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The Universe in Super Definition
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30-Doradus.jpg30 Doradus and R-13654 visiteThe massive, young stellar grouping, called R136, is only a few million years old and resides in the 30 Doradus Nebula, a turbulent star-birth region in the Large Magellanic Cloud (LMC), a satellite galaxy of our Milky Way. Many of the stars are among the most massive known. Several of them are over 100 times more massive than our Sun. These hefty stars are destined to become supernovae in a few million years.
The image, taken by Hubble's Wide Field Camera 3, spans about 100 light-years. The nebula is close enough to Earth that Hubble can resolve individual stars, giving astronomers important information about the stars' birth and evolution.
The brilliant stars are carving deep cavities in the surrounding material by unleashing a torrent of ultraviolet light, and hurricane-force stellar winds (streams of charged particles), which are etching away the enveloping hydrogen gas cloud in which the stars were born. The image reveals a fantasy landscape of pillars, ridges, and valleys, as well as a dark region in the center that roughly looks like the outline of a holiday tree. Besides sculpting the gaseous terrain, the brilliant stars can also help create a successive generation of offspring. When the winds hit dense walls of gas, they create shocks, which may be generating a new wave of star birth.
The movement of the LMC around the Milky Way may have triggered the massive cluster's formation in several ways. The gravitational tug of the Milky Way and the companion Small Magellanic Cloud may have compressed gas in the LMC. Also, the pressure resulting from the LMC plowing through the Milky Way's halo may have compressed gas in the satellite. The cluster is a rare, nearby example of the many super star clusters that formed in the distant, early universe, when star birth and galaxy interactions were more frequent. Previous Hubble observations have shown astronomers that super star clusters in faraway galaxies are ubiquitous. The LMC is located 170,000 light-years away and is a member of the Local Group of Galaxies, which also includes the Milky Way.
The Hubble image was taken at infrared wavelengths (1.1 microns and 1.6 microns). Hubble sees through the dusty nebula, revealing many stars that cannot be seen in visible light. The large bright star just above the center of the image is in the 30 Doradus nebula. The Hubble observations of 30 Doradus were made October 20-27, 2009.MareKromium
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30-Doradus_and_R-136.jpg30 Doradus and R-13657 visiteJust in time for the holidays: a Hubble Space Telescope picture postcard of hundreds of brilliant blue stars wreathed by warm, glowing clouds. The festive portrait is the most detailed view of the largest stellar nursery in our local galactic neighborhood. The massive, young stellar grouping, called R136, is only a few million years old and resides in the 30 Doradus Nebula, a turbulent star-birth region in the Large Magellanic Cloud (LMC), a satellite galaxy of our Milky Way. There is no known star-forming region in our galaxy as large or as prolific as 30 Doradus. Many of the diamond-like icy blue stars are among the most massive stars known. Several of them are over 100 times more massive than our Sun. These hefty stars are destined to pop off, like a string of firecrackers, as supernovas in a few million years.
The image, taken in ultraviolet, visible, and red light by Hubble's Wide Field Camera 3, spans about 100 light-years. The nebula is close enough to Earth that Hubble can resolve individual stars, giving astronomers important information about the birth and evolution of stars in the universe. The Hubble observations were taken Oct. 20-27, 2009. The blue color is light from the hottest, most massive stars; the green from the glow of oxygen; and the red from fluorescing hydrogen.MareKromium
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ARP-147.jpgARP 14753 visiteJust a couple of days after the orbiting observatory was brought back online, Hubble aimed its prime working camera, the Wide Field Planetary Camera 2 (WFPC2), at a particularly intriguing target, a pair of Gravitationally Interacting Galaxies called Arp 147.
The image demonstrated that the camera is working exactly as it was before going offline, thereby scoring a "perfect 10" both for performance and beauty.
