#Cosmology
Early Universe was a liquid

In an experiment to collide lead nuclei together at CERN’s Large Hadron Collider physicists from the ALICE detector team have discovered that the very early Universe was not only very hot and dense but behaved like a hot liquid.
 
By accelerating and smashing together lead nuclei at the highest possible energies, the ALICE experiment has generated incredibly hot (over ten trillion degrees) and dense sub-atomic fireballs, recreating the conditions that existed in the first few microseconds after the Big Bang. At these temperatures normal matter is expected to melt into an exotic, primordial ‘soup’ known as quark-gluon plasma.

These first results from lead collisions have already ruled out a number of theoretical physics models, including ones predicting that the quark-gluon plasma created at these energies would behave like a gas. The latest results would seem to suggest that the Universe would have behaved like a super-hot liquid immediately after the Big Bang.

The team has also discovered that more sub-atomic particles are produced in these head-on collisions than some theoretical models previously suggested. The fireballs resulting from the collision only lasts a short time, but when the ‘soup’ cools down, the researchers are able to see thousands of particles radiating out from the fireball. It is in this debris that they are able to draw conclusions about the soup’s behaviour.

Image: Real lead-lead collision in ALICE.

• Source: PhysOrg.com • Two papers detailing this research are available at http://arXiv:1011.3914v1 and http://arXiv:1011.3916v2

Early Universe was a liquid

In an experiment to collide lead nuclei together at CERN’s Large Hadron Collider physicists from the ALICE detector team have discovered that the very early Universe was not only very hot and dense but behaved like a hot liquid.

By accelerating and smashing together lead nuclei at the highest possible energies, the ALICE experiment has generated incredibly hot (over ten trillion degrees) and dense sub-atomic fireballs, recreating the conditions that existed in the first few microseconds after the Big Bang. At these temperatures normal matter is expected to melt into an exotic, primordial ‘soup’ known as quark-gluon plasma.

These first results from lead collisions have already ruled out a number of theoretical physics models, including ones predicting that the quark-gluon plasma created at these energies would behave like a gas. The latest results would seem to suggest that the Universe would have behaved like a super-hot liquid immediately after the Big Bang.

The team has also discovered that more sub-atomic particles are produced in these head-on collisions than some theoretical models previously suggested. The fireballs resulting from the collision only lasts a short time, but when the ‘soup’ cools down, the researchers are able to see thousands of particles radiating out from the fireball. It is in this debris that they are able to draw conclusions about the soup’s behaviour.

Image: Real lead-lead collision in ALICE.

• Source: PhysOrg.com Two papers detailing this research are available at http://arXiv:1011.3914v1 and http://arXiv:1011.3916v2

Scientists glimpse universe before the Big Bang

Oxford University physicist Roger Penrose and Vahe Gurzadyan from the Yerevan Physics Institute in Armenia have found an effect in the cosmic microwave background (CMB) that allows them to “see through” the Big Bang into what came before, roughly 14 billion years ago.
 
The CMB temperature has anisotropies: tiny random fluctuations that occurred in the fraction of a second after the Big Bang when the inflation started. These tiny fluctuations made the radiation nearly uniform, and are thought to have grown into the large-scale structures we see today.

However, Penrose and Gurzadyan have now discovered concentric circles within the CMB in which the temperature variation is much lower than expected, implying that CMB anisotropies are not completely random. They think that these circles stem from collisions between supermassive black holes that released considerably huge isotropic bursts of energy. The strange part is that the scientists calculated that some of the larger of these nearly isotropic circles must have occurred before the time of the Big Bang.

The discovery suggest that there could have been many Big Bang events. The CMB circles support the possibility that we live in a cyclic universe, in which the end of one “aeon” (or universe) triggers another Big Bang that starts another aeon (another universe), and the process repeats indefinitely. The black hole encounters that caused the circles likely occurred within the later stages of the aeon right before ours.

Cyclic cosmology models provide a better explanation than the inflationary theory of why there was such low entropy at the beginning of the universe, which was essential for making complex matter possible: when a universe expands to its full extent, black holes will evaporate and all the information they contain will vanish, removing entropy from the universe and allowing the beginning of another.

The scientists will do further work to confirm their existence of these little circles and see which models can best explain them. But even if the circles really do stem from sources in a pre-Big Bang era, cyclic cosmology may not offer the best explanation for them. Among its challenges, cyclic cosmology still needs to explain the vast shift of scale between aeons, as well as why it requires all particles to lose their mass at some point in the future.

Image: Black hole encounters would have repeated themselves several times, with the center of each event remaining at almost exactly the same point in the CMB sky, even when occurring in different aeons. The huge amounts of energy released would appear as spherical, low-variance radiation bursts in the CMB.

• Source: PhysOrg.com/physicsworld.com • The paper is available at http://arxiv.org/abs/1011.3706

Scientists glimpse universe before the Big Bang

Oxford University physicist Roger Penrose and Vahe Gurzadyan from the Yerevan Physics Institute in Armenia have found an effect in the cosmic microwave background (CMB) that allows them to “see through” the Big Bang into what came before, roughly 14 billion years ago.

The CMB temperature has anisotropies: tiny random fluctuations that occurred in the fraction of a second after the Big Bang when the inflation started. These tiny fluctuations made the radiation nearly uniform, and are thought to have grown into the large-scale structures we see today.

However, Penrose and Gurzadyan have now discovered concentric circles within the CMB in which the temperature variation is much lower than expected, implying that CMB anisotropies are not completely random. They think that these circles stem from collisions between supermassive black holes that released considerably huge isotropic bursts of energy. The strange part is that the scientists calculated that some of the larger of these nearly isotropic circles must have occurred before the time of the Big Bang.

The discovery suggest that there could have been many Big Bang events. The CMB circles support the possibility that we live in a cyclic universe, in which the end of one “aeon” (or universe) triggers another Big Bang that starts another aeon (another universe), and the process repeats indefinitely. The black hole encounters that caused the circles likely occurred within the later stages of the aeon right before ours.

Cyclic cosmology models provide a better explanation than the inflationary theory of why there was such low entropy at the beginning of the universe, which was essential for making complex matter possible: when a universe expands to its full extent, black holes will evaporate and all the information they contain will vanish, removing entropy from the universe and allowing the beginning of another.

The scientists will do further work to confirm their existence of these little circles and see which models can best explain them. But even if the circles really do stem from sources in a pre-Big Bang era, cyclic cosmology may not offer the best explanation for them. Among its challenges, cyclic cosmology still needs to explain the vast shift of scale between aeons, as well as why it requires all particles to lose their mass at some point in the future.

