| Piú votate - The Universe Inside |
CloudsandClouds.jpgClouds and Clouds116 visiteThe clouds in the foreground are much different than the clouds in the background. In the foreground are a photogenic deck of Earth-based water clouds. The long exposure used to create the above photograph makes the light from the left, reflected from Phoenix, Arizona, USA, appear like a sunset. Far in the distance, however, are star clouds from the disk of our Milky Way Galaxy. Billions of stars like our Sun live there, circling our Galactic center every 200 million years. Contrast between the water clouds and the star clouds has been digitally enhanced. Between the two, visible on the upper right, is the planet Jupiter.
(21 voti)
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CollidingGalaxies-PIA02180_modest.jpgHearts of Glass129 visiteThis artist's concept shows delicate greenish crystals sprinkled throughout the violent core of a pair of colliding galaxies. The white spots represent a thriving population of stars of all sizes and ages. NASA's Spitzer Space Telescope detected more than 20 bright and dusty galactic mergers like the one depicted here, all teeming with the tiny gem-like crystals.
When galaxies collide, they trigger the birth of large numbers of massive stars. Astronomers believe these blazing hot stars act like furnaces to produce silicate crystals in the same way that glass is made from sand. The stars probably shed the crystals as they age, and as they blow apart in supernovae explosions.
At the same time the crystals are being churned out, they are also being destroyed. Fast-moving particles from supernova blasts easily convert silicates crystals back to their amorphous, or shapeless, form.
How is Spitzer seeing the crystals if they are rapidly disappearing? Astronomers say that, for a short period of time at the beginning of galactic mergers, massive stars might be producing silicate crystals faster than they are eliminating them. When our own galaxy merges with the Andromeda galaxy in a few billion years, a similar burst of massive stars and silicate crystals might occur.
Crystal Storm in Distant Galaxy
The graph (see inset above) of infrared data from NASA's Spitzer Space Telescope tells astronomers that a distant galaxy called IRAS 08752+3915 is experiencing a storm of tiny crystals made up of silicates. The crystals are similar to the glass-like grains of sand found on Earth's many beaches.
The data were taken by Spitzer's infrared spectrograph, which splits light open to reveal its rainbow-like components. The resulting spectrum shown here reveals the signatures of both crystalline (green) and non-crystalline (brown) silicates.
Spitzer detected the same crystals in 20 additional galaxies, all belonging to a class called ultraluminous infrared galaxies. These extremely bright and dusty galaxies usually consist of two galaxies in the process of smashing into each other. Astronomers believe massive stars at the hearts of the galaxies are churning out clouds of silicate crystals. This phenomenon may represent a short-lived phase in the evolution of galactic mergers.
(21 voti)
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ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-PIA07997-2-plusRover-A667R1.jpgVirtual Presence in Space109 visiteThis synthetic image of the Spirit MER on top of a rock called "Jibsheet" was produced using "Virtual Presence in Space" technology. Developed at NASA's Jet Propulsion Laboratory, Pasadena, Calif., this technology combines visualization and image-processing tools with Hollywood-style special effects. The image was created using a photorealistic model of the Rover and a false-color mosaic. The size of the Rover in the image is approximately correct and was based on the size of the Rover tracks in the mosaic. The mosaic was assembled from frames taken by the Pan-Cam on the Rover's 489th Martian day (May 19, 2005); see PIA07997.
Because this synthesis provides viewers with a sense of their own "virtual presence" (as if they were there themselves), such views can be useful to mission teams in planning exploration by enhancing perspective and a sense of scale.
(21 voti)
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Titan-Huygens Lens.jpgThe Discovery of Titan86 visiteIl 25 Marzo 1655 l'Astronomo Olandese Christiaan Huygens scopriva "Luna Saturni" - ossia Titano. In questo frame vediamo tutto ciò che resta del telescopio che egli usò (nota: telescopio concepito e costruito in collaborazione con suo fratello, Constantijn Huygens): la lente.
Essa ha un diametro di 57 mm e reca sul bordo la dicitura "X 3 FEBR. MDCLV": si tratta della lunghezza focale e della data di completamento del lavoro (e cioé la "lucidatura" della lente stessa): il 3 February 1655.
Si leggono altresì (in alto) questi versi di Ovidio, "Admovere Oculis Distantia Sidera Nostris".
Un pizzico di romanticismo? No, solo la porzione di un anagramma: un semplice gioco enigmistico (molto comune ai suoi tempi) che riportava alcuni dettagli della sua scoperta (data inclusa).
Decodificato e tradotto l'anagramma di Huygens recita "Una luna orbita intorno a Saturno in 16 giorni e 4 ore".
Oggi sappiamo che il periodo orbitale di Titano è pari a poco meno di 16 giorni.
