#Cosmology
scienceisbeauty:

The images above illustrate the formation of clusters and large-scale filaments in the Cold Dark Matter model with dark energy. The frames show the evolution of structures in a 43 million parsecs (or 140 million light years) box from redshift of 30 to the present epoch (upper left z=30 to lower right z=0).

Source: Formation of the large-scale structure in the Universe: filaments, From quantum foam to galaxies: formation of the large-scale structure in the Universe, Kavli Institute for Cosmological Physics at The University of Chicago.

scienceisbeauty:

The images above illustrate the formation of clusters and large-scale filaments in the Cold Dark Matter model with dark energy. The frames show the evolution of structures in a 43 million parsecs (or 140 million light years) box from redshift of 30 to the present epoch (upper left z=30 to lower right z=0).

Source: Formation of the large-scale structure in the Universe: filaments, From quantum foam to galaxies: formation of the large-scale structure in the UniverseKavli Institute for Cosmological Physics at The University of Chicago.

2 years ago ★ Reblogged from: scienceisbeauty 440
Astronomers find clouds of primordial gas from the early universe, just moments after big bang
For the first time, astronomers have found pristine clouds of the primordial gas that formed in the first few minutes after the Big Bang. The composition of the gas matches theoretical predictions, providing direct evidence in support of the modern cosmological explanation for the origins of elements in the universe.
Only the lightest elements, mostly hydrogen and helium, were created in the Big Bang. Then a few hundred million years passed before clumps of this primordial gas condensed to form the first stars, where heavier elements were forged. Until now, astronomers have always detected “metals” (their term for all elements heavier than hydrogen and helium) wherever they have looked in the universe.
The researchers discovered the two clouds of pristine gas by analyzing the light from distant quasars, using the HIRES spectrometer at the Keck Observatory in Hawaii. By spreading out the bright light from a quasar into a spectrum of different wavelengths, the researchers can see which wavelengths were absorbed by material in between the quasar and the telescope. In the spectra from the gas clouds, the researchers saw only hydrogen and its heavy isotope deuterium.
Prior to this discovery, the lowest measurements of metal abundance in the universe were about one-thousandth the metallicity of the sun. Scientists had thought that nothing could be less than one-thousandth the solar enrichment. That’s because the metals produced in galaxies were so widely dispersed in the universe. The researchers estimated a metallicity for the pristine gas of about one-ten-thousandth that of the sun. At the other extreme, stars and gas with the highest metallicities are almost ten times as enriched as the sun.
The spectrographic analysis of the pristine gas clouds places them in time at about 2 billion years after the Big Bang, or nearly 12 billion years ago. At that time, theoretical models predict that galaxies were growing by pulling in vast streams of cold gas, but these “cold flows” have never been seen. The pristine gas clouds are potential candidates for these elusive cold flows.
Above: This image from a simulation of galaxy formation shows streams of gas feeding the growing galaxy. The newly discovered gas clouds may be part of a “cold flow” of gas similar to these streams.

Astronomers find clouds of primordial gas from the early universe, just moments after big bang

For the first time, astronomers have found pristine clouds of the primordial gas that formed in the first few minutes after the Big Bang. The composition of the gas matches theoretical predictions, providing direct evidence in support of the modern cosmological explanation for the origins of elements in the universe.

Only the lightest elements, mostly hydrogen and helium, were created in the Big Bang. Then a few hundred million years passed before clumps of this primordial gas condensed to form the first stars, where heavier elements were forged. Until now, astronomers have always detected “metals” (their term for all elements heavier than hydrogen and helium) wherever they have looked in the universe.

The researchers discovered the two clouds of pristine gas by analyzing the light from distant quasars, using the HIRES spectrometer at the Keck Observatory in Hawaii. By spreading out the bright light from a quasar into a spectrum of different wavelengths, the researchers can see which wavelengths were absorbed by material in between the quasar and the telescope. In the spectra from the gas clouds, the researchers saw only hydrogen and its heavy isotope deuterium.

Prior to this discovery, the lowest measurements of metal abundance in the universe were about one-thousandth the metallicity of the sun. Scientists had thought that nothing could be less than one-thousandth the solar enrichment. That’s because the metals produced in galaxies were so widely dispersed in the universe. The researchers estimated a metallicity for the pristine gas of about one-ten-thousandth that of the sun. At the other extreme, stars and gas with the highest metallicities are almost ten times as enriched as the sun.

