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| Piú votate - The Universe in Super Definition |
NGC-0253-HST.jpgCosmic Alignment! (2MASX J00482185-2507365)54 visiteNASA's Hubble Space Telescope has captured a rare alignment between two spiral galaxies. The outer rim of a small, foreground galaxy is silhouetted in front of a larger background galaxy. Skeletal tentacles of dust can be seen extending beyond the small galaxy's disk of starlight.
Such outer dark dusty structures, which appear to be devoid of stars, like barren branches, are rarely so visible in a galaxy because there is usually nothing behind them to illuminate them. Astronomers have never seen dust this far beyond the visible edge of a galaxy. They do not know if these dusty structures are common features in galaxies.
Understanding a galaxy's color and how dust affects and dims that color are crucial to measuring a galaxy's true brightness. By knowing the true brightness, astronomers can calculate the galaxy's distance from Earth.
Astronomers calculated that the background galaxy is 780 MLY away. They have not as yet calculated the distance between the two galaxies, although they think the two are relatively close, but not close enough to interact. The background galaxy is about the size of the Milky Way Galaxy and is about 10 times larger than the foreground galaxy.
Most of the stars speckled across this image belong to the nearby spiral galaxy NGC 253, which is out of view to the right. Astronomers used Hubble's Advanced Camera for Surveys to snap images of NGC 253 when they spied the two galaxies in the background. From ground-based telescopes, the two galaxies look like a single blob. But the Advanced Camera's sharp "eye" distinguished the blob as two galaxies, cataloged as 2MASX J00482185-2507365. The images were taken on Sept. 19, 2006.
The results have been submitted for publication in The Astronomical Journal.
For additional information, contact:
Donna Weaver/Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu
Benne Holwerda
Space Telescope Science Institute, Baltimore, Md.
/University of Cape Town, South Africa
holwerda@stsci.edu
Object Name: 2MASX J00482185-2507365
MareKromium
(6 voti)
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GRB-080319B.jpgSpace "Flash"! GRB-080319B54 visiteCaption NASA:"Peering across 7,5 BLY (Billion Light-Years) and halfway back to the Big Bang, NASA's Hubble Space Telescope has photographed the fading optical counterpart of a powerful Gamma Ray Burst (GRB) that holds the record for being the intrinsically brightest naked-eye object ever seen from Earth. For nearly a minute this single star was as bright as 10 million galaxies.
Hubble Wide Field and Planetary Camera 2 (WFPC2) images of GRB 080319B, taken on Monday, April 7, 2008, show the fading optical counterpart of the titanic blast. The object erupted in a brilliant flash of Gamma Rays and other electromagnetic radiation at 2:12 a.m. EDT on March 19, and was detected by Swift, NASA's Gamma Ray Burst "Watchdog Satellite". Immediately after the explosion, the Gamma Ray Burst glowed as a dim 5th magnitude "star" in the spring constellation Bootes.
Designated GRB 080319B, the intergalactic firework has been fading away ever since then. Hubble astronomers had hoped to see the host galaxy where the burst presumably originated, but were taken aback that the light from the GRB is still drowning out the galaxy's light even three weeks after the explosion.
This is particularly surprising because it was such a bright GRB initially. Previously, bright bursts have tended to fade more rapidly, which fits in to the theory that brighter GRBs emit their energy in a more tightly confined beam. The slow fading leaves astronomers puzzling about just where the energy came from to power this GRB, and makes Hubble's next observations of this object in May 2008 all the more crucial.
Called a Long-Duration GRB, such events are theorized to be caused by the death of a very massive star, perhaps weighing as much as 50 times our Sun. Such explosions, sometimes dubbed "hypernovae", are more powerful than ordinary supernova explosions and are far more luminous, in part because their energy seems to be concentrated into a blowtorch-like beam that, in this case, was aimed directly at Earth. The Hubble exposure also shows field galaxies around the fading optical component of the gamma ray burst, which are probably unrelated to the burst itself".MareKromium
(6 voti)
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Abell-1763-PIA10227.jpgCelestial Cities and the Roads that connect Them58 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
(6 voti)
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NGC-1333-PIA09967.jpgNGC 133355 visiteNASA's Spitzer Space Telescope observed a fledgling Solar System like the one depicted in this artist's concept, and discovered deep within it enough water vapor to fill the oceans on Earth five times. This water vapor starts out in the form of ice in a cloudy cocoon (not pictured) that surrounds the embryonic star, called NGC 1333-IRAS 4B (buried in center of image).
