Shannon Hall, Author at Universe Today

June 3, 2014December 23, 2015 by Shannon Hall

Amazing New X-Ray Image of the Whirlpool Galaxy Shows it is Dotted with Black Holes

The Whirlpool galaxy seen in both optical and X-ray light. Image Credit: X-ray: NASA/CXC/Wesleyan Univ./R.Kilgard, et al; Optical: NASA/STScI

In any galaxy there are hundreds of X-ray binaries: systems consisting of a black hole capturing and heating material from a relatively low-mass orbiting companion star. But high-mass X-ray binaries — systems consisting of a black hole and an extremely high-mass companion star — are hard to come by. In the Milky Way there’s only one: Cygnus X-1. But 30 million light-years away in the Whirlpool galaxy, M51, there are a full 10 high-mass X-ray binaries.

Nearly a million seconds of observing time with NASA’s Chandra X-ray Observatory has revealed these specks. “This is the deepest, high-resolution exposure of the full disk of any spiral galaxy that’s ever been taken in the X-ray,” said Roy Kilgard, from Wesleyan University, at a talk presented at the American Astronomical Society meeting today in Boston. “It’s a remarkably rich data set.”

Within the image there are 450 X-ray points of light, 10 of which are likely X-ray binaries.

The Whilpool galaxy is thought to have so many X-ray binaries because it’s in the process of colliding with a smaller companion galaxy. This interaction triggers waves of star formation, creating new stars at a rate seven times faster than the Milky Way and supernova deaths at a rate 10-100 times faster. The more-massive stars simply race through their evolution in a few million years and collapse to form neutron stars or black holes quickly.

“In this image, there’s a very strong correlation between the fuzzy purple stuff, which is hot gas in the X-ray, and the fuzzy red stuff, which is hydrogen gas in the optical,” said Kilgard. “Both of these are tracing the star formation very actively. You can see it really enhanced in the northern arm that approaches the companion galaxy.”

Eight of the 10 X-ray binaries are located close to star forming regions.

Chandra is providing astronomers with an in depth look at a class of objects that has only one example in the Milky Way.

“We’re catching them at a short window in their evolutionary cycle,” said Kilgard. “The massive star that formed the black hole has died, and the massive star that is accreting material onto the black hole has not yet died. The window at which these objects are X-ray bright is really short. It’s maybe only tens of thousands of years.”

Additional information available on the Chandra website.

June 3, 2014December 23, 2015 by Shannon Hall

The New and Improved Hubble Ultra Deep Field

The Hubble Ultra Deep Field seen in ultraviolet, visible, and infrared light. Image Credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)

It’s perhaps one of the most famous images in astronomy. The Hubble Ultra Deep Field displays nearly 10,000 galaxies across the observable Universe in both visible and near-infrared light. The smallest, reddest galaxies are among the youngest known, existing when the Universe was just 800 million years old.

But now, with the addition of ultraviolet light the renowned image is even better than ever.

“We’ve taken new observations with the Hubble Space Telescope and made a new image of this very famous region of the sky — the Hubble Ultra Deep Field — which gives us one of the most comprehensive pictures of galaxy evolution ever obtained,” said Harry Teplitz from Caltech, in a talk presented at the American Astronomical Society meeting in Boston today.

The image has undoubtedly captured the minds of amateurs and provided astronomers with a wealth of data, from which to study galaxies in their most primitive stages.

But there was a caveat: without ultraviolet light, which tells us about the youngest and hottest stars, there was a significant gap in our understanding of these forming galaxies. Between 5 and 10 billion light-years away from us — corresponding to a time period when most of the stars in the Universe were born — we were left in the dark.

Compare the new image to an older version:

The original Hubble Ultra-Deep Field (Credit NASA, ESA, and S. Beckwith (STScI) and the HUDF Team).

Now, with the addition of ultraviolet data to the Hubble Ultra Deep Field, astronomers can see unobscured regions of star formation throughout this time period. It will help us understand how galaxies grew in size from small collections of very hot stars — now visible across the observable Universe — to the elegant structures we see today.

Here’s a ‘pan and zoom’ video version of the new image:

For more information on the new and improved Ultra Deep Field, check out the HubbleSite.