The spectrographic analysis of the pristine gas clouds places them in time at about 2 billion years after the Big Bang, or nearly 12 billion years ago. At that time, theoretical models predict that galaxies were growing by pulling in vast streams of cold gas, but these “cold flows” have never been seen. The pristine gas clouds are potential candidates for these elusive cold flows.

Above: This image from a simulation of galaxy formation shows streams of gas feeding the growing galaxy. The newly discovered gas clouds may be part of a “cold flow” of gas similar to these streams.

sciencedaily.com »

Distant galaxies reveal the clearing of the cosmic fog
Astronomers have used the VLT to look back into the early Universe and observe several of the most distant galaxies ever detected as they were 780 million years after the Big Bang. This allowed them to establish a timeline for what is known as the age of reionisation, when the fog of hydrogen gas in the early Universe was clearing, allowing ultraviolet light to pass unhindered for the first time.
Different chemical elements glow brightly at characteristic colours known as emission lines. One of the strongest ultraviolet emission lines is the Lyman-alpha line, which comes from hydrogen gas and is bright enough to be seen even in the most faint and far galaxies. Spotting the Lyman-alpha line for five very distant galaxies allowed the team to determine their distances and the extent to which the Lyman-alpha emission was reabsorbed by the neutral hydrogen fog in intergalactic space at different points in time.
The team found a dramatic difference in the amount of ultraviolet light that was blocked between the earliest and latest galaxies. When the Universe was only 780 million years old this neutral hydrogen was quite abundant, filling from 10 to 50% of the Universe’ volume. But only 200 million years later the amount of neutral hydrogen had dropped to a very low level, similar to what we see today. It seems that reionisation must have happened quicker than astronomers previously thought.
As well as probing the rate at which the primordial fog cleared, the team’s observations also hint at the likely source of the ultraviolet light which provided the energy necessary for reionisation to occur, which came from either the Universe’s first generation of stars or the intense radiation emitted by matter as it falls towards black holes.
Above: Artist impression showing galaxies at a time less than a billion years after the Big Bang, when the Universe was still partially filled with hydrogen fog that absorbed ultraviolet light.

Distant galaxies reveal the clearing of the cosmic fog

Astronomers have used the VLT to look back into the early Universe and observe several of the most distant galaxies ever detected as they were 780 million years after the Big Bang. This allowed them to establish a timeline for what is known as the age of reionisation, when the fog of hydrogen gas in the early Universe was clearing, allowing ultraviolet light to pass unhindered for the first time.

Different chemical elements glow brightly at characteristic colours known as emission lines. One of the strongest ultraviolet emission lines is the Lyman-alpha line, which comes from hydrogen gas and is bright enough to be seen even in the most faint and far galaxies. Spotting the Lyman-alpha line for five very distant galaxies allowed the team to determine their distances and the extent to which the Lyman-alpha emission was reabsorbed by the neutral hydrogen fog in intergalactic space at different points in time.

The team found a dramatic difference in the amount of ultraviolet light that was blocked between the earliest and latest galaxies. When the Universe was only 780 million years old this neutral hydrogen was quite abundant, filling from 10 to 50% of the Universe’ volume. But only 200 million years later the amount of neutral hydrogen had dropped to a very low level, similar to what we see today. It seems that reionisation must have happened quicker than astronomers previously thought.

As well as probing the rate at which the primordial fog cleared, the team’s observations also hint at the likely source of the ultraviolet light which provided the energy necessary for reionisation to occur, which came from either the Universe’s first generation of stars or the intense radiation emitted by matter as it falls towards black holes.

