Black Holes Archives

June 25, 2016August 21, 2016 by Matt Williams

A Star Is About To Go 2.5% The Speed Of Light Past A Black Hole

Artist’s impression of the star S2 passing very close to the supermassive black hole at the centre of the Milky Way. Credit: ESO

Since it was first discovered in 1974, astronomers have been dying to get a better look at the Supermassive Black Hole (SBH) at the center of our galaxy. Known as Sagittarius A*, scientists have only been able to gauge the position and mass of this SBH by measuring the effect it has on the stars that orbit it. But so far, more detailed observations have eluded them, thanks in part to all the gas and dust that obscures it.

Luckily, the European Southern Observatory (ESO) recently began work with the GRAVITY interferometer, the latest component in their Very Large Telescope (VLT). Using this instrument, which combines near-infrared imaging, adaptive-optics, and vastly improved resolution and accuracy, they have managed to capture images of the stars orbiting Sagittarius A*. And what they have observed was quite fascinating.

One of the primary purposes of GRAVITY is to study the gravitational field around Sagittarius A* in order to make precise measurements of the stars that orbit it. In so doing, the GRAVITY team – which consists of astronomers from the ESO, the Max Planck Institute, and multiple European research institutes – will be able to test Einstein’s theory of General Relativity like never before.

The core of the Milky Way. Credit: NASA/JPL-Caltech/S. Stolovy (SSC/Caltech) — *Spitzer image of the core of the Milky Way Galaxy. Credit: NASA/JPL-Caltech/S. Stolovy (SSC/Caltech)*

In what was the first observation conducted using the new instrument, the GRAVITY team used its powerful interferometric imaging capabilities to study S2, a faint star which orbits Sagittarius A* with a period of only 16 years. This test demonstrated the effectiveness of the GRAVITY instrument – which is 15 times more sensitive than the individual 8.2-metre Unit Telescopes the VLT currently relies on.

This was an historic accomplishment, as a clear view of the center of our galaxy is something that has eluded astronomers in the past. As GRAVITY’s lead scientist, Frank Eisenhauer – from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany – explained to Universe Today via email:

“First, the Galactic Center is hidden behind a huge amount of interstellar dust, and it is practically invisible at optical wavelengths. The stars are only observable in the infrared, so we first had to develop the necessary technology and instruments for that. Second, there are so many stars concentrated in the Galactic Center that a normal telescope is not sharp enough to resolve them. It was only in the late 1990′ and in the beginning of this century when we learned to sharpen the images with the help of speckle interferometry and adaptive optics to see the stars and observe their dance around the central black hole.”

But more than that, the observation of S2 was very well timed. In 2018, the star will be at the closest point in its orbit to the Sagittarius A* – just 17 light-hours from it. As you can see from the video below, it is at this point that S2 will be moving much faster than at any other point in its orbit (the orbit of S2 is highlighted in red and the position of the central black hole is marked with a red cross).

When it makes its closest approach, S2 will accelerate to speeds of almost 30 million km per hour, which is 2.5% the speed of light. Another opportunity to view this star reach such high speeds will not come again for another 16 years – in 2034. And having shown just how sensitive the instrument is already, the GRAVITY team expects to be able make very precise measurements of the star’s position.

In fact, they anticipate that the level of accuracy will be comparable to that of measuring the positions of objects on the surface of the Moon, right down to the centimeter-scale. As such, they will be able to determine whether the motion of the star as it orbits the black hole are consistent with Einstein’s theories of general relativity.

“[I]t is not the speed itself to cause the general relativistic effects,” explained Eisenhauer, “but the strong gravitation around the black hole. But the very high orbital speed is a direct consequence and measure of the gravitation, so we refer to it in the press release because the comparison with the speed of light and the ISS illustrates so nicely the extreme conditions.

Artist's impression of the influence gravity has on space time. Credit: space.com — *Artist’s impression of the influence gravity has on space-time. Credit: space.com*

As recent simulations of the expansion of galaxies in the Universe have shown, Einstein’s theories are still holding up after many decades. However, these tests will offer hard evidence, obtained through direct observation. A star traveling at a portion of the speed of light around a supermassive black hole at the center of our galaxy will certainly prove to be a fitting test.

And Eisenhauer and his colleagues expect to see some very interesting things. “We hope to see a “kick” in the orbit.” he said. “The general relativistic effects increase very strongly when you approach the black hole, and when the star swings by, these effects will slightly change the direction of the
orbit.”