Image: Black hole encounters would have repeated themselves several times, with the center of each event remaining at almost exactly the same point in the CMB sky, even when occurring in different aeons. The huge amounts of energy released would appear as spherical, low-variance radiation bursts in the CMB.

• Source: PhysOrg.com/physicsworld.com The paper is available at http://arxiv.org/abs/1011.3706

Detailed dark matter map yields clues to galaxy cluster growth

Astronomers using the Hubble Space Telescope received a boost from a cosmic magnifying glass to construct one of the sharpest maps of dark matter in the universe.

They used Hubble’s Advanced Camera for Surveys to chart the invisible matter in the massive galaxy cluster Abell 1689, located 2.2 billion light-years away. The cluster contains about 1,000 galaxies and trillions of stars.

Dark matter is an invisible form of matter that accounts for most of the universe’s mass. Hubble cannot see the dark matter directly. Astronomers inferred its location by analyzing the effect of gravitational lensing, where light from galaxies behind Abell 1689 is distorted by intervening matter within the cluster.

Researchers used the observed positions of 135 lensed images of 42 background galaxies to calculate the location and amount of dark matter in the cluster. They superimposed a map of these inferred dark matter concentrations, tinted blue, on a Hubble image of the cluster. The new dark matter observations may yield new insights into the role of dark energy in the universe’s early formative years.

• Source: Full article at HubbleSite.org

Detailed dark matter map yields clues to galaxy cluster growth

Astronomers using the Hubble Space Telescope received a boost from a cosmic magnifying glass to construct one of the sharpest maps of dark matter in the universe.

They used Hubble’s Advanced Camera for Surveys to chart the invisible matter in the massive galaxy cluster Abell 1689, located 2.2 billion light-years away. The cluster contains about 1,000 galaxies and trillions of stars.

Dark matter is an invisible form of matter that accounts for most of the universe’s mass. Hubble cannot see the dark matter directly. Astronomers inferred its location by analyzing the effect of gravitational lensing, where light from galaxies behind Abell 1689 is distorted by intervening matter within the cluster.

Researchers used the observed positions of 135 lensed images of 42 background galaxies to calculate the location and amount of dark matter in the cluster. They superimposed a map of these inferred dark matter concentrations, tinted blue, on a Hubble image of the cluster. The new dark matter observations may yield new insights into the role of dark energy in the universe’s early formative years.

• Source: Full article at HubbleSite.org

New horizons for Hawking radiation

In 1974, Steven Hawking predicted that black holes were not completely black, but were actually weak emitters of blackbody radiation generated close to the event horizon—the boundary where light is forever trapped by the black hole’s gravitational pull.

Hawking’s insight was to realize how the presence of the horizon could separate virtual photon pairs (constantly being created from the quantum vacuum) such that while one was sucked in, the other could escape, causing the black hole to lose energy.

Hawking’s idea was significant in suggesting a possible optical signature of a black hole’s existence. Yet, even though the prediction created an extensive theoretical literature in cosmology, calculations have since shown that Hawking radiation from black holes is so weak that it would be practically impossible to measure.

It turns out, however, that the physics of how waves interact with a horizon does not depend in a fundamental way on the presence of gravity at all.

In principle, an analogous Hawking radiation should occur in other systems. The key requirement is simply that the interaction between waves and the medium in which they propagate causes there to be a boundary between zones where the wave and the medium have different velocities.

In a paper in Physical Review Letters, Franco Belgiorno at the Università degli Studi di Milano, in collaboration with researchers at several other institutes, also in Italy, describe a series of experiments where high-intensity filaments of light in glass perturb the optical propagation environment in an analogous manner to the way a gravitational field affects light near a black hole horizon.

This perturbation creates the optical equivalent of an event horizon that allows the team to make convincing measurements of analog Hawking radiation at optical frequencies. These results are highly significant in suggesting a system in which Hawking’s prediction can be fully explored in a convenient laboratory environment.

Image: Creating an analog gravitational potential in an optical system. (Left) A suitable change in the index of refraction in a moving medium creates an effective event horizon for photons that propagate with it. As indicated by the pink arrow, photons are forbidden from entering beyond the optical event horizon. The equation below relates the analog black body temperature of the optical white hole to how the change in the index varies in time (τ). (Right) Researchers use a high-intensity light filament to perturb the index of refraction in glass and create an optical event horizon and measure the analog Hawking radiation emerging at right angles from the filament.

• Source: Full article at APS Physics • The paper is available at http://physics.aps.org/pdf/10.1103/

New horizons for Hawking radiation

In 1974, Steven Hawking predicted that black holes were not completely black, but were actually weak emitters of blackbody radiation generated close to the event horizon—the boundary where light is forever trapped by the black hole’s gravitational pull.

Hawking’s insight was to realize how the presence of the horizon could separate virtual photon pairs (constantly being created from the quantum vacuum) such that while one was sucked in, the other could escape, causing the black hole to lose energy.

Hawking’s idea was significant in suggesting a possible optical signature of a black hole’s existence. Yet, even though the prediction created an extensive theoretical literature in cosmology, calculations have since shown that Hawking radiation from black holes is so weak that it would be practically impossible to measure.

It turns out, however, that the physics of how waves interact with a horizon does not depend in a fundamental way on the presence of gravity at all.

In principle, an analogous Hawking radiation should occur in other systems. The key requirement is simply that the interaction between waves and the medium in which they propagate causes there to be a boundary between zones where the wave and the medium have different velocities.

In a paper in Physical Review Letters, Franco Belgiorno at the Università degli Studi di Milano, in collaboration with researchers at several other institutes, also in Italy, describe a series of experiments where high-intensity filaments of light in glass perturb the optical propagation environment in an analogous manner to the way a gravitational field affects light near a black hole horizon.

This perturbation creates the optical equivalent of an event horizon that allows the team to make convincing measurements of analog Hawking radiation at optical frequencies. These results are highly significant in suggesting a system in which Hawking’s prediction can be fully explored in a convenient laboratory environment.

Image: Creating an analog gravitational potential in an optical system. (Left) A suitable change in the index of refraction in a moving medium creates an effective event horizon for photons that propagate with it. As indicated by the pink arrow, photons are forbidden from entering beyond the optical event horizon. The equation below relates the analog black body temperature of the optical white hole to how the change in the index varies in time (τ). (Right) Researchers use a high-intensity light filament to perturb the index of refraction in glass and create an optical event horizon and measure the analog Hawking radiation emerging at right angles from the filament.