June 2, 2014December 23, 2015 by Shannon Hall

President Obama Unveils a New Carbon Plan

A coal-fired plant in Glenrock, Wyoming. Image Credit: Greg Goebel

At the end of his first year in office, President Obama made a bold promise: the United States would cut its greenhouse gas emissions substantially by 2020.

Unfortunately it was a risky pledge that hinged on Congress. After President Obama was unable to get his major climate change proposal through Congress in his first term, it seemed as though his pledge to the rest of the World and planet Earth might disintegrate into thin air.

But today, President Obama announced plans to bypass Congress entirely. By using his executive authority under the Clean Air Act, he proposed an Environmental Protection Agency regulation to cut carbon pollution from the nation’s power plants 30 percent from 2005 levels by 2030. It’s one of the strongest actions ever taken by the United States government to fight climate change.

“The shift to a cleaner-energy economy won’t happen overnight, and it will require tough choices along the way,” President Obama said Saturday in his weekly radio and Internet address, previewing Monday’s announcement. “But a low-carbon, clean-energy economy can be an engine of growth for decades to come. America will build that engine. America will build the future, a future that’s cleaner, more prosperous and full of good jobs.”

The regulation targets the largest source of carbon pollution in the United States: coal-fired power plants. So naturally it has already met huge opposition.

“The administration has set out to kill coal and its 800,000 jobs,” said Senator Michael B. Enzi of Wyoming, the nation’s top coal-producing state, in response to President Obama’s Saturday address. “If it succeeds in death by regulation, we’ll all be paying a lot more money for electricity — if we can get it. Our pocketbook will be lighter, but our country will be darker.”

But rather than forcing coal plants to immediately shutdown, the E.P.A. will allow States several years to retire existing plants. They estimate that by 2030, 30 percent of U.S. electricity will still come from coal, down from about 40 percent today.

The regulation also gives a wide range of options to achieve the pollution cuts. States are encouraged to reduce emissions by making changes across the electricity systems. They’re encouraged to install new wind and solar generation technology. This will create a huge demand for designing and building energy-efficient technology.

The plan is flexible. “That’s what makes it ambitious, but achievable,” said Gina McCarthy, the E.P.A. administrator, in a speech this morning. “That’s how we can keep our energy affordable and reliable. The glue that holds this plan together — and the key to making it work — is that each state’s goal is tailored to its own circumstances, and states have the flexibility to reach their goal in whatever way works best for them.”

The proposal will also help the economy, not hurt it. The E.P.A. estimates that the regulation will cost $7.3 billion to $8.8 billion annually, but will lead to economic benefits of $55 billion to $93 billion throughout the regulation’s lifetime.

The proposal unveiled today is only a draft, open to public comment. Already it has received criticism and praise from industry groups and environmentalists alike. President Obama plans to finalize the regulation by June 2015 so that it will be in place before he leaves office.

To see why Universe Today writes on climate change, and even climate policy, please read a past article on the subject.

June 2, 2014December 23, 2015 by Shannon Hall

Surprise! Fireballs Light up the Radio Sky, Hinting at Unexplored Physics

A series of All-Sky (fish eye) images showing the plasma trail left by a fireball, which extends 92 degrees across the northern half of the sky. These images are 5 second snapshots captured at 37.8 MHz with the LWA1 radio telescope. The bright steady sources (Cygnus A, Cassiopeia A, the galactic plane, etc) have been removed using image subtraction. Image Credit: Gregory Taylor (University of New Mexico)

At any given moment, it seems, the sky is sizzling with celestial phenomena waiting to be stumbled upon. New research using the Long Wavelength Array (LWA), a collection of radio dishes in New Mexico, found quite the surprise. Fireballs — those brilliant meteors that leave behind glowing streaks in the night sky — unexpectedly emit a low radio frequency, hinting at new unexplored physics within these meteor streaks.

The LWA keeps its eyes to the sky day and night, probing a poorly explored region of the electromagnetic spectrum. It’s one of only a handful of blind searches carried out below 100 MHz.

Over the course of 11,000 hours, graduate student Kenneth Obenberger from the University of New Mexico and colleagues found 49 radio bursts, 10 of which came from fireballs.

Most of the bursts appear as large point sources, limited to four degrees, roughly eight times the size of the full Moon. Some, however, extend several degrees across the sky. On January 21, 2014, a source left a trail covering 92 degrees in less than 10 seconds (see above). The end point continued to glow for another 90 seconds.