While those of us here at Earth will not be able to “star gaze” on this occasion and see R2 whipping past Sagittarius A*, we will still be privy to all the results. And then, we just might see if Einstein really was correct when he proposed what is still the predominant theory of gravitation in physics, over a century later.

Further Reading: eso.org

April 29, 2016May 15, 2016 by Evan Gough

Fermi Links Neutrino Blast To Known Extragalactic Blazar

This image shows the galaxy PKS B1424-418, and the blazar that lives there. The dotted circle is the area in which Fermi detected the neutrino Big Bird. Image: NASA/DOE/LAT Collaboration.

A unique observatory buried deep in the clear ice of the South Pole region, an orbiting observatory that monitors gamma rays, a powerful outburst from a black hole 10 billion light years away, and a super-energetic neutrino named Big Bird. These are the cast of characters that populate a paper published in Nature Physics, on Monday April 18th.

The observatory that resides deep in the cold dark of the Antarctic ice has one job: to detect neutrinos. Neutrinos are strange, standoffish particles, sometimes called ‘ghost particles’ because they’re so difficult to detect. They’re like the noble gases of the particle world. Though neutrinos vastly outnumber all other atoms in our Universe, they rarely interact with other particles, and they have no electrical charge. This allows them to pass through normal matter almost unimpeded. To even detect them, you need a dark, undisturbed place, isolated from cosmic rays and background radiation.

This explains why they built an observatory in solid ice. This observatory, called the IceCube Neutrino Observatory, is the ideal place to detect neutrinos. On the rare occasion when a neutrino does interact with the ice surrounding the observatory, a charged particle is created. This particle can be either an electron, muon, or tau. If these charged particles are of sufficiently high energy, then the strings of detectors that make up IceCube can detect it. Once this data is analyzed, the source of the neutrinos can be known.

The next actor in this scenario is NASA’s Fermi Gamma-Ray Space Telescope. Fermi was launched in 2008, with a specific job in mind. Its job is to look at some of the exceptional phenomena in our Universe that generate extraordinarily large amounts of energy, like super-massive black holes, exploding stars, jets of hot gas moving at relativistic speeds, and merging neutron stars. These things generate enormous amounts of gamma-ray energy, the part of the electromagnetic spectrum that Fermi looks at exclusively.

Next comes PKS B1424-418, a distant galaxy with a black hole at its center. About 10 billion years ago, this black hole produced a powerful outburst of energy, called a blazar because it’s pointed at Earth. The light from this outburst started arriving at Earth in 2012. For a year, the blazar in PKS B1424-418 shone 15-30 times brighter in the gamma spectrum than it did before the burst.

Detecting neutrinos is a rare occurrence. So far, IceCube has detected about a hundred of them. For some reason, the most energetic of these neutrinos are named after characters on the popular children’s show called Sesame Street. In December 2012, IceCube detected an exceptionally energetic neutrino, and named it Big Bird. Big Bird had an energy level greater than 2 quadrillion electron volts. That’s an enormous amount of energy shoved into a particle that is thought to have less than one millionth the mass of an electron.

The IceCube Neutrino Observatory is a series of strings of detectors, drilled deep into the Antarctic ice. Image: Nasa-verve - IceCube Science Team - Francis Halzen, Department of Physics, University of Wisconsin, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=26350372 — The IceCube Neutrino Observatory is a series of strings of detectors, drilled deep into the Antarctic ice. Image: Nasa-verve – IceCube Science Team – Francis Halzen, Department of Physics, University of Wisconsin, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=26350372

Big Bird was clearly a big deal, and scientists wanted to know its source. IceCube was able to narrow the source down, but not pinpoint it. Its source was determined to be a 32 degree wide patch of the southern sky. Though helpful, that patch is still the size of 64 full Moons. Still, it was intriguing, because in that patch of sky was PKS B1424-418, the source of the blazar energy detected by Fermi. However, there are also other blazars in that section of the sky.

The scientists looking for Big Bird’s source needed more data. They got it from TANAMI, an observing program that used the combined power of several networked terrestrial telescopes to create a virtual telescope 9,650 km(6,000 miles) across. TANAMI is a long-term program monitoring 100 active galaxies that are located in the southern sky. Since TANAMI is watching other active galaxies, and the energetic jets coming from them, it was able to exclude them as the source for Big Bird.

