|
|
LLM-Itokawa.jpg25143-Itokawa53 visiteA Japanese spacecraft has provided one of the best arguments yet in favor of a conception of asteroids which was pioneered by PSI (Planet Science Institute) scientists Don Davis and Clark Chapman in the late 70's. The evidence comes in startling closeup pictures of the tiny asteroid 25143-Itokawa, photographed by the Japanese Hayabusa spacecraft during a two-month encounter in late 2005. The asteroid illustrates the concept of a "Rubble-Pile" asteroid, which is composed of a mixture of boulders and dust gravitationally bound together.
The scientific results, recently highlighted in the journal Science, show that, unlike other asteroids recently imaged by spacecraft, which are mostly rounded and potato-like, dotted by craters, and with a few scattered boulders on the surface, Itokawa appears to be composed of massive splinter-like boulders protruding from a matrix of smaller fragments.
The largest boulders sticking out of the body appear to be some tens of meters across.
The Hayabusa science team includes PSI scientists Paul Abell and Bob Gaskell, and PSI affiliate scientists Hirdy Miyamoto and Faith Vilas.
|
|
![Comets-Halley-Giotto-86hc145[1].jpg](albums/userpics/10008/small_Comets-Halley-Giotto-86hc145%5B1%5D.jpg "Nome del file=Comets-Halley-Giotto-86hc145[1].jpg
Dimensione del file=634KiB
Dimensioni=1756x1788
Aggiunta il=%17 %374 %2006")
Comets-Halley-Giotto-86hc145[1].jpgThe "Halley Comet", from Giotto52 visitenessun commento
|
|
Eris.jpgAnother "Dwarf Planet" with satellite: 136199-Eris and Dysnomia53 visiteDa "NASA - Picture of the Day" del 18 Settembre 2006:"Is Pluto the largest Dwarf Planet? No! Currently, the largest known dwarf planet is 136199-Eris, renamed last week from 2003 UB313. Eris is just slightly larger than Pluto, but orbits as far as twice Pluto's distance from the Sun. Eris is shown above in an image taken by a 10-meter Keck Telescope from Hawaii, USA.
Like Pluto, Eris has a moon, which has been officially named by the International Astronomical Union as (136199) Eris I (Dysnomia). Dysnomia is visible above just to the right of Eris. Dwarf Planets Pluto and Eris are Trans-Neptunian Objects that orbit in the Kuiper belt of objects past Neptune. Eris was discovered in 2003, and is likely composed of frozen water-ice and methane. Since Pluto's recent demotion by the IAU from planet to dwarf planet status, Pluto has recently also been given a new numeric designation: 134340-Pluto.
Currently, the only other officially designated Dwarf Planet is 1-Ceres".
|
|
Comets-Comet_SWAN-3.jpgComet "SWAN"52 visiteDa "NASA - Picture of the Day" del 4 Ottobre 2006:"A newly discovered comet has brightened enough to be visible this week with binoculars. The picturesque comet is already becoming a favored target for northern sky imagers. Pictured above just last week, Comet SWAN showed a bright blue-green coma and an impressive tail. Comet C/2006 M4 (SWAN) was discovered in June in public images from the Solar Wind Anisotropies (SWAN) instrument of NASA and ESA's Sun-orbiting SOHO spacecraft. Comet SWAN, near magnitude six, will be visible with binoculars in the North-Eastern sky not far from the Big Dipper over the next few days before dawn. The comet is expected to reach its peak brightness this week. Passing its closest to the Sun two days ago, Comet SWAN and will be at its closest to the Earth toward the end of this month. Comet SWAN's unusual orbit appears to be hyperbolic, meaning that it will likely go off into interstellar space, never to return".
|
|
Comets-Comet_SWAN-0.jpgComet SWAN82 visiteDa "NASA - Picture of the Day", del 19 Ottobre 2006:" This cosmic portrait recorded October 9th features the lovely blue-green coma of Comet SWAN posing with spiral galaxy NGC 5005 in the northern constellation Canes Venatici. At the time the comet (center) was in the close foreground, a mere 9 LM (Light-Minutes) from planet Earth, with the galaxy a more substantial 60 million LY (Light-Years) distant. Not actually related to a bird, Comet SWAN (C/2006 M4) was so named as it was first spotted in image data from the SWAN (Solar Wind ANisotropies) camera aboard the Sun-staring SOHO spacecraft. Having rounded the Sun, this comet is headed for interstellar space, but first it will make its closest approach to Earth on October 24. With binoculars, northern hemisphere observers can now spot the comet above the northwestern horizon, near the handle of the Big Dipper in the early evening sky".
|
|
Comets-Comet_SWAN-2.jpgComet SWAN52 visiteCaption NASA originale:"Near its closest approach to planet Earth, comet SWAN (C/2006 M4) brightened unexpectedly earlier this week, becoming visible to naked-eye observers under dark night skies. Telescopic observers also noticed dramatic changes in the comet's colorful coma and tail, seen in this view recorded on October 25th, 2006.
