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| Piú viste - The Universe in Super Definition |
Spectrum-PIA09199.jpgSpectrum of an Alien World55 visiteThis infrared data from NASA's Spitzer Space Telescope - called a spectrum - tells astronomers that a distant gas planet, a so-called "hot Jupiter" called HD 189733b, might be smothered with high clouds. It is one of the first spectra of an alien world.
A spectrum is created when an instrument called a spectrograph cracks light from an object open into a rainbow of different wavelengths. Patterns or ripples within the spectrum indicate the presence, or absence, of molecules making up the object.
Astronomers using Spitzer's spectrograph were able to obtain infrared spectra for two so-called "transiting" hot-Jupiter planets using the "secondary eclipse" technique. In this method, the spectrograph first collects the combined infrared light from the planet plus its star, then, as the planet is eclipsed by the star, the infrared light of just the star. Subtracting the latter from the former reveals the planet's own rainbow of infrared colors.
Astronomers were perplexed when they first saw the infrared spectrum above. It doesn't look anything like what theorists had predicted. Theorists thought the spectra of hot, Jupiter-like planets like this one would be filled with the signatures of molecules in the planets' atmospheres. But the spectrum doesn't show any molecules, and is instead what astronomers call "flat." For example, theorists thought there'd be a strong signature of water in the form of a big drop in the wavelength range between 7 and 10 microns. The fact that water is not detected may indicate that it is hidden underneath a thick blanket of high, dry clouds. The average brightness of the spectrum is also a bit lower than theoretical predictions, suggesting that very high winds are rapidly moving the terrific heat of the noonday sun from the day side of HD 189733b to the night side.
This spectrum was produced by Dr. Carl Grillmair of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena, Calif., and his colleagues. The data were taken by Spitzer's infrared spectrograph on November 22, 2006.
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NGC-2808-2.jpgTriple Stellar Evolution Epochs in NGC 280855 visiteLike a simplified version of the Hertzsprung-Russell (HR) Diagram and by using the original HST data, this graph schematically plots the brightness of the stars in Globular Cluster NGC 2808 (along the vertical axis) against stellar color and temperature (along the horizontal axis).
The cooler a star is, the redder it appears, and it diminishes in brightness.
The bluer stars are to the left; redder stars are to the right.
The brightest stars are near the top.
The 3 curves represent the 3 different populations of stars that are present in NGC 2808.MareKromium
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NGC-0362-PIA09653.jpgNGC 362 - Globular Star Cluster55 visiteThe Galaxy Evolution Explorer's ultraviolet eyes have captured a globular star cluster, called NGC 362, in our own Milky Way galaxy. In this new image, the cluster appears next to stars from a more distant neighboring galaxy, known as the Small Magellanic Cloud.
Globular clusters are densely packed bunches of old stars scattered in galaxies throughout the universe. NGC 362, located 30,000 light-years away, can be spotted as the dense collection of mostly yellow-tinted stars surrounding a large white-yellow spot toward the top-right of this image. The white spot is actually the core of the cluster, which is made up of stars so closely packed together that the Galaxy Evolution Explorer cannot see them individually.
The light blue dots surrounding the cluster core are called extreme horizontal branch stars. These stars used to be very similar to our sun and are nearing the end of their lives. They are very hot, with temperatures reaching up to about four times that of the surface of our sun (25,000 Kelvin or 45,500 degrees Fahrenheit).
A star like our sun spends most of its life fusing hydrogen atoms in its core into helium. When the star runs out of hydrogen in its core, its outer envelope will expand. The star then becomes a red giant, which burns hydrogen in a shell surrounding its inner core. Throughout its life as a red giant, the star loses a lot of mass, then begins to burn helium at its core. Some stars will have lost so much mass at the end of this process, up to 85 percent of their envelopes, that most of the envelope is gone. What is left is a very hot ultraviolet-bright core, or extreme horizontal branch star.
