| |
|
|
Eros-NorHem-PIA02923.jpgThe Northern Hemisphere of Eros66 visiteCaption NASA originale:"This spectacular view - looking down on the North Polar Region of Asteroid Eros - was constructed from 6 images taken February 29, 2000, from an orbital altitude of about 200 Km (approx. 124 miles). This vantage point highlights the major physiographic features of the Northern Hemisphere: the saddle seen at the bottom; the 5,3-Km diameter crater at the top and a major ridge system running between the two features that spans at least one-third of the asteroid's circumference".
Note: this a mosaic of images 0127275100, 0127275164, 0127275246, 0127275310, 0127275456, 0127275520
|
|
Eros-PIA02488.jpgCraters' "Trio"65 visiteCaption NASA originale:"The Near Earth Asteroid Rendezvous (NEAR) spacecraft snapped the image on the left (Image of the Day Feb. 13, 2000 B) during its approach to Eros on Feb. 11, 2000, from a range of 2590 Km (approx 1.609 miles). This image shows a heart-shaped depression about 5 Km long. The image mosaic on the right was taken from 204 Km on March 3, 2000 and reveals that the mysterious heart-shaped feature is actually 3 separate craters. The oblique lighting conditions and low resolution of the earlier image created the illusion of a heart shape".
|
|
Eros-PIA02495_modest.jpgSide view and front view of a bright crater64 visiteLighting and viewing geometries make a huge difference in the appearance of Eros' surface features. One of the most striking examples is the 2.7 Km diameter crater shown in these two images. The image at left, looking at the crater nearly edge-on, was taken February 16, 2000, from a range of 341 Km. The image at right was taken high over the crater on March 2, 2000, from a range of 226 Km. In the first image the only visible part of the crater's interior is the far, bright wall, which at the time was well-lit. The lighting, in combination with the particular viewing angle, make the crater appear stunningly bright. In the second view, the brighter material occupies only part of the slightly-shaded interior, greatly reducing the overall brightness contrast between the crater and the surrounding terrain.
|
|
Eros-PIA02499.jpgA deep impact on Eros means short daylight hours...77 visiteCaption NASA originale:"For people who live in mountain valleys, daylight can be a short-lived experience. Mountains to the east make the Sun rise later in the morning, while mountains to the west make the Sun set earlier in the evening. The brevity of daytime in a valley is accentuated during the shortened days of winter. The floor of the 5,5-Km (3,4-mile) diameter impact crater that dominates one face of Eros experiences the ultimate in short daylight hours. Three factors conspire to make this true. Firstly, Eros rotates rapidly, once every 5,27 hours. Secondly, the crater's 0,9-Km (0,56-mile) high walls tend to block direct sunlight from the floor, even while the outside of the crater is illuminated. Thirdly, during the current season on Eros, the Sun never makes it high in the sky in this location".
|
|
FD1-Asteroid.jpg2022 FD1245 visiteA sole due settimane di distanza dal precedente, un nuovo asteroide ha raggiunto il nostro pianeta. Gli scienziati lo hanno chiamato 2022 FD1: il corpo celeste ha solo sfiorato la Terra, passando più in basso dei nostri stessi satelliti Gps.
Grazie ai miglioramenti nel campo della tecnologia, l'uomo è ora in grado di avvistare tempestivamente un corpo celeste in avvicinamento, anche di dimensioni ridotte, e tutto viene regolarmente riportato nei registri del settore. Secondo quanto affermato dagli esperti del settore, il fenomeno non deve stupire, perché ogni giorno tantissimo materiale spaziale raggiunge il nostro pianeta (si va dalle 40 alle 100 tonnellate). Fortunatamente si tratta di corpi di piccole dimensioni che non suscitano pertanto preoccupazione.
L'11 marzo scorso è stata la volta dell' asteroide 2022 EB5, questo il nome che gli è stato dato da chi lo ha catalogato. Senza che la maggior parte delle persone se ne rendesse conto, il corpo celeste ha colpito la Terra, a differenza di 2022 FD1.
