| |
The Universe in Super Definition
|
|
|
GALEX Portrait-PIA03295.jpgPortrait of the Universe55 visiteFrom sparkling blue rings to dazzling golden disks, Galaxy Evolution Explorer (Galex) scientists are handing out a collection of their finest galactic treasures at the January 2006 American Astronomical Society meeting in Washington, D.C.
Mined from the mission's Survey of Nearby Galaxies data, these cosmic gems were collected with the telescope's sensitive ultraviolet instruments. The gallery of galaxies has been made into a poster for meeting attendees visiting the mission's booth. Organized from far-ultraviolet to near-ultraviolet bright galaxies, this poster encapsulates the heart of the mission to study how galaxies and star formation rates have changed over the past 10 billion years.
Events in space take millions or billions of years to unfold, which means that astronomers can't watch individual galaxies and stars age over time. Luckily, because the physics of light travel dictates that the farther away an object is from Earth, the longer it takes for its light to travel to us, the universe can be thought of as a time machine. By building telescopes sensitive enough to capture objects that are 10 billion light-years away, astronomers can essentially see an object the way it looked 10 billion years ago. Galex astronomers are using this phenomenon to their advantage by taking snapshots of different galaxies at various distances in space. By comparing portraits of numerous objects at various times in the universe's history, the team can begin to piece together the life cycle of stars and galaxies.
For the poster, Galex scientists organized 196 different nearby galaxies in bins of increasing ultraviolet color. By placing the various snapshots side by side, astronomers can see how galaxies age differently. When viewed in ultraviolet, active star-forming regions in galaxies can be seen as glittering blue structures, while a soft, golden glow indicates the presence of older stars.
The 196 galaxies represented in the poster were selected from more than 1,000 galaxies in the "Ultraviolet Atlas of Nearby Galaxies." So far, the Galex mission has surveyed more than 100 million galaxies.
|
|
GLS-SDSSJ0946+1006.jpgHubble Finds Double "Einstein Ring"53 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.
MareKromium
|
|
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
|
|
Galactic_Center-PIA12074.jpgNewborn Stars found near the Galactic Centre54 visiteThis InfraRed image from NASA's Spitzer Space Telescope shows 3 "baby stars" in the bustling center of our Milky Way galaxy.
The three stars are the first to be discovered in the region — previous attempts to find them were unsuccessful because there is so much dust standing between us and our galaxy's core.
Spitzer was able to find the newborn stars with its sharp InfraRed eyes, which can cut through dust.
The center of our galaxy is a hectic place. It's stuffed with stars, gas and dust. Astronomers have long wondered how stars can form in such chaotic circumstances. While they have known that stars are born there, they weren't able to see the stars forming until now. Astronomers plan to search for more newborn stars in the region, and ultimately learn more about stellar births at the center of the Milky Way.MareKromium
|
|
Galaxies-HST.jpgGalaxies!54 visiteThese images taken with NASA's Hubble Space Telescope are close-up views of four galaxies from a large survey of nearby galaxies.
The galaxies have very different masses and sizes and showcase the diversity of galaxies found in the ANGST study. Although the galaxies are separated by many light-years, they are presented as if they are all at the same distance to show their relative sizes.
The images, taken with Hubble's Advanced Camera for Surveys, reveal rich detail in the stellar populations and in the interstellar dust scattered between the stars. Hubble's sharp views reveal the colors and brightnesses of individual stars, which astronomers used to derive the history of star formation in each galaxy.
In the composite image at the top, NGC 253 is ablaze with the light from thousands of young, blue stars. The spiral galaxy is undergoing intense star formation. The image demonstrates the sharp "eye" of the Advanced Camera, which resolved individual stars. The dark filaments are clouds of dust and gas. NGC 253 is the dominant galaxy in the Sculptor Group of galaxies and it resides about 13 million light-years from Earth.
In the view of the spiral galaxy NGC 300, second from top, young, blue stars are concentrated in spiral arms that sweep diagonally through the image. The yellow blobs are glowing hot gas that has been heated by radiation from the nearest young, blue stars. NGC 300 is a member of the Sculptor Group of galaxies and it is located 7 million light-years away.
