by a high powered supercomputer… but in the laboratory. Using lasers, a length of optical fiber and depending on some bizarre quantum mechanics, a “singularity” may be created to alter a laser’s wavelength, synthesizing the effects of an event horizon. If this experiment can produce an event horizon, the theoretical phenomenon of Hawking Radiation may be tested, perhaps giving Stephen Hawking the best chance yet of winning the Nobel Prize.

So how do you create a black hole? In the cosmos, black holes are created by the collapse of massive stars. The mass of the star collapses down to a single point (after running out of fuel and undergoing a supernova) due to the massive gravitational forces acting on the body. Should the star exceed a certain mass “limit” (i.e. the Chandrasekhar limit – a maximum at which the mass of a star cannot support its structure against gravity), it will collapse into a discrete point (a singularity). Space-time will be so warped that all local energy (matter and radiation) will fall into the singularity. The distance from the singularity at which even light cannot escape the gravitational pull is known as the event horizon. High energy particle collisions by cosmic rays impacting the upper atmosphere might produce micro-black holes (MBHs). The Large Hadron Collider (at CERN, near Geneva, Switzerland) may also be capable of producing collisions energetic enough to create MBHs. Interestingly, if the LHC can produce MBHs, Stephen Hawking’s theory of “Hawking Radiation” may be proven should the MBHs created evaporate almost instantly.

Hawking predicts that black holes emit radiation. This theory is paradoxical, as no radiation can escape the event horizon of a black hole. However, Hawking theorizes that due to a quirk in quantum dynamics, black holes can produce radiation.
The principal of Hawking Radiation (source: http://library.thinkquest.org)
Put very simply, the Universe allows particles to be created within a vacuum, “borrowing” energy from their surroundings. To conserve the energy balance, the particle and its anti-particle can only live for a short time, returning the borrowed energy very quickly by annihilating with each other. So long as they pop in and out of existence within a quantum time limit, they are considered to be “virtual particles”. Creation to annihilation has net zero energy.

However, the situation changes if this particle pair is generated at or near an event horizon of a black hole. If one of the virtual pair falls into the black hole, and its partner is ejected away from the event horizon, they cannot annihilate. Both virtual particles will become “real”, allowing the escaping particle to carry energy and mass away from the black hole (the trapped particle can be considered to have negative mass, thus reducing the mass of the black hole). This is how Hawking radiation predicts “evaporating” black holes, as mass is lost to this quantum quirk at the event horizon. Hawking predicts that black holes will gradually evaporate and disappear, plus this effect will be most prominent for small black holes and MBHs.

So… back to our St. Andrews laboratory…

Prof Ulf Leonhardt is hoping to create the conditions of a black hole event horizon by using laser pulses, possibly creating the first direct experiment to test Hawking radiation. Leonhardt is an expert in “quantum catastrophes”, the point at which wave physics breaks down, creating a singularity. In the recent “Cosmology Meets Condensed Matter” meeting in London, Leonhardt’s team announced their method to simulate one of the key components of the event horizon environment.

Light travels through materials at different velocities, depending on their wave properties. The St. Andrews group use two laser beams, one slow, one fast. First, a slow propagating pulse is fired down the optical fiber, followed by a faster pulse. The faster pulse should “catch up” with the slower pulse. However, as the slow pulse passes through the medium, it alters the optical properties of the fiber, causing the fast pulse to slow in its wake. This is what happens to light as it tries to escape from the event horizon – it is slowed down so much that it becomes “trapped”.

We show by theoretical calculations that such a system is capable of probing the quantum effects of horizons, in particular Hawking radiation.” – From a forthcoming paper by the St. Andrews group.

The effects that two laser pulses have on eachother to mimic the physics within an event horizon sounds strange, but this new study may help us understand if MBHs are being generated in the LHCs and may push Stephen Hawking a little closer toward a deserved Nobel Prize.
Source: Telegraph.co.uk

“Listening” for Gravitational Waves to Track Down Black Holes

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Gravitational waves are predicted by Einstein’s 1916 general theory of relativity, but they are notoriously hard to detect and it’s taken many decades to come close to observing them. Now, with the help of a supercomputer named SUGAR (Syracuse University Gravitational and Relativity Cluster), two years of data collected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) will be analyzed to find gravitational waves. Once detected, it is hoped that the location of some of the Universes most powerful collisions and explosions will be found, perhaps even hearing the distant ringing of celestial black holes…

Gravitational waves travel at the speed of light and propagate throughout the cosmos. Like ripples on the surface of a universe-sized pond, they travel away from their point of origin and should be detected as they traverse through the fabric of space-time, passing though our cosmic neighborhood. Gravitational waves are generated by massive stellar events such as supernovae (when giant stars run out of fuel and explode) or collisions between Massive Astrophysical Compact Halo Objects (MACHOs) like black holes or neutron stars. Theoretically they should be generated by any sufficiently massive body in the Universe oscillating, propagating or colliding.