The two galaxies happen to be oriented so that they appear to mark the number 10. The left-most galaxy, or the "one" in this image, is relatively undisturbed apart from a smooth ring of starlight. It appears nearly on edge to our line of sight. The right-most galaxy, resembling a zero, exhibits a clumpy, blue ring of intense star formation.
The blue ring was most probably formed after the galaxy on the left passed through the galaxy on the right. Just as a pebble thrown into a pond creates an outwardly moving circular wave, a propagating density wave was generated at the point of impact and spread outward. As this density wave collided with material in the target galaxy that was moving inward due to the gravitational pull of the two galaxies, shocks and dense gas were produced, stimulating star formation.
The dusty reddish knot at the lower left of the blue ring probably marks the location of the original nucleus of the galaxy that was hit.
Arp 147 appears in the Arp Atlas of Peculiar Galaxies, compiled by Halton Arp in the 1960s and published in 1966.
This picture was assembled from WFPC2 images taken with three separate filters. The blue, visible-light, and infrared filters are represented by the colors blue, green, and red, respectively.
The galaxy pair was photographed on October 27-28, 2008. Arp 147 lies in the constellation Cetus, and it is more than 400 MLY away from Earth.MareKromium
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ARP194-HST-2009-18-a-full_jpg.jpgArp 194 (Galaxy Cluster)53 visiteTo commemorate the Hubble Space Telescope's 19 years of historic, trailblazing science, the orbiting telescope has photographed a peculiar system of galaxies known as Arp 194. This interacting group contains several galaxies, along with a "cosmic fountain" of stars, gas, and dust that stretches over 100.000 LY.
The Northern (upper) component of Arp 194 appears as a haphazard collection of dusty spiral arms, bright blue star-forming regions, and at least two Galaxy Nuclei that appear to be connected and in the early stages of merging. A third, relatively normal, spiral galaxy appears off to the right.
The Southern (lower) component of the galaxy group contains a single large spiral galaxy with its own blue star-forming regions.
However, the most striking feature of this galaxy troupe is the impressive blue stream of material extending from the Northern Component. This "fountain" contains complexes of "Super Star Clusters", each one of which may contain dozens of individual young Star Clusters. The blue color is produced by the hot, massive stars which dominate the light in each cluster. Overall, the "fountain" contains many millions of stars.
These young star clusters probably formed as a result of the interactions between the galaxies in the Northern Component of Arp 194. The compression of gas involved in galaxy interactions can enhance the star-formation rate and give rise to brilliant bursts of star formation in merging systems.
Hubble's resolution shows clearly that the stream of material lies in front of the southern component of Arp 194, as evidenced by the dust that is silhouetted around the star-cluster complexes. It is therefore not entirely clear whether the southern component actually interacts with the northern pair.
The details of the interactions among the multiple galaxies that make up Arp 194 are complex. The shapes of all the galaxies involved appear to have been distorted, possibly by their gravitational interactions with one another.
Arp 194, located in the constellation Cepheus, resides approximately 600 MLY away from Earth. It contains some of the many interacting and merging galaxies known in our relatively nearby universe. These observations were taken in January of 2009 with the Wide Field Planetary Camera 2. Images taken through blue, green, and red filters were combined to form this picturesque image of galaxy interaction.MareKromium
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ARP_274-HST-2009-14-a-print.jpgGalaxy Triplet Arp 27453 visiteArp 274, also known as NGC 5679, is a system of 3 galaxies that appear to be partially overlapping in the image, although they may be at somewhat different distances. The spiral shapes of 2 of these galaxies appear mostly intact. The third galaxy (to the far left) is more compact, but shows evidence of star formation.
Two of the three galaxies are forming new stars at a high rate. This is evident in the bright blue knots of star formation that are strung along the arms of the galaxy on the right and along the small galaxy on the left.
The largest component is located in the middle of the triplet. It appears as a Spiral Galaxy, which may be barred. The entire system resides at about 400 Million Light-Years away from Earth in the Virgo constellation.