Material from the cocoon, including ice, falls toward the center of the cloud. The ice then smacks down onto a dusty pre-planetary disk circling the stellar embryo (doughnut-shaped cloud) and vaporizes.
Eventually, this water might make its way into developing planets.MareKromium
(6 voti)
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Mira-PIA09959.jpgMira: anatomy of a "Celestial Shooting Star"...55 visiteA close-up view of a star racing through space faster than a speeding bullet can be seen in this image from NASA's Galaxy Evolution Explorer. The star, called Mira (pronounced My-rah), is traveling at 130 kilometers per second, or 291,000 miles per hour. As it hurls along, it sheds material that will be recycled into new stars, planets and possibly even life.
In this image, Mira is moving from left to right. It is visible as the pinkish dot in the bulb shape at right. The yellow dot below is a foreground star. Mira is traveling so fast that it's creating a bow shock, or build-up of gas, in front of it, as can be seen here at right.
Like a boat traveling through water, a bow shock forms ahead of the star in the direction of its motion. Gas in the bow shock is heated and then mixes with the cool hydrogen gas in the wind that is blowing off Mira. This heated hydrogen gas then flows around behind the star, forming a wake.
Why is the wake of material glowing? When the hydrogen gas is heated, it transitions into a higher-energy state, which then loses energy by emitting ultraviolet light - a process called fluorescence. The Galaxy Evolution Explorer has special instruments that can detect this ultraviolet light.
A similar fluorescence process is responsible for the Northern Lights -- a glowing, green aurora that can be seen from northern latitudes. However, in that case nitrogen and oxygen gas are fluorescing with visible light.
Streams and a loop of material can also be seen coming off Mira. Astronomers are still investigating what these streams are, but they suspect that they are denser parts of Mira's wind perhaps flowing out of the star's poles.
This image consists of data captured by both the far- and near-ultraviolet detectors on the Galaxy Evolution Explorer between November 18 and December 15, 2006. It has a total exposure time of about 3 hours.
MareKromium
(6 voti)
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NGC-2264.jpgNGC 2264 - The "Snowflake Cluster" versus the "Cone Nebula"53 visiteCaption NASA:"Strange shapes and textures can be found in the neighborhood of the Cone Nebula.
These patterns result from the tumultuous unrest that accompanies the formation of the open cluster of stars known as NGC 2264, the Snowflake Cluster. To better understand this process, a detailed image of this Region was taken in two colors of infrared light by the orbiting Spitzer Space Telescope (SST). Bright stars from the Snowflake cluster dot the field. These stars soon heat up and destroy the gas and dust mountains in which they formed. One such dust mountain is the famous Cone Nebula, visible in the above image on the left, pointing toward a bright star near the center of the field.
The entire NGC 2264 Region is located about 2500 LY away toward the constellation of the Unicorn (Monoceros)".MareKromium
(6 voti)
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LonelyPlanet-PIA09118.jpgWhat's the weather like over there?56 visiteCaption NASA:"An artist's conception shows a gas-giant planet orbiting very close to its parent star, creating searingly hot conditions on the planet's surface.
New research suggests that for three such planets lying from 50 to 150 light-years from Earth, strong winds thousands of miles per hour mix the atmosphere so that the temperature is relatively uniform from the permanently light side to the permanently dark side.
This illustration represents an infrared view of a planetary system, in which brightness indicates warmer temperatures. For example, the bright band around the equator of the planet denotes warmer temperatures on both the dark and sunlit sides.