The Northern leg of the LIGO Interferometer near Richland, Washington (Credit: LIGO)
LIGO, a very ambitious $365 million (National Science Foundation funded) joint project between MIT and Caltech founded by Kip Thorne, Ronald Drever and Rainer Weiss, began taking data in 2005. LIGO uses a laser interferometer to detect the passage of gravitational waves. As a wave passes through local space-time, the laser should be slightly distorted, allowing the interferometer to detect a space-time fluctuation. After two years of taking data from LIGO, the search for the gravitational wave signatures can begin. But how can LIGO detect waves being generated by black holes? This is where SUGAR comes in.

Syracuse University assistant professor Duncan Brown, with colleagues in the Simulating eXtreme Spacetimes (SXS) project (a collaboration with Caltech and Cornell University), is assembling SUGAR in the aim to simulate two black holes colliding. This is such a complex situation that a network of 80 computers, containing 320 CPUs with 640 Gigabytes of RAM is required to compute the collision and the creation of gravitational waves (as a comparison, the laptop I’m typing on has one CPU with two Gigabytes of RAM…). Brown also has 96 Terabytes of hard disk space on which to store the LIGO data SUGAR will be analyzing. This will be a massive resource for the SXS team, but it will be needed to calculate Einstein’s relativity equations.

Looking for gravitational waves is like listening to the universe. Different kinds of events produce different wave patterns. We want to try to extract a wave pattern — a special sound — that matches our model from all of the noise in the LIGO data.” – Duncan Brown

By combining the observational capabilities of LIGO and the computing power of SUGAR (characterizing the signature of black hole gravitational waves), perhaps direct evidence of gravitational waves may be found; making the first direct observations of black holes possible by “listening” to the gravitational waves they produce.

Source: Science Daily

New Technique for Finding Intermediate Mass Black Holes

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It’s one of the big mysteries in astronomy. There are stellar mass black holes and the supermassive variety, but nothing in between. Where are all the intermediate mass black holes? Astronomers theorize that they could be located in globular star clusters, but nothing definitive has turned up yet. A team of researchers think they’ve come up with a new way to detect intermediate black holes – a way to see them for billions of light-years.

First a little background. When white dwarf stars are in a close binary system with another star, they pull off material, piling it up on their surface. When the white dwarf reaches 1.4 times the mass of our Sun, it reignites in a reaction that happens so quickly the star detonates. This is a Type 1a supernova, and astronomers use them as standard candles to determine distance since they always explode with the same amount of energy.

But researchers from UC Santa Cruz think there’s another situation where you might get a supernova explosion from a white dwarf: when it’s orbiting an intermediate mass black hole.

If a black hole has just the right amount of mass – 500 to 1000 times the mass of the Sun – a white dwarf might get torn apart in a particularly spectacular way. As the dwarf passes the whole, it would get compressed and heated. Its formerly dead material would now have the pressure and temperature to reignite in a powerful explosion similar to a Type 1a supernova.

The explosion would eject more than half of the debris into space, but the rest would fall back into the black hole and form an accretion disk around it. This disk would then emit X-ray radiation detectable by space telescopes like the Chandra X-Ray Observatory.

“This is a new mechanism for ignition of a white dwarf that results in a very different type of supernova than the standard type Ia, and it is followed by an x-ray source,” said Enrico Ramirez-Ruiz, assistant professor of astronomy and astrophysics at the University of California, Santa Cruz.

According to Ramirez-Ruiz, events like this would happen in about 1% of Type 1a supernova explosions. Future surveys, such as the Large Synoptic Survey Telescope, due for completion in 2013, is expected to discover hundreds of thousands of Type 1a supernovae each there. With those kinds of numbers, there should be many of these intermediate black hole interactions detected.

The mass of the white dwarf doesn’t really matter. They ran various sized stars through their simulation and found that you would still get the same outcome; the white dwarf would be tidally disrupted and then it would detonate.

