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00-Libration-250px-Lunar_libration_with_phase2.gifThe "Lunation": such as a full "Lunar Cycle"58 visitenessun commentoMareKromium
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Comets-Comet_Holmes-0.jpgA "Light Arrow" is heading towards "Heart & Soul"...64 visiteCaption NASA:"Two spectacular comets graced Earth's skies during 2007.
Both comets became bright enough to be seen by the unaided eye of the casual sky enthusiast. Early in 2007, Comet McNaught grew brighter than any comet in 40 years, displaying a beautiful dust tail that flowed across the sky.
Comet McNaught (a.k.a. c/2006 P1) became known as the "Great Comet" of 2007, sported unusual striations in its expansive dust tail, and showed unexpectedly complex chemistry in its ion tail.
Toward the year's end, normally docile and faint Comet Holmes brightened suddenly and unexpectedly to naked eye visibility. Remarkably, Comet 17P/Holmes stayed bright for weeks even though it lies beyond the orbit of Mars.
No distant comet in recent history has remained so bright for so long.
In this view, a white Comet Holmes was photographed in early December posing with the Heart and Soul Nebulae".MareKromium
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Comets-Comet_Holmes-UX.jpgComet 17-P-Holmes and its - now - Green Coma54 visiteCaption NASA:"This gorgeous skyscape spans some 10° across the Constellation of Perseus, about the size of a generous binocular field of view.
The deep exposure includes bright stars, emission nebulae, star clusters, and, of course, the famous Comet Holmes.
The brightest star in view, Alpha Persei, is itself surrounded by a loose cluster of stars - the Alpha Per Moving Cluster - at a distance of about 600 LY.
But, at a distance of a mere 14 Light-Minutes (LM), bright Comet 17-P-Holmes still dominates the scene with its fluorescing greenish coma and foreshortened blue tail".MareKromium
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Comets-Comet_Holmes-UZ-1.jpgComet 17-P-Holmes, from Earth and from HST54 visiteNASA's HST has probed the bright core of Comet 17P/Holmes, which, to the delight of sky watchers, mysteriously brightened by nearly a millionfold in a 24-hour period beginning Oct. 23, 2007.
Astronomers used Hubble's powerful resolution to study Comet Holmes' core for clues about how the comet brightened. The orbiting observatory's Wide Field Planetary Camera 2 (WFPC2) monitored the comet for several days, snapping images on Oct. 29, Oct. 31, and Nov. 4. Hubble's crisp "eye" can see objects as small as 33 miles (54 Km) across, providing the sharpest view yet of the source of the spectacular brightening.
The Hubble image at right, taken Nov. 4, shows the heart of the comet. The central portion of the image has been specially processed to highlight variations in the dust distribution near the nucleus. About twice as much dust lies along the east-west direction (the horizontal direction) as along the north-south direction (the vertical direction), giving the comet a "bow tie" appearance.
The composite color image at left, taken Nov. 1 by an amateur astronomer, shows the complex structure of the entire coma, consisting of concentric shells of dust and a faint tail emanating from the comet's right side.
The nucleus-the small solid body that is the ultimate source of all the comet's activity- is still swaddled in bright dust, even 12 days after the spectacular outburst. "Most of what Hubble sees is sunlight scattered from microscopic particles," explained Hal Weaver of The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., who led the Hubble investigation. "But we may finally be starting to detect the emergence of the nucleus itself in this final Hubble image."
Hubble first observed Comet 17P/Holmes on June 15, 1999, when there was virtually no dusty shroud around the nucleus. Although Hubble cannot resolve the nucleus, astronomers inferred its size by measuring its brightness. Astronomers deduced that the nucleus' diameter was approximately 2.1 miles (3.4 kilometers), about the length of New York City's Central Park. They hope to use the new Hubble images to determine the size of the comet's nucleus to see how much of it was blasted away during the outburst.
Hubble's two earlier snapshots of Comet Holmes also showed some interesting features. On Oct. 29, the telescope spied three "spurs" of dust emanating from the nucleus, while the Hubble images taken on Oct. 31 revealed an outburst of dust just west of the nucleus.