To make the picture, images totaling eight minutes in exposure time were stacked and centered on the comet as it moved relatively quickly against the background star field. The picture covers about 1 of the sky.
Northern Hemisphere observers should still find the comet an easy binocular target in the early evening, even though moonlight will increase the overall sky brightness in the next few days.
Look toward the North-Western horizon and the Constellation Hercules".
|
|
Comets-Comet_SWAN-1.jpgThe SWAN Comet52 visiteComet SWAN, which unexpectedly flared up to naked-eye brightness, has been showing detail in its ion tail that might be described as ghostly. The ion tail is made of ionized gas, energized by ultraviolet light from the Sun and pushed outward by the solar wind. The solar wind itself is quite structured and sculpted by the Sun's complex and ever changing magnetic field. Following the wind, structure in Comet SWAN's tail can be seen to move outward from the Sun even alter its wavy appearance over time.
The blue color of the ion tail is dominated by recombining Carbon Monoxide atoms. The color of the coma surrounding the head of the comet is tinged green by slight amounts of the molecule cyanogen. This week (6-13 Nov. 2006) may be the best remaining chance for Northern Hemisphere observers to see the fading interplanetary snowball. SWAN has now past both the Earth and the Sun and will fade as it moves away from the Earth and heads out into the vast space between the stars.
|
|
Comets-Comet_Machholtz.jpgComet Machholtz, from SST52 visitenessun commentoMareKromium
|
|
McNaught-04.jpgComet McNaught (5)53 visiteCaption NASA:"The brightest comet of recent decades was a surprising first sight for a new camera in space.
The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument onboard the Solar TErrestrial RElations Observatory (STEREO) satellite had just opened up on January 11, 2007, when it snapped the above image of Comet McNaught. Visible was a spectacular view of the ion tail of Comet McNaught being swept away from the Sun by the solar wind in filamentary rays. The comet tail is seen to extend at least seven degrees across the above image, while the central coma is so bright it saturates. Comet McNaught is now reportedly so bright that it is visible even in broad daylight by blocking out the Sun with your hand.
Comet McNaught has rounded the Sun and will slowly fade away for observers in Earth's Southern Hemisphere as it recedes from the Sun".
|
|
McNaught-03.jpgComet McNaught (4)53 visiteCaption NASA:"This past weekend Comet McNaught peaked at a brightness that surpassed even Venus. Fascinated sky enthusiasts in the Earth's Northern Hemisphere were treated to an instantly visible comet head and a faint elongated tail near sunrise and sunset. Recent brightness estimates had Comet McNaught brighter than magnitude - 5 (minus five) over this past weekend, making it the brightest comet since Comet Ikeya-Seki in 1965, which was recorded at - 7 (minus seven). The Great Comet of 2007 reached its brightest as it rounded the Sun well inside the orbit of Mercury. Over the next week Comet McNaught will begin to fade as it moves south and away from the Sun. The unexpectedly bright comet should remain visible to observers in the Southern Hemisphere with unaided eyes for the rest of January.
The above image, vertically compressed, was taken at sunset last Friday from mountains above Catalonia, Spain".
|
|
McNaught-02.jpgComet McNaught (3)53 visiteCaption NASA:" Bright Comet McNaught (C/2006 P1) graced the twilight this week, seen by many and often described with superlatives. Watching the skies over Krakow, Poland, Andrzej Sawow recorded this view on Wednesday - with an ordinary handheld digital camera. He notes that "... astronomy is really for everyone who loves to look at the night sky. And fortunately (sometimes) the sky generously rewards its observer". Now very close to the Sun, Comet McNaught (along with Mercury) is visible in realtime images from the SOHO spacecraft. Otherwise, skywatchers will find the comet hard to see this weekend. But southern hemisphere observers could be rewarded next week as Comet McNaught begins to climb higher in southern skies".
|
|
McNaught-01.jpgComet McNaught (2)53 visiteCaption NASA:"The brightest comet in decades is unexpectedly now visible. The most optimistic predictions have Comet McNaught (C/2006 P1) shortly becoming one of the brightest comets of the past century. For the next few days, its short tail and bright coma can be spotted with the unaided eye close to the Sun and near the horizon in both evening and morning skies. This dramatic picture of the comet shining through cloudy skies was taken near sunset on January 7, 2007, from Bad Mergentheim, Germany".
|
|
| 271 immagini su 23 pagina(e) |
 |
|
|
|
|
11 | |
|
|
|
|