L'impatto di 2022 EB5
Tornando a 2022 EB5, alle 20.24, ora italiana, l'astronomo Krisztián Sárneczky ha individuato il corpo celeste servendosi di un telescopio Schmidt da 60 cm. La scoperta è stata effettuata presso l'osservatorio Piszkéstető, in Ungheria. La notizia è stata immediatamente diramata, ed in tanti, professionisti o semplici appassionati, hanno deciso di seguire il percorso dell'asteroide, un oggetto con diametro di circa 1 metro che fin da subito non ha destato timori.
Trascorse 2 ore dal primo avvistamento, si è verificato l'impatto con la Terra. Nessun danno. Come abbiamo detto, 2022 EB5 era un corpo celeste di piccole dimensioni ed è andato a schiantarsi in una zona disabitata nei pressi del ghiacciaio Vatnajokull, Islanda sudorientale. Stando ai dati rilevati dagli scienziati, l'impatto ha rilasciato un'energia equiparabile ad un terremoto di magnitudo 4.
Più vicino dei satelliti Gps
Sárneczky non ha però scoperto solo 2022 EB5. Pochi giorni fa, ossia venerdì 25 marzo, l'astronomo ha infatti individuato un altro corpo celeste, ribattezzato prima Sar2594 e poi denominato ufficialmente 2022 FD1. Individuato poco prima del suo passaggio, 2022 FD1 ha soltanto sfiorato la Terra, attraversando lo spazio ad una velocità di 61.200 km/h. In Italia erano le 10:13. Il piccolo asteroide è passato davvero molto vicino, a una distanza di 8.700 km, quando i nostri satelliti Gps si trovano ad un'altitudine media di 20.200 km.
Grazie al calcolo della sua orbita, è stato possibile prevedere che 2022 FD1 non tornerà ad incontrare il nostro pianeta nei prossimi due secoli, anche se nel 2032 potrebbe comunque avvicinarsi di poco (fino a 6 milioni di km). Nel 2053, invece, il corpo celeste passerà vicino a Venere.MareKromium
|
|
GASPRA-PIA00119.jpgAsteroid Gaspra81 visiteThis picture of asteroid 951 Gaspra is a mosaic of 2 images taken by the Galileo spacecraft from a range of 5.300 Km, some 10 minutes before closest approach on October 29, 1991. The Sun is shining from the right; phase angle is 50 degrees. The resolution, about 54 meters/pixel, is the highest for the Gaspra encounter and is about three times better than that in the view released in November 1991. Additional images of Gaspra remain stored on Galileo's tape recorder, awaiting playback in November. Gaspra is an irregular body with dimensions about 19 x 12 x 11 Km. The portion illuminated in this view is about 18 Km from lower left to upper right. The north pole is located at upper left; Gaspra rotates counterclockwise every 7 hours. The large concavity on the lower right limb is about 6 Km across, the prominent crater on the terminator, center left, about 1.5 Km. A striking feature of Gaspra's surface is the abundance of small craters. More than 600 craters, 100-500 meters (330-1650 feet) in diameter are visible here. The number of such small craters compared to larger ones is much greater for Gaspra than for previously studied bodies of comparable size such as the satellites of Mars.
|
|
Gaspra-Deimos-Phobos-PIA00078_modest.jpgGaspra, Deimos and Phobos66 visiteCaption NASA originale:"This montage shows asteroid 951 Gaspra (top) compared with Deimos (lower left) and Phobos (lower right), the moons of Mars. The three bodies are shown at the same scale and nearly the same lighting conditions. Gaspra is about 17 Km (10 miles) long. All three bodies have irregular shapes, due to past catastrophic conditions. However their surfaces appear remarkably different, possibly because of differences in composition but most likely because of very different impact histories. The Phobos and Deimos images were obtained by the Viking Orbiter spacecraft in 1977; the Gaspra image is the best of a series obtained by the Galileo spacecraft on October 29, 1991".
|
|
Haumea-1.jpgHaumea: an "Egg" in the Outer Solar System...101 visitenessun commentoMareKromium
|
|
Haumea2.jpgHaumea and other "Dwarf" Companions89 visiteCaption NASA:"One of the strangest objects in the Outer Solar System was classified as a Dwarf Planet last week (September 2008) and given the name Haumea.
