| Ultimi arrivi - 1-Ceres and 4-Vesta |
015-Ceres_and_Vesta.jpg4-Vesta and 1-Ceres from HST (natural colors)59 visiteThese Hubble Space Telescope images of Vesta and 1-Ceres show two of the most massive asteroids in the Asteroid Belt, a Region between Mars and Jupiter.
The images are helping astronomers plan for the Dawn spacecraft’s tour of these hefty asteroids. On July 7, 2007, NASA is scheduled to launch the spacecraft on a 4-year journey to the Asteroid Belt. Once there, Dawn will do some asteroid-hopping, going into orbit around Vesta in 2011 and Ceres in 2015. Dawn will be the first spacecraft to orbit two targets. At least 100.000 asteroids inhabit the Asteroid Belt, a reservoir of leftover material from the formation of our Solar-System planets some 4,6 Billion Years (BY) ago.MareKromiumGiu 29, 2007
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099-DawnTrajectory.jpgThe "Dawn" Mission to 4-Vesta and 1-Ceres57 visiteGerman mathematician Karl F. Gauss calculated from Piazzi's few observations that 1-Ceres circled around the Sun once every 4,6 years or about 4 years, 220 days. The asteroid has a very primitive surface, say scientists on NASA's Dawn mission, which will launch in 2007 and examine 1-Ceres in 2015. The asteroid, like a young planet, contains water-bearing minerals, and possibly a very weak atmosphere and frost. Infrared observations show that the surface is warm.
NASA's HST observed that 1-Ceres' surface has a large spot, which could be a crater formed when another asteroid struck Ceres.
A second explanation may be that the spot is a brighter substance in the asteroid's soil. In July 2001, an object larger than 1-Ceres was found in the vast Kuiper Belt of asteroids, stretching from 30 to 100 AU (2,8 to 9,3 BMs away from the Sun.) This brightest and therefore biggest non-planet space rock, 2001 KX76, could be as big as 1300 Km across.
Per maggiori informazioni sulla Missione "Dawn", visitate il Sito:
http://dawn.jpl.nasa.gov/mission/index.aspAgo 21, 2006
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005-Ceres.jpgMoments of 1-Ceres (2)58 visiteFor 2 centuries it was the largest known rock in the Solar System. The Texas-sized asteroid Ceres, about 930 Km (about 580 miles) across, was the first asteroid ever detected. The space rock was identified in 1801 by astronomer Giuseppe Piazzi, a monk in Sicily and the founding director of the Palermo Astronomical Observatory. He noted over a few nights a shifting point in the sky that wasn't one of the planets, their moons or a star. Thus, he discovered the rock.
After discovering the asteroid, Piazzi was invited to join the Celestial Police, a group of 24 international astronomers looking for what they called "guest planets" between Mars and Jupiter. The Celestial Police noted that the spacing between planets was fairly regular, but that there was a large gap between Mars and Jupiter.
Soon other small bodies were discovered in that region (Pallas in 1802, Juno in 1804 and Vesta in 1807), so the Celestial Police concluded that not just one, but many minor planets had to exist in a Main Asteroid Belt.Ago 21, 2006
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004-Ceres.jpgMoments of 1-Ceres (1)56 visiteDa "NASA - Picture of the Day", del 21 Agosto 2006:"Is 1-Ceres an Asteroid or a Planet?
Although a trivial designation to some, the recent suggestion by the Planet Definition Committee of the International Astronomical Union would have 1-Ceres reclassified from Asteroid to Planet.
A change in taxonomy might lead to more notoriety for the frequently overlooked world. Ceres, at about 1000 Km across, is the largest object in the main Asteroid Belt between Mars and Jupiter. Under the newly proposed criteria, Ceres would qualify as a planet because it is nearly spherical and sufficiently distant from other planets. Pictured above is the best picture yet of Ceres, taken by the Hubble Space Telescope as part of a series of exposures ending in 2004 January. Currently, NASA's Dawn mission is scheduled to launch in 2007 June to explore Ceres and Vesta, regardless of their future designations".Ago 21, 2006
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001-Ceres-alone.jpg1-Ceres from Hubble Space Telescope62 visiteNASA's Hubble Space Telescope took these images of the asteroid 1 Ceres over a 2-hour and 20-minute span, the time it takes the Texas-sized object to complete one quarter of a rotation. One day on Ceres lasts 9 hours.
Hubble snapped 267 images of Ceres as it watched the asteroid make more than one rotation. By observing the asteroid during a full rotation, astronomers confirmed that Ceres has a nearly round body like Earth's. Ceres' shape suggests that its interior is layered like those of terrestrial planets such as Earth. Ceres may have a rocky inner core, an icy mantle, and a thim, dusty, outer crust.
The "Bright Spot" that we see is a mistery: it is (obviously) brighter than its surroundings, but it is still very dark (very low albedo) reflecting only a small portion of Sunlight.Ago 21, 2006
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000-Ceres~0.jpgBig Asteroid or Small Planet?69 visiteLa decisione non è stata ancora presa, ma il problema rimane: 1-Cerere è un "grande" Asteroide o un "piccolo" Pianeta?
A parte tutto, Cerere sembra proprio essere un mondo a sè: le sue dimensioni (circa 930 Km di iametro) sono modeste ma, per un asteroide, alquanto consistenti (Cerere è comunque l'oggetto conosciuto più grande fra le (decine di) migliaia che si trovano in quella regione di spazio compresa fra le orbite di Marte e Giove e che è comunemente conosciuta come "Cintura degli Asteroidi" (o Asteroids' Belt).
Di 1-Cerere si parla molto in questi giorni perchè la IAU (International Astronomical Union) sta valutando se conferire a questo Corpo Celeste lo "status" di Pianeta vero e proprio oppure no, ma la NASA - a quanto si sa - era già da tempo interessata a questo piccolo mondo ed infatti, proprio in questi giorni, è in fase di completamento la preparazione della Sonda "Dawn" (alba) la quale verrà lanciata nel 2007 (forse a Giugno) e che dovrebbe raggiungere e studiare MOLTO da vicino l'asteroide Vesta (nel 2011) e - guarda caso... - proprio 1-Cerere, nel 2015 (l'Anno del possibile - ed auspicabile - "contatto" fra l'altra Sonda New Horizons ed il Doppio Pianeta - o Sistema Binario formato da - Plutone e Caronte.Ago 21, 2006
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024-Vesta.jpg4-Vesta58 visite4-Vesta (o anche solo Vesta) è uno dei tanti asteroidi conosciuti da tantissimo tempo e che sembra, di quando in quando, avvicinarsi (in senso cosmico...) in maniera "perigliosa" al nostro pianeta.
Ma lo sanno tutti - gli Scienziati per primi - che, un giorno o l'altro, da oggi a fra qualche milione di anni nel futuro, qualche "roccia vagante" finirà con l'incrociare la sua orbita con quella della Terra e, quindi, con il produrre - con ogni probabilità - una catastrofe di dimensioni globali la quale sarà causa di sostanziali cambiamenti dell'intero ecosistema.
E' inevitabile, si sa.
Così come si sa che, quando questo momento arriverà, gli ultimi a prenderne atto saranno proprio quelli che, questo Pianeta, lo abitano...Dic 03, 2005
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