The only known astrophysical object with this ability is a fireball. So Obenberger and colleagues set out to see if NASA’s All Sky Fireball Network had detected anything at the same location and time as the bursts.

While the network shares only a portion of the sky with the LWA, the fireballs seen in this direction matched fireballs caught by NASA. Additionally, most bursts did occur directly after the peak of a bright meteor shower.

The top panel is a histogram showing the number of events per day as compared to several major meteor showers (red lines).

The fireballs detected here are extremely energetic, traveling with an average velocity of 68 km/s, near the upper end of the meteorite velocity spectrum (from 11 km/s to 72 km/s).

They can be seen in the radio due to radio forward scattering. When fast-moving meteoroids strike Earth’s atmosphere they heat and ionize the air in their path. The luminous ionized trails reflect radio waves. During a meteor shower these waves can not only be picked up by vast arrays, such as the one in New Mexico, but by your TV and AM/FM radio transmitter.

Whereas most fireballs have been detected well over 100 MHz, “we’ve discovered that they also produce a low frequency pulse,” says Obenberger’s PhD advisor, Gregory Taylor.

This pulse is telling us something about the physical conditions in the plasma created by the meteor. “It could be cyclotron radiation (emitted from moving charges in a magnetic field), or perhaps some sort of plasma wave leakage from the trail, or maybe something completely different,” says Obenberger. “It’s too early to tell at the moment.”

Meteors come in a range of energies and sizes. So investigating this unexpected signature further will yield new insights into the interaction between meteors and our atmosphere.

“This is just the beginning,” says Taylor. “Now we have to put this new technique to use — find out more about the spectrum of the pulse and the meteors that produce it. It’s an entirely new way of looking at meteors and how they interact with our atmosphere.”

If you’re curious what’s currently emitting radio waves in the New Mexico sky check out the LWA’s live radio cam.

The paper was published in Astrophysical Journal Letters today and is available for download here.

May 27, 2014December 23, 2015 by Shannon Hall

Want to Measure the Distance to the Moon Yourself? Now You Can!

The dazzling full moon sets behind the Very Large Telescope in Chile’s Atacama Desert in this photo released June 7, 2010 by the European Southern Observatory. The moon appears larger than normal due to an optical illusion of perspective. Image Credit: Gordon Gillet, ESO.

Astronomy is a discipline pursued at a distance. And yet, actually measuring that last word — distance — can be incredibly tricky, even if we set our sights as nearby as the Moon.

But now astronomers from the University of Antioquia, Colombia, have devised a clever method that allows citizen scientists to measure the Moon’s distance with only their digital camera and smartphone.

“Today a plethora of advanced and accessible technological devices such as smartphones, tablets, digital cameras and precise clocks, is opening a new door to the realm of ‘do-it-yourself-science’ and from there to the possibility of measuring the local Universe by oneself,” writes lead author Jorge Zuluaga in his recently submitted paper.

While ancient astronomers devised clever methods to measure the local Universe, it took nearly two millennia before we finally perfected the distance to the Moon. Now, we can bounce powerful lasers off the mirrors placed on the Lunar surface by the Apollo Astronauts. The amount of time it takes for the laser beam to return to Earth gives an incredibly precise measurement of the Moon’s distance, within a few centimeters.

But this modern technique is “far from the realm and technological capacities of amateur astronomers and nonscientist citizens,” writes Zuluaga. In order to bring the local Universe into the hands of citizen scientists, Zuluaga and colleagues have devised an easy method to measure the distance to the Moon.

The trick is in observing how the apparent size of the Moon changes with time.

As the moon rises its distance to an observer on the surface of the Earth is slightly reduced. Image Credit: Zuluaga et al. — As the moon rises its distance to an observer on the surface of the Earth is slightly reduced.
Image Credit: Zuluaga et al.

While the Moon might seem larger, and therefore closer, when it’s on the horizon than when it’s in the sky — it’s actually the opposite. The distance from the Moon to any observer on Earth decreases as the Moon rises in the sky. It’s more distant when it’s on the horizon than when it’s at the Zenith. Note: the Moon’s distance to the center of the Earth remains approximately constant throughout the night.

The direct consequence of this is that the angular size of the moon is larger — by as much as 1.7 percent — when it’s at the Zenith than when it’s on the horizon. While this change is far too small for our eyes to detect, most modern personal cameras have now reached the resolution capable of capturing the difference.