The team behind this new paper, including lead author Matthias Kadler of the University of Wuerzberg in Germany, think they’ve found the source for Big Bird. They say, with only a 5 percent chance of being wrong, that PKS B1424-418 is indeed Big Bird’s source. As they say in their paper, “The outburst of PKS B1424–418 provides an energy output high enough to explain the observed petaelectronvolt event (Big Bird), suggestive of a direct physical association.”

So what does this mean? It means that we can pinpoint the source of a neutrino. And that’s good for science. Neutrinos are notoriously difficult to detect, and they’re not that well understood. The new detection method, involving the Fermi Telescope in conjunction with the TANAMI array, will not only be able to locate the source of super-energetic neutrinos, but now the detection of a neutrino by IceCube will generate a real-time alert when the source of the neutrino can be narrowed down to an area about the size of the full Moon.

This promises to open a whole new window on neutrinos, the plentiful yet elusive ‘ghost particles’ that populate the Universe.

April 20, 2016May 5, 2016 by Matt Williams

Supermassive Black Holes In Distant Galaxies Are Mysteriously Aligned

A supermassive black hole has been found in an unusual spot: an isolated region of space where only small, dim galaxies reside. Image credit: NASA/JPL-Caltech — A team of astronomers from South Africa have noticed a series of supermassive black holes in distant galaxies that are all spinning in the same direction. Credit: NASA/JPL-Caltech

In 1974, astronomers detected a massive source of radio wave emissions coming from the center of our galaxy. Within a few decades time, it was concluded that the radio wave source corresponded to a particularly large, spinning black hole. Known as Sagittarius A, this particular black hole is so large that only the designation “supermassive” would do. Since its discovery, astronomers have come to conclude that supermassive black holes (SMBHs) lie at the center of almost all of the known massive galaxies.

But thanks to a recent radio imaging by a team of researchers from the University of Cape Town and University of the Western Cape, in South Africa, it has been further determined that in a region of the distant universe, the SMBHs are all spinning out radio jets in the same direction. This finding, which shows an alignment of the jets of galaxies over a large volume of space, is the first of its kind, and could tell us much about the early Universe.

Continue reading “Supermassive Black Holes In Distant Galaxies Are Mysteriously Aligned”

April 10, 2016April 20, 2016 by Matt Williams

Can We Now Predict When A Neutron Star Will Give Birth To A Black Hole?

A black hole is the final form a massive star collapses to. The light (and spacetime itself) is warped around the black hole's event horizon due to extreme gravitational effects. This is as accurate as we can be to visualizing an actual black hole as it was generated with a code that implemented General Relativity accurately. Credit and Copyright: Paramount Pictures/Warner Bros. Mathematical Model used to create the image developed by Dr. Kip Thorne

A neutron star is perhaps one of the most awe-inspiring and mysterious things in the Universe. Composed almost entirely of neutrons with no net electrical charge, they are the final phase in the life-cycle of a giant star, born of the fiery explosions known as supernovae. They are also the densest known objects in the universe, a fact which often results in them becoming a black hole if they undergo a change in mass.

For some time, astronomers have been confounded by this process, never knowing where or when a neutron star might make this final transformation. But thanks to a recent study by a team of researchers from Goethe University in Frankfurt, Germany, it may now be possible to determine the absolute maximum mass that is required for a neutron star to collapse, giving birth to a new black hole.

Continue reading “Can We Now Predict When A Neutron Star Will Give Birth To A Black Hole?”

March 29, 2016 by Evan Gough

Japan’s Black Hole Telescope Is In Trouble

An artist's drawing of Japan's Hitomi observatory. Image Credit: JAXA/Akihiro Ikeshita

The Japanese Aerospace Exploration Agency (JAXA) has lost contact with its X-ray Astronomy Satellite Hitomi (ASTRO-H.) Hitomi was launched on February 17th, for a 3-year mission to study black holes. But now that mission appears to be in jeopardy.

Hitomi is a collaboration between JAXA and NASA. Its mission was to investigate how galaxy clusters were formed and influenced by dark matter and dark energy, and to understand how super-massive black holes form and evolve at the center of galaxies. Hitomi was also to “unearth the physical laws governing extreme conditions in neutron stars and black holes,” according to JAXA.