• Source: Full article at APS Physics The paper is available at http://physics.aps.org/pdf/10.1103/

The holographic principle of the universe has been a popular theory among crazies and string theorists for years.

In a larger and more speculative sense, the theory suggests that the entire universe can be seen as a two-dimensional information structure “painted” on the cosmological horizon, such that the three dimensions we observe are only an effective description at macroscopic scales and at low energies. Cosmological holography has not been made mathematically precise, partly because the cosmological horizon has a finite area and grows with time.[2][3]

Take a look at the back of a credit card. You can see the metallic two-dimensional sticker on the back, right? When you tilt it back and forth, the image on the sticker appears to be three-dimensional as light reflects off of it in the changing light. The holographic prinicple of the universe says that this is how the universe behaves: the entire universe is two-dimensional and we only perceive it to be three dimensional because of a quirk of light, but also that we’re incapable of recognizing the holography of the universe as a result of the precision of the hologram (much like a really convincing 3D movie that you’ve been watching your whole life).

The idea that spacetime may not be entirely smooth – like a digital image that becomes increasingly pixelated as you zoom in – had been previously proposed by Stephen Hawking and others. Possible evidence for this model appeared last year in the unaccountable “noise” plaguing the GEO600 experiment in Germany, which searches for gravitational waves from black holes. To Hogan, the jitteriness suggested that the experiment had stumbled upon the lower limit of the spacetime pixels’ resolution.

The universe is probably not smooth. This has been theorized since the days of Max Planck around the turn of the last century and today the supposed graininess of the universe is relatively well-accepted, as far as new and crazy/mind-blowing/debilitating theories go.

Proponents of this theory have long been resigned to the ranks of stoner philosophy majors going on about how the universe is totally flat, man, totally. In the background, though, theorists have been refining the theory and now it’s time for them to shine.

“So we want to build a machine which will be the most sensitive measurement ever made of spacetime itself,” says Hogan. “That’s the holometer.”

The holometer’s precision means that it doesn’t have to be large; at 40 meters in length, it is only one hundredth of the size of current interferometers, which measure gravitational waves from black holes and supernovas. Yet because the spacetime frequencies it measures are so rapid, it will be more precise over very short time intervals by seven orders of magnitude than any atomic clock in existence.

The results from this experiment will likely be a hot topic of debate for a long time, but if a definitive answer is shown then it could revolutionize not only the field of quantum mechanics, but physics as a whole.

(via fuckyeahphysics)

3 years ago ★ Reblogged from: fuckyeahphysics 164
The most distant galaxy ever measured

A European team of astronomers using ESO’s Very Large Telescope (VLT) has measured the distance to the most remote galaxy so far, seeing it when the Universe was only about 600 million years old (a redshift of 8.6). The astrophysical implications of this detection is very important, since this is the first time we are looking at one of the galaxies that cleared out the opaque hydrogen fog which had filled the very early Universe.

Studying these first galaxies is extremely difficult. By the time that their initially brilliant light gets to Earth they appear very faint and small. Furthermore, this dim light falls mostly in the infrared part of the spectrum because its wavelength has been stretched by the expansion of the Universe — an effect known as redshift.

To make matters worse, at this early time, less than a billion years after the Big Bang, the Universe was not fully transparent and much of it was filled with a hydrogen fog that absorbed the fierce ultraviolet light from young galaxies (image). The period when the fog was still being cleared by this ultraviolet light is known as the era of reionization.

Despite these challenges the new Wide Field Camera 3 on the Hubble Space Telescope discovered several candidate objects in 2009 that were thought to be galaxies shining in the era of reionization. Confirming the distances to such faint and remote objects is an enormous challenge and can only reliably be done using spectroscopy from very large ground-based telescopes.

Astronomers used the VLT’s SINFONI instrument to observe a candidate galaxy called UDFy-38135539 with a long exposure time of 16 hours. After two months of very careful analysis and testing, the team found that they had clearly detected the very faint glow from hydrogen at a redshift of 8.6, which makes this galaxy the most distant object ever confirmed by spectroscopy. A redshift of 8.6 corresponds to a galaxy seen just 600 million years after the Big Bang.

One of the surprising things about this discovery is that the glow from UDFy-38135539 seems not to be strong enough on its own to clear out the hydrogen fog. There must be other galaxies, probably fainter and less massive nearby companions of UDFy-38135539, which also helped make the space around the galaxy transparent. Without this additional help the light from the galaxy, no matter how brilliant, would have been trapped in the surrounding hydrogen fog and we would not have been able to detect it.

Studying the era of reionization and galaxy formation is pushing the capability of current telescopes and instruments to the limit, but this is just the type of science that will be routine when the biggest optical and near infrared telescope in the world — European Extremely Large Telescope — becomes operational.

Image: (Top) A simulation that depicts how galaxies looked like during the era of reionization in the early Universe. [paper]. (Bottom) The infrared Hubble Ultra Deep Field taken by the Hubble Space Telescope in 2009. The galaxy UDFy-38135539 is the faint object shown in the excerpt on the left.

• Source: ESO • See also: Video version of this story

The most distant galaxy ever measured

A European team of astronomers using ESO’s Very Large Telescope (VLT) has measured the distance to the most remote galaxy so far, seeing it when the Universe was only about 600 million years old (a redshift of 8.6). The astrophysical implications of this detection is very important, since this is the first time we are looking at one of the galaxies that cleared out the opaque hydrogen fog which had filled the very early Universe.

Studying these first galaxies is extremely difficult. By the time that their initially brilliant light gets to Earth they appear very faint and small. Furthermore, this dim light falls mostly in the infrared part of the spectrum because its wavelength has been stretched by the expansion of the Universe — an effect known as redshift.

To make matters worse, at this early time, less than a billion years after the Big Bang, the Universe was not fully transparent and much of it was filled with a hydrogen fog that absorbed the fierce ultraviolet light from young galaxies (image). The period when the fog was still being cleared by this ultraviolet light is known as the era of reionization.

Despite these challenges the new Wide Field Camera 3 on the Hubble Space Telescope discovered several candidate objects in 2009 that were thought to be galaxies shining in the era of reionization. Confirming the distances to such faint and remote objects is an enormous challenge and can only reliably be done using spectroscopy from very large ground-based telescopes.