Above: Artist impression showing galaxies at a time less than a billion years after the Big Bang, when the Universe was still partially filled with hydrogen fog that absorbed ultraviolet light.

eso.org »

Clearing the cosmic fog of the early universe: Massive stars may be responsible
The space between the galaxies wasn’t always transparent. In the earliest times, it was an opaque, dense fog. Astronomers believed that early star-forming galaxies could have provided enough of the right kind of radiation to evaporate the fog, or turn the neutral hydrogen intergalactic medium into the charged hydrogen plasma that remains today. But they couldn’t figure out how that radiation could escape a galaxy. Until now.
Astronomers from the University of Michigan observed and imaged the relatively nearby NGC 5253, a dwarf starburst galaxy in the southern constellation Centaurus. The researchers used special filters to see where and how the galaxy’s extreme ultraviolet radiation was interacting with nearby gas. They found that the UV light is, indeed, evaporating gas in the interstellar medium. And it is doing so along a narrow cone emanating from the galaxy.
In starburst galaxies, which were very common in the early universe, a superwind from these massive stars can clear a passageway through the gas in the galaxy, allowing the radiation to escape. The shape of the cone they observed could help explain why similar processes in other galaxies have been difficult to detect.
Above: This is a three-color image of the dwarf starburst galaxy NGC 5253. Green corresponds to star light. The yellow shows the gas that is being lit up by the starburst at the galaxy’s core. The red shows where ultraviolet light from massive stars is evaporating gas, exposing the central starburst along a narrow cone.

Clearing the cosmic fog of the early universe: Massive stars may be responsible

The space between the galaxies wasn’t always transparent. In the earliest times, it was an opaque, dense fog. Astronomers believed that early star-forming galaxies could have provided enough of the right kind of radiation to evaporate the fog, or turn the neutral hydrogen intergalactic medium into the charged hydrogen plasma that remains today. But they couldn’t figure out how that radiation could escape a galaxy. Until now.

Astronomers from the University of Michigan observed and imaged the relatively nearby NGC 5253, a dwarf starburst galaxy in the southern constellation Centaurus. The researchers used special filters to see where and how the galaxy’s extreme ultraviolet radiation was interacting with nearby gas. They found that the UV light is, indeed, evaporating gas in the interstellar medium. And it is doing so along a narrow cone emanating from the galaxy.

In starburst galaxies, which were very common in the early universe, a superwind from these massive stars can clear a passageway through the gas in the galaxy, allowing the radiation to escape. The shape of the cone they observed could help explain why similar processes in other galaxies have been difficult to detect.

Above: This is a three-color image of the dwarf starburst galaxy NGC 5253. Green corresponds to star light. The yellow shows the gas that is being lit up by the starburst at the galaxy’s core. The red shows where ultraviolet light from massive stars is evaporating gas, exposing the central starburst along a narrow cone.

physorg.com »

Vast cosmic filament discovered connecting Milky Way to the Universe
Astronomers at The Australian National University have discovered proof of a vast filament of material that connects our Milky Way galaxy to nearby clusters of galaxies, which are similarly interconnected to the rest of the Universe. By examining the positions of globular clusters, they found that the clusters form a narrow plane around the Milky Way rather than being scattered across the sky.
Furthermore, the Milky Way’s entourage of small satellites are seen to inhabit the same plane. This is evidence for the cosmic thread that connects us to the vast expanse of the Universe. The filament of star clusters and small galaxies around the Milky Way is like the umbilical cord that fed our Galaxy during its youth.
A consequence of the Big Bang and the dominance of dark matter is that ordinary matter is driven, like foam on the crest of a wave, into vast interconnected sheets and filaments stretched over enormous cosmic voids – much like the structure of a kitchen sponge. Unlike a sponge, however, gravity draws the material over these interconnecting filaments towards the largest lumps of matter, and the globular clusters and satellite galaxies of the Milky Way trace this cosmic filament.
In the picture, most of these star clusters are the central cores of small galaxies that have been drawn along the filament by gravity. Once these small galaxies got too close the Milky Way the majority of stars were stripped away and added to our galaxy, leaving only their cores. It is thought that the Milky Way has grown to its current size by the consumption of hundreds of such smaller galaxies over cosmic time.

Vast cosmic filament discovered connecting Milky Way to the Universe

Astronomers at The Australian National University have discovered proof of a vast filament of material that connects our Milky Way galaxy to nearby clusters of galaxies, which are similarly interconnected to the rest of the Universe. By examining the positions of globular clusters, they found that the clusters form a narrow plane around the Milky Way rather than being scattered across the sky.

Furthermore, the Milky Way’s entourage of small satellites are seen to inhabit the same plane. This is evidence for the cosmic thread that connects us to the vast expanse of the Universe. The filament of star clusters and small galaxies around the Milky Way is like the umbilical cord that fed our Galaxy during its youth.