Blue dots scattered throughout the image are hot, young stars in the Small Magellanic Cloud, a satellite galaxy of the Milky Way located approximately 200,000 light-years away. The stars in this galaxy are much brighter intrinsically than extreme horizontal branch stars, but they appear just as bright because they are farther away. The blue stars in the Small Magellanic Cloud are only about a few tens of millions of years old, much younger than the approximately 10-million-year-old stars in NGC 362.
Because NGC 362 sits on the northern edge of the Small Magellanic Cloud galaxy, the blue stars are denser toward the south, or bottom, of the image.
Some of the yellow spots in this image are stars in the Milky Way galaxy that are along this line of sight. Astronomers believe that some of the other spots, particularly those closer to NGC 362, might actually be a relatively ultraviolet-dim family of stars called "blue stragglers." These stars are formed from collisions or close encounters between two closely orbiting stars in a globular cluster.
This image is a false-color composite, where light detected by the Galaxy Evolution Explorer's far-ultraviolet detector is colored blue, and light from the telescope's near-ultraviolet detector is red.
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HD_189733b-PIA09715_01.jpgExoplanet HD 189733b55 visiteCaption NASA:"This plot of data from NASA's Spitzer Space Telescope (SST) tells astronomers that a toasty gas exoplanet, or a planet beyond our Solar System, contains water vapor.
Spitzer observed the Planet, called HD 189733b, cross in front of its star at three different infrared wavelengths: 3,6; 4,5 and 8 microns (see lime-colored dots). For each wavelength, the Planet's Atmosphere absorbed different amounts of the starlight that passed through it. The pattern by which this absorption varies with wavelength matches known signatures of water, as shown by the theoretical model in blue".MareKromium
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NGC-2237_and_NGC-2244.jpgHot Stars in the Rosette Nebula55 visiteWinds and radiation from massive hot stars in the Rosette Nebula have cleared the natal gas and dust from the center of the nearby star-forming region. They also pose a danger to planet forming disks around young, cooler stars in the neighborhood. This Spitzer Space Telescope (SST) infrared image of dust clouds near the Rosette's central region, shows the cleared-out cavity.
The view spans about 45 LY at the the nebula's estimated distance of 5.200 LY. MareKromium
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HD_61005.jpgCircumstellar Dust Takes Flight in 'The Moth'55 visiteWhat superficially resembles a giant moth floating in space is giving astronomers new insight into the formation and evolution of planetary systems.
This is not your typical flying insect. It has a wingspan of about 22 billion miles. The wing- like structure is actually a dust disk encircling the nearby, young star HD 61005, dubbed "The Moth." Its shape is produced by starlight scattering off dust.
Dust disks around roughly 100-million-year-old stars like HD 61005 are typically flat, pancake-shaped structures where planets can form. But images taken with NASA's Hubble Space Telescope of "The Moth" are showing that some disks sport surprising shapes.
"It is completely unexpected to find a dust disk with this unusual shape," said senior research scientist Dean Hines of the Space Science Institute, New Mexico Office in Corrales, New Mexico, and a member of the Hubble team that discovered the disk. "We think HD 61005 is plowing through a local patch of higher-density gas in the interstellar medium, causing material within HD 61005's disk to be swept behind the star. What effect this might have on the disk, and any planets forming within it, is unknown."
Hines called this possible collision "unusual, because we don't expect very much interstellar material to be in the solar neighborhood. That's because the area through which our Sun is moving was evacuated within the past few million years by at least one supernova, the explosion of a massive star. Yet, here's evidence of dense material that's very close, only 100 light-years away."
Astronomers have found evidence that the environment in which a star forms influences its prospects for planet formation. Hubble has actually seen that young planet-forming disks can be affected directly by their environment. The harsh stellar radiation from the Trapezium stars in the Orion Nebula has altered some disks. It is unclear, however, what effect passage through a cloud similar to the one in which HD 61005 finds itself would have on planet formation. Researchers have speculated that passage through dense regions of the interstellar medium could impact the atmospheres of evolving planets.