The Hubble images, however, do not show any large fragments near the nucleus of Comet Holmes, unlike the case of Comet 73P/Schwassmann-Wachmann 3 (SW3). In the spring of 2006 Hubble observations revealed a multitude of "mini-comets" ejected by SW3 after the comet increased dramatically in brightness.
Ground-based images of Comet Holmes show a large, spherically symmetrical cloud of dust that is offset from the nucleus, suggesting that a large fragment broke off and subsequently disintegrated into tiny dust particles after moving away from the main nucleus.
Unfortunately, the huge amount of dust near the comet's nucleus and the comet's relatively large distance from Earth (149 million miles, or 1.6 astronomical units, for Holmes versus 9 million, or 0.1 astronomical unit for SW3), make detecting fragments near Holmes nearly impossible right now, unless the fragments are nearly as large as the nucleus itself.
The Hubble Comet Holmes observing team comprises H. Weaver and C. Lisse (The Johns Hopkins University Applied Physics Laboratory); P. Lamy (Laboratoire d'Astrophysique de Marseille, France); I. Toth (Konkoly Observatory, Hungary); M. Mutchler (Space Telescope Science Institute); W. Reach (California Institute of Technology); and J. Vaubaillon (California Institute of Technology).
MareKromium
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Comets-Comet_Holmes-UZ_PIA11228-1.jpgComet 17-P Holmes now in the Outer Solar System (IR)54 visiteNASA's Spitzer Space Telescope captured the picture of comet Holmes in March 2008, 5 months after the comet suddenly erupted and brightened a millionfold overnight. The contrast of the picture has been enhanced (see the next frame) to show the anatomy of the comet.
Every 6 years, comet 17P/Holmes speeds away from Jupiter and heads inward toward the Sun, traveling the same route typically without incident. However, twice in the last 116 years, in November 1892 and October 2007, comet Holmes mysteriously exploded as it approached the Asteroid Belt. Astronomers still do not know the cause of these eruptions.
Nota Lunexit: la "causa" di queste repentine eruzioni della Cometa 17-P Holmes le quali avvengono - guarda caso - durante il transito della medesima attraverso la Fascia degli Asteroidi potrebbe essere RAGIONEVOLMENTE rinvenuta nella verificazione di impatti con corpi erranti di piccole/piccolissime dimensioni (l'occorrere di impatti con uno o più oggetti di dimensioni medie o medio/grandi porterebbe inevitabilmente alla frammentazione/distruzione completa del nucleo di 17-P Holmes ed alla sua relativa e definitiva sparizione). Che gli "outbursts" possano essere (anche) l'ovvia conseguenza di un impatto ad altissima velocità è stato recentemente dimostrato dall'esperimento (come ricorderete contestatissimo) effettuato dalla NASA sulla Cometa Tempel-1, la quale fu centrata da un'ogiva metallica e, all'atto dello "scontro spaziale", aumentò la sua luminosità in maniera agevolmente percepibile anche da Terra.MareKromium
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Comets-Comet_Holmes-UZ_PIA11228-2.jpgComet 17-P Holmes now in the Outer Solar System54 visiteSpitzer's infrared picture at left hand side of this frame reveals fine dust particles that make up the Outer Shell, or "Coma", of the Comet. The Nucleus of the Comet is within the bright whitish spot in the center, while the yellow area shows solid particles that were blown from the Comet in the explosion.
The Comet is headed away from the Sun, which lies beyond the right-hand side of these pictures.
The contrast-enhanced picture on the right shows the Comet's Outer Shell, and strange "filaments", or "Streamers", of dust. The Streamers and shell are a yet another mystery surrounding Comet Holmes. Scientists had initially suspected that the Streamers were small dust particles ejected from fragments of the Nucleus, or from hyerpactive jets on the Nucleus, during the October 2007 explosion.
If so, both the Streamers and the Shell should have shifted their orientation as the Comet followed its orbit