This designation makes Haumea the 5th designated Dwarf Planet after Pluto, Ceres, Eris, and Makemake. Haumea's smooth but oblong shape make it extremely unusual. Along one direction, Haumea is significantly longer than Pluto, while in another direction Haumea has an extent very similar to Pluto, while in the third direction is much smaller.
Haumea's orbit sometimes brings it closer to the Sun than Pluto, but usually Haumea is further away.
Illustrated above, an artist visualizes Haumea as a nearly featureless ellipsoid. Quite possibly, however, Haumea has interesting craters and surface features that currently remain unknown. Originally discovered in 2003 and given the temporary designation of 2003 EL61, Haumea was recently renamed by the IAU for a Hawaiian goddess. Haumea has two small moons discovered in 2005, recently renamed Hi'iaka and Namaka after the daughters of the Goddess".MareKromium
|
|
Hycean_Planet.jpgThe "Hycean Planets"100 visite(ANSA) - Milano, 26 Agosto – Identificata una nuova classe di pianeti potenzialmente abitabili al di fuori del Sistema solare: caldi, ricoperti da oceani e con un'atmosfera ricca di Idrogeno, i quali potrebbero ospitare microrganismi adatti a vivere in condizioni estreme. La scoperta è pubblicata su The Astrophysical Journal dai ricercatori dell'Università di Cambridge, che hanno chiamato questi mondi alieni 'Hycean Planets': più numerosi e meglio osservabili degli esopianeti di tipo terrestre, potrebbe accelerare la ricerca di tracce di vita portando ad avere le prime risposte già nel giro di due o tre anni. Questi nuovi esopianeti possono essere fino a 2,6 volte più grandi della Terra e possono avere temperatura atmosferiche che arrivano ai 200°: nonostante ciò presentano grandi oceani che potrebbero supportare forme di vita microbica simili ai batteri estremi che vivono sulla Terra. Inoltre hanno una zona abitabile molto più ampia rispetto agli esopianeti terrestri: ciò significa che possono ospitare la vita anche se orbitano intorno alla loro stella a distanze diverse rispetto a quelle considerate vincolanti affinché un pianeta terrestre possa presentare acqua liquida in superficie.
I ricercatori di Cambridge hanno già selezionato un numero consistente di potenziali 'Hycean Planets' che saranno i primi candidati per le osservazioni con i telescopi di nuova generazione, come il James Webb Space Telescope che sarà lanciato entro l'anno.MareKromium
|
|
IDA&DACTYL-PIA00333.jpgIda and Dactyl in "natural colors"89 visiteThis color picture is made from images taken by the imaging system on the Galileo spacecraft about 14 minutes before its closest approach to asteroid 243 Ida on August 28, 1993. The range from the spacecraft was about 10,500 kilometers (6,500 miles). The images used are from the sequence in which Ida's moon was originally discovered; the moon is visible to the right of the asteroid. This picture is made from images through the 4100-angstrom (violet), 7560 A (infrared) and 9680 A (infrared) filters. The color is 'enhanced' in the sense that the CCD camera is sensitive to near infrared wavelengths of light beyond human vision; a 'natural' color picture of this asteroid would appear mostly gray. Shadings in the image indicate changes in illumination angle on the many steep slopes of this irregular body as well as subtle color variations due to differences in the physical state and composition of the soil (regolith).
|
|
IDA-PIA00135.jpgAsteroid Ida (HR)63 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.
|
|
| 288 immagini su 24 pagina(e) |
|
|
|
|
|
15 | |
|
|
|
|
|
|