Original Source: UC Santa Cruz News Release

Hyperfast Star Ejected from the Large Magellenic Cloud

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Occasionally, stars minding their own business around the supermassive black hole at the center of our galaxy get chucked out of the Milky Way, never to return. Fraser wrote about the discovery of two of these exiled stars, hurling away at the mind-blowing speed of over 1 million miles an hour. A recent study of another shows that not all of them originate in the center of our own galaxy.

New results from astronomers at the Carnegie Institute show that one star rocketing away from the Milky Way hearkens from the Large Magellanic Cloud, our neighboring galaxy. There have been ten such hypervelocity stars discovered, but where this one came from was quite a conunudrum.

Named HE 0437-5439, it’s nine times the mass of the Sun, and is traveling at 1.6 million miles an hour (2.6 million km an hour). The origin of the star has been a mystery until now because of its youth: it is 35 million years old, but it would have taken 100 million years to get to its current location if it were from the center of the Milky Way.

This meant that the star either came from somewhere else, or had to have formed out of the merger of two low-mass stars from the Milky Way, a so-called “blue straggler.”

Carnegie astronomers Alceste Bonanos and Mercedes López-Morales, and collaborators Ian Hunter and Robert Ryans from Queen’s University Belfast took measurements of the composition of the star – the first time this has been done on any hypervelocity star – and determined that its metal-poor makeup pointed towards the Large Magellanic Cloud as the former home of the castaway.

Bonanos said,“We’ve ruled out that the star came from the Milky Way. The concentration of [heavy] elements in Large Magellanic Cloud stars are about half those in our Sun. Like evidence from a crime scene, the fingerprints point to an origin in the Large Magellanic Cloud.�

Hypervelocity stars get their kick of energy from their interaction with a black hole. The stars were once part of a binary system, and as one star in the system gets captured by the black hole, the other is abruptly released, booting it clear out of the galaxy.

The mere fact that the Large Magellanic Cloud produced this hyperfast star hints at the presence of a black hole there, which has never previously been observed to exist.

Source: Carnegie Institute Press Release

Fat Black Holes Can Lurk in Thin Galaxies

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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

Death Echos of Material Destroyed Near a Black Hole

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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

Black Holes Seen Spinning at the Limits Predicted by Einstein

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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

There May Be Hundreds of Rogue Black Holes in the Milky Way

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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

Hidden Quasars – Found!

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Quasars are some of the brightest objects in the Universe. Just a single quasar can blaze more than a hundred times more brightly than our entire Milky Way galaxy. It turns out, though, that some of the brightest quasars in the Universe are hidden, cloaked behind a shroud of gas and dust. But now researchers have developed a technique to find the galaxies hiding these bright quasars. It turns out, they’re everywhere, we just couldn’t see them.

This blazing material surrounding a supermassive black hole is a quasar. The relatively tiny region around a black hole can blaze more than a hundred times as brightly as our own Milky Way galaxy. But there’s a paradox. The more powerful the quasar, the better a job it can do to hide itself within a shroud of gas and dust.

To see the hidden quasars, you can’t look in the visible spectrum. You need to use a wavelength that isn’t obscured by gas and dust, such as infrared and X-rays. However, previous surveys in these wavelengths have only revealed small portions of the sky.

Astronomers from Princeton and the Institute for Advanced Study announced today that they have developed a technique to see the telltale signs that a galaxy contains a bright quasar – without having to perform an extensive survey in these other wavelengths. By sifting through the Sloan Digital Sky Survey, looking for very special characteristics of the light coming from a galaxy, the team uncovered 887 hidden quasars; the largest number ever detected.

“We determined how common hidden quasars are, especially the most luminous ones. Perhaps more interestingly, we determined how common they are relative to normal quasars,” said team member Nadia Zakamska, a NASA Spitzer Fellow at the Institute for Advanced Study in Princeton.

“We found that hidden quasars make up at least half of the quasars in the relatively recent Universe, implying that most of the powerful black holes in our neighborhood had previously been unrecognized.”

This means that there are many hidden quasars out there. And it also means that quasars are much more efficient at converting matter into light than astronomers previously realized. In fact, most of the light released by quasars is probably absorbed by intervening gas and dust.

In other words, even though quasars are incredibly bright objects, blazing with hundreds of times the light of an entire galaxy, that’s probably just the tip of the iceberg.

They’re much much brighter.

Original Source: SDSS News Release