So with a good camera, a smart phone and a little trig you can measure the distance to the Moon yourself. Here’s how:

1.) Step outside on a clear night when there’s a full Moon. Set your camera up on a tripod, pointing at the Moon.

2.) With every image of the Moon you’ll need to know the Moon’s approximate elevation. Most smartphones have various apps that allow you to measure the camera’s angle based on the tilt of the phone. By aligning the phone with the camera you can measure the elevation of the Moon accurately.

3.) For every image you’ll need to measure the apparent diameter of the Moon in pixels, seeing an increase as the Moon rises higher in the sky.

4.) Lastly, the Moon’s distance can be measured from only two images (of course the more images the better you beat down any error) using this relatively simple equation:

where d(t) is the distance from the Moon to your location on Earth, R_E is the radius of the Earth, h_t(t) is the elevation of the Moon for your second image, α(t)
is the relative apparent size of the Moon, or the apparent size of the Moon in your second image divided by the initial apparent size of the Moon in your first image and h_t,0 is the initial elevation of the Moon for your first image.

So with a few pictures and a little math, you can measure the distance to the Moon.

“Our aim here is not to provide an improved measurement of a well-known astronomical quantity, but rather to demonstrate how the public could be engaged in scientific endeavors and how using simple instrumentation and readily available technological devices such as smartphones and digital cameras, any person can measure the local Universe as ancient astronomers did,” writes Zuluaga.

The paper has been submitted to the American Journal of Physics and is available for download here.

May 26, 2014December 23, 2015 by Shannon Hall

Gas Cloud Survives Collision With Milky Way

A false-color image of the Smith Cloud made with data from the Green Bank Telescope (GBT). New analysis indicates that it is wrapped in a dark matter halo. Credit: NRAO/AUI/NSF

A high-velocity cloud hurtling toward the Milky Way should have disintegrated long ago when it first collided with and passed through our Galaxy. The fact that it’s still intact suggests it’s encased in a shell of dark matter, like a Hobbit wrapped in a mithril coat.

Mapping dark matter — the unseen stuff that makes up more than 80 percent of cosmic matter — near our Galaxy is crucial to fully understanding how the Milky Way assembled over cosmic time.

This firstly requires detailed observations of nearby dwarf galaxies — galaxies each totaling a mass less than 10% of the Milky Way’s 200 to 400 billion stars — because they’re enshrouded in dark matter. More recently, it has been suggested that nearby high velocity clouds of hydrogen gas are encased in dark matter as well. But the effects of their dark matter halos remain unknown.

So Matthew Nichols from the Sauverny Observatory in Switzerland and colleagues set out to observe the Smith Cloud — a high-velocity cloud of hydrogen gas located 8,000 lightyears away in the constellation Aquila — in order to better constrain its dark matter halo. They used the Green Bank Telescope (GBT) in west Virginia in order to detect the faint radio emission of neutral hydrogen.

“The Smith Cloud is really one of a kind. It’s fast, quite extensive, and close enough to study in detail,” said Nichols in a press release. At its distance the cloud (9,800 lightyears long and 3,300 lightyears wide) covers almost as much sky as the constellation Orion.

“It’s also a bit of a mystery; an object like this simply shouldn’t survive a trip through the Milky Way, but all the evidence points to the fact that it did,” said Nichols. Previous studies of the Smith Cloud revealed that it first passed through our Galaxy many millions of years ago. By reexamining and carefully modeling the cloud, Nichols’ team now believes that it’s actually wrapped in a substantial halo of dark matter.

“Based on the currently predicted orbit, we show that a dark matter free cloud would be unlikely to survive this disk crossing,” said coauthor Jay Lockman from the National Radio Astronomy Observatory. “While a cloud with dark matter easily survives the passage and produces an object that looks like the Smith Cloud today.”

Not only does this study help astronomers start to characterize the dark matter enshrouding these seemingly harmless clouds, but it helps strengthen the case that the Smith Cloud isn’t purely a cloud of hydrogen gas, but a failed dwarf galaxy, originating from farther away in space. The presence of dark matter, however, will have to be further confirmed.

The paper has been submitted to the Monthly Notices of the Royal Astronomical Society and is available for download here.

