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| Piú votate - The Universe in Super Definition |
Black Hole-PIA08697_fig1.jpgBlack Holes56 visiteThis diagram illustrates research from NASA's Galaxy Evolution Explorer showing that black holes -- once they reach a critical size -- can put the brakes on new star formation in elliptical galaxies.
In this graph, galaxies and their supermassive black holes are indicated by the drawings (the black circle at the center of each galaxy represents the black hole). The relative masses of the galaxies and their black holes are reflected in the sizes of the drawings. Blue indicates that the galaxy has new stars, while red means the galaxy does not have any detectable new stars.
The Galaxy Evolution Explorer observed the following trend: the biggest galaxies and black holes (shown in upper right corner) are more likely to have no observable star formation (red) than the smaller galaxies with smaller black holes. This is evidence that black holes can create environments unsuitable for stellar birth.
The white line in the diagram illustrates that, for any galaxy no matter what the mass, its black hole must reach a critical size before it can shut down star formation.
(8 voti)
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N76-PIA08516-2.jpgThe "N 76 Nebula"54 visiteThe supernova remnant1E0102.2-7219 sits next to the Nebula N76 in a bright, Star-Forming Region of the Small Magellanic Cloud, a satellite galaxy to our Milky Way galaxy located about 200.000 LY from Earth. A Supernova Remnant is made up of the messy bits and pieces of a massive star that exploded, or went Supernova. This image shows glowing dust grains in three wavelengths of infrared radiation: 24 microns (red) measured by the Multiband Imaging Photometer aboard NASA's Spitzer Space Telescope; and 8.0 microns (green) and 3.6 microns (blue) measured by Spitzer's infrared array camera. The red bubble is a dust envelope around the supernova remnant E0102, which is being heated by the shock wave created in the explosion of the remnant's massive progenitor star some 1,000 years ago. Most of the blue stars are in the Small Magellanic Cloud, though some are in our own galaxy.
(8 voti)
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Stephan_s Quintet-PIA02587.jpgStephan's Quintet55 visiteThis false-color composite image of the Stephan's Quintet galaxy cluster clearly shows one of the largest shock waves ever seen (green arc). The wave was produced by one galaxy falling toward another at speeds of more than one million miles per hour. The image is made up of data from NASA's Spitzer Space Telescope and a ground-based telescope in Spain.
Four of the five galaxies in this picture are involved in a violent collision, which has already stripped most of the hydrogen gas from the interiors of the galaxies. The centers of the galaxies appear as bright yellow-pink knots inside a blue haze of stars, and the galaxy producing all the turmoil, NGC7318b, is the left of two small bright regions in the middle right of the image. One galaxy, the large spiral at the bottom left of the image, is a foreground object and is not associated with the cluster.
The titanic shock wave, larger than our own Milky Way galaxy, was detected by the ground-based telescope using visible-light wavelengths. It consists of hot hydrogen gas. As NGC7318b collides with gas spread throughout the cluster, atoms of hydrogen are heated in the shock wave, producing the green glow.
Spitzer pointed its infrared spectrograph at the peak of this shock wave (middle of green glow) to learn more about its inner workings. This instrument breaks light apart into its basic components. Data from the instrument are referred to as spectra and are displayed as curving lines that indicate the amount of light coming at each specific wavelength.
The Spitzer spectrum showed a strong infrared signature for incredibly turbulent gas made up of hydrogen molecules. This gas is caused when atoms of hydrogen rapidly pair-up to form molecules in the wake of the shock wave. Molecular hydrogen, unlike atomic hydrogen, gives off most of its energy through vibrations that emit in the infrared.
This highly disturbed gas is the most turbulent molecular hydrogen ever seen. Astronomers were surprised not only by the turbulence of the gas, but by the incredible strength of the emission. The reason the molecular hydrogen emission is so powerful is not yet completely understood.
Stephan's Quintet is located 300 million light-years away in the Pegasus constellation.
This image is composed of three data sets: near-infrared light (blue) and visible light called H-alpha (green) from the Calar Alto Observatory in Spain, operated by the Max Planck Institute in Germany; and 8-micron infrared light (red) from Spitzer's infrared array camera.
(8 voti)
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NGC-2207-PIA08097.jpgNGC 2207 and IC 2163: Colliding Galaxies54 visiteThese shape-shifting galaxies have taken on the form of a giant mask. The icy blue eyes are actually the cores of two merging galaxies, called NGC 2207 and IC 2163, and the mask is their spiral arms. The false-colored image consists of infrared data from NASA's Spitzer Space Telescope (red) and visible data from NASA's Hubble Space Telescope (blue/green).
NGC 2207 and IC 2163 met and began a sort of gravitational tango about 40 million years ago. The two galaxies are tugging at each other, stimulating new stars to form. Eventually, this cosmic ball will come to an end, when the galaxies meld into one. The dancing duo is located 140 million light-years away in the Canis Major constellation.
The infrared data from Spitzer highlight the galaxies' dusty regions, while the visible data from Hubble indicates starlight. In the Hubble-only image (not pictured here), the dusty regions appear as dark lanes.
The Hubble data correspond to light with wavelengths of .44 and .55 microns (blue and green, respectively). The Spitzer data represent light of 8 microns.
(8 voti)
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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"?
(8 voti)
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COROT7b-ESO.jpgExo-Planet CoRoT-7b55 visiteHow similar is exoplanet CoRoT-7b to Earth?
The newly discovered Extra-Solar Planet is the closest physical match yet, with a mass about five Earths and a radius of about 1,7 Earths. Also, the home star to CoRoT-7b, although 500 LY distant, is very similar to our Sun.