A consequence of the Big Bang and the dominance of dark matter is that ordinary matter is driven, like foam on the crest of a wave, into vast interconnected sheets and filaments stretched over enormous cosmic voids – much like the structure of a kitchen sponge. Unlike a sponge, however, gravity draws the material over these interconnecting filaments towards the largest lumps of matter, and the globular clusters and satellite galaxies of the Milky Way trace this cosmic filament.

In the picture, most of these star clusters are the central cores of small galaxies that have been drawn along the filament by gravity. Once these small galaxies got too close the Milky Way the majority of stars were stripped away and added to our galaxy, leaving only their cores. It is thought that the Milky Way has grown to its current size by the consumption of hundreds of such smaller galaxies over cosmic time.

dailygalaxy.com »

Scientists release most accurate simulation of the universe to date

The Bolshoi supercomputer simulation, the most accurate and detailed large cosmological simulation run to date, gives physicists and astronomers a powerful new tool for understanding such cosmic mysteries as galaxy formation, dark matter, and dark energy.

The simulation, which was run on the Pleiades supercomputer at NASA Ames Research Center, traces the evolution of the large-scale structure of the universe, including the evolution and distribution of the dark matter halos in which galaxies coalesced and grew.

The Bolshoi simulation focused on a representative section of the universe, computing the evolution of a cubic volume measuring about one billion light-years on a side and following the interactions of 8.6 billion particles of dark matter. It took 6 million CPU-hours to run the full computation on the Pleiades supercomputer, recently ranked as the seventh fastest supercomputer in the world.

physorg.com »

Hubble rules out one alternative to dark energy The universe appears to be expanding at an increasing rate. Some believe that is because the universe is filled with a dark energy that works in the opposite way of gravity. One alternative to that hypothesis is that an enormous bubble of relatively empty space eight billion light-years across surrounds our galactic neighborhood. If we lived near the center of this void, observations of galaxies being pushed away from each other at accelerating speeds would be an illusion. This hypothesis has been invalidated because astronomers have refined their understanding of the universe’s present expansion rate. The Hubble observations helped determine a figure for the universe’s current expansion rate to an uncertainty of just 3.3%. The new measurement reduces the error margin by 30% over Hubble’s previous best measurement of 2009. The value for the expansion rate is 73.8 kilometers per second per megaparsec. It means that for every additional million parsecs (3.26 million light-years) a galaxy is from Earth, the galaxy appears to be traveling 73.8 kilometers per second faster away from us. Every decrease in uncertainty of the universe’s expansion rate helps solidify our understanding of its cosmic ingredients. Knowing the precise value of the universe’s expansion rate further restricts the range of dark energy’s strength and helps astronomers tighten up their estimates of other cosmic properties, including the universe’s shape and its roster of neutrinos, or ghostly particles, that filled the early universe. Image: The brilliant, blue glow of young stars trace the graceful spiral arms of galaxy NGC 5584 in this Hubble Space Telescope image. Thin, dark dust lanes appear to be flowing from the yellowish core, where older stars reside. The reddish dots sprinkled throughout the image are largely background galaxies.

Hubble rules out one alternative to dark energy

The universe appears to be expanding at an increasing rate. Some believe that is because the universe is filled with a dark energy that works in the opposite way of gravity. One alternative to that hypothesis is that an enormous bubble of relatively empty space eight billion light-years across surrounds our galactic neighborhood. If we lived near the center of this void, observations of galaxies being pushed away from each other at accelerating speeds would be an illusion.

This hypothesis has been invalidated because astronomers have refined their understanding of the universe’s present expansion rate. The Hubble observations helped determine a figure for the universe’s current expansion rate to an uncertainty of just 3.3%. The new measurement reduces the error margin by 30% over Hubble’s previous best measurement of 2009.

The value for the expansion rate is 73.8 kilometers per second per megaparsec. It means that for every additional million parsecs (3.26 million light-years) a galaxy is from Earth, the galaxy appears to be traveling 73.8 kilometers per second faster away from us.

Every decrease in uncertainty of the universe’s expansion rate helps solidify our understanding of its cosmic ingredients. Knowing the precise value of the universe’s expansion rate further restricts the range of dark energy’s strength and helps astronomers tighten up their estimates of other cosmic properties, including the universe’s shape and its roster of neutrinos, or ghostly particles, that filled the early universe.

