| Piú viste - Asteroids and Comets |
LL-Itokawa.jpgTarget Marker located on Itokawa (1)56 visiteOn Nov. 26, spacecraft "Hayabusa" challenged the second trial to execute landing on and sampling from the asteroid Itokawa. Hayabusa team confirmed the whole process to have been implemented and it is sure that the team succeeded in sampling materials on the surface of an asteroid for the first time in World History. Detailed data to be sent from Hayabusa will further verify the sampling.
Hayabusa started its last descent phase from the altitude of 1 km above Itokawa by command from Earth around 10:00 p.m. Nov.25 (JST). It was followed by starting the vertical descent from around 6:00 a.m. Nov.26., and, around 6:25 a.m., Sagamihara Deep Space Control Room sent a command to continue the descent.
Hayabusa challenged landing and sampling operation after a hovering phase. Hayabusa team is now sure, through the analysis of telemetry data, that a series of sequence for sampling was successfully done. Hayabusa then flew up to several kilometers altitude with normal solar paddles power, spacecraft attitude, etc.
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Comets-Comet_Pojmanski-2.jpgThe "Pojmanski" Comet56 visiteE' passata inosservata, lontana dalla nostra Terra, ed stata ben lungi dall'essere spettacolare come lo fu, qualche anno fa, la meravigliosa Hale-Bopp.
Certo, la cometina Pojmanski non aveva - forse - i numeri giusti per entrare nell'Albo delle (cosiddette) Grandi Comete, ma certo che i media (TUTTI!) se ne sono guardati bene dal pubblicizzarla. E la NASA? Leggerete Voi stessi le scarne note prodotte al riguardo nel "NASA - Picture of the Day" del giorno 6 Marzo 2006. Noi, nel nostro piccolo, dato che ci meravigliamo per niente, siamo andati in cerca di fotografie di questa cometa ed abbiamo "scoperto" una straordinaria somiglianza fra C/2006 A1 (la Pojmanski Comet appunto) e la C/2004 Q2 (meglio nota come Machholz Comet). Uguale tipologia - o classe visuale - di appartenenza (nucleo sferico e chioma filiforme) e, soprattutto, uguale colore (ergo uguale - o comunque molto simile - composizione chimica). Deduzione logica: si tratta di "Sister-Comets". Domanda: ci sono altre "sorelle" in arrivo?!?
Have you ever seen a comet? Comets bright enough to be visible to the unaided eye appear only every few years. Right now, however, a new comet has brightened unexpectedly and is visible as a faint streak to the unaided northern observer in the eastern morning sky just before sunrise. Binoculars may help. Comet Pojmanski, officially designated C/2006 A1 and discovered only in January, now sports a turquoise tail several times longer than the full moon. Comet Pojmanski's ion tail is due to gas particles expelled by the comet being pushed away from the Sun by the solar wind, the same wind that ionizes gas in the tail causing its blue tint. Pictured above as it appeared only last week, Comet Pojmanski has now begun to fade as its orbit around the Sun takes it further from the Earth.
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Asteroids-Asteroid_2002JF56-PIA09230-01.jpgFormer "Unknown Asteroid" is now "Asteroid 2002 JF56"56 visiteThe two "spots" in this image are a composite of two images of asteroid 2002 JF56 taken on June 11 and June 12, 2006, with the Multispectral Visible Imaging Camera (MVIC) component of the New Horizons Ralph imager. In the bottom image, taken when the asteroid was about 3,36 MKM (approx. 2,1 MMs) away from the Spacecraft, 2002 JF56 appears like a dim star. At top, taken at a distance of about 1,34 MKM (such as about 833.000 miles), the object is more than a factor of six brighter.
The best current, estimated diameter of the asteroid is approx. 2,5 Km.
The asteroid observation was a chance for the New Horizons team to test the spacecraft's ability to track a rapidly moving object. On June 13 New Horizons came to within about 102.000 Km of the small asteroid, when the Spacecraft was nearly 368 MKM (about 228 MMs) from the Sun and about 273 MKM (approx 170 MMs) from Earth.MareKromium
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EROS-GIFMovie-051.gif433-Eros: features in motion! (GIF-Movie; credits: Dr G. Barca)56 visitenessun commentoMareKromium
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IDA-PIA00135.jpgAsteroid Ida (HR)55 visiteThis view of the asteroid 243 Ida is a mosaic of 5 image frames acquired by the Galileo spacecraft's solid-state imaging system at ranges of 3.057 to 3.821 Km on August 28, 1993, about 3-1/2 minutes before the spacecraft made its closest approach to the asteroid. Galileo flew about 2.400 Km from Ida at a relative velocity of 12.4 km/sec (28,000 mph). Asteroid and spacecraft were 441 million Km from the Sun. Ida is the second asteroid ever encountered by a spacecraft. It appears to be about 52 Km in length, more than twice as large as Gaspra, the first asteroid observed by Galileo in October 1991. Ida is an irregularly shaped asteroid placed by scientists in the S class (believed to be like stony or stony iron meteorites). It is a member of the Koronis family, presumed fragments left from the breakup of a precursor asteroid in a catastrophic collision. This view shows numerous craters, including many degraded craters larger than any seen on Gaspra.
