#Cosmic velocity web: Motions of thousands of galaxies mapped

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How do you weigh one of the largest objects in the entire universe? Very carefully, according to new research. The cosmic web is the largest pattern found in nature. It is made of galaxies the same way your body is made of cells…if your cells were a million times smaller than they are. It is truly gigantic, with its individual parts stretching for millions of light-years at a time. The intricate filaments of the cosmic web are made of hundreds of thousands of galaxies stretching hundreds of thousands of light-years between the clusters. They are like super highways, connecting one cluster to another. Cosmologists aren’t just interested in the cosmic web because it’s pretty. It also encodes vital information about the universe. It has been growing for over 13 billion years and its properties are closely tied to the nature of dark matter and dark energy. If you change how much dark matter is in the universe or vary the strength of dark energy, then you can end up with radically different cosmic web patterns. However, most of that information about dark matter and dark energy is very difficult to extract. This is because the cosmic web itself is a very complex structure. When it comes to the filaments, their width, length, and density all respond to the nature of dark matter and dark energy. But we have a very difficult time measuring those properties because most of the filaments are made of invisible dark matter. Using a suite of simulations that tracked the evolution of both galaxies and dark matter, a team of researchers have developed a technique for weighing these giant filaments. The technique relies on the relationship between the amount of dark matter and the motion of galaxies within the filament. All galaxies are moving, and some of them are moving in our direction and some are moving further away. The researchers found that there was a close relationship between the spread in these velocities and the amount of dark matter within that section of the filament. In other words, the higher the average speed of the galaxies, the more mass contained in the invisible dark matter. This means that we can potentially go out and map filaments, measuring the spread ingGalaxy velocities along the length of those filaments, and map that result onto the mass of the underlying filament. This is just the beginning of the new approach. The next step is to connect the filament mass to the properties of dark matter and dark energy, and then see if we can go out in the universe and learn something new. The post Here’s How to Weigh Gigantic Filaments of Dark Matter appeared first on Universe Today.

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Cosmic Velocity Web: Motions Of Thousands Of Galaxies Mapped

The cosmic web -- the distribution of matter on the largest scales in the universe -- has usually been defined through the distribution of galaxies. Now, a new study by a team of astronomers from France, Israel and Hawaii demonstrates a novel approach. Instead of using galaxy positions, they mapped the motions of thousands of galaxies. Because galaxies are pulled toward gravitational attractors and move away from empty regions, these motions allowed the team to locate the denser matter in clusters and filaments and the absence of matter in regions called voids.

Matter was distributed almost homogeneously in the very early universe, with only miniscule variations in density. Over the 14-billion-year history of the universe, gravity has been acting to pull matter together in some places and leave other places more and more empty. Today, the matter forms a network of knots and connecting filaments referred to as the cosmic web. Most of this matter is in a mysterious form, the so-called "dark matter." Galaxies have formed at the highest concentrations of matter and act as lighthouses illuminating the underlying cosmic structure. The newly defined cosmic velocity web defines the structure of the universe from velocity information alone. In those regions with abundant observations, the structure of the velocity web and the web inferred from the locations of the galaxy lighthouses are similar. This agreement provides strong confirmation of the fundamental idea that structure developed from the growth of initially tiny fluctuations through gravitational attraction. The cosmic velocity web analysis was led by Daniel Pomarede, Atomic Energy Center, France, with the collaboration of Helene Courtois at the University of Lyon, France; Yehuda Hoffman at the Hebrew University, Israel; and Brent Tully at the University of Hawaii's Institute for Astronomy. "With the motions of the galaxies, we can infer where all of the mass is located: the galaxies and the 5 times more abundant transparent matter (usually wrongly called dark matter). This total gravitating mass, together with the expansion of the universe, is responsible for the motions that create the architecture of the universe. The gravity from galaxies alone cannot create this network we see," said Dr. Courtois. Dr. Tully adds, "Moreover, a wide swath of the universe is hidden behind the obscuring disk of our own Milky Way galaxy. Our reconstruction of structure with the velocity web is revealing for the first time filaments of matter that stretch all the way around the sky and are easily followed through these regions of obscuration." This definition of the cosmic velocity web was made possible by the large and coherent collection of galaxy distances and velocities in the Cosmicflows series. The current analysis is based on a study of 8,000 galaxies in the second release of Cosmicflows. The third release, with over twice as many galaxy distances and velocities is already available, and will reveal the cosmic velocity web in increasingly rich detail. The key element of the program is the acquisition of good distances to galaxies. Several methods are used, such as exploiting the known luminosities of old stars that are just beginning to burn Helium in their cores, and the relationship between the rotation speed of galaxies and the number of stars they possess. The observations have involved dozens of telescopes around the world and in space and at wavelengths from visible light through the infrared to radio. "The velocity web method for mapping the cosmos is analogous to using plate tectonics in geology. It helps understand not just the current layout of the universe, but also the movement of the invisible underlying masses responsible for that topology," said Dr. Courtois. The team has produced an extensive video demonstrating the cosmic velocity web. It first explains the concepts underlying the cosmic velocity web reconstruction, followed by a description of its major elements. The video then shows how cosmic flows are organized within its structure, and how the basin of attraction of the recently mapped Laniakea Supercluster resides within its elements. In the final sequence, the viewer enters an immersive exploration of the filamentary structure of the local universe, navigating inside the filaments and visiting the major nodes such as the Great Attractor. Click to Post

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Scientists Discovered a Gigantic Structure in a Hidden Zone of Space

Scientists have spotted a gargantuan bow-like structure made of galaxies that stretches for 1.4 billion light years across the skies above the South Pole.