Astronomers used the VLT’s SINFONI instrument to observe a candidate galaxy called UDFy-38135539 with a long exposure time of 16 hours. After two months of very careful analysis and testing, the team found that they had clearly detected the very faint glow from hydrogen at a redshift of 8.6, which makes this galaxy the most distant object ever confirmed by spectroscopy. A redshift of 8.6 corresponds to a galaxy seen just 600 million years after the Big Bang.

One of the surprising things about this discovery is that the glow from UDFy-38135539 seems not to be strong enough on its own to clear out the hydrogen fog. There must be other galaxies, probably fainter and less massive nearby companions of UDFy-38135539, which also helped make the space around the galaxy transparent. Without this additional help the light from the galaxy, no matter how brilliant, would have been trapped in the surrounding hydrogen fog and we would not have been able to detect it.

Studying the era of reionization and galaxy formation is pushing the capability of current telescopes and instruments to the limit, but this is just the type of science that will be routine when the biggest optical and near infrared telescope in the world — European Extremely Large Telescope — becomes operational.

Image: (Top) A simulation that depicts how galaxies looked like during the era of reionization in the early Universe. [paper]. (Bottom) The infrared Hubble Ultra Deep Field taken by the Hubble Space Telescope in 2009. The galaxy UDFy-38135539 is the faint object shown in the excerpt on the left.

• Source: ESO • See also: Video version of this story

Mass limits of dark matter particles derived from neutron stars and strange quark matter

Much of the matter in our universe may be made of a type of dark matter called weakly interacting massive particles, better known as WIMPs. Although some scientists predict that these hypothetical particles possess many of the necessary properties to account for dark matter, so far scientists have not been able to make any definite predictions of their mass. Now, in a new study, physicists have derived a limit on the WIMP mass by calculating how these dark matter particles can transform neutron stars into stars made of strange quark matter, or “strange” stars.

WIMP mass is an important quantity to know since WIMPS are considered to be constituents of dark matter, which form most of the matter in the universe. By knowing this value, scientists would be able to put another piece of fundamental information on our current knowledge of the building blocks of our universe and after that see, for example, how dark matter interacts with regular matter, how it is distributed spatially, etc.

As dark matter particles, WIMPs are thought to be largely located in the halos of galaxies. Although galaxy halos are not visible, they contain most of a galaxy’s mass in the form of the heavy WIMPs. In their study, the scientists focused on what happens when WIMPs from galactic halos are captured by neutron stars located deeper within the galaxy.

Neutron stars are known for their extreme density: although a typical neutron star has a radius of only 10 km, it has more mass than our Sun. Theories predict that neutron stars and black holes are gravitational accretors of dark matter. Some models even discuss that WIMPs could have formed the first stars in our universe, known as dark stars, powered by dark matter annihilation instead of nuclear fusion.

In their study, the scientists theoretically showed that, when a neutron star gravitationally captures nearby WIMPs, the WIMPs may trigger the conversion of the neutron star into a strange star. The conversion occurs as a result of the WIMPs seeding the neutron stars with long-lived lumps of strange quark matter, or strangelets. When WIMPs are captured in the neutron star’s core, they self-annihilate, releasing energy in the process.

At certain energy levels, the energy will partly convert into heat that causes thermal fluctuations, which in turn can “burn” the star’s nucleons into quark bubbles that eventually become strangelets. Some of these strangelets decay rapidly and have no effect on the neutron star. But if they have a high enough baryon number, they can live up to several days. Previous research has shown that it takes about 100 seconds to convert a neutron star into a strange star, a process that could potentially be triggered by long-lived strangelets.

By figuring out the minimum required baryon number and efficiency rate for a strangelet to trigger the conversion of a neutron star into a strange star, the scientists could calculate the parent WIMP mass as a function of this baryon number. In this relationship, the more massive the WIMPs are, the higher the conversion rate from neutron star to strange star.

The predicted WIMP mass limits can be investigated with current observational and experimental searches. For example, observing a strange star and measuring simultaneously its mass and radius could provide more constraints on strangelets’ properties. The researchers also predict that the neutron star conversion process could generate detectable gamma-ray bursts. In the future, the physicists hope to investigate whether WIMP annihilation inside neutron stars has other observable consequences, such as altering its temperature and rotation patterns.

Image: A simulated dark matter halo. Physicists have put a new limit on WIMP mass by investigating how WIMPs can convert neutron stars into strange stars.

• Source: PhysOrg.com • The paper of this research is available at Physical Review Letters

Mass limits of dark matter particles derived from neutron stars and strange quark matter

Much of the matter in our universe may be made of a type of dark matter called weakly interacting massive particles, better known as WIMPs. Although some scientists predict that these hypothetical particles possess many of the necessary properties to account for dark matter, so far scientists have not been able to make any definite predictions of their mass. Now, in a new study, physicists have derived a limit on the WIMP mass by calculating how these dark matter particles can transform neutron stars into stars made of strange quark matter, or “strange” stars.

WIMP mass is an important quantity to know since WIMPS are considered to be constituents of dark matter, which form most of the matter in the universe. By knowing this value, scientists would be able to put another piece of fundamental information on our current knowledge of the building blocks of our universe and after that see, for example, how dark matter interacts with regular matter, how it is distributed spatially, etc.

As dark matter particles, WIMPs are thought to be largely located in the halos of galaxies. Although galaxy halos are not visible, they contain most of a galaxy’s mass in the form of the heavy WIMPs. In their study, the scientists focused on what happens when WIMPs from galactic halos are captured by neutron stars located deeper within the galaxy.

Neutron stars are known for their extreme density: although a typical neutron star has a radius of only 10 km, it has more mass than our Sun. Theories predict that neutron stars and black holes are gravitational accretors of dark matter. Some models even discuss that WIMPs could have formed the first stars in our universe, known as dark stars, powered by dark matter annihilation instead of nuclear fusion.

In their study, the scientists theoretically showed that, when a neutron star gravitationally captures nearby WIMPs, the WIMPs may trigger the conversion of the neutron star into a strange star. The conversion occurs as a result of the WIMPs seeding the neutron stars with long-lived lumps of strange quark matter, or strangelets. When WIMPs are captured in the neutron star’s core, they self-annihilate, releasing energy in the process.

At certain energy levels, the energy will partly convert into heat that causes thermal fluctuations, which in turn can “burn” the star’s nucleons into quark bubbles that eventually become strangelets. Some of these strangelets decay rapidly and have no effect on the neutron star. But if they have a high enough baryon number, they can live up to several days. Previous research has shown that it takes about 100 seconds to convert a neutron star into a strange star, a process that could potentially be triggered by long-lived strangelets.

