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M-020-2.jpgM 20 - The "Trifid Nebula" - SST (infrared vision)86 visite"...Iniquum est conlapsis manum non porrigere..."
(Seneca)
"...E' atteggiamento spregevole il non porgere la mano a chi è caduto..."
(14 voti)
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Vega-PIA07218_fig1.jpgVega77 visiteCaption NASA originale:"NASA's Spitzer Space Telescope recently captured these images of the star Vega, located 25 LY away in the constellation Lyra. SST was able to detect the heat radiation from the cloud of dust around the star and found that the debris disc is much larger than previously thought.
This side by side comparison, taken by Spitzer's multiband imaging photometer, shows the warm infrared glows from dust particles orbiting the star at wavelengths of 24 microns (in blue) and 70 microns (in red).
Both images show a very large, circular and smooth debris disc. The disc radius extends to at least 815 Astronomical Units. (One astronomical unit is the distance from Earth to the Sun, which is 150 MKMs or 93 MMs).
Scientists compared the surface brightness of the disc in the infrared wavelengths to determine the temperature distribution of the disc and then infer the corresponding particle size in the disc. Most of the particles in the disc are only a few microns in size. These fine dust particles originate from collisions of embryonic planets near the star at a radius of approximately 90 astronomical units, and are then blown away by Vega's intense radiation. The mass and short lifetime of these small particles indicate that the disc detected by Spitzer is the aftermath of a large and relatively recent collision, involving bodies perhaps as big as the planet Pluto".
(14 voti)
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RCW 38.jpgRCW 38 Star Cluster in Vela89 visite"...Brevis a Natura nobis Vita data est; at memoria bene redditae Vitae sempiternae..."
(Cicerone)
"...Breve è il Tempo (Vita) concessoci dalla Natura; ma eterna è la memoria di una Vita spesa bene..."
(14 voti)
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Craters-Pollack_Crater-00.jpgThe "White Rock" inside Pollack Crater (NASA/JPL/MSSS)87 visiteCaption NASA originale:"White Rock" is a ridged mound that was first seen and informally named "White Rock" in pictures from the Mariner 9 orbiter in 1972. In black-and-white photos, the feature appears much brighter than its surrounding terrain, giving the impression that the material is white. Later analyses of Mariner 9, Viking and MGS data showed that the feature isn't actually white: it is somewhat red and reflects only about 20-25% of the sunlight that falls upon it (a white surface would reflect 100%). Located in Pollack Crater, a 95 Km wide impact basin at 7.9°S, 334.7°W, White Rock is the light-red/orange feature with the rectangular white box drawn on it in the context view. The light-toned material that gives White Rock its name forms steep cliffs with valleys between them covered by dark, windblown, rippled sand".
(14 voti)
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Craters-Lomonosov_Crater.jpgLomonosov Crater in Wintertime81 visiteCaption NASA originale:"On April 20, 2000 (Wintertime on Mars), the Mars Orbiter Camera (MOC) onboard Mars Global Surveyor (MGS) captured this view of a chilly Lomonosov Crater. The rims of the crater appear white because they are covered with wintertime frost. A dark patch just right of center on the crater floor is a sand dune field. Both low-lying ground fogs (fuzzy, patchy areas around the lower perimeter of the crater) and higher cloud layers (fuzzy white arcs seen within the crater and towards the upper right) obscure much of the surface. The Sun, only 12° above the horizon, bathes the scene in a reddish-brown hue. Lomonosov Crater is about 150 Km (93 mi) across and located on the martian northern plains at 64.8° N, 8.8° W. The crater is named for the 18th Century Russian chemist, Mikhail V. Lomonosov (1711-1765)".