The dark clumps of material scattered around the bright nucleus of NGC 3077, the small, dense galaxy at bottom, left, are pieces of wreckage from the galaxy's interactions with its larger neighbors. NGC 3077 is a member of the M81 group of galaxies and it resides 12.5 million light-years from Earth.
The image at bottom, right, shows a swarm of young, blue stars in the diffuse dwarf irregular galaxy NGC 4163. NGC 4163 is a member of a group of dwarf galaxies near our Milky Way and is located roughly 10 million light-years away.
These galaxies are part of a detailed survey called the ACS Nearby Galaxy Survey Treasury program (ANGST). In the census, Hubble observed roughly 14 million stars in 69 galaxies. The survey explored a region called the "Local Volume," and the galaxy distances ranged from 6.5 million light-years to 13 million light-years from Earth. The Local Volume resides beyond the Local Group of galaxies, an even nearer collection of a few dozen galaxies within about 3 million light-years of our Milky Way Galaxy.
The natural-color images were constructed using observations taken in infrared, visible, and blue light. The observations of NGC 253 and NGC 300 were taken in September 2006; of NGC 3077 in November 2006; and of NGC 4163 in December 2006.
Object Names: NGC 253, NGC 300, NGC 3077, NGC 4163
MareKromium
|
|
GasGiant-PIA09117.jpgA "young" Gas-Giant63 visiteCaption NASA:"This is an artist's concept of a hypothetical 10-million-year-old star system. The bright blur at the center is a star much like our Sun. The other orb in the image is a gas-giant planet like Jupiter. Wisps of white throughout the image represent traces of gas.
Astronomers using NASA's Spitzer Space Telescope have found evidence showing that gas-giant planets either form within the first 10 million years of a Sun-like star's life, or not at all. The lifespan for sun-like stars is about 10 billion years.
The scientists came to this conclusion after searching for traces of gas around 15 different Sun-like stars, most with ages ranging from 3 to 30 million years. With the help of Spitzer's Infrared Spectrometer Instrument, they were able to search for relatively warm gas in the inner regions of these star systems, an area comparable to the zone between Earth and Jupiter in our own solar system. They also used ground-based radio telescopes to search for cooler gas in the outer regions of these systems, an area comparable to the zone around Saturn and beyond".MareKromium
|
|
HD-113766-PIA09931.jpgHD 11376653 visiteThis artist's conception shows a binary-star, or two-star, system, called HD 113766, where astronomers suspect a rocky Earth-like planet is forming around one of the stars. At approximately 10 to 16 MY old, astronomers suspect this star is at just the right age for forming rocky planets. The System is located approx. 424 LY away from Earth.
The two yellow spots in the image represent the System's two stars. The brown ring of material circling closest to the central star depicts a huge belt of dusty material, more than 100 times as much as in our asteroid belt, or enough to build a Mars-size planet or larger. The rocky material in the belt represents the early stages of planet formation, when dust grains clump together to form rocks, and rocks collide to form even more massive rocky bodies called planetesimals. The belt is located in the middle of the system's terrestrial Habitable Zone, or the region around a star where liquid water could exist on any rocky planets that might form.
Earth is located in the middle of our sun's terrestrial habitable zone.
Using NASA's Spitzer Space Telescope, astronomers learned that the belt material in HD 113766 is more processed than the snowball-like stuff that makes up infant solar systems and comets, which contain pristine ingredients from the early solar system. However, it is not as processed as the stuff found in mature planets and asteroids. This means that the dust belt is made out of just the right mix of materials to be forming an Earth-like planet. It is composed mainly of rocky silicates and metal sulfides (like fool's gold), similar to the material found in lava flows.
The white outer ring shows a concentration of icy dust also detected in the system. This material is at the equivalent position of the asteroid belt in our solar system, but only contains about one-sixth as much material as the inner ring. Astronomers say it is not clear from the Spitzer observations if anything is occurring in the icy belt, but they believe it could be a source of water later on for the planet that grows from the inner warm ring.
MareKromium
|
|
HD-15115.jpgLopsided debris disk around the young star HD 1511554 visiteThe disk, seen edge-on, is the dense blue line extending from the star to the upper right and lower left of the image. As seen from Earth, the edge-on disk resembles a needle sticking out from the star. The disk appears thicker and longer at upper right than at lower left, evidence of the disk's lopsided structure.
