| |
| Piú viste - The Universe in Super Definition |
Black_Hole-PIA13275.jpgDisk around a massive "Baby Star"?66 visiteCaption NASA:"Astronomers have obtained the first clear look at a Dusty Disk closely encircling a massive "Baby Star", providing direct evidence that massive stars do form in the same way as their smaller brethren -- and closing an enduring debate.
This artist's concept shows what such a massive Disk might look like. The Flared Disk extends to about 130 times the Earth-Sun distance (such as 130 UA), and has a mass similar to that of the star, roughly twenty times the Sun. The inner parts of the Disk are shown to be devoid of dust).
Nota Lunexit: questa è dunque, according to NASA, la rappresentazione artistica di un Disco di polveri e materiale Primordiale posizionato attorno ad una giovane stella supermassiva.
Può anche darsi, ma secondo noi la NASA ha scelto male l'immagine da abbinare alla caption e questa, in effetti, è la rappresentazione artistica di un Buco Nero, oppure di un Quasar.
Chissà...MareKromium
|
|
M-087.jpgM 87 - Elliptical Galaxy64 visiteElliptical galaxy M 87 is a type of galaxy that looks much different than our own Milky Way Galaxy. Even for an elliptical galaxy, though, M 87 is peculiar. M 87 is MUCH bigger than an average galaxy, appears near the center of a whole cluster of galaxies (known as the Virgo Cluster) and shows an unusually high number of globular clusters. These globular clusters are visible as faint spots surrounding the bright center of M 87. In general, elliptical galaxies contain similar numbers of stars as spiral galaxies, but are ellipsoidal in shape (spirals are mostly flat), have no spiral structure and little gas and dust.
|
|
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
|
|
Asteroid-PIA11735.jpgUnsuccesful crossing of the Roche Limit62 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
|
|
M 84.jpgM 84 - Galactic nucleus and... a Black Hole?61 visiteIs this "almost artistic graph" the signature of a supermassive Black Hole in the center of distant galaxy M 84 (based on data recorded by Hubble's new Space Telescope Imaging Spectrograph (STIS)?. The presence of a Black Hole can also be revealed by watching matter fall into it.
In fact, material spiraling into a Black Hole would find its speed increasing at a drastic rate. These extreme velocity increases provide what we call a 'signature' of the Black Hole's presence. The STIS data show that radiation from approaching gas, shifted to blue wavelengths left of the centerline, is suddenly redshifted to the right of center indicating a rapidly rotating disk of material near the galactic nucleus. The resulting sharp S-shape is effectively the signature of a Black Hole estimated to contain at least 300 million solar masses. Now the question is: do all galaxies have central Black Holes? And, if "Yes", then "Why"?
|
|
M 42 - HST-1.jpgOrion's Nebula an LL Orionis (the "Bow-Shock" effect)61 visiteThis close-up of cosmic clouds and stellar winds features LL Orionis interacting with the Orion Nebula flow. Adrift in Orion's stellar nursery and still in its formative years, variable star LL Orionis produces a wind more energetic than the wind from our own middle-aged Sun.
As the fast stellar wind runs into slow moving gas, a shock front is formed, analogous to the bow wave of a boat moving through water or a plane traveling at supersonic speed.
The small and graceful structure just above and left of center, is LL Ori's "Cosmic Bow Shock", measuring about 1/2 a LY across.
The slower gas is flowing away from the Orion Nebula's hot central star cluster, the Trapezium, located off the upper left corner of the picture.
In 3D, LL Ori's wrap-around shock front is shaped like a bowl that appears brightest when viewed along the bottom edge.
The beautiful picture is part of a large mosaic view of the complex stellar nursery in Orion, filled with a myriad of fluid shapes associated with star formation.
|
|
PIA13120.jpgWISE Eyes...61 visiteThis frame shows the progress of the WISE All-Sky Survey at the present time. WISE, or NASA's Wide-field InfraRed Survey Explorer, is perched up in the sky like a wise, old owl, scanning the whole sky one-and-a-half times in IR Light. On July 17, 2010, it will have completed its first scan of the entire sky, delivering more than one million image frames so far.