The Moth is part of a survey of Sun-like stars that Hines and collaborators observed with Hubble's Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) and NASA's Spitzer Space Telescope to study the formation and evolution of planetary systems. Under the lead of Michael Meyer of the University of Arizona in Tucson, the team initially used Spitzer to look for heat radiation—the tell-tale sign of dust warmed by the star—to identify interesting star systems.
Hines then teamed with Glenn Schneider of the University of Arizona to use Hubble's high- contrast imaging capability of the NICMOS coronagraph to image these disks and reveal where the dust detected by Spitzer resides. The NICMOS coronagraph blocked out the starlight so that astronomers could see details in the surrounding disk.
"These symbiotic capabilities, uniquely implemented in NASA's Great Observatories, provide astronomers with the powerful observational tools to study the circumstellar environments of potentially planet-forming systems," Schneider said.
Added Meyer: "Combining observations from these two spacecraft gives us information about the composition of the dust grains, whether they're icy or sandy, or whether they're like the sooty smoke particles rising from a chimney. The composition and sizes of the dust can tell us a lot about the dynamics and evolution of a solar system. In our solar system, for example, astronomers have evidence of rocks smashing into each other and generating dust, as in the asteroid and Kuiper belts. We're seeing these same processes unfold in other planetary systems."
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GLS-SDSSJ0946+1006.jpgHubble Finds Double "Einstein Ring"55 visiteNASA's Hubble Space Telescope has revealed a never-before-seen optical alignment in space: a pair of glowing rings, one nestled inside the other like a bull's-eye pattern. The double-ring pattern is caused by the complex bending of light from two distant galaxies strung directly behind a foreground massive galaxy, like three beads on a string.
More than just a novelty, this very rare phenomenon can offer insight into dark matter, dark energy, the nature of distant galaxies, and even the curvature of the universe.
The ring was found by an international team of astronomers led by Raphael Gavazzi and Tommaso Treu of the University of California, Santa Barbara. The discovery is part of the ongoing Sloan Lens Advanced Camera for Surveys (SLACS) program. The team is reporting its results at the 211th meeting of the American Astronomical Society in Austin, Texas. A paper has been submitted to The Astrophysical Journal.
The phenomenon, called gravitational lensing, occurs when a massive galaxy in the foreground bends the light rays from a distant galaxy behind it, in much the same way as a magnifying glass would. When both galaxies are exactly lined up, the light forms a circle, called an "Einstein ring," around the foreground galaxy. If another background galaxy lies precisely on the same sightline, a second, larger ring will appear.
Because the odds of seeing such a special alignment are estimated to be 1 in 10,000, Tommaso says that they "hit the jackpot." The odds of seeing this phenomenon are less than winning two consecutive bets on a single number at Roulette.
"Such stunning cosmic coincidences reveal so much about nature. Dark matter is not hidden to lensing," added Leonidas Moustakas of the Jet Propulsion Laboratory in Pasadena, Calif. "The elegance of this lens is trumped only by the secrets of nature that it reveals."
The massive foreground galaxy is almost perfectly aligned in the sky with two background galaxies at different distances. The foreground galaxy is 3 billion light-years away. The inner ring and outer ring are comprised of multiple images of two galaxies at a distance of 6 billion and approximately 11 billion light-years.
SLACS team member Adam Bolton of the University of Hawaii's Institute for Astronomy in Honolulu first identified the lens in the Sloan Digital Sky Survey (SDSS). "The original signature that led us to this discovery was a mere 500 photons (particles of light) hidden among 500,000 other photons in the SDSS spectrum of the foreground galaxy," commented Bolton.
"The twin rings were clearly visible in the Hubble image, added Tommaso. "When I first saw it I said 'wow, this is insane!' I could not believe it!"