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EROS-PIA02907_modest.jpgA strange drawing made by lights and shadows...55 visiteEros' irregular shape creates interesting and beautiful scenes where the Sun shines obliquely on the surface. In the absence of an atmosphere, and hence no secondary illumination reflecting from atmospheric molecules, shade appears nearly as black as space. This image, taken from the NEAR Shoemaker spacecraft on May 2, 2000, from an orbital altitude of 50 kilometers (31 miles), shows one of the more telling and yet comical combinations of light and shadow. The entire scene is about 1.8 kilometers (1.1 miles) across. High spots near the edges of shadows, like the 35-meter (115-foot) diameter boulder just below the center of the frame, seem almost to "float" above the surface. With a little imagination, the shadow dominating the right side of the frame could be seen as a small, long-eared terrier bending over to sniff his dinner!
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EROS-PIA02906_modest.jpgHorizon view55 visiteThis image of Eros, taken from the NEAR Shoemaker spacecraft on May 2, 2000, from an orbital altitude of 52 kilometers (32 miles), shows a view toward Eros' horizon. The section shown is about 1.8 kilometers (1.1 miles) across. This particular view provides a snapshot of three of the most common types of features seen on the asteroid: craters whose rims have been rounded by erosion due to smaller impacts and blanketing by the impact debris, or regolith (impact debris); variations in the brightness of material on the walls of the craters; and a scattering of boulders ranging in size from nearly 100 meters (328 feet) down to about 8 meters (26 feet).
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Itokawa-08.jpgSurface details (1)55 visiteFor the scientific aspects of the mission, Hayabusa carries 4 instruments that have
performed successful observations to date:
1) AMICA, a Visible Imager with multi-band filters, has exposed 1500 images amounting to almost 1 GB of data;
2) NIRS, a near infrared spectrometer that has already taken 75.000 measurements distributed globally over the body;
3) LIDAR, a laser altimeter that has accumulated 1,4 million measurements globally, and
4) XRS, an X-ray spectrometer that has already received and integrated its signal for 700 hours.
In addition to these, spacecraft tracking data has been used to measure properties of the asteroid as well.
These unprecedented scientific measurements are briefly described and reported in what follows.
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Xena.jpgXena: another "Tenth Planet"? (2003 UB313)55 visiteNASA's Hubble Space Telescope has resolved the Tenth Planet, now nicknamed Xena, for the first time and has found that it is only just a little larger than Pluto.
Though previous ground-based observations suggested that Xena was about 30% greater in diameter than Pluto, Hubble observations taken on Dec. 9 and 10, 2005, yield a diameter of 1.490 miles (with an uncertainty of 60 miles) for Xena. Pluto's diameter, as measured by Hubble, is 1.422 miles. Xena is the large object at the bottom of this artist's concept. A portion of its surface is lit by the Sun, located in the upper left corner of the image. Xena's companion, Gabrielle, is located just above and to the left of Xena.
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Dactyl.JPGDactyl55 visitenessun commento
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McNaught-06.jpgComet McNaught (7)55 visitenessun commento
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Comets-Comet_Holmes-TView.jpgTelescopic View of the Comet Holmes55 visiteCaption NASA, da "NASA - Picture of the Day" del 29 Ottobre 2007:"What's happened to Comet Holmes? A normally docile comet discovered over 100 years ago, Comet 17P/Holmes suddenly became nearly one million times brighter last week, possibly over just a few hours. In astronomical terms, the comet brightened from magnitude 17, only visible through a good telescope, to magnitude 3, becoming visible with the unaided eye. Comet Holmes had already passed its closest to the Sun in 2007 May outside the orbit of Mars and was heading back out near Jupiter's orbit when the outburst occurred. The comet's sudden brightening is likely due to some sort of sunlight-reflecting outgassing event, possibly related to ice melting over a gas-filled cavern, or possibly even a partial breakup of the comet's nucleus. Pictured above through a small telescope, Comet Holmes appeared as a fuzzy yellow spot, significantly larger in angular size than Earth-atmosphere blurred distant stars. Although Comet Holmes' orbit will place it in northern hemisphere skies for the next two years, whether it will best be viewed through a telescope or sunglasses remains unknown".MareKromium
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