May 22, 2014December 23, 2015 by Shannon Hall

Largest Crater Spotted on Mars Using Before-and-After Pictures

When it comes to the Universe, things often go bump in the night. But whether two galaxies collide, a star explodes in a brilliant supernova, or a meteor hits a massive planet, we tend to catch the aftermath tens to hundreds of thousands of years later.

Of course, there’s always an exception to the rule. In today’s news, astronomers using NASA’s Mars Reconnaissance Orbiter have found a fresh meteor-impact crater. And it’s the biggest seen using before-and-after pictures.

When it comes to the red planet, we’ve seen evidence of fresh craters before, but usually the impact can’t be nailed down to better than a few years’ time. The constant sweep of the obiter’s weather-monitoring camera, the Mars Color Imager (MARCI), however, allowed us to pinpoint the impact to within a day.

The orbiter began its systematic observation of Mars in 2006. Ever since, Bruce Cantor, MARCI’s principle investigator, has examined the camera’s daily images, searching for evidence of dust storms and other observable weather events. Cantor’s findings help NASA operators plan for weather events that may be harmful to the solar-powered rover, Opportunity.

Nearly two months ago, Cantor noticed a black smudge — a telltale sign of an impact — on the red planet. “It wasn’t what I was looking for,” Cantor said in a NASA press release. “I was doing my usual weather monitoring and something caught my eye. It looked usual, with rays emanating from a central spot.”

So Cantor dug through earlier images, discovering that the dark spot wasn’t visible on March 27, 2012, but appeared on March 28, 2012.

MARCI is a low resolution camera, which is what allows it to see a large area of Mars constantly. But without a high resolution image, we can’t pick out the details of the impact-like black smudge. So Cantor performed follow-up observations with the orbiter’s telescope Context Camera (CTX) and the High Resolution Imaging Science Experiment (HiRISE).

CTX has imaged nearly the entire surface of Mars at least once during the orbiter’s seven-plus years of observations. It photographed the site of the newly-discovered crater in January 2012, revealing nothing prior to the impact. But two new craters appear in the recent image.

The largest crater is slightly elongated and spans 48.5 by 43.5 meters, roughly half the length of a football field. “The biggest crater is unusual, quite shallow compared to other fresh craters we have observed,” said HiRISE Principal Investigator Alfred McEwen of the University of Arizona, Tucson.

The impacting object is likely a few meters across. Something that small would burn up in the Earth’s atmosphere, but with a much thinner atmosphere (about 1% as thick as Earth’s), Mars lets most debris right on through.

To add to the details, images from HiRISE revealed more than a dozen smaller craters near the two larger ones seen by CTX. It’s likely that Mars’ atmosphere, as thin as it is, supplied enough pressure to break the incoming meteoroid into smaller pieces, leaving multiple impacts behind.

Image Credit: NASA/JPL-Caltech/Univ. of Arizona — This image from the HiRISE camera, on board NASA’s Mars Reconnaissance Orbiter reveals the two impact craters and many smaller craters around them. Image Credit: NASA / JPL-Caltech / University of Arizona

“Studies of fresh impact craters on Mars yield valuable information about impact rates and about subsurface material exposed by the excavations,” said Leslie Tamppari, deputy project scientist for the Mars Reconnaissance Orbiter mission at NASA’s Jet Propulsion Laboratory. “The combination of HiRISE and CTX has found and examined many of them, and now MARCI’s daily coverage has given great precision about when a significant impact occurred.”

The initial NASA press release can be viewed here.

May 22, 2014December 23, 2015 by Shannon Hall

“With a Little Help From Their Friends,” Magnetars Form in Binary Systems, New Study Suggests

An artist's impression of a magnetar, a highly magnetic, slowly rotating neutron star. Credit: ESO/L. Calçada

Astronomy is a discipline of extremes. We’re constantly searching for the most powerful, the most explosive, and the most energetic objects in the Universe. Magnetars — extremely dense and highly magnetic neutron stars — are no exception to the rule. They’re the strongest known magnets in the Universe, millions of times more powerful than the strongest magnets on Earth.

But their origin has eluded astronomers for 35 years. Now, an international team of astronomers think they’ve found the partner star of a magnetar for the first time, an observation that suggests magnetars form in binary star systems.