The distribution of dark matter in the foreground galaxies that is warping space to create the gravitational lens can be precisely mapped. Tommaso finds that the fall-off in density of the dark matter is similar to what is seen in spiral galaxies (as measured by the speed of a galaxy's rotation, which yields a value for the amount of dark matter pulling on it), though he emphasizes there is no physical reason to explain this relationship.
In addition, the geometry of the two Einstein rings allowed the team to measure the mass of the middle galaxy precisely to be a value of 1 billion solar masses. The team reports that this is the first measurement of the mass of a dwarf galaxy at cosmological distance (redshift of z=0.6).
A sample of several dozen double rings such as this one would offer a purely independent measure. The comparative radius of the rings could also be used to provide an independent measure of the curvature of space by gravity. This would help in determining the matter content of the universe and the properties of dark energy.
Observations of the cosmic microwave background (a relic from the Big Bang) favor flat geometry. A sample of 50 suitable double Einstein rings would be sufficient to measure the dark matter content of the universe and the equation of state of the dark energy (a measure of its pressure) to 10 percent precision. Other double Einstein rings could be found with wide-field space telescope sky surveys that are being proposed for the Joint Dark Energy Mission (JDEM) and recently recommended by the National Research Council.
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Rho_Ophiuci-PIA10182.jpgRho Ophiuci55 visiteNewborn stars peek out from beneath their natal blanket of dust in this dynamic image of the Rho Ophiuchi dark cloud from NASA's Spitzer Space Telescope. Called "Rho Oph" by astronomers, it's one of the closest star-forming regions to our own solar system. Located near the constellations Scorpius and Ophiuchus, the nebula is about 407 light years away from Earth.
Rho Oph is a complex made up of a large main cloud of molecular hydrogen, a key molecule allowing new stars to form from cold cosmic gas, with two long streamers trailing off in different directions. Recent studies using the latest X-ray and infrared observations reveal more than 300 young stellar objects within the large central cloud. Their median age is only 300,000 years, very young compared to some of the universe's oldest stars, which are more than 12 billion years old.
This false-color image of Rho Oph's main cloud, Lynds 1688, was created with data from Spitzer's infrared array camera, which has the highest spatial resolution of Spitzer's three imaging instruments. Blue represents 3.6 micron light, green is 4.5 micron light, orange is 5.8, and red is 8.0. The multiple wavelengths reveal different aspects of the dust surrounding and between the embedded stars, yielding information about the stars and their birthplace.
The colors in this image reflect the relative temperatures and evolutionary states of the various stars. The youngest stars are surrounded by dusty disks of gas from which they, and their potential planetary systems, are forming. These young disk systems show up as yellow-green tinted stars in this image. Some of these young stellar objects are surrounded by their own compact nebulae. More evolved stars, which have shed their natal material, are blue-white.
The extended white nebula in the center right of the image is a region of the cloud which is glowing in infrared light due to the illumination of dust by bright young stars near the right edge of the cloud. Red and pink diffuse emission from carbon-rich dust molecules fills the image. Most of the stars forming now are concentrated in a filament of cold, dense gas that shows up as a dark cloud in the lower center and left side of the image against the bright background of the warm dust. Although infrared radiation at 8 microns pierces through dust easily, this dark filament is incredibly opaque, appearing dark even at the longest wavelengths in the image.
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M 74-PIA08533_fig2.jpgSupernova SN2003gd in July 2004 (1)54 visiteThe dust factory, also known as supernova SN 2003gd, is shown at the center of the two small insets from Spitzer's infrared array camera. A white arrow points to its exact location.
The yellow-green dot shown in the July 2004 inset (here) shows that the source's temperature is warmer than the surrounding material. This is because newly formed dust within the Supernova is just starting to cool.
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Spectrum-PIA09198.jpgSpectrum of an Alien World54 visiteThis infrared data from NASA's Spitzer Space Telescope - called a spectrum - tells astronomers that a distant gas planet, a so-called "hot Jupiter" called HD 209458b, might be smothered with high clouds. It is one of the first spectra of an alien world.