Japan has managed two very short communications with Hitomi, but they were very brief, and JAXA has not been able to determine the nature of the problem. Now, JSpOC, the US Joint Space Operations Center, say they have detected debris in the vicinity of Hitomi, and in a press release this morning (March 29th), JAXA says “it is estimated that Hitomi separated to five pieces at about 10:42 a.m.”

Hitomi was going to be an important contribution to the fleet of space telescopes used by astrophysicists and cosmologists. It has a cutting edge instrument called the X-ray micro-calorimeter, which would have observed X-rays from space with the greatest sensitivity of any instrument so far. If all that is lost, it will be quite a blow.

There’s no definitive word yet on what exactly has happened to Hitomi. Japan is using ground stations in different parts of the world to try to communicate with their observatory. It’s important to note that there is no agreement that the craft has broken apart. The press releases are translations from Japanese to English, so the exact meaning of “separated to five pieces” is unclear.

It’s possible that there was a small explosion of some sort, and that some debris from that explosion is in the vicinity of Hitomi. It’s also possible that JAXA will re-establish communications with the craft as time goes on.

Other observatories have suffered serious problems, and have eventually been brought back under control and completed their missions. The ESA/NASA Solar and Heliospheric Observatory (SOHO) suffered serious problems at the beginning of its mission in 1995, entering emergency mode 3 times before all contact was lost. Eventually, SOHO was brought under control, and what was supposed to be a 2-year mission has lasted 20.

Universe Today will be following this story to see if Hitomi can be made operational. For readers wanting to know more about Hitomi’s mission, read JAXA’s excellent Hitomi press kit.

March 18, 2016February 23, 2017 by Fraser Cain

Where is the Closest Black Hole?

Black_Hole_in_the_universe — If you saw this, it would already be too late. Credit: NASA

You know that saying, “keep your friends close, but keep your enemies closer?” That advice needs to go right out the window when we’re talking black holes. They’re the worst enemies you could have and you want them as far away as possible.

We’re talking regions of space where matter is compressed so densely that the only way to escape is to be traveling faster than the speed of light. And as we know, you can’t go faster than the speed of light. So… there’s no escape.

Get too close to the black hole and you’ll be compressed beyond comprehension, perhaps into an infinitely small point.

But you can be reasonably distant from a black hole too, and still have your day ruined. A black hole reaches out through the light years with its gravity. And if one were to wander too close to our Solar System, it would wreak havoc on all our precious planets.

The planets and even the Sun would be gobbled up, or smashed together, or even thrown out of the Solar System entirely.

And as we learned in a previous episode, black holes are unkillable. Anything you might try to do to them just makes them bigger, stronger and angrier. Your only hope is to just wait them out over the eons it takes for them to evaporate.

It makes sense to keep track of all the black holes out there, just in case we might need to evacuate this Solar System in a hurry.

Where are the closest black holes?

There are two kinds of black holes out there: the supermassive black holes at the heart of every galaxy, and the stellar mass black holes formed when massive stars die in a supernova.

This artist’s impression shows the surroundings of the supermassive black hole at the heart of the active galaxy NGC 3783. Credit: ESO/M. Kornmesser

The supermassive ones are relatively straightforward. There’s one at the heart of pretty much every single galaxy in the Universe. One in the middle of the Milky Way, located about 27,000 light-years away. One in Andromeda 2.5 million light years away, and so on.

No problem, they supermassive ones are really far away, no threat to us.

The stellar mass ones might be more of a problem.

Here’s the problem. Black holes don’t emit any radiation, they’re completely invisible, so there’s no easy way to see them in the sky. The only you’d know there’s a black hole is if you were close enough to see the background starlight getting distorted. And if you’re close enough to see that, you’re already dead.

The closest black hole we know of is V616 Monocerotis, also known as V616 Mon. It’s located about 3,000 light years away, and has between 9-13 times the mass of the Sun. We know it’s there because it’s located in a binary system with a star with about half the mass of the Sun. Only a black hole could make its binary partner buzz around so quickly. Astronomers can’t see the black hole, they just know it’s there by the whirling gravity dance.

The next closest black hole is the classic Cygnus X-1, which is about 6,000 light-years away. It has about 15 times the mass of the Sun, and once again, it’s in a binary system.

The third closest black hole, is also in a binary system.