The planet's poles, shown in darker colors, would be cooler".MareKromium
(6 voti)
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Dark_Matter.jpgBright Universe, Dark Matter56 visiteAn international team of astronomers using NASA's Hubble Space Telescope has created a three-dimensional map that provides the first direct look at the large-scale distribution of dark matter in the universe.
Dark matter is an invisible form of matter that accounts for most of the universe's mass.
The map provides the best evidence yet that normal matter, largely in the form of galaxies, accumulates along the densest concentrations of dark matter. The map reveals a loose network of filaments that grew over time and intersect in massive structures at the locations of clusters of galaxies.
The map stretches halfway back to the beginning of the universe and shows how dark matter has grown increasingly "clumpy" as it collapses under gravity.
This milestone takes astronomers from inference to direct observation of dark matter's influence in the universe. Previous studies of dark matter are based largely on numerical simulations of the expected evolution of large-scale structure. This evolution is driven by the gravitational attraction of dark matter.
Mapping dark matter's distribution in space and time is fundamental to understanding how galaxies grew and clustered over billions of years. Tracing the growth of clustering in the dark matter may eventually also shed light on dark energy, a repulsive form of gravity that influences how dark matter clumps.
The new maps of dark matter and galaxies will provide critical observational underpinnings to future theories for how structure formed in the evolving universe under the relentless pull of gravity. Theories suggest the universe transitioned from a smooth distribution of matter into a sponge-like structure of long filaments.
The research results appeared online today in the journal Nature and were presented at the 209th meeting of the American Astronomical Society in Seattle, Wash., by Richard Massey for the dark matter and Nick Scoville for the galaxies. Both researchers are from the California Institute of Technology, Pasadena, Calif.
"It's reassuring how well our map confirms the standard theories for structure formation." said Massey. He calls dark matter the "scaffolding" inside of which stars and galaxies have been assembled over billions of years.
Researchers created the map using Hubble's largest survey of the universe, the Cosmic Evolution Survey ("COSMOS") with an international team of 70 astronomers led by Scoville. The COSMOS survey covers a sufficiently wide area of sky – nine times the area of the Earth's Moon. This allows for the large-scale filamentary structure of dark matter to be evident. To add 3-D distance information, the Hubble observations were combined with multicolor data from powerful ground-based telescopes. "The 3-D information is vital to studying the evolution of the structures over cosmic time," said Jason Rhodes, a collaborator in the study at the Jet Propulsion Laboratory in Pasadena, Calif.
The dark matter map was constructed by measuring the shapes of half a million faraway galaxies. To reach us, the galaxies' light has traveled through intervening dark matter. The dark matter deflected the light slightly as it traveled through space. Researchers used the observed, subtle distortion of the galaxies' shapes to reconstruct the distribution of intervening mass along Hubble's line of sight — a method called weak gravitational lensing. This effect is analogous to deducing the rippling pattern in a glass shower door by measuring how light from behind it is distorted as it passes through the glass.
"Although this technique has been employed previously, the depth of the COSMOS image and its superior resolution enables a more precise and detailed map, covering a large enough area to see the extended filamentary structures," said co-investigator Richard Ellis of the California Institute of Technology.
For astronomers, the challenge of mapping the universe has been similar to mapping a city from nighttime aerial snapshots showing only streetlights. Dark matter is invisible, so only the luminous galaxies can be seen directly. The new images are equivalent to seeing a city, its suburbs and country roads — in daylight, for the first time. Major arteries and intersections become evident, and a variety of neighborhoods are revealed.
A separate COSMOS team led by Scoville presented images of the large scale galactic structures in the same area with the dark matter. Galaxies appear in visible light seen with Hubble and in ground-based Subaru telescope images by Yoshiaku Taniguchi and colleagues. The hot gas in the densest galaxy clusters was imaged in X-rays by Gunther Hasinger and colleagues using the European Space Agency's XMM-Newton telescope.