(14 voti)
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Comets-Comet_Machholz.jpgComet Machholz74 visiteDa "NASA - Picture of the Day" del 5 Gennaio 2005:"Good views of Comet Machholz are in store for northern hemisphere comet watchers in January. Now making its closest approach to planet Earth, the comet will pass near the lovely Pleiades star cluster on January 7th and the double star cluster in Perseus on January 27th as Machholz moves relatively quickly through the evening sky. Currently just visible to the unaided eye from dark locations, the comet should be an easy target in binoculars or a small telescope. In fact, this telephoto time exposure from January 1, shows Comet Machholz sporting two lovely tails in skies over Colorado, USA. Extending to the left, strands of the comet's ion or gas tail are readily affected by the solar breeze and point away from the Sun. Dust, which tends to trail along the comet's orbit, forms the tail jutting down and to the right".
(14 voti)
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NGC-6293-6.jpgNGC 6293 - The Helix Nebula (HD)78 visite"...Il progresso della vera Scienza si realizza, come la Storia dimostra ampiamente, attraverso salti intuitivi...La Verità, si badi bene, non è sempre dimostrabile..."
Edgar Allan Poe - "Eureka"
(14 voti)
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A - The Sun.jpgThe Sun (and a "Sun-Grazer") from Soho71 visiteSun Data and Statistics
Mass (kg) = 1.989e+30
Mass (Earth = 1) = 332,830
Equatorial radius = 695.000 Km
Equatorial radius (Earth = 1) = 108,97
Mean density (gm/cm^3) = 1,410
Rotational period (days) = from 25 up to 36
Escape velocity = 618,02 Km per second
Luminosity (ergs/sec) = 3.827e33
Magnitude (Vo) = - 26,8
Mean surface temperature = 6.000°C
Age (billion years) = approx. 4.5
Principal chemistry: Hydrogen 92,1%; Helium 7,8%; Oxygen 0,061%; Carbon 0,030%; Nitrogen 0,0084%; Neon 0,0076%; Iron 0,0037%; Silicon 0,0031%; Magnesium 0,0024%; Sulfur 0,0015%; others 0,0015%
(14 voti)
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NGC-6334-00.jpgNGC 6334 - The "Cat-Paw" Nebula74 visite"...Qui sua metitur pondera, ferre potest..."
(Marziale)
"...(solo) chi conosce il proprio peso, riesce a portarlo..."
(14 voti)
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Keyhole Nebula 1 - HST.jpgThe "Keyhole" Nebula - HST139 visite"...Cogitationis poenam nemo patitur..."
(Ulpiano)
"...Nessuno può essere punito per ciò che pensa..."
(14 voti)
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CW Leonis.jpgCW Leonis155 visite"Nemo doctus unquam mutationem consilii incostantiam dixit esse..."
(Cicerone)
"...Nessun uomo saggio ha mai detto che il cambiare idea è sinonimo di volubilità..."
(Voltaire riprese il medesimo concetto nel suo "Candide" con la frase - poi divenuta proverbiale - secondo cui "Soltanto le vacche non cambiano mai idea")
(14 voti)
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ZA-Pluto-NOT.jpgPluto & Charon107 visiteUn esempio di eccellente immagine del Sistema (Binario) costituito da Plutone e Caronte ottenuta direttamente dalla Terra. Certo, non è possibile cogliere dettagli della superficie di Plutone (nè, tantomeno, di Caronte), ma la risoluzione dei due dischi ci pare davvero buona. Plutone è un mondo estremamente lontano e non ha mai costituito un obbiettivo di primario interesse, almeno sino a qualche tempo fa.
Tuttavia, alcune recenti scoperte relative, fra l'altro, alle peculiari caratteristiche della sua orbita, al tipo di relazione - in termini di rotazione - che intercorre fra Plutone stesso e Caronte e, infine, a delle (per ora inspiegabili) variazioni della sua albedo, hanno tutte contribuito ad accendere l'interesse degli Scienziati per questo mondo lontano che, forse, un giorno (fra qualche miliardo di anni, quando il Sole sarà una Gigante Rossa e se l'Umanità - ma ne dubitiamo... - esisterà ancora) potrebbe anche diventare la nostra "casa".
(14 voti)
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