Hubble's Wide Field Planetary Camera 2 was used to image Arp 274. Blue, visible, and infrared filters were combined with a filter that isolates hydrogen emission. The colors in this image reflect the intrinsic color of the different stellar populations that make up the galaxies. Yellowish older stars can be seen in the central bulge of each galaxy.
A bright central cluster of stars pinpoint each nucleus. Younger blue stars trace the spiral arms, along with pinkish nebulae that are illuminated by new star formation. Interstellar dust is silhouetted against the starry population. A pair of foreground stars inside our own Milky Way are at far right.MareKromium
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Abell-1689.jpgGravitational "Lensing" for Abell 168953 visiteA massive cluster of yellowish galaxies is seemingly caught in a spider web of eerily distorted background galaxies in the left-hand image, taken with the Advanced Camera for Surveys (ACS) aboard NASA's Hubble Space Telescope.
The gravity of the cluster's trillion stars acts as a cosmic "zoom lens," bending and magnifying the light of the galaxies located far behind it, a technique called gravitational lensing. The faraway galaxies appear in the Hubble image as arc-shaped objects around the cluster, named Abell 1689. The increased magnification allows astronomers to study remote galaxies in greater detail.
One galaxy is so far away, however, it does not show up in the visible-light image taken with ACS [top, right], because its light is stretched to invisible infrared wavelengths by the universe's expansion.
Astronomers used Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and NASA's Spitzer Space Telescope with its Infrared Array Camera (IRAC)—with help from the gravitational lensing cluster—to see the faraway galaxy.
The distant galaxy, dubbed A1689-zD1, appears as a grayish-white smudge in the close-up view taken with Hubble's NICMOS [center, right], and as a whitish blob in the Spitzer IRAC close-up view [bottom, right]. The galaxy is brimming with star birth. Hubble and Spitzer worked together to show that it is one of the youngest galaxies ever discovered. Astronomers estimate that the galaxy is 12.8 billion light-years away. Abell 1689 is 2.2 billion light-years away.
A1689-zD1 was born during the middle of the "dark ages," a period in the early universe when the first stars and galaxies were just beginning to burst to life. The dark ages lasted from about 400,000 to roughly a billion years after the Big Bang. Astronomers think that A1689-zD1 was one of the galaxies that helped end the dark ages.
The ACS images were taken in 2002, the NICMOS images in 2005 and 2007, and the Spitzer IRAC images in 2006.
MareKromium
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Abell-1763-PIA10227.jpgCelestial Cities and the Roads that connect Them53 visiteThis is a representation of galaxies in and surrounding a galaxy cluster called Abell 1763. The placement of each dot is based on the actual coordinates of galaxies in the region. Blue dots are active star-forming galaxies; red dots show galaxies that are not actively forming stars.
Galaxies across the universe reside in cosmic communities big and small. Large, densely populated galactic communities are called galaxy clusters (highlighted in the orange circle). Like cities on Earth, galaxy clusters are scattered throughout the universe and are connected by a web of dusty highways called filaments (highlighted in purple). Smaller galactic communities are sprinkled along the filaments, creating celestial suburbs.
Over time, astronomers suspect that all galactic suburbanites make their way to a galaxy cluster by way of filaments. Observations from NASA's Spitzer Space Telescope show that filamentary galaxies form stars at twice the rate of their densely clustered counterparts.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA.
MareKromium
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Abell-901_and_902-PM.jpgAbell 901 and 902 Supercluster53 visiteAstronomers are using NASA's Hubble Space Telescope to dissect one of the largest structures in the universe as part of a quest to understand the violent lives of galaxies. Hubble is providing indirect evidence of unseen dark matter tugging on galaxies in the crowded, rough-and-tumble environment of a massive supercluster of hundreds of galaxies.
Dark matter is an invisible form of matter that accounts for most of the universe's mass. Hubble's Advanced Camera for Surveys has mapped the invisible dark matter scaffolding of the supercluster Abell 901/902, as well as the detailed structure of individual galaxies embedded in it.