By figuring out the minimum required baryon number and efficiency rate for a strangelet to trigger the conversion of a neutron star into a strange star, the scientists could calculate the parent WIMP mass as a function of this baryon number. In this relationship, the more massive the WIMPs are, the higher the conversion rate from neutron star to strange star.

The predicted WIMP mass limits can be investigated with current observational and experimental searches. For example, observing a strange star and measuring simultaneously its mass and radius could provide more constraints on strangelets’ properties. The researchers also predict that the neutron star conversion process could generate detectable gamma-ray bursts. In the future, the physicists hope to investigate whether WIMP annihilation inside neutron stars has other observable consequences, such as altering its temperature and rotation patterns.

Image: A simulated dark matter halo. Physicists have put a new limit on WIMP mass by investigating how WIMPs can convert neutron stars into strange stars.

• Source: PhysOrg.com The paper of this research is available at Physical Review Letters

Physicists are searching for the fingerprints of cosmic strings

A team of physicists from the University at Buffalo in N.Y. have announced what they think are the first indirect observations of one of the strangest theorized structures in the universe, the ancient cosmic strings, bizarre objects thought to have contributed to the arrangement of objects throughout the universe.

First predicted back in the 1970s, cosmic strings are thought to be enormous fault lines that once existed in space. Not to be confused with the subatomic strings of string theory, cosmic strings are widely believed by astrophysicists to have formed billions of years ago, just moments after the Big Bang when the universe was still a soupy mass of extremely hot matter. As the universe cooled, cosmic strings formed between different regions of space that cooled in different ways.

The presumed cosmic strings were incredibly narrow, thinner than the diameter of a proton, but so dense that a string less than a mile in length would weigh more than the Earth. As the universe expanded, so too did these strings until they either stretched across the known universe, or into enormous rings thousands of times larger than our galaxy.

Although researchers have not yet directly observed the strings themselves, the team believes they found evidence of them hidden in ancient quasars. The team analyzed the observational data of 355 quasars that reside in the far off corners of the universe. With careful scrutiny of the light emitted by these quasars, it is possible to determine the direction their jets are facing in space. The team found that 183 of them lined up to form two enormous rings that stretch across the sky in a pattern unlikely to have formed by chance.

The team members think that the magnetic fields of the two cosmic strings affected the direction the quasars are pointing. The strings themselves should have long since dissipated by emitting gravitational radiation as they vibrated; however the original effect on the alignment of the quasars would have remained. To check their hypothesis, they modeled the theorized effects of the strings on the formation of quasars, and found their predictions closely matched their observations.

More follow-up observations and analysis need to be conducted before they can be completely sure they have found evidence of the strings. The detection of a cosmic string would be an important cosmological discovery because of their theorized importance to the formation of galaxies in the early universe. However, other researchers are cautious about the results and don’t want to jump to conclusions too quickly. The strings are believed to have formed nanoseconds after the big bang, they probably would have decayed so quickly that their magnetic effect wouldn’t last until today.

Image: The postulated location of Earth (blue dot) and the A1-A3 axis are shown above. Two electroweak strings initially linked form around the electroweak phase transition. The strings decay, but leave a magnetic imprint behind in the highly conducting plasma of the early universe. This magnetic field is carried by the expansion of the universe and today is on the order of Gpc scales.

• Source: InsideScience.org • The paper of this research is available at Physical Review Letters

Physicists are searching for the fingerprints of cosmic strings

A team of physicists from the University at Buffalo in N.Y. have announced what they think are the first indirect observations of one of the strangest theorized structures in the universe, the ancient cosmic strings, bizarre objects thought to have contributed to the arrangement of objects throughout the universe.

First predicted back in the 1970s, cosmic strings are thought to be enormous fault lines that once existed in space. Not to be confused with the subatomic strings of string theory, cosmic strings are widely believed by astrophysicists to have formed billions of years ago, just moments after the Big Bang when the universe was still a soupy mass of extremely hot matter. As the universe cooled, cosmic strings formed between different regions of space that cooled in different ways.

The presumed cosmic strings were incredibly narrow, thinner than the diameter of a proton, but so dense that a string less than a mile in length would weigh more than the Earth. As the universe expanded, so too did these strings until they either stretched across the known universe, or into enormous rings thousands of times larger than our galaxy.

Although researchers have not yet directly observed the strings themselves, the team believes they found evidence of them hidden in ancient quasars. The team analyzed the observational data of 355 quasars that reside in the far off corners of the universe. With careful scrutiny of the light emitted by these quasars, it is possible to determine the direction their jets are facing in space. The team found that 183 of them lined up to form two enormous rings that stretch across the sky in a pattern unlikely to have formed by chance.

The team members think that the magnetic fields of the two cosmic strings affected the direction the quasars are pointing. The strings themselves should have long since dissipated by emitting gravitational radiation as they vibrated; however the original effect on the alignment of the quasars would have remained. To check their hypothesis, they modeled the theorized effects of the strings on the formation of quasars, and found their predictions closely matched their observations.

More follow-up observations and analysis need to be conducted before they can be completely sure they have found evidence of the strings. The detection of a cosmic string would be an important cosmological discovery because of their theorized importance to the formation of galaxies in the early universe. However, other researchers are cautious about the results and don’t want to jump to conclusions too quickly. The strings are believed to have formed nanoseconds after the big bang, they probably would have decayed so quickly that their magnetic effect wouldn’t last until today.

Image: The postulated location of Earth (blue dot) and the A1-A3 axis are shown above. Two electroweak strings initially linked form around the electroweak phase transition. The strings decay, but leave a magnetic imprint behind in the highly conducting plasma of the early universe. This magnetic field is carried by the expansion of the universe and today is on the order of Gpc scales.

• Source: InsideScience.org The paper of this research is available at Physical Review Letters

Astronomers Uncover an Overheated Early Universe

If you think global warming is bad, 11 billion years ago the entire universe underwent, well, universal warming. The consequence was that fierce blasts of radiation from voracious black holes stunted the growth of some small galaxies for a stretch of 500 million years. This is the conclusion of a team of astronomers from the University of Colorado who used the new capabilities of NASA’s Hubble Space Telescope to probe the invisible, remote universe.