This map is filled in to show the sky areas that WISE scanned over time. Red indicates regions with the greatest coverage, and blue the least. The Poles received the most coverage because WISE orbits Earth around the Poles, scanning out strips of sky as Earth moves around the Sun. The red lines between the Poles show areas that received extra coverage because of the mission's strategy to avoid the Moon.
When the moon is in WISE's field of view, about twice every month, the space telescope captures the region it blocks, by first moving ahead of the moon and then behind it. This results in overlapped coverage for certain slices of sky. During this first all-sky scan, every point was covered by at least eight image frames.
The Infrared Astronomical Satellite was a joint project of the United States, United Kingdom and the Netherlands.
The Two-Micron All-Sky Survey was a project of NASA; the National Science Foundation; the University of Massachusetts, Amherst, and the California Institute of Technology, Pasadena, California.MareKromium
|
|
M 55.jpgM 55 - Globular Star Cluster60 visiteM 55 is a large Globular Star Cluster of around 100.000 stars. Only 20.000 LY away in the constellation Sagittarius, M 55 appears to earth-bound observers to be nearly 2/3 the size of the full Moon. Globular star clusters like M 55 roam the halo of our Milky Way Galaxy as gravitationally bound populations of stars known to be much older than stellar groups found in the galactic disk. Astronomers who make detailed studies of globular cluster stars can accurately measure the cluster ages and distances. Their results ultimately constrain the age of the Universe and provide a fundamental rung on the astronomical distance ladder.
|
|
Rho_Ophiuci-PIA10181.jpgRho Ophiuci60 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, and its multiband imaging photometer, best for detecting cooler materials. Blue represents 3.6-micron light; green shows light of 8 microns; and red is 24-micron light. 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 red 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.
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 heating of dust by bright young stars near the right edge of the cloud. Fainter multi-hued diffuse emission fills the image. The color of the nebulosity depends on the temperature, composition and size of the dust grains. 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 24 microns pierces through dust easily, this dark filament is incredibly opaque, appearing dark even at the longest wavelengths in the image.
MareKromium
|
|
TwoSuns-PIA09229.jpgTwin Suns, Planets and Asteroids59 visiteThis artist's image depicts a faraway Solar System like our own -- except for one big difference: planets and asteroids circle around not one, but two Suns. NASA's Spitzer Space Telescope found evidence that such Solar Systems might be common in the Universe. Spitzer did not see any planets directly, but it detected dust that is kicked up from disks like this one. The disks were spotted circling all the way around several double, or binary, stars, some of which were closer together than Earth is to our sun. In fact, Spitzer found more disks in orbit around close-knit binary stars than single stars. This could mean that planets prefer two parent stars to one, but more research is needed to figure out exactly what's going on.
|
|
The_Missing_Matter.jpgWhat is "missing" in the Universe?59 visiteIn the May 20, 2008, issue of The Astrophysical Journal, Charles Danforth and Mike Shull (University of Colorado, Boulder) report on NASA's Hubble Space Telescope and NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) observations taken along sight-lines to 28 quasars. Their analysis represents the most detailed observations to date of how the intergalactic medium looks within about 4 Billion Light-Years of Earth.
The astronomers say they have definitively found about half of the missing normal matter, called "Baryons", in the space between the galaxies.
This illustration shows how the Hubble Space Telescope searches for missing Baryons, by looking at the light from quasars several Billion Light-Years away. Imprinted on that light are the spectral fingerprints of the missing ordinary matter that absorbs the light at specific frequencies (shown in the colorful spectra at right).
The missing Baryonic Matter helps trace out the structure of intergalactic space, called the "Cosmic Web".MareKromium
|
|
30-Doradus_and_R-136.jpg30 Doradus and R-13659 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
|
|
| 157 immagini su 14 pagina(e) |
|
3 | |
|
|
|
|
|
|
|
|
|
|