The images are part of the Space Telescope Abell 901/902 Galaxy Evolution Survey (STAGES), which covers one of the largest patches of sky ever observed by the Hubble telescope. The area surveyed is so wide that it took 80 Hubble images to cover the entire STAGES field. The new work is led by Meghan Gray of the University of Nottingham in the United Kingdom and Catherine Heymans of the University of British Columbia in Vancouver, along with an international team of scientists.
The Hubble study pinpointed four main areas in the supercluster where dark matter has pooled into dense clumps, totaling 100 trillion times the Sun's mass. These areas match the location of hundreds of old galaxies that have experienced a violent history in their passage from the outskirts of the supercluster into these dense regions. These galaxies make up four separate galaxy clusters.
"Thanks to Hubble's Advanced Camera for Surveys, we are detecting for the first time the irregular clumps of dark matter in this supercluster," Heymans said. "We can even see an extension of the dark matter toward a very hot group of galaxies that are emitting X-rays as they fall into the densest cluster core."
The dark matter map was constructed by measuring the distorted shapes of over 60,000 faraway galaxies. To reach Earth, the galaxies' light traveled through the dark matter that surrounds the supercluster galaxies and was bent by the massive gravitational field. Heymans used the observed, subtle distortion of the galaxies' shapes to reconstruct the dark matter distribution in the supercluster using a method called weak gravitational lensing. The dark matter map is 2.5 times sharper than a previous ground-based survey of the supercluster.
"The new map of the underlying dark matter in the supercluster is one key piece of this puzzle," Gray explained. "At the same time we're looking in detail at the galaxies themselves." The survey's broader goal is to understand how galaxies are influenced by the environment in which they live.
On Earth, the pace of quiet country life is vastly different from the hustle of the big city. In the same way, galaxies living lonely isolated lives look very different from those found in the most crowded regions of the universe, like a supercluster. "We've known for a long time that galaxies in crowded environments tend to be older, redder, and rounder than those in the field," Gray said. "Galaxies are continually drawn into larger and larger groups and clusters by the inevitable force of gravity as the universe evolves."
In such busy environments galaxies are subject to a life of violence: high-speed collisions with other galaxies; the stripping away of gas, the fuel supply they use to form new stars; and distortion due to the strong gravitational pull of the underlying invisible dark matter. "Any or all of these effects may play a role in the transformation of galaxies, which is what we're trying to determine," Gray said.
The STAGES survey's simultaneous focus on both the big picture and the details can be likened to studying a big city. "It's as if we're trying to learn everything we can about New York City and New Yorkers," Gray explained. "We're examining large-scale features, like mapping the roads, counting skyscrapers, monitoring traffic. At the same time we're also studying the residents to figure out how the lifestyles of people living downtown differ from those out in the suburbs. But in our case the city is a supercluster, the roads are dark matter, and the people are galaxies."
Further results by other team members support this view. "In the STAGES supercluster we clearly see that transformations are happening in the outskirts of the supercluster, where galaxies are still moving relatively slowly and first feel the influence of the cluster environment," said Christian Wolf, an Advanced Research Fellow at the University of Oxford in the U.K.
Assistant professor Shardha Jogee and graduate student Amanda Heiderman, both of the University of Texas in Austin, concur. "We see more collisions between galaxies in the regions toward which the galaxies are flowing than in the centers of the clusters," Jogee said. "By the time they reach the center, they are moving too fast to collide and merge, but in the outskirts their pace is more leisurely, and they still have time to interact."
The STAGES team also finds that the outer parts of the clusters are where star formation in the galaxies is slowly switching off and where the supermassive black holes at the hearts of the galaxies are most active.
Added Heiderman: "The galaxies at the centers of the clusters may have been there for a long time and have probably finished their transformation. They are now old, round, red, and dead."
The team plans more studies to understand how the supercluster environment is responsible for producing these changes.
Abell 901/902 resides 2.6 billion light-years from Earth and measures more than 16 million light-years across.