Using the newly installed Cosmic Origins Spectrograph (COS) they have identified an era, from 11.7 to 11.3 billion years ago, when the universe stripped electrons off from primeval helium atoms — a process called ionization. This process heated intergalactic gas and inhibited it from gravitationally collapsing to form new generations of stars in some small galaxies. The lowest-mass galaxies were not even able to hold onto their gas, and it escaped back into intergalactic space.

The telltale helium spectral absorption lines were measured in the ultraviolet light from a quasar — the brilliant core of an active galaxy. The quasar beacon shines light through intervening clouds of otherwise invisible gas, like a headlight shining through a fog. The beam allows for a core-sample probe of the clouds of gas interspersed between galaxies in the early universe.

The universe went through an initial heat wave over 13 billion years ago when energy from early massive stars ionized cold interstellar hydrogen from the big bang. This epoch is actually called reionization because the hydrogen nuclei were originally in an ionized state shortly after the big bang.

But Hubble found that it would take another 2 billion years before the universe produced sources of ultraviolet radiation with enough energy to do the heavy lifting and reionize the primordial helium that was also cooked up in the big bang. This radiation didn’t come from stars, but rather from quasars. In fact the epoch when the helium was being reionized corresponds to a transitory time in the universe’s history when quasars were most abundant.

The universe was a rambunctious place back then. Galaxies frequently collided, and this engorged supermassive black holes in the cores of galaxies with infalling gas. The black holes furiously converted some of the gravitational energy of this mass to powerful far-ultraviolet radiation that would blaze out of galaxies. This heated the intergalactic helium from 18,000 degrees Fahrenheit to nearly 40,000 degrees. After the helium was reionized in the universe, intergalactic gas again cooled down and dwarf galaxies could resume normal assembly.

• Source: HubbleSite.org

Astronomers Uncover an Overheated Early Universe

If you think global warming is bad, 11 billion years ago the entire universe underwent, well, universal warming. The consequence was that fierce blasts of radiation from voracious black holes stunted the growth of some small galaxies for a stretch of 500 million years. This is the conclusion of a team of astronomers from the University of Colorado who used the new capabilities of NASA’s Hubble Space Telescope to probe the invisible, remote universe.

Using the newly installed Cosmic Origins Spectrograph (COS) they have identified an era, from 11.7 to 11.3 billion years ago, when the universe stripped electrons off from primeval helium atoms — a process called ionization. This process heated intergalactic gas and inhibited it from gravitationally collapsing to form new generations of stars in some small galaxies. The lowest-mass galaxies were not even able to hold onto their gas, and it escaped back into intergalactic space.

The telltale helium spectral absorption lines were measured in the ultraviolet light from a quasar — the brilliant core of an active galaxy. The quasar beacon shines light through intervening clouds of otherwise invisible gas, like a headlight shining through a fog. The beam allows for a core-sample probe of the clouds of gas interspersed between galaxies in the early universe.

The universe went through an initial heat wave over 13 billion years ago when energy from early massive stars ionized cold interstellar hydrogen from the big bang. This epoch is actually called reionization because the hydrogen nuclei were originally in an ionized state shortly after the big bang.

But Hubble found that it would take another 2 billion years before the universe produced sources of ultraviolet radiation with enough energy to do the heavy lifting and reionize the primordial helium that was also cooked up in the big bang. This radiation didn’t come from stars, but rather from quasars. In fact the epoch when the helium was being reionized corresponds to a transitory time in the universe’s history when quasars were most abundant.

The universe was a rambunctious place back then. Galaxies frequently collided, and this engorged supermassive black holes in the cores of galaxies with infalling gas. The black holes furiously converted some of the gravitational energy of this mass to powerful far-ultraviolet radiation that would blaze out of galaxies. This heated the intergalactic helium from 18,000 degrees Fahrenheit to nearly 40,000 degrees. After the helium was reionized in the universe, intergalactic gas again cooled down and dwarf galaxies could resume normal assembly.

• Source: HubbleSite.org

First Observation of Hawking Radiation

For some time now, astronomers have been scanning the heavens looking for signs of Hawking radiation, predicted it in 1974. So far, they’ve come up with zilch. Today, it looks as if they’ve been beaten to the punch by a group of physicists who say they’ve created Hawking radiation in their lab. These guys reckon they can produce Hawking radiation in a repeatable unambiguous way, finally confirming Hawking’s prediction. Here’s how they did it.

Physicists have long realised that on the smallest scale, space is filled with a bubbling melee of particles leaping in and out of existence. These particles form as particle-antiparticle pairs and rapidly annihilate, returning their energy to the vacuum.

Hawking’s prediction came from thinking about what might happen to particle pairs that form at the edge of a black hole. He realised that if one of the pair were to cross the event horizon, it could never return. But its partner on the other side would be free to go. To an observer it would look as if the black hole were producing a constant stream of quantum particles, which became known as Hawking radiation.

Since then, other physicists have pointed out that black holes aren’t the only place where event horizons can form. Any medium in which waves travel can support an event horizon and in theory, it should be possible to see Hawking radiation in these media too.

Now, physicists at the University of Milan say they’ve produced Hawking radiation by firing an intense laser pulse through a so-called nonlinear material, that is one in which the light itself changes the refractive index of the medium. As the pulse moves through the material, so too does the change in refractive index, creating a kind of bow wave in which the refractive index is much higher than the surrounding material.

This increase in refractive index causes any light heading into it to slow down. By choosing appropriate conditions, it is possible to bring the light waves to a standstill. This creates a horizon beyond which light cannot penetrate, what physicists call a white hole event horizon, the inverse of a black hole.

White holes aren’t so different to black holes. And it’s not hard to imagine what happens to particle pairs that form at this type of horizon. If one of the pair crosses the horizon, it can make no headway and so becomes trapped. The other is free to go. So the horizon ought to look as if it is generating quantum particles.

It is this radiation that physicists say they’ve seen by watching from the side as a high power infrared laser pulse ploughs through a lump of fused silica. That’s an astounding claim and one that many physicists will want to pour over before popping any champagne corks.

Why is it important? One reason is that Hawking radiation is the only known a way in which black holes can evaporate and so a proof of its existence will have profound effects for cosmology and the way the universe will end. And now that it’s been observed once, expect a rash of other announcemetns as researchers race to repeat the result.

Image: In the experimental set-up, a laser beam strikes a sample of fused silica glass (FS). An imaging lens (I) collects the photons emitted at 90 degrees and sends them to a spectrometer and CCD camera.