Unfortunately, the similarities likely end there, as CoRoT-7b orbits its home star well inside the orbit of Mercury, making its year last only 20 hours, and making its peak temperature much hotter than humans might find comfortable. CoRoT-7b was discovered in February by noting a predictable slight decrease in the brightness of its parent star.
Pictured above, an artist's depiction shows how CoRoT-7b might appear in front of its Parent Star. The composition of CoRoT-7b remains unknown, but given its size and mass, it cannot be a gas giant like Jupiter, and is very likely composed predominantly of rock. Future observations will likely narrow the composition of one of the first known rocky planets discovered outside of our Solar System.MareKromium
(7 voti)
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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
(7 voti)
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NGC-1569.jpgStarburst Galaxy NGC 156954 visiteThis image taken by NASA's Hubble Space Telescope showcases the brilliant core of one of the most active galaxies in our local neighborhood. The entire core is 5,000 light-years wide.
The galaxy, called NGC 1569, sparkles with the light from millions of newly formed young stars. NGC 1569 is pumping out stars at a rate that is 100 times faster than the rate observed in our Milky Way Galaxy. This frenzied pace has been almost continuous for the past 100 million years.
The core's centerpiece is a grouping of three giant star clusters, each containing more than a million stars. (Two of the clusters are so close they appear as one grouping.) The clusters reside in a large, central cavity. The gas in the cavity has been blown out by the multitude of massive, young stars that already exploded as supernovae. These explosions also triggered a violent flow of gas and particles that is sculpting giant gaseous structures. The sculpted structure at lower right is about 3,700 light-years long.
Huge bubbles of gas, such as the two at left, appear like floating islands. The largest bubble is about 378 light-years wide and the smallest 119 light-years wide. They are being illuminated by the radiation from the bright, young stars within them. Some of those stars are peaking through their gaseous cocoons.
The biggest and brightest objects surrounding the core are stars scattered throughout our Milky Way Galaxy. In contrast, the thousands of tiny white dots in the image are stars in the halo of NGC 1569. The galaxy is 11 million light-years from Earth.
A new analysis of NGC 1569 shows that it is one and a half times farther from Earth than astronomers previously thought. The extra distance places the galaxy in the middle of a group of about 10 galaxies centered on the spiral galaxy IC 342. Gravitational interactions among the group's galaxies may be compressing gas in NGC 1569 and igniting the star-birthing frenzy.
MareKromium
(7 voti)
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M-081-PIA09579.jpgThe M 81 Galaxy is "Pretty in Pink"53 visiteThe perfectly picturesque Spiral Galaxy known as Messier 81, or M81, looks sharp in this new composite from NASA's Spitzer (SST) and Hubble Space Telescopes (HST) and NASA's Galaxy Evolution Explorer.
M81 is a "grand design" spiral galaxy, which means its elegant arms curl all the way down into its center. It is located about 12 MLY away in the Ursa Major Constellation and is one of the brightest galaxies that can be seen from Earth through telescopes.
The colors in this picture represent a trio of light wavelengths: blue is ultraviolet light captured by the Galaxy Evolution Explorer; yellowish white is visible light seen by Hubble; and red is infrared light detected by Spitzer.
The blue areas show the hottest, youngest stars, while the reddish-pink denotes lanes of dust that line the spiral arms. The orange center is made up of older stars. MareKromium
(7 voti)
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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
(7 voti)
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YoungStar-PIA09266.jpgThe "O"-Star68 visite"The further on the edge, the hotter the intensity," sings Kenny Loggins in "Danger Zone," a song made famous by the movie "Top Gun." The same words ring true for young, cooler stars like our sun that live in the danger zones around scorching hot stars, called O-stars. The closer a young, maverick star happens to be to a super hot O-star, the more likely its burgeoning planets will be blasted into space.
This artist's animation illustrates how this process works. The movie begins by showing an O-star in a murky star-forming region. It then pans out to show a young, cooler star and its swirling disk of planet-forming material. Disks like this one, called protoplanetary disks, are where planets are born. Gas and dust in a disk clumps together into tiny balls that sweep through the material, growing in size to eventually become full-grown planets.
The young star happens to lie within the "danger zone" around the O-star, which means that it is too close to the hot star to keep its disk. Radiation and winds from the O-star boil and blow away the material, respectively. This process, called photoevaporation, is sped up here but takes anywhere from 100,000 to about 1,000,000 years. Without a disk, the young star will not be able to produce planets.
Our own sun and its suite of planets might have grown up on the edge of an O-star's danger zone before migrating to its current, spacious home. However, we know that our young sun didn't linger for too long in any hazardous territory, or our planets, and life, wouldn't be here today.
NASA's Spitzer Space Telescope surveyed the danger zones around five O-stars in the Rosette nebula. It was able to determine that the zones are spheres with a radius of approximately 1.6 light-years, or 10 trillion miles.
MareKromium
(7 voti)
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The_Evaporating_Planet.jpgWater Claimed in Evaporating Planet HD 209458b57 visitePlanet HD 209458b is evaporating. It is so close to its parent star that its heated atmosphere is simply expanding away into space. Some astronomers studying this distant planetary system now believe they have detected water vapor among the gases being liberated. This controversial claim, if true, would mark the first instance of planetary water beyond our Solar System, and indicate anew that life might be sustainable elsewhere in the universe. HD 209458b is known as a hot Jupiter type system because it involves a Jupiter-type planet in a Mercury-type orbit. Although spectroscopic observations from the Hubble Space Telescope are the basis for the water detection claim, the planetary system is too small and faint to image. Therefore, an artist's impression of the HD 209458b system is shown above. Research into the atmospheric composition of HD 209458b and other extrasolar planets is continuing.MareKromium
(7 voti)
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