MareKromium
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AlienWorld-PIA09228.jpgTwin Suns' Sunset53 visiteOur solitary sunsets here on Earth might not be all that common in the grand scheme of things. New observations from NASA's Spitzer Space Telescope have revealed that mature planetary systems -- dusty disks of asteroids, comets and possibly planets -- are more frequent around close-knit twin, or binary, stars than single stars like our sun. That means sunsets like the one portrayed in this artist's photo concept, and more famously in the movie "Star Wars," might be quite commonplace in the universe.
Binary and multiple-star systems are about twice as abundant as single-star systems in our galaxy, and, in theory, other galaxies. In a typical binary system, two stars of roughly similar masses twirl around each other like pair-figure skaters. In some systems, the two stars are very far apart and barely interact with each other. In other cases, the stellar twins are intricately linked, whipping around each other quickly due to the force of gravity.
Astronomers have discovered dozens of planets that orbit around a single member of a very wide stellar duo. Sunsets from these worlds would look like our own, and the second sun would just look like a bright star in the night sky.
But do planets exist in the tighter systems, where two suns would dip below a planet's horizon one by one? Unveiling planets in these systems is tricky, so astronomers used Spitzer to look for disks of swirling planetary debris instead. These disks are made of asteroids, comets and possibly planets. The rocky material in them bangs together and kicks up dust that Spitzer's infrared eyes can see. Our own solar system is swaddled in a similar type of disk.
Surprisingly, Spitzer found more debris disks around the tightest binaries it studied (about 20 stars) than in a comparable sample of single stars. About 60 percent of the tight binaries had disks, while the single stars only had about 20 percent. These snug binary systems are as close or closer than just three times the distance between Earth and the sun. And the disks in these systems were found to circumnavigate both members of the star pair, rather than just one.
Though follow-up studies are needed, the results could mean that planet formation is more common around extra-tight binary stars than single stars. Since these types of systems would experience double sunsets, the artistic view portrayed here might not be fiction.
The original sunset photo used in this artist's concept was taken by Robert Hurt of the Spitzer Science Center at the California Institute of Technology, Pasadena, Calif.
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Asteroid-PIA11735.jpgUnsuccesful crossing of the Roche Limit60 visiteIl Limite di Roche è la distanza minima dal centro di un Pianeta o di una Stella (qui di seguito definiti "Corpo Maggiore"), al di sotto della quale un satellite, o un pianeta (qui di seguito definito "Corpo Minore"), si può frammentare a causa delle Onde Gravitazionali Mareali (o "Forze di Marea"). Se si suppone che entrambi i Corpi (Maggiore e Minore) considerati abbiano la medesima densità, il Limite di Roche viene fatto pari a circa 2,5 volte il raggio del Corpo Maggiore (Pianeta o Stella che sia).
È possibile che all'interno di tale Limite esistano dei satelliti, ma essi devono essere sufficientemente piccoli e leggeri, così che le tensioni ad essi interne gli impediscano la frammentazione.
In un disco di frammenti che avvolge un pianeta appena formato (cd. "Protoplanetary Cloud Remainders" o anche "Accretion Disk"), la materia esistente oltre il Limite di Roche può assemblarsi in uno o più satelliti di modeste dimensioni, poichè all'interno di tale Limite le Forze di Marea impediscono la formazione di satelliti grandi.
Un buon esempio di questo tipo di fenomeno è negli anelli che vediamo intorno a Giove, Saturno, Urano e Nettuno: tutti questi anelli, infatti e ad esempio, si trovano all'interno del Limite di Roche.
Nel Sistema Solare sono quattro i pianeti che presentano anelli e per ciascuno di essi è stato calcolato il relativo Limite di Roche:
Giove = 175.000 Km
Saturno = 147.000 Km
Urano = 62.000 Km
Nettuno = 59.000 Km
Édouard Albert Roche, nel 1850, studiò in particolare gli Anelli di Saturno e giunse a dimostrare che il valore di 2,44 Raggi Planetari Saturniani si posizionava leggermente al di fuori dell'Anello più esterno, dentro il quale effettivamente non esistevano corpi di rilevanza.