Astronomers think the disk's odd imbalanced look is caused by dust particles following a highly elliptical orbit around the star, which is slightly brighter than the Sun. The lopsidedness may have been caused by planets sweeping up debris in the disk or by the gravity of a nearby star.
Astronomers used an occulting mask on Hubble's Advanced Camera for Surveys to block out the bright starlight so they could see the dim disk. The occulting masks can be seen in the image as the dark circle in the center and the dark bar on the left. The star is behind the central mask.
HD 15115 is among nearly 30 stars that belong to the Beta Pictoris Moving Group. Moving groups are expanded clusters of stars believed to have a common birthplace and age, in this case about 12 million years, that are traveling together loosely through space. HD 15115 is 150 light-years from Earth.
Dusty disks are known to exist around at least 100 stars, but because of the difficulty in observing material close to the brightness of a star, less than a dozen have been studied closely.
Astronomers described the disk as one of the most peculiar debris disks that Hubble has ever imaged. They in fact made follow-up observations with the W.M. Keck Observatory in Hawaii to confirm the disk's presence.
Hubble's Advanced Camera for Surveys snapped the image on July 17, 2006.
MareKromium
|
|
HD-209458b-00.jpgExtra-Solar Planet HD-209458b (1)53 visiteThe powerful vision of NASA's HST has allowed astronomers to study for the first time the layer-cake structure of the atmosphere of a planet orbiting another star. HST discovered a dense upper layer of hot Hydrogen gas where the super-hot planet's atmosphere is bleeding off into space.
The planet, designated HD 209458b, is unlike any world in our Solar System. It orbits so close to its star and gets so hot that its gas is streaming into space, making the planet appear to have a comet-like tail. This new research reveals the layer in the planet's upper atmosphere where the gas becomes so heated it escapes, like steam rising from a boiler.
"The layer we studied is actually a transition zone where the temperature skyrockets from about 1340 deg. Fahrenheit (1000 Kelvin) to about 25.540 degrees (15.000 Kelvin), which is hotter than the Sun " said Gilda Ballester of the University of Arizona in Tucson, leader of the research team.
"With this detection we see the details of how a planet loses its atmosphere."
The findings by Ballester, David K. Sing of the University of Arizona and the Institut d'Astrophysique de Paris, and Floyd Herbert of the University of Arizona will appear Feb. 1 in a letter to the journal Nature.
The Hubble data show how intense ultraviolet radiation from the host star heats the gas in the upper atmosphere, inflating the atmosphere like a balloon. The gas is so hot that it moves very fast and escapes the planet's gravitational pull at a rate of 10,000 tons a second, more than three times the rate of water flowing over Niagara Falls. The planet, however, will not wither away any time soon. Astronomers estimate its lifetime is more than 5 billion years.
The scorched planet is a big puffy version of Jupiter. In fact, it is called a "hot Jupiter," a large gaseous planet orbiting very close to its parent star. Jupiter might even look like HD 209458b if it were close to the Sun, Ballester said.
The planet completes an orbit around its star every 3.5 days. It orbits 4.7 million miles from its host, 20 times closer than the Earth is to the Sun. By comparison, Mercury, the closest planet to our Sun, is 10 times farther away from the Sun than HD 209458b is from its star. Unlike HD 209458b, Mercury is a small ball of iron with a rocky crust.
|
|
HD-209458b-01.jpgExtra-Solar Planet HD-209458b (2)53 visiteAlthough HD 209458b does not have a twin in our Solar System, it has plenty of relatives beyond our Solar System. About 10 to 15% of the more than 200 known extrasolar planets are hot Jupiters. A recent HST survey netted 16 hot Jupiter candidates in the central region of our Milky Way Galaxy, suggesting that there may be billions of these gas-giant star huggers in our galaxy.
HD 209458b is one of the most intensely studied extrasolar planets because it is one of the few known alien worlds that can be seen passing in front of, or transiting, its star, causing the star to dim slightly. In fact, the gas giant is the first such alien world discovered to transit its star.
HD 209458b is 150 LY from Earth, in the Constellation of Pegasus.
The planet's transits allow astronomers to analyze the structure and chemical makeup of the gas giant's atmosphere by sampling the starlight that passes through it. The effect is similar to finding fingerprints on a window by watching how sunlight filters through the glass.