A spectrum is created when an instrument called a spectrograph spreads light from an object apart into a rainbow of different wavelengths. Patterns or ripples within the spectrum indicate the presence, or absence, of molecules making up the object.
Astronomers using Spitzer's spectrograph were able to obtain infrared spectra for two so-called "transiting" hot-Jupiter planets using the "secondary eclipse" technique. In this method, the spectrograph first collects the combined infrared light from the planet plus its star, then, as the planet is eclipsed by the star, the infrared light of just the star. Subtracting the latter from the former reveals the planet's own rainbow of infrared colors.
When astronomers first saw the infrared spectrum above, they were shocked. It doesn't look anything like what theorists had predicted. Theorists though the spectra for hot, Jupiter-like planets like this one would be filled with the signatures of molecules in the planets' atmospheres. But the spectrum doesn't show any molecules. It is what astronomers call "flat." For example, theorists thought there'd be signatures of water in the wavelength ranges of 8 to 9 microns. The fact that water is not seen there might indicate that the water is hidden under a thick blanket of high, dry clouds.
This spectrum was produced by Dr. Mark R. Swain of NASA's Jet Propulsion Laboratory in Pasadena, Calif., using a complex set of mathematical tools. It was derived using two different methods, both of which led to the same result. The data were taken on July 6 and 13, 2005, by Dr. Jeremy Richardson of NASA's Goddard Space Flight Center and his team using Spitzer's infrared spectrograph.
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SNR-N132D-PIA09604.jpgThe "Shock-Waves" of N132D54 visiteSupernovae are the explosive deaths of the universe's most massive stars. In death, these volatile creatures blast tons of energetic waves into the cosmos, destroying much of the dust surrounding them.
This false-color composite from NASA's Spitzer Space Telescope and NASA's Chandra X-ray Observatory shows the remnant of one such explosion. The remnant, called N132D, is the wispy pink shell of gas at the center of this image. The pinkish color reveals a clash between the explosion's high-energy shockwaves and surrounding dust grains.
In the background, small organic molecules called polycyclic aromatic hydrocarbons are shown as tints of green. The blue spots represent stars in our galaxy along this line of sight.
N132D is located 163.000 LY away in the Large Magellanic Cloud.
In this image, infrared light at 4,5 microns is mapped to blue, 8,0 microns to green and 24 microns to red. Broadband X-ray light is mapped purple. The infrared data were taken by Spitzer's infrared array camera and multiband imaging photometer, while the X-ray data were captured by Chandra.
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SN-Cassiopeia_A_-PIA10207.jpgCassiopeia "A": Dissecting the Wake of a Supernova Explosion54 visiteThe elements and molecules that flew out of the Cassiopeia A star when it exploded about 300 years ago can be seen clearly for the first time in this plot of data, called a Spectrum, taken by NASA's SST.
The Spectrum, which was created by splitting light into its basic components, reveals the composition of gas and dust that were synthesized in the explosion. It also provides some of the best evidence yet that stellar explosions, called Supernovae, were a significant source of fresh dust in the very young universe.
Prior to these observations, nobody was certain where this early dust — the same dust that ultimately made its way into future stars, planets and people — came from.
One of the most interesting features of the plot is a bump labeled Cassiopeia A Dust Feature. This bump is actually the signature of a collection of dust composed of proto-silicates, Silicon Dioxide and Iron Oxide. The Spectrum reveals that the brightness of the dust feature is correlated to that of Argon gas (yellow vertical line at left), known to have been expelled and synthesized during the star's explosion. The fact that the dust is associated with the expelled gas, or ejecta, tells astronomers that this Supernova manufactured new dust.
Each of the 3 lines of this plot represents a different layer of the Supernova remnant, with the top yellow and red line being the outermost layer.
Similar correlations between gas and dust are also seen in the middle layer (green line). For example, neon gas correlates with dust composed of Carbon and Aluminum Oxide.MareKromium
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