Galaxy structures inside the dark matter scaffolding show clusters of galaxies in the process of assembly. These structures can be traced over more than 80 million light-years in the COSMOS survey – approximately five times the extent of the nearby Virgo galaxy cluster. In the densest early universe structures, many galaxies already have old stellar populations, implying that these galaxies formed first and accumulated the greatest masses in a bottom-up assembly process where smaller galaxies merge to make bigger galaxies — like tributaries converging to form a large river.
The COSMOS survey shows that galaxies with on-going star formation, even to the present epoch, dwell in less populated voids and dark matter filaments. "It is remarkable how the environment on the enormous cosmic scales seen in the dark matter structures can influence the properties of individual stars and galaxies — both the maturity of the stellar populations and the progressive 'downsizing' of star formation to smaller galaxies is clearly dependent on the dark matter environment," said Scoville.
"The comparison is of fundamental importance," said Massey. "Almost all current scientific knowledge concerns only baryonic matter. Now that we have begun to map out where dark matter is, the next challenge is to determine what it is, and specifically its relationship to normal matter."
In making the COSMOS survey, Hubble photographed 575 slightly overlapping views of the universe using the Advanced Camera for Surveys' (ACS) Wide Field Camera onboard Hubble. It took nearly 1,000 hours of observations. Thousands of galaxies' spectra were obtained by using the European Southern Observatory's Very Large Telescope in Chile, and the Subaru telescope in Hawaii. The distances to the galaxies were accurately determined through their spectral redshifts. The distribution of the normal matter was partly determined with the European Space Agency's XMM-Newton telescope.
MareKromium
(6 voti)
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M 42-PIA08655-ed.jpgThe "Great Cloud" around Orion53 visiteThis image composite shows a part of the Orion constellation surveyed by NASA's Spitzer Space Telescope. The shape of the main image was designed by astronomers to roughly follow the shape of Orion cloud A, an enormous star-making factory containing about 1,800 young stars. This giant cloud includes the famous Orion nebula (bright circular area in "blade" part of hockey stick-shaped box at the bottom), which is visible to the naked eye on a clear, dark night as a fuzzy star in the hunter constellation's sword.
The region that makes up the shaft part of the hockey stick box stretches 70 light-years beyond the Orion nebula. This particular area does not contain massive young stars like those of the Orion nebula, but is filled with 800 stars about the same mass as the sun. These sun-like stars don't live in big "cities," or clusters, of stars like the one in the Orion nebula; instead, they can be found in small clusters (right inset), or in relative isolation (middle insert).
In the right inset, developing stars are illuminating the dusty cloud, creating small wisps that appear greenish. The stars also power speedy jets of gas (also green), which glow as the jets ram into the cloudy material.
Since infrared light can penetrate through dust, we see not only stars within the cloud, but thousands of stars many light-years behind it, which just happen to be in the picture like unwanted bystanders. Astronomers carefully separate the young stars in the Orion cloud complex from the bystanders by looking for their telltale infrared glow.
The infrared image shows light captured by Spitzer's infrared array camera. Light with wavelengths of 8 and 5.8 microns (red and orange) comes mainly from dust that has been heated by starlight. Light of 4.5 microns (green) shows hot gas and dust; and light of 3.6 microns (blue) is from starlight.
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M 74-PIA08533_fig3.jpgSupernova SN2003gd in January 2005 (2)53 visiteBy January 2005, the dust had cooled and completely faded from the camera's view (here). However, it was still detected in January 2005 by another instrument aboard Spitzer called the Multiband Imaging Photometer.
All the images are false-color, infrared composites, in which 3,6-micron light is blue, 4,5-micron light is green, and 8-micron light is red.
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Proxima_Centauri_B_-_4.jpgNightside of Proxima Centauri "b" (Imagination)117 visitenessun commentoMareKromium
(5 voti)
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Proxima_Centauri_B_-_3~0.jpgProxima Centauri "b" - Just like Tharsis, BUT ACTIVE! (Extra Mgnf - 3)129 visiteE' come Tharsis, attiva, enorme e situata sul Pianeta (una "Super-Terra") Proxima Centauri b.MareKromium
(5 voti)
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