• Source: The Physics ArXiv Blog • The paper is available at arXiv.org

First Observation of Hawking Radiation

For some time now, astronomers have been scanning the heavens looking for signs of Hawking radiation, predicted it in 1974. So far, they’ve come up with zilch. Today, it looks as if they’ve been beaten to the punch by a group of physicists who say they’ve created Hawking radiation in their lab. These guys reckon they can produce Hawking radiation in a repeatable unambiguous way, finally confirming Hawking’s prediction. Here’s how they did it.

Physicists have long realised that on the smallest scale, space is filled with a bubbling melee of particles leaping in and out of existence. These particles form as particle-antiparticle pairs and rapidly annihilate, returning their energy to the vacuum.

Hawking’s prediction came from thinking about what might happen to particle pairs that form at the edge of a black hole. He realised that if one of the pair were to cross the event horizon, it could never return. But its partner on the other side would be free to go. To an observer it would look as if the black hole were producing a constant stream of quantum particles, which became known as Hawking radiation.

Since then, other physicists have pointed out that black holes aren’t the only place where event horizons can form. Any medium in which waves travel can support an event horizon and in theory, it should be possible to see Hawking radiation in these media too.

Now, physicists at the University of Milan say they’ve produced Hawking radiation by firing an intense laser pulse through a so-called nonlinear material, that is one in which the light itself changes the refractive index of the medium. As the pulse moves through the material, so too does the change in refractive index, creating a kind of bow wave in which the refractive index is much higher than the surrounding material.

This increase in refractive index causes any light heading into it to slow down. By choosing appropriate conditions, it is possible to bring the light waves to a standstill. This creates a horizon beyond which light cannot penetrate, what physicists call a white hole event horizon, the inverse of a black hole.

White holes aren’t so different to black holes. And it’s not hard to imagine what happens to particle pairs that form at this type of horizon. If one of the pair crosses the horizon, it can make no headway and so becomes trapped. The other is free to go. So the horizon ought to look as if it is generating quantum particles.

It is this radiation that physicists say they’ve seen by watching from the side as a high power infrared laser pulse ploughs through a lump of fused silica. That’s an astounding claim and one that many physicists will want to pour over before popping any champagne corks.

Why is it important? One reason is that Hawking radiation is the only known a way in which black holes can evaporate and so a proof of its existence will have profound effects for cosmology and the way the universe will end. And now that it’s been observed once, expect a rash of other announcemetns as researchers race to repeat the result.

Image: In the experimental set-up, a laser beam strikes a sample of fused silica glass (FS). An imaging lens (I) collects the photons emitted at 90 degrees and sends them to a spectrometer and CCD camera.

• Source: The Physics ArXiv Blog • The paper is available at arXiv.org

Black Strings: Black Holes With Extra Dimensions

These hypothetical objects might form if our universe has hidden extra dimensions beyond the three of space and one of time that we can see. A new study of five-dimensional black strings offers a glimpse into how these strange objects might evolve over time.

Black strings would be cylindrical; think of a three-dimensional spherical black hole that’s copied and stacked out in one direction to create an oblong shape. Like black holes, black strings would be created when matter is squished so dense that the curvature of space-time becomes so large that even light cannot escape.

Holes and strings

Black string probably wouldn’t be stable for long. Any small perturbation or deformation of its shape would set off a cascading pattern. For example, the cylinder was squeezed slightly in its center, giving it the shape of an hourglass. Gravity would then tug at the neck, causing it to stretch out until the object becomes a set of spherical black holes connected by a filament of black string.

Then, on the string segment, smaller black holes would likely form like beads on a wire, in a process that would go on repeating. For certain models, small perturbations to the extra dimensions would probably cause all the black holes and strings to ultimately merge into one giant black hole.

Hidden dimensions

String Theory postulate we live in a 10- or 11-dimensional universe. If there are extra dimensions they might be very, very small – little curled up dimensions that would not be visible in our macroscopic three-dimensional space. If this is the case, we may not be able to recognize the hidden dimensions in everything, including black holes. The things we know of as black holes might really be black strings but we can’t see the other dimensions.

And black holes aren’t the only possible black objects that could exist in higher-dimensions. Another hypothetical black object is a black Saturn, which would look like a spherical black hole surrounded by a donut-shaped torus. Or there might be black rings, which would simply be ring-shaped.

Image: Five-dimensional black strings evolve into black holes connected by black string filaments, in this computer simulation.

• Source: LiveScience

Black Strings: Black Holes With Extra Dimensions

These hypothetical objects might form if our universe has hidden extra dimensions beyond the three of space and one of time that we can see. A new study of five-dimensional black strings offers a glimpse into how these strange objects might evolve over time.

Black strings would be cylindrical; think of a three-dimensional spherical black hole that’s copied and stacked out in one direction to create an oblong shape. Like black holes, black strings would be created when matter is squished so dense that the curvature of space-time becomes so large that even light cannot escape.

Holes and strings

Black string probably wouldn’t be stable for long. Any small perturbation or deformation of its shape would set off a cascading pattern. For example, the cylinder was squeezed slightly in its center, giving it the shape of an hourglass. Gravity would then tug at the neck, causing it to stretch out until the object becomes a set of spherical black holes connected by a filament of black string.

Then, on the string segment, smaller black holes would likely form like beads on a wire, in a process that would go on repeating. For certain models, small perturbations to the extra dimensions would probably cause all the black holes and strings to ultimately merge into one giant black hole.

Hidden dimensions

String Theory postulate we live in a 10- or 11-dimensional universe. If there are extra dimensions they might be very, very small – little curled up dimensions that would not be visible in our macroscopic three-dimensional space. If this is the case, we may not be able to recognize the hidden dimensions in everything, including black holes. The things we know of as black holes might really be black strings but we can’t see the other dimensions.

And black holes aren’t the only possible black objects that could exist in higher-dimensions. Another hypothetical black object is a black Saturn, which would look like a spherical black hole surrounded by a donut-shaped torus. Or there might be black rings, which would simply be ring-shaped.

Image: Five-dimensional black strings evolve into black holes connected by black string filaments, in this computer simulation.

• Source: LiveScience

Large-scale structures

Snapshot from a computer simulation of the formation of large-scale structures in the Universe, showing a patch of 100 million light-years and the resulting coherent motions of galaxies flowing towards the highest mass concentration in the centre.

The snapshot refers to an epoch about 10 billion years back in time. The colour scale represents the mass density, with the highest density regions painted in red and the lowest in black.