Previous HST observatoins revealed Oxygen, Carbon and Sodium in the planet's atmosphere, as well as a huge Hydrogen upper atmosphere with a comet-like tail. These landmark studies provided the first detection of the chemical makeup of an extrasolar planet's atmosphere.
Additional observations by NASA's SST captured the infrared glow from the planet's hot atmosphere.
The new study by Ballester and her team is based on an analysis of archival observations made in 2003 with HST's Imaging Spectrograph by David Charbonneau of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Ballester's team analyzed spectra from hot hydrogen atoms in the planet's upper atmosphere, a region not studied by Charbonneau's group.
|
|
HD-80606b.jpgA Dangerous Summer on HD 80606b54 visiteOn the distant planet HD 80606b, Summers might be dangerous.
Hypothetic life forms floating in HD 080606b's Atmosphere or lurking on one of its (presently hypothetical) moons might fear the 1500 Kelvin Summer heat, which is hot enough not only to melt Lead but also Nickel. Although Summers are defined for Earth by the daily amount of Sunlight, Summers on HD 80606b are more greatly influenced by how close the Planet gets to its Parent Star.
HD 80606b, about 200 LY distant, has the most elliptical orbit of any planet yet discovered. In comparison to the Solar System, the distance to its Parent Star would range from outside the orbit of Venus to well inside the orbit of Mercury.
In this sequence, the night side of HD 80606b is computer simulated as it might glow in infrared light in nearly daily intervals as it passed the closest point in its 111-day orbit around its Parent Star.
The simulation is based on infrared data taken in late 2007 by the Spitzer Space Telescope.
Nota Lunexit (a chi interessa): la Formula di Conversione per le Temperature espresse in Kelvin in Temperature espresse in Celsius è la seguente: T° Celsius = T Kelvin - 273,15
Nel nostro caso di specie, quindi, la temperatura diurna media Estiva di HD 80606b dovrebbe essere pari a circa 1227° C.
Un bel "tepore", davvero...MareKromium
|
|
HD149026b_-PIA09378.jpgHot, Black and (relatively) Close...55 visiteThis artist's concept illustrates the hottest planet yet observed in the universe.
The scorching ball of gas, a "Hot Jupiter" called HD 149026b, is a sweltering 3700° Fahrenheit (2040° Celsius) -- about 3 times hotter than the rocky surface of Venus, the hottest planet in our Solar System. The Planet is so hot that astronomers believe it is absorbing almost all of the heat from its star and reflecting very little to no light. Objects that reflect no sunlight are black. Consequently, HD 149026b might be the blackest known planet in the universe, in addition to the hottest.
The temperature of this dark and balmy planet was taken with NASA's SST. While the planet reflects no visible light, its heat causes it to radiate a little visible and a lot of infrared light. Spitzer, an infrared observatory, was able to measure this infrared light through a technique called secondary eclipse. HD 149026b is what is known as a transiting planet, which means that it crosses in front of in front of and passes behind its star -- the secondary eclipse -- when viewed from Earth. By determining the drop in total infrared light that occurs when the planet disappears, astronomers can figure out how much infrared light is coming from the planet alone.
The Spitzer observations of HD 149026b also suggest a hot spot in the middle of the side of the planet that always faces its star. Even though the planet is black, the spot would glow like a black lump of charcoal. HD 149026b is thought to be tidally locked, just as our moon is to Earth, such that one side of the planet is perpetually baked under the heat of its sun.
Astronomers think that HD 149026b is probably blazing hot on its sunlit side, and much cooler on its dark side. A similar phenomenon was observed previously by Spitzer for the planet Upsilon Andromedae b.
In the case of both planets, heat is not being evenly distributed across their surfaces. This is the opposite of what happens on Jupiter, where temperature differences are minimal all around.
HD 149026b is located 256 light-years away in the constellation Hercules. It is the smallest known transiting planet, with a size similar to Saturn's and a suspected dense core 70 to 90 times the mass of Earth. It speeds around its star every 2.9 days.
MareKromium
|
|
| 157 immagini su 14 pagina(e) |
|
3 | |
|
|
|
|
|
|
|
|
|
|