Artist's illustration of Cygnus X-1. Credit: NASA/CXC/M.Weiss — Artist’s illustration of Cygnus X-1, a stellar-mass black hole in a binary system. Credit: NASA/CXC/M.Weiss

See the problem here? The reality is that a fraction of black holes are in binary systems, but that’s our only way to detect them.

More likely there are more black holes much more close than the ones astronomers have been able to discover.

This all sounds terrifying, I’m sure, and now you’ve probably got one eye on the sky, watching for that telltale distortion of light from an approaching black hole. But these events are impossibly rare.

The Solar System has been around for more than 4.5 billion years, with all the planets going around and around without interruption. Even if a black hole passed the Solar System within a few dozen light years, it would have messed up the orbits significantly, and life probably wouldn’t be here to consider this fact.

We didn’t encounter a black hole in billions of years, and probably won’t encounter one for billions or trillions more years.

Sadly, the answer to this question is… we don’t know. We just don’t know if the closest black holes is a few light years away, or it’s actually V616 Mon. We’ll probably never know.

But that’s fine. They’re so rare it’s not worth worrying about.

March 13, 2016March 18, 2016 by Bob King

18 Billion Solar Mass Black Hole Rotates At 1/3 Speed Of Light

Black-hole-powered galaxies called blazars are the most common sources detected by NASA's Fermi Gamma-ray Space Telescope. They are sources of neutrinos and cosmic rays. Credits: M. Weiss/CfA

Way up in the constellation Cancer there’s a 14th magnitude speck of light you can claim in a 10-inch or larger telescope. If you saw it, you might sniff at something so insignificant, yet it represents the final farewell of chewed up stars as their remains whirl down the throat of an 18 billion solar mass black hole, one of the most massive known in the universe.

Astronomers know the object as OJ 287, a quasar that lies 3.5 billion light years from Earth. Quasars or quasi-stellar objects light up the centers of many remote galaxies. If we could pull up for a closer look, we’d see a brilliant, flattened accretion disk composed of heated star-stuff spinning about the central black hole at extreme speeds.

An illustration of the binary black hole system in OJ287. The predictions of the model are verified by observations. Credit: University of Turku — An illustration of the binary black hole system, OJ 287, showing the massive black hole surrounded by an accretion disk. A second, smaller black hole is believed to orbit the larger. When it intersects the larger’s disk coming and going, astronomers see a pair of bright flares. The predictions of the model are verified by observations. Credit: University of Turku

As matter gets sucked down the hole, jets of hot plasma and energetic light shoot out perpendicular to the disk. And if we’re so privileged that one of those jet happens to point directly at us, we call the quasar a “blazar”. Variability of the light streaming from the heart of a blazar is so constant, the object practically flickers.

Long exposures made with the Hubble Space Telescope showing brilliant quasars flaring in the hearts of six distant galaxies. Credit: NASA/ESA

A recent observational campaign involving more than two dozen optical telescopes and NASA’s space based SWIFT X-ray telescope allowed a team of astronomers to measure very accurately the rotational rate the black hole powering OJ 287 at one third the maximum spin rate — about 56,000 miles per second (90,000 kps) — allowed in General Relativity A careful analysis of these observations show that OJ 287 has produced close-to-periodic optical outbursts at intervals of approximately 12 years dating back to around 1891. A close inspection of newer data sets reveals the presence of double-peaks in these outbursts.

Illustration of a gradually precessing orbit similar to the precessing orbit of the smaller smaller black hole orbiting the larger in OJ 287. Credit: Willow W / Wikipedia

To explain the blazar’s behavior, Prof. Mauri Valtonen of the University of Turku (Finland) and colleagues developed a model that beautifully explains the data if the quasar OJ 287 harbors not one buy two unequal mass black holes — an 18 billion mass one orbited by a smaller black hole.

OJ 287 is visible due to the streaming of matter present in the accretion disk onto the largest black hole. The smaller black hole passes through the larger’s the accretion disk during its orbit, causing the disk material to briefly heat up to very high temperatures. This heated material flows out from both sides of the accretion disk and radiates strongly for weeks, causing the double peak in brightness.

The orbit of the smaller black hole also precesses similar to how Mercury’s orbit precesses. This changes when and where the smaller black hole passes through the accretion disk. After carefully observing eight outbursts of the black hole, the team was able to determine not only the black holes’ masses but also the precession rate of the orbit. Based on Valtonen’s model, the team predicted a flare in late November 2015, and it happened right on schedule.