Image: The brilliant, blue glow of young stars trace the graceful spiral arms of galaxy NGC 5584 in this Hubble Space Telescope image. Thin, dark dust lanes appear to be flowing from the yellowish core, where older stars reside. The reddish dots sprinkled throughout the image are largely background galaxies.

nasa.gov »

The Cosmos is at least 250 times bigger than visible universe Is our universe infinite or closed? Because the visible Universe is expanding, the most distant visible things are much further away than its estimated 14-billion year age. In fact, the photons in the cosmic microwave background have traveled a cool 45 billion light years to get here. That makes the visible universe some 90 billion light years across. The real universe, however, is much bigger. We now know this thanks to statistical analysis by Mihran Vardanyan at the University of Oxford and colleagues. The key to measuring the actual size of the universe is to measure its curvature. Astronomers have come up with various methods to measure this curvature. One method is to search for a distant object of known size and measure how big it looks: If it’s bigger than it ought to be, the Universe is closed; if it’s the right size, the universe is flat and if it’s smaller, the Universe is open. Astronomers know that waves in the early universe became frozen in the cosmic microwave background. They can measure the size of these waves, called baryonic acoustic oscillations, using space observatories such as WMAP. Another metric is the luminosity of type Ia supernovae in distant galaxies. The problem is that when scientists examine the various data from the different models they get different answers to the question of its curvature and size. So, which is the most accurate? The breakthrough that Vardanyan and team used is called Bayesian model averaging and it is much more sophisticated than the usual curve fitting that scientists often use to explain their data. The Bayesian model asks: given the data, how likely is the model to be correct. This approach is automatically biased against complex models—it’s a kind of statistical Occam’s razor. The Vardanyan model says that the curvature of the Universe is tightly constrained around 0. In other words, the most likely model is that the Universe is flat. A flat Universe would also be infinite and their calculations are consistent with this too. These show that the Universe is at least 250 times bigger than the Hubble volume. (The Hubble volume is similar to the size of the observable universe.) Source: MIT Technology Review via The Daily GalaxyThe paper is available at http://arxiv.org/abs/1101.5476

The Cosmos is at least 250 times bigger than visible universe

Is our universe infinite or closed? Because the visible Universe is expanding, the most distant visible things are much further away than its estimated 14-billion year age. In fact, the photons in the cosmic microwave background have traveled a cool 45 billion light years to get here. That makes the visible universe some 90 billion light years across. The real universe, however, is much bigger. We now know this thanks to statistical analysis by Mihran Vardanyan at the University of Oxford and colleagues.

The key to measuring the actual size of the universe is to measure its curvature. Astronomers have come up with various methods to measure this curvature. One method is to search for a distant object of known size and measure how big it looks: If it’s bigger than it ought to be, the Universe is closed; if it’s the right size, the universe is flat and if it’s smaller, the Universe is open.

Astronomers know that waves in the early universe became frozen in the cosmic microwave background. They can measure the size of these waves, called baryonic acoustic oscillations, using space observatories such as WMAP. Another metric is the luminosity of type Ia supernovae in distant galaxies. The problem is that when scientists examine the various data from the different models they get different answers to the question of its curvature and size. So, which is the most accurate?

The breakthrough that Vardanyan and team used is called Bayesian model averaging and it is much more sophisticated than the usual curve fitting that scientists often use to explain their data. The Bayesian model asks: given the data, how likely is the model to be correct. This approach is automatically biased against complex models—it’s a kind of statistical Occam’s razor.

The Vardanyan model says that the curvature of the Universe is tightly constrained around 0. In other words, the most likely model is that the Universe is flat. A flat Universe would also be infinite and their calculations are consistent with this too. These show that the Universe is at least 250 times bigger than the Hubble volume. (The Hubble volume is similar to the size of the observable universe.)