When the core of a massive star runs out of energy, it collapses to form an incredibly dense neutron star or black hole. Meanwhile the outer layers of the star blow away in a stupendously powerful explosion, known as a supernova. A teaspoon of “neutron star stuff” would have a mass of about a billion tonnes, and a few cups would outweigh Mount Everest.

Magnetars are an unusual form of neutron stars with powerful magnetic fields. While there are roughly a dozen known magnetars in the Milky Way, one stands out as being the most peculiar. CXOU J164710.2-455216 — located 16,000 light-years away in the young star cluster Westerlund 1 — is unlike any other magnetar because astronomers can’t see how it formed in the first place.

Astronomers estimate that this magnetar must have been born in the explosive death of a star about 40 times the mass of the Sun. “But this presents its own problem, since stars this massive are expected to collapse to form black holes after their deaths, not neutron stars,” said Simon Clark, lead author on the paper, in a press release. “We did not understand how it could have become a magnetar.”

So astronomers went back to the drawing board. The most promising solution suggested that the magnetar formed through the interactions of two massive stars orbiting one another. Once the more massive star began to run out of fuel, it transferred mass to the less massive companion, causing it to rotate more and more rapidly — a crucial ingredient to creating ultra-strong magnetic fields.

In turn, the companion star became so massive that it shed a large amount of its recently gained mass. This caused it “to shrink to low enough levels that a magnetar was born instead of a black hole — a game of stellar pass-the-parcel with cosmic consequences” said coauthor Francisco Najarro from the Centro de Astrobiología in Spain.

This image of the young star cluster Westerlund 1 was taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. Although most stars in the cluster are hot blue supergiants, they appear reddish in this image as they are seen through interstellar dust and gas. European astronomers have for the first time demonstrated that the magnetar in this cluster — an unusual type of neutron star with an extremely strong magnetic field — probably was formed as part of a binary star system. The discovery of the magnetar’s former companion (Westerlund 1-5) elsewhere in the cluster helps solve the mystery of how a star that started off so massive could become a magnetar, rather than collapse into a black hole. Credit: ESO — This image shows both the magnetar and its former binary companion, which has been kicked far away. Image Credit: ESO

There was only one slight problem: no companion star had been found. So Clark and colleagues set out to search for a star in other parts of the cluster. They used ESO’s Very Large Telescope to hunt for a hypervelocity star — an object escaping the cluster at an incredible speed — that might have been kicked out of orbit by the supernova explosion that formed the magnetar.

One star, known as Westerlund 1-5, matched their prediction.

“Not only does this star have the high velocity expected if it is recoiling from a supernova explosion, but the combination of its low mass, high luminosity and carbon-rich composition appear impossible to replicate in a single star — a smoking gun that shows it must have originally formed with a binary companion,” said coauthor Ben Ritchie from Open University.

The discovery suggests that double star systems may be essential for forming these enigmatic stars.

The paper has been published in Astronomy & Astrophysics, and is available for download here.

May 21, 2014December 23, 2015 by Shannon Hall

Physicists Pave the Way to Turn Light into Matter

This artist's conception shows two photons (in green) colliding. Image Credit: ATLAS / LHC

E = mc². It’s one of the most basic and fundamental equations throughout astrophysics. But it does more than suggest that mass and energy are interconnected, it implies that light can be physically transformed into matter.

But can it really — physically — be done? Scientists proposed the theory more than 80 years ago, but only today have they paved the way to make this transformation routinely on Earth.

The concept calls for a new kind of photon-photon collider. It sounds like science fiction, but it could be turned into reality with existing technology.

“Although the theory is conceptually simple, it has been very difficult to verify experimentally,” said lead researcher Oliver Pike from London’s Imperial College in a press release. “We were able to develop the idea for the collider very quickly, but the experimental design we propose can be carried out with relative ease.”

In 1934, two physicists Gregory Breit and John Wheeler proposed that it should be possible to turn light into matter by smashing together only two photons, the fundamental particles of light, to create an electron and a positron. It was the simplest method of turning light into matter ever predicted, but it has never been observed in the laboratory.

Past experiments have required the addition of massive high-energy particles. We’ve seen from the development of nuclear weapons and fission reactors that a tiny amount of matter can yield a tremendous amount of energy. So it seems Breit and Wheeler’s theory would require the opposite effect: tremendous amounts of energy from photons to yield a tiny amount of matter.