(21 voti)
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The_Indwellers.jpgThe Indwellers (by Roberto Tremolada)75 visitenessun commentoMareKromium
(20 voti)
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SolarHalo-1-MF.jpgSolar Halo (credits: Dr Marco Faccin)102 visiteUna splendida immagine rappresentante una porzione dell'arco iridescente che forma ci che tecnicamente si chiama "Alone Solare" (Sun o Solar "Halo").
Un "Alone" si verifica quando i raggi del Sole riflettono e rifrangono micro-cristalli di ghiaccio che si trovano in sospensione negli strati medio-alti dell'atmosfera ed il prodotto di questa doppia azione di riflessione e rifrazione lo vediamo nella verificazione di questo affascinante (e certamente non raro) fenomeno il quale, se ci pensate, non altro che un arcobaleno "a tutto tondo".
Un arcobaleno che, anzich mostrarsi nella sua tipica forma di arco o di ponte (completo od incompleto), viene a disegnare un anello perfetto che circonda il disco solare.
Gli "Aloni", dipendendo - come detto - dal verificarsi di fenomeni di riflessione e rifrazione di luce proveniente dallo spazio, possono essere sia Solari, sia Lunari e, in quest'ultimo caso, la Tradizione Popolare li ritiene come dei segni premonitori del prossimo arrivo di una perturbazione.MareKromium
(20 voti)
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Voyagers-02.jpgMessage in a "Bottle"...89 visiteCaption NASA:" Launched 30 years ago, NASA's Voyager 1 and 2 Spacecraft are now respectively 15 and 12,5 BKM from the Sun, equivalent to about 14 and 11,5 Light-Hours distant. Still functioning, the Voyagers are being tracked and commanded through the Deep Space Network. Having traveled beyond the outer planets, they are only the third and fourth spacecraft from planet Earth to escape toward interstellar space, following in the footsteps of Pioneer 10 and 11.
A 12" gold plated copper disk (a phonograph record) containing recorded sounds and images representing human cultures and life on Earth, is affixed to each Voyager - a Message in a Bottle, cast into the Cosmic Sea.
The recorded material was selected by a committee chaired by astronomer Carl Sagan. Simple diagrams on the cover symbolically represent the Spacecraft's origin and give instructions for playing the disk. The exotic construction of the disks should provide them with a long lifetime as they coast through the interstellar space". MareKromium
(20 voti)
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TwentythreeBC.jpg23 Million Years B.C.86 visiteMareKromium
(20 voti)
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SOL694-2P187972203EFFAKBAP0050L7M1~0.jpgDawn on Mars75 visitenessun commento
(20 voti)
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DAWN.jpgThe Dawn of Man112 visiteUn fotogramma storico, dall'indimenticabile "2001 - A Space Odyssey": l'Alba dell'Uomo.
(20 voti)
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MoonoverAntarctica.jpgAlien Landscape (Moon over Antarctica)131 visiteDa "NASA - Picture of the Day" del 25 Novembre 2005:"Last week, the nearly Full Moon set along the Northern Horizon - as seen from Davis Station, Antarctica. The squashed orange pumpkin shape just silhouettes the peak of a distant iceberg in this stunning view.
The Moon's apparently squashed shape is due to atmospheric bending of light or refraction - an effect which is more severe closer to the horizon. Skimming low along the stark features of the frozen landscape, the Moon's lower edge appears noticeably more distorted than the upper limb. Along with about 70 others present at Davis Station, Dr. Jim Behrens had a chance to enjoy the view while studying the ongoing detachment of a large iceberg known as "Loose Tooth".
(20 voti)
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VENUS_MERCURY.jpgMercury and Venus from Earth109 visiteGli elementi sino ad ora individuati in questa "esosfera" sono H, He, O2, Na, K e Ca.
I primi 2 elementi giungono, molto probabilmente, dalla corrente di gas ionizzati proveniente dal Sole (ci che comunemente chiamiamo "Vento Solare"), mentre gli altri 4 potrebbero scaturire direttamente dalle rocce esistenti sulla (o al di sotto della) superficie di Mercurio.
Come? Abbiamo tre ipotesi al riguardo (e tutte ugualmente plausibili):
1) potrebbe trattarsi di una lenta "evaporazione" (!) delle rocce superficiali causata dalla (e, per lunghi periodi di tempo, costante) temperatura elevatissima;
2) fenomeni di "outgassing" simili a quelli che - si dice - accadano anche sulla nostra Luna (si tratta di sacche di gas, imprigionate da ere ed ere al di sotto della superficie del Pianeta, che si liberano improvvisamente - a seguito di eventi sismici o di impatti veri e propri - e fuoriescono, ora incendiandosi e generando delle "flares" - fiammate o fiaccole -, ora disperdendosi nell'ambiente circostante);
(20 voti)
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