Source: MIT Technology Review via The Daily Galaxy
The paper is available at http://arxiv.org/abs/1101.5476

Evidence emerges that laws of physics are not fine-tuned for life The value of the cosmological constant suggests that the laws of nature could not have been fine-tuned for life by an omnipotent being. One of the more curious debates in science focuses on the laws of physics and why they seem fine-tuned for life. The problem is that the laws of physics contain various constants that have very specific, mysterious values that nobody can explain. These constants are balanced in such a way that life has evolved at least once, in one small part of the Universe. But why do the constants have these values? Various scientists have calculated that even the tiniest of changes to these constants would make life impossible. That raises the question of why they are so finely balanced. One explanation is that this is pure accident and that there is no deeper reason for the coincidence. Another idea is that there is some deeper law of nature, which we have yet to discover, that sets the constants as they are. Yet another is that the constants can take more or less any value in an infinite multitude of universes. In ours, they are just right, which is why we have been able to evolve to observe them. None of these arguments is easy to prove or disprove, although that may change as other evidence accrues, says Don Page, a theoretical physicist at the University of Alberta in Canada. But there is a fourth line of thought which Page says is easier to attack. This is the idea that the constants have been fine-tuned by some unseen omnipotent being who has set them up in a way that maximises the amount of life that form. So instead of directly creating life, God simply sets the conditions to maximise the chances of it forming. Today, Page says this idea is potentially falsifiable and says we already have evidence that does the trick. Here’s the thinking. The cosmological constant is a number that determines the energy density of the vacuum. It acts like a kind of pressure that, depending on its value, acts against gravity to push the universe apart or acts with gravity to pull the universe together towards a final Big Crunch. Until recently, cosmologists had assumed that the constant was zero, a neat solution. But the recent evidence that the universe is not just expanding but accelerating away from us, suggests that the constant is positive. But although positive, the cosmological constant is tiny, some 122 orders of magnitude smaller than Planck’s constant, which itself is a small number. So Page and others have examined the effects of changing this constant. It’s straightforward to show that if the the constant were any larger, matter would not form into galaxies and stars meaning that life could not form, at least not in the form we know it. So what value of the cosmological constant best encourages galaxy and star formation, and therefore the evolution of life? Page says that a slightly negative value of the constant would maximise this process. And since life is some small fraction of the amount of matter in galaxies, then this is the value that an omnipotent being would choose. In fact, he says that any positive value of the constant would tend to decrease the fraction of matter that forms into galaxies, reducing the amount available for life. Therefore the measured value of the cosmological constant, which is positive, is evidence against the idea that the constants have been fine-tuned for life. An interesting argument and one that adds to the fine body of work that attempts to prove or disprove the existence of an omnipotent interferer. But not one that is likely to settle the matter one way or the other. • Source: MIT Technology Review • The paper is available at http://arxiv.org/abs/1101.2444.pdf

Evidence emerges that laws of physics are not fine-tuned for life

The value of the cosmological constant suggests that the laws of nature could not have been fine-tuned for life by an omnipotent being.

One of the more curious debates in science focuses on the laws of physics and why they seem fine-tuned for life.

The problem is that the laws of physics contain various constants that have very specific, mysterious values that nobody can explain. These constants are balanced in such a way that life has evolved at least once, in one small part of the Universe. But why do the constants have these values? Various scientists have calculated that even the tiniest of changes to these constants would make life impossible. That raises the question of why they are so finely balanced.

One explanation is that this is pure accident and that there is no deeper reason for the coincidence. Another idea is that there is some deeper law of nature, which we have yet to discover, that sets the constants as they are. Yet another is that the constants can take more or less any value in an infinite multitude of universes. In ours, they are just right, which is why we have been able to evolve to observe them.

None of these arguments is easy to prove or disprove, although that may change as other evidence accrues, says Don Page, a theoretical physicist at the University of Alberta in Canada.

But there is a fourth line of thought which Page says is easier to attack. This is the idea that the constants have been fine-tuned by some unseen omnipotent being who has set them up in a way that maximises the amount of life that form. So instead of directly creating life, God simply sets the conditions to maximise the chances of it forming.

Today, Page says this idea is potentially falsifiable and says we already have evidence that does the trick.

Here’s the thinking. The cosmological constant is a number that determines the energy density of the vacuum. It acts like a kind of pressure that, depending on its value, acts against gravity to push the universe apart or acts with gravity to pull the universe together towards a final Big Crunch.

Until recently, cosmologists had assumed that the constant was zero, a neat solution. But the recent evidence that the universe is not just expanding but accelerating away from us, suggests that the constant is positive. But although positive, the cosmological constant is tiny, some 122 orders of magnitude smaller than Planck’s constant, which itself is a small number.