The tiny yellow lines describe the intensity and direction of the galaxy’s velocities. Like compass needles, they map the infall pattern and measure the rate of growth of the central structure.

This depends on the subtle balance between dark matter, dark energy and the expansion of the Universe. Astronomers can measure this effect using large survey of galaxies at different epochs in time, as shown by the new research.

[ESO]

Large-scale structures

Snapshot from a computer simulation of the formation of large-scale structures in the Universe, showing a patch of 100 million light-years and the resulting coherent motions of galaxies flowing towards the highest mass concentration in the centre.

The snapshot refers to an epoch about 10 billion years back in time. The colour scale represents the mass density, with the highest density regions painted in red and the lowest in black.

The tiny yellow lines describe the intensity and direction of the galaxy’s velocities. Like compass needles, they map the infall pattern and measure the rate of growth of the central structure.

This depends on the subtle balance between dark matter, dark energy and the expansion of the Universe. Astronomers can measure this effect using large survey of galaxies at different epochs in time, as shown by the new research.

[ESO]

Model describes universe with no big bang, no beginning, and no end

By suggesting that mass, time, and length can be converted into one another as the universe evolves, a new study has proposed a new class of cosmological models that may fit observations of the universe better than the current big bang model.

Wun-Yi Shu, an associate professor at National Tsing Hua University in Taiwan, explains that the new models emerge from a new perspective of some of the most basic entities: time, space, mass, and length. In his proposal, time and space can be converted into one another, with a varying speed of light as the conversion factor. Mass and length are also interchangeable, with the conversion factor depending on both a varying gravitational “constant” and a varying speed of light (G/c²).

Basically, as the universe expands, time is converted into space, and mass is converted into length. As the universe contracts, the opposite occurs.

The speed of light is simply a conversion factor between time and space in spacetime. It is simply one of the properties of the spacetime geometry. Since the universe is expanding, the conversion factor somehow varies in accordance with the evolution of the universe, hence the speed of light varies with cosmic time.

The newly proposed models have four distinguishing features:

  • The speed of light and the gravitational “constant” are not constant, but vary with the evolution of the universe.
  • Time has no beginning and no end; i.e., there is neither a big bang nor a big crunch singularity.
  • The spatial section of the universe is a 3-sphere [a higher-dimensional analogue of a sphere], ruling out the possibility of a flat or hyperboloid geometry.
  • The universe experiences phases of both acceleration and deceleration.

The models were tested against current cosmological observations of Type Ia supernovae that have revealed that the universe appears to be expanding at an accelerating rate. Because acceleration is an inherent part of this model, it fits the redshift data of the observed supernovae quite well. In contrast, the currently accepted big bang model does not fit the data, which has caused scientists to search for other explanations such as dark energy that theoretically makes up 75% of the mass-energy of the universe.

The new models may also account for other problems faced by the standard big bang model. For instance, the flatness problem arises in the big bang model from the observation that a seemingly flat universe such as ours requires finely tuned initial conditions. But because the universe is a 3-sphere in this models, the flatness problem “disappears automatically.”

Similarly, the horizon problem occurs in standard cosmology because it should not be possible for distant places in the universe to share the same physical properties (as they do), since it should require communication faster than the speed of light due to their great distances. However, the models solve this problem due to their lack of big bang origin and intrinsic acceleration.

Essentially, this work is a theory about how the magnitudes of the three basic physical dimensions, mass, time, and length, are converted into each other, or equivalently, a theory about how the geometry of spacetime and the distribution of mass-energy interact.

Source: PhysOrg.com | Read the full story at The Physics ArXiv Blog
The paper is available via arXiv.org

Radio Astronomers Develop New Technique for Studying Dark Energy

Pioneering observations with the National Science Foundation’s giant Robert C. Byrd Green Bank Telescope (GBT) have given astronomers a new tool for mapping large cosmic structures. The new tool promises to provide valuable clues about the nature of the mysterious dark energy.

Sound waves in the matter-energy soup of the extremely early Universe are thought to have left detectable imprints on the large-scale distribution of galaxies in the Universe. The researchers developed a way to measure such imprints by observing the radio emission of hydrogen gas. Their technique, called intensity mapping, when applied to greater areas of the Universe, could reveal how such large-scale structure has changed over the last few billion years, giving insight into which theory of dark energy is the most accurate.

To get their results, the researchers used the GBT to study a region of sky that previously had been surveyed in detail in visible light by the Keck II telescope in Hawaii. This optical survey used spectroscopy to map the locations of thousands of galaxies in three dimensions. With the GBT, the team used their intensity-mapping technique to accumulate the radio waves emitted by the hydrogen gas in large volumes of space including many galaxies.

The astronomers also developed new techniques that removed both man-made radio interference and radio emission caused by more-nearby astronomical sources, leaving only the extremely faint radio waves coming from the very distant hydrogen gas. The result was a map of part of the “cosmic web” that correlated neatly with the structure shown by the earlier optical study.

This is a demonstration of an important technique that has great promise for future studies of the evolution of large-scale structure in the Universe.

Source: NRAO

Radio Astronomers Develop New Technique for Studying Dark Energy

Pioneering observations with the National Science Foundation’s giant Robert C. Byrd Green Bank Telescope (GBT) have given astronomers a new tool for mapping large cosmic structures. The new tool promises to provide valuable clues about the nature of the mysterious dark energy.

Sound waves in the matter-energy soup of the extremely early Universe are thought to have left detectable imprints on the large-scale distribution of galaxies in the Universe. The researchers developed a way to measure such imprints by observing the radio emission of hydrogen gas. Their technique, called intensity mapping, when applied to greater areas of the Universe, could reveal how such large-scale structure has changed over the last few billion years, giving insight into which theory of dark energy is the most accurate.

To get their results, the researchers used the GBT to study a region of sky that previously had been surveyed in detail in visible light by the Keck II telescope in Hawaii. This optical survey used spectroscopy to map the locations of thousands of galaxies in three dimensions. With the GBT, the team used their intensity-mapping technique to accumulate the radio waves emitted by the hydrogen gas in large volumes of space including many galaxies.

The astronomers also developed new techniques that removed both man-made radio interference and radio emission caused by more-nearby astronomical sources, leaving only the extremely faint radio waves coming from the very distant hydrogen gas. The result was a map of part of the “cosmic web” that correlated neatly with the structure shown by the earlier optical study.

This is a demonstration of an important technique that has great promise for future studies of the evolution of large-scale structure in the Universe.

Source: NRAO

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