OJ 287 has been fluctuating around 13.5-140 magnitude lately. You can spot in a 10-inch or larger scope in Cancer not far from the Beehive Cluster. Click the image for a detailed AAVSO finder chart. Diagram: Bob King, source: Stellarium — OJ 287 has been fluctuating around 13.5-140 magnitude lately. You can spot it in a 10-inch or larger scope in Cancer not far from the Beehive Cluster. Click the image for a detailed AAVSO finder chart. Diagram: Bob King, source: Stellarium

The timing of this bright outburst allowed Valtonen and his co-workers to directly measure the rotation rate of the more massive black hole to be nearly 1/3 the speed of light. I’ve checked around and as far as I can tell, this would make it the fastest spinning object we know of in the universe. Getting dizzy yet?

February 29, 2016August 21, 2016 by Matt Williams

Are Supermassive Black Holes Hiding Matter?

Illustris simulation, showing the distribution of dark matter in 350 million by 300,000 light years. Galaxies are shown as high-density white dots (left) and as normal, baryonic matter (right). Credit: Markus Haider/Illustris

Mapping the Universe with satellites and ground-based observatories have not only provided scientists with a pretty good understanding of its structure, but also of its composition. And for some time now, they have been working with a model that states that the Universe consists of 4.9% “normal” matter (i.e. that which we can see), 26.8% “dark matter” (that which we can’t), and 68.3% “dark energy”.

From what they have observed, scientists have also concluded that the normal matter in the Universe is concentrated in web-like filaments, which make up about 20% of the Universe by volume. But a recent study performed by the Institute of Astro- and Particle Physics at the University of Innsbruck in Austria has found that a surprising amount of normal matter may live in the voids, and that black holes may have deposited it there.

In a paper submitted to the Royal Astronomical Society, Dr. Haider and his team described how they performed measurements of the mass and volume of the Universe’s filamentary structures to get a better idea of where the Universe’s mass is located. To do this, they used data from the Illustris project – a large computer simulation of the evolution and formation of galaxies.

Illustration of the Big Bang Theory — *The Big Bang Theory: A history of the Universe starting from a singularity and expanding ever since. Credit: grandunificationtheory.com*

As an ongoing research project run by an international collaboration of scientists (and using supercomputers from around the world), Illustris has created the most detailed simulations of our Universe to date. Beginning with conditions roughly 300,000 years after the Big Bang, these simulations track how gravity and the flow of matter changed the structure of the cosmos up to the present day, roughly 13.8 billion years later.

The process begins with the supercomputers simulating a cube of space in the universe, which measures some 350 million light years on each side. Both normal and dark matter are dealt with, particularly the gravitational effect that dark matter has on normal matter. Using this data, Haider and his team noticed something very interesting about the distribution of matter in the cosmos.

Essentially, they found that about 50% of the total mass of the Universe is compressed into a volume of 0.2%, consisting of the galaxies we see. A further 44% is located in the enveloping filaments, consisting of gas particles and dust. The remaining 6% is located in the empty spaces that fall between them (aka. the voids), which make up 80% of the Universe.

However, a surprising faction of this normal matter (20%) appears to have been transported there, apparently by the supermassive black holes located at the center of galaxies. The method for this delivery appears to be in how black holes convert some of the matter that regularly falls towards them into energy, which is then delivered to the sounding gas, leading to large outflows of matter.

These outflows stretch for hundreds of thousands of lights years beyond the host galaxy, filling the void with invisible mass. As Dr. Haider explains, these conclusions supported by this data are rather startling. “This simulation,” he said, “one of the most sophisticated ever run, suggests that the black holes at the center of every galaxy are helping to send matter into the loneliest places in the universe. What we want to do now is refine our model, and confirm these initial findings.”

The findings are also significant because they just may offer an explanation to the so-called “missing baryon problem”. In short, this problem describes how there is an apparent discrepancy between our current cosmological models and the amount of normal matter we can see in the Universe. Even when dark matter and dark energy are factored in, half of the remaining 4.9% of the Universe’s normal matter still remains unaccounted for.

For decades, scientists have been working to find this “missing matter”, and several suggestions have been made as to where it might be hiding. For instance, in 2011, a team of students at the Monash School of Physics in Australia confirming that some of it was in the form of low-density, high energy matter that could only be observed in the x-ray wavelength.