So Page and others have examined the effects of changing this constant. It’s straightforward to show that if the the constant were any larger, matter would not form into galaxies and stars meaning that life could not form, at least not in the form we know it.

So what value of the cosmological constant best encourages galaxy and star formation, and therefore the evolution of life? Page says that a slightly negative value of the constant would maximise this process. And since life is some small fraction of the amount of matter in galaxies, then this is the value that an omnipotent being would choose.

In fact, he says that any positive value of the constant would tend to decrease the fraction of matter that forms into galaxies, reducing the amount available for life. Therefore the measured value of the cosmological constant, which is positive, is evidence against the idea that the constants have been fine-tuned for life.

An interesting argument and one that adds to the fine body of work that attempts to prove or disprove the existence of an omnipotent interferer. But not one that is likely to settle the matter one way or the other.

• Source: MIT Technology Review
• The paper is available at http://arxiv.org/abs/1101.2444.pdf

Cosmology standard candle not so standard after all This image illustrates how NASA’s Spitzer Space Telescope was able to show that a standard candle used to measure cosmological distances is shrinking — a finding that affects precise measurements of the age, size and expansion rate of our universe. The image on the left, taken by Spitzer in infrared light, shows Delta Cephei, a type of standard candle used to measure the distances to galaxies that are relatively close to us. Cepheids like this one are the first rungs on the so-called cosmological distance ladder — a tool needed to measure farther and farther distances. Spitzer showed that the star has a bow shock in front of it. This can be seen as the red arc shape to the left of the star, which is depicted in blue-green. The presence of the bow shock told astronomers that Delta Cephei must have a wind made up of gas and dust blowing off the star that is forming the shock. Before this finding, there was no direct proof that Cepheid stars could lose mass, or shrink.  The diagram on the right illustrates how Delta Cephei’s bow shock was formed. As the star speeds along through space, its wind hits interstellar gas and dust, causing it to pile up in the bow shock. A companion star to Delta Cephei, seen just below it, is lighting up the region, allowing Spitzer to better see the region. By examining the structure of the bow shock, astronomers were able to calculate how fast the star is losing mass.  • Source: NASA JPL

Cosmology standard candle not so standard after all

This image illustrates how NASA’s Spitzer Space Telescope was able to show that a standard candle used to measure cosmological distances is shrinking — a finding that affects precise measurements of the age, size and expansion rate of our universe.

The image on the left, taken by Spitzer in infrared light, shows Delta Cephei, a type of standard candle used to measure the distances to galaxies that are relatively close to us. Cepheids like this one are the first rungs on the so-called cosmological distance ladder — a tool needed to measure farther and farther distances.

Spitzer showed that the star has a bow shock in front of it. This can be seen as the red arc shape to the left of the star, which is depicted in blue-green. The presence of the bow shock told astronomers that Delta Cephei must have a wind made up of gas and dust blowing off the star that is forming the shock. Before this finding, there was no direct proof that Cepheid stars could lose mass, or shrink.

The diagram on the right illustrates how Delta Cephei’s bow shock was formed. As the star speeds along through space, its wind hits interstellar gas and dust, causing it to pile up in the bow shock. A companion star to Delta Cephei, seen just below it, is lighting up the region, allowing Spitzer to better see the region. By examining the structure of the bow shock, astronomers were able to calculate how fast the star is losing mass.

Source: NASA JPL

Under just the right conditions it could be possible to create something out of nothing.

The University of Michigan scientists and engineers have developed new equations that show how a high-energy electron beam combined with an intense laser pulse could rip apart a vacuum into its fundamental matter and antimatter components, and set off a cascade of events that generates additional several hundred pairs of particles and antiparticles. A process that happens in nature near pulsars and neutron stars.

At the heart of this work is the idea that a vacuum is not exactly nothing, but rather the combination of matter and antimatter — particles and antiparticles. Their density is tremendous, but we cannot perceive any of them because their observable effects entirely destroy each other when they come into contact under normal conditions.

But in a strong electromagnetic field, this annihilation can be the source of new particles. In the course of the annihilation, gamma photons —a high-energy particle of light— appear, which can produce additional electrons and positrons. These new equations model how a strong laser field could promote the creation of more particles than were initially injected into an experiment through a particle accelerator.

If the electron has a capability to become three particles within a very short time, this means it’s not an electron any longer. The theory of the electron is based on the fact that it will be an electron forever. But in this experiment each of the charged particles becomes a combination of three particles plus some number of photons.

The basic question what is a vacuum, and what is nothing, goes beyond science. It’s embedded deeply in the base not only of theoretical physics, but of our philosophical perception of everything—-of reality, of life, even the religious question of could the universe have come from nothing.

• Source: PhysOrg.com The paper is available at http://arxiv.org/abs/1009.0703

Sloan Digital Sky Survey

This visualization presents a 3-D view of the largest structures in the Universe via data from the Sloan Digital Sky Survey. The SDSS is the most ambitious astronomical survey ever undertaken. It provides a 3-dimensional map of about a million galaxies and quasars. As the survey progresses, the data are released to the scientific community and the general public in annual increments.

For more info visit www.sdss.org

• Source: NASA Goddard Photo and Video

“X” particle explains dark matter and antimatter at the same time A new hypothetical particle could solve two cosmic mysteries at once: what dark matter is made of, and why there’s enough matter for us to exist at all. This new approach is completely different from the WIMP idea. The proposed particle, named simply “X,” has a separate antiparticle called anti-X. Equal amounts of X and anti-X were created in the Big Bang, and then decayed to lighter particles. Each X decayed into either a neutron or two dark matter particles, called Y and Φ. Every anti-X converted to an anti-neutron or some anti-dark matter. But the hypothetical X particle would rather decay into ordinary matter than dark matter, so it produced more neutrons than dark matter. Anti-X preferred decaying into anti-dark matter, and so produced more of it. After all the particles and anti-particles that could find each other collided and eliminated each other, the universe was left with some extra neutrons and a corresponding number of extra anti-dark matter particles. “The protons and neutrons can’t annihilate completely with their antiparticles, because there’s not enough to annihilate with,” said theoretical physicist Sean Tulin of the Canadian physics institute TRIUMF. “The same story happens in the hidden sector as well… Some dark matter can’t annihilate with anything. So you’re left with some extra dark matter in the universe.” Image: Physicists paddle around the Super Kamiokande detector in a rubber raft as it fills with water. The detector was designed to hunt neutrinos and decaying protons, but could catch the signatures of Particle X. Read the full article at Wired.com

“X” particle explains dark matter and antimatter at the same time

A new hypothetical particle could solve two cosmic mysteries at once: what dark matter is made of, and why there’s enough matter for us to exist at all. This new approach is completely different from the WIMP idea.

The proposed particle, named simply “X,” has a separate antiparticle called anti-X. Equal amounts of X and anti-X were created in the Big Bang, and then decayed to lighter particles. Each X decayed into either a neutron or two dark matter particles, called Y and Φ. Every anti-X converted to an anti-neutron or some anti-dark matter.

But the hypothetical X particle would rather decay into ordinary matter than dark matter, so it produced more neutrons than dark matter. Anti-X preferred decaying into anti-dark matter, and so produced more of it. After all the particles and anti-particles that could find each other collided and eliminated each other, the universe was left with some extra neutrons and a corresponding number of extra anti-dark matter particles.

“The protons and neutrons can’t annihilate completely with their antiparticles, because there’s not enough to annihilate with,” said theoretical physicist Sean Tulin of the Canadian physics institute TRIUMF. “The same story happens in the hidden sector as well… Some dark matter can’t annihilate with anything. So you’re left with some extra dark matter in the universe.”

Image: Physicists paddle around the Super Kamiokande detector in a rubber raft as it fills with water. The detector was designed to hunt neutrinos and decaying protons, but could catch the signatures of Particle X.

Read the full article at Wired.com

The Visible Universe

This map attempts to show the entire visible Universe, zooming in to the Sun and its local neighbors. The galaxies in the universe tend to collect into vast sheets and superclusters of galaxies surrounding large voids giving the universe a cellular appearance.

• Source: atlasoftheuniverse.com

The Visible Universe

This map attempts to show the entire visible Universe, zooming in to the Sun and its local neighbors. The galaxies in the universe tend to collect into vast sheets and superclusters of galaxies surrounding large voids giving the universe a cellular appearance.

• Source: atlasoftheuniverse.com

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