This experiment will be a first in that it doesn’t require the addition of massive high-energy particles. It will be performed purely from photons.

The concept calls for using a high-intensity laser to speed up electrons to just below the speed of light, and then smash them into a slab of gold to create a beam of photons a billion times more energetic than visible light. At the same time, another laser beam would be blasted onto a hohlraum — a small gold container meaning “empty can” in German — that would create a radiation field with photons buzzing inside.

The initial photon beam would be directed into the center of the hohlraum. When the photons from the two sources collide, some would be converted into pairs of electrons and positrons. A detector would then pick up the signatures form the matter and antimatter as they flew out of the container.

Theories describing light and matter interactions. Image Credit: Oliver Pike, Imperial College London

“Within a few hours of looking for applications of hohlraums outside their traditional role in fusion energy research, we were astonished to find they provided the perfect conditions for creating a photon collider,” Pike said. “The race to carry out and complete the experiment is on!”

The demonstration, if carried out successfully, would be a new type of high-energy physics experiment. It would complete physicists’ list of the fundamental ways in which light and matter interact, and both recreate a process that was important 100 seconds after the Big Bang and a process visible in gamma ray bursts, the most powerful explosions in the cosmos.

The paper has been published in Nature Photonics.

May 6, 2014December 23, 2015 by Shannon Hall

Surprise Gamma-Ray Burst Behaves Differently Than Expected

Artist's impression of a gamma-ray burst, showing the two intense beams of relativistic matter emitted by the black hole. To be visible from Earth, the beams must be pointing directly towards us. Credit : NASA/Swift/Mary Pat Hrybyk-Keith and John Jones

Roughly once a day the sky is lit up by a mysterious torrent of energy. These events — known as gamma-ray bursts — represent the most powerful explosions in the cosmos, sending out as much energy in a fraction of a second as our Sun will give off during its entire lifespan.

Yet no one has ever witnessed a gamma-ray burst directly. Instead astronomers are left to study their fading light.

New research from an international team of astronomers has discovered a puzzling feature within one Gamma-ray burst, suggesting that these objects may behave differently than previously thought.

These powerful explosions are thought to be triggered when dying stars collapse into jet-spewing black holes. While this stage only lasts a few minutes, its afterglow — slowly fading emission that can be seen at all wavelengths (including visible light) — will last for a few days to weeks. It is from this afterglow that astronomers meticulously try to understand these enigmatic explosions.

The afterglow emission is formed when the jets collide with the material surrounding the dying star. They cause a shockwave, moving at high velocities, in which electrons are being accelerated to tremendous energies. However, this acceleration process is still poorly understood. The key is in detecting the afterglow’s polarization — the fraction of light waves that move with a preferred plane of vibration.

“Different theories for electron acceleration and light emission within the afterglow all predict different levels of linear polarization, but theories all agreed that there should be no circular polarization in visible light,” said lead author Klaas Wiersema in a press release.

“This is where we came in: we decided to test this by carefully measuring both the linear and circular polarization of one afterglow, of GRB 121024A, detected by the Swift satellite.”

Gamma-ray burst 121024A, as seen on the day of burst by ESO’s Very Large Telescope (VLT) in Chile. Only a week later the source had faded completely. Credit: Dr Klaas Wiersema, University of Leicester, UK and Dr Peter Curran, ICRAR. — Gamma-ray burst 121024A, as seen on the day of the burst by ESO’s Very Large Telescope in Chile. Only a week later the source had faded completely. Image Credit: Dr Klaas Wiersema, University of Leicester, UK and Dr Peter Curran, ICRAR.

And to their surprise, the team detected circular polarization, meaning that the light waves are moving together in a uniform, spiral motion as they travel. The gamma-ray burst was 1000 times more polarized than expected. “It is a very nice example of observations ruling out most of the existing theoretical predictions,” said Wiersema.

The detection shows that current theories need to be re-examined. Scientists expected any circular polarization to be washed out. The radiation of so many electrons travelings billions of light-years would erase any signal. But the new discovery suggests that there could be some sort of order in the way these electrons travel.

Of course the possibility remains that this particular afterglow was simply an oddball and not all afterglows behave like this.

Nonetheless “extreme shocks like the ones in GRB afterglows are great natural laboratories to push our understanding of physics beyond the ranges that can be explored in laboratories,” said Wiersema.

The paper has been published in Nature.