This “South Pole Wall” is one of the biggest structures ever glimpsed by humans, and its discovery was announced in a study published on Friday in The Astrophysical Journal.

“When our visualizations indicated something going on at the celestial South Pole, we were surprised: indeed there were no reports of a large scale structure in this region,” said Daniel Pomarède, a cosmographer at Paris-Saclay University in France who led the new study, in an email.

The South Pole Wall is comparable in size to the Sloan Great Wall, the sixth-largest known structure in the universe, though the South Pole Wall is located about 500 million light years from Earth, twice as close as the Sloan structure.

The universe contains many of these enormous belts that connect objects in space to a fundamental matrix known as the cosmic web. Galaxies tend to cluster at the crossroads of these long filaments, which are made of hydrogen gas and a mysterious non-luminous substance called dark matter. The largest known structure is the Hercules-Corona Borealis Great Wall, which is 10 billion light years wide—equal to about a tenth of the diameter of the entire observable universe.

The South Pole Wall is not quite that big, but it is the largest structure ever spotted within a radius of about 650 millions light years around Earth, according to Pomarède. The crooked shape of the structure enabled the team to detect the wall’s extent, relative to a straight-line structure, because so much of it fit within the observational aperture.

“It is because it is shaped like a bow that its 1.4 billion light-years length can fit the observed sphere,” Pomarède explained, though he added that the map the team used “fades away just beyond the wall.”

“So, perhaps we are not seeing the whole of it, if it happens to bend away from us beyond our observational limit,” he said.

You might think that it would be hard to miss a filament as colossal as the South Pole Wall, given that it appears to be some 14,000 times longer than the diameter of our galaxy, the Milky Way, and contains thousands of galaxies within its boundaries. It is so big, in fact, that if it were to magically get outlined in the night sky, like a celestial chalk drawing, skywatchers on Earth would not be able to see it all from one hemisphere.

However, this particular structure is located in the “Zone of Avoidance,” which is the region of space right behind the dusty center of the Milky Way from our perspective on Earth. As a result, our galaxy’s bulk has blocked it from view—until now.

The discovery occurred when Pomarède and his colleagues noticed that the gravitational influence of some gigantic structure was pulling galaxies towards it in all directions.

Pomarède and his colleagues used Cosmicflows-3, a comprehensive catalog that visualizes the distances and motions of 18,000 galaxies, to indirectly peer at the knots and filaments that make up the cosmic web. One of the team’s main goals—and a major quest for astronomers in general—is to figure out how the gravitational heft of the web’s large-scale structures influences the motions of galaxies, including our own Milky Way.

Decades of research has revealed that the Local Group, a cluster of galaxies that includes the Milky Way, is moving at about 630 kilometers per second, at least in part due to gravitational attraction from large-scale structures as well as repulsion from empty regions of space known as voids.

The Cosmicflows-3 map recorded peculiar velocities of galaxies on one side of the obscured South Pole Wall that seemed slower than expected, while galaxies on the side closer to Earth moved a bit faster than expected.

“Our study told us that the South Pole Wall, due to its gravitational attraction, is acting upon us, giving us a velocity of about 40 km/s,” Pomarède said. “We would like to know whether other structures are contributing: in particular, is there something hidden in the Zone of Avoidance? There might be filaments crossing this zone. We are looking for them.”

Following those breadcrumbs, the researchers were able to reconstruct some of the South Pole Wall using models and algorithms, though they said they will not be sure of its full size until more detailed versions of Cosmicflows become available in the coming years. In other words, the South Pole Wall may be much larger than its current estimated dimensions of 1.4 billion light years across, and some 600 million light years deep, but we would need a bigger map to know for sure.

“Our scientific discipline is called cosmography, a branch of cosmology, that aims at establishing a cartography of the cosmos around us (our local universe),” Pomarède said. “Like cartographers who mapped Earth, we map the structure of the sky, and thus we learn more about the structures we live in, and we study whether what we find is compatible with the current theory of structure formation (in the context of the standard model of cosmology).”

Finding one of the top-ten biggest structures in the universe is pretty wild by itself, but these discoveries also reveal threads of the larger cosmic tapestry that undergirds our surroundings and reality. The more we learn about these elongated bubbles filled with dark matter and galaxies, the more we will understand how we came to live in this weird and ever-evolving universe.

Scientists Discovered a Gigantic Structure in a Hidden Zone of Space syndicated from https://triviaqaweb.wordpress.com/feed/

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Cosmic velocity web: Motions of thousands of galaxies mapped http://ift.tt/2vY8PCE

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Cosmic velocity web: Motions of thousands of galaxies mapped

The cosmic web -- the distribution of matter on the largest scales in the universe -- has usually been defined through the distribution of galaxies. Now, a new study by a team of astronomers demonstrates a novel approach. Instead of using galaxy positions, they mapped the motions of thousands of galaxies. Latest Science News -- ScienceDaily https://www.sciencedaily.com/releases/2017/08/170815095132.htm

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#NEW. Cosmic velocity web: Motions of thousands of galaxies mapped https://t.co/TZz5ZNUXBz http://pic.twitter.com/Y8BOv5Wt6I

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Cosmic velocity web: Motions of thousands of galaxies mapped http://ift.tt/2vY8PCE