In 2012, using data from the Chandra X-ray Observatory, a NASA research team reported that our galaxy, and the nearby Large and Small Magellanic Clouds, were surrounded by an enormous halo of hot gas that was invisible at normal wavelengths. These findings indicated that all galaxies may be surrounded by mass that, while not visible to the naked eye, is nevertheless detectable using current methods.

And just days ago, researchers from the Commonwealth Scientific and Industrial Research Organization (CSIRO) described how they had used fast radio bursts (FRBs) to measure the density of cosmic baryons in the intergalactic medium – which yielded results that seem to indicate that our current cosmological models are correct.

Factor in all the mass that is apparently being delivered to the void by supermassive black holes, and it could be that we finally have a complete inventory of all the normal matter of the Universe. This is certainly an exciting prospect, as it means that one of the greatest cosmological mysteries of our time could finally be solved.

Now if we could just account for the “abnormal” matter in the Universe, and all that dark energy, we’d be in business!

Further Reading: Royal Astronomical Society

February 25, 2016February 25, 2016 by David Dickinson

The Future of Gravitational Wave Astronomy: Pulsar Webs, Space Interferometers and Everything

A merging of two massive objects, sending ripples through the fabric of space and time. Image credit: R. Hurt/Caltech JPL

It’s the hot new field in modern astronomy. The recent announcement of the direct detection of gravitational waves by the Laser Interferometer Gravitational-wave Observatory (LIGO) ushers in a new era of observational astronomy that is completely off the electromagnetic spectrum. This detection occurred on September 14^th, 2015 and later earned itself the name GW150914. This occurred shortly after Advanced LIGO turned on in early September, a great sign concerning the veracity of the equipment. Continue reading “The Future of Gravitational Wave Astronomy: Pulsar Webs, Space Interferometers and Everything”

February 18, 2016March 18, 2016 by Evan Gough

Did a Gamma Ray Burst Accompany LIGO’s Gravity Wave Detection?

An artist's impression of a Gamma Ray Burst. Credit: Stanford.edu

Last week’s announcement that Gravitational Waves (GW) have been detected for the first time—as a result of the merger of two black holes—is huge news. But now a Gamma Ray Burst (GRB) originating from the same place, and that arrived at Earth 0.4 seconds after the GW, is making news. Isolated black holes aren’t supposed to create GRB’s; they need to be near a large amount of matter to do that.

NASA’s Fermi telescope detected the GRB, coming from the same point as the GW, a mere 0.4 seconds after the waves arrived. Though we can’t be absolutely certain that the two phenomena are from the same black hole merger, the Fermi team calculates the odds of that being a coincidence at only 0.0022%. That’s a pretty solid correlation.

So what’s going on here? To back up a little, let’s look at what we thought was happening when LIGO detected gravitational waves.

Our understanding was that the two black holes orbited each other for a long time. As they did so, their massive gravity would have cleared the area around them of matter. By they time they finished circling each other and merged, they would have been isolated in space. But now that a GRB has been detected, we need some way to account for it. We need more matter to be present.

According to Abraham Loeb, of Harvard University, the missing piece of this puzzle is a massive star—itself the result of a binary star system combining into one—a few hundred times larger than the Sun, that spawned two black holes. A star this size would form a black hole when it exhausted its fuel and collapsed. But why would there be two black holes?

Again, according to Loeb, if the star was rotating at a high enough rate—just below its break up frequency—the star could actually form two collapsing cores in a dumbbell configuration, and hence two black holes. But now these two black holes would not be isolated in space, they would actually be inside a massive star. Or what was left of one. The remnants of the massive star is the missing matter.

When the black holes joined together, an outflow would be generated, which would produce the GRB. Or else the GRB came “from a jet originating out of the accretion disk of residual debris around the BH remnant,” according to Loeb’s paper. So why the 0.4 s delay? This is the time it took the GRB to cross the star, relative to the gravitational waves.

It sounds like a nice tidy explanation. But, as Loeb notes, there are some problems with it. The main question is, why was the GRB so weak, or dim? Loeb’s paper says that “observed GRB may be just one spike in a longer and weaker transient below the GBM detection threshold.”

But was the GRB really weak? Or was it even real? The European Space Agency has their own gamma ray detecting spacecraft, called Integral. Integral was not able to confirm the GRB signal, and according to this paper, the gamma ray signal was not real after all.

As they say in show business, “Stay tuned.”