Dalle riprese effettuate durante i Programmi Voyager e CASSINI-Huygens, si è potuto notare che gli Anelli di Saturno (al pari di quelli di tutti i Giganti Gassosi) non sono "unitari e compatti", bensì composti da aggregazioni promiscue di rocce di modeste dimensioni e ghiaccio: tutti elementi, questi, che - come detto - trovandosi all'interno del Limite di Roche ed avendo resistito alle Onde Gravitazionali emanate da Saturno, ci dimostrano una scarsissima densità intrinseca (e dunque una evidente idoneità alla "sopravvivenza" verso le Onde Gravitazionali Mareali).MareKromium
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BHR71-PIA09338.jpgProtostellar Jet in BHR 71 Dark Cloud53 visiteTwo rambunctious young stars are destroying their natal dust cloud with powerful jets of radiation, in an infrared image from NASA's Spitzer Space Telescope.
The stars are located approximately 600 light-years away in a cosmic cloud called BHR 71. In visible light (left panel), BHR 71 is just a large black structure. The burst of yellow light toward the bottom of the cloud is the only indication that stars might be forming inside. In infrared light (center panel), the baby stars are shown as the bright yellow smudges toward the center. Both of these yellow spots have wisps of green shooting out of them. The green wisps reveal the beginning of a jet. Like a rainbow, the jet begins as green, then transitions to orange, and red toward the end. The combined visible-light and infrared composite (right panel) shows that a young star's powerful jet is responsible for the rupture at the bottom of the dense cloud in the visible-light image. Astronomers know this because burst of light in the visible-light image overlaps exactly with a jet spouting-out of the left star, in the infrared image.
The jets' changing colors reveal a cooling effect, and may suggest that the young stars are spouting out radiation in regular bursts. The green tints at the beginning of the jet reveal really hot hydrogen gas, the orange shows warm gas, and the reddish wisps at the end represent the coolest gas. The fact that gas toward the beginning of the jet is hotter than gas near the middle suggests that the stars must give off regular bursts of energy -- and the material closest to the star is being heated by shockwaves from a recent stellar outburst. Meanwhile, the tints of orange reveal gas that is currently being heated by shockwaves from a previous stellar outburst. By the time these shockwaves reach the end of the jet, they have slowed down so significantly that the gas is only heated a little, and looks red. The combination of views also brings out some striking details that evaded visible-light detection. For example, the yellow dots scattered throughout the image are actually young stars forming inside BHR 71. Spitzer also uncovered another young star with jets, located to the right of the powerful jet seen in the visible-light image. Spitzer can see details that visible-light telescopes don't, because its infrared instruments are sensitive to "heat."
The infrared image is made up of data from Spitzer's infrared array camera. Blue shows infrared light at 3.6 microns, green is light at 4.5 microns, and red is light at 8.0 microns.
MareKromium
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BLG-109.jpgBLG-109: A Distant Version of our own Solar System53 visiteCaption NASA:"How common are planetary systems like our own?
Perhaps quite common, as the first system of planets like our own Solar System has been discovered using a newly adapted technique that, so far, has probed only six planetary systems.
The technique, called "Gravitational Microlensing", looks for telling brightness changes in measured starlight when a foreground star with planets chances almost directly in front of a more distant star. The distant star's light is slightly deflected in predictable ways by the gravity of the closer system.
Recently a detailed analysis of Microlensing System OGLE-2006-BLG-109 has related brightness variations to two planets that are similar to Jupiter and Saturn of our own Solar System. This discovery carries the tantalizing implication that interior planets, possibly including Earth-like planets, might also be common.
Pictured above is an artistic conception of how the BLG-109 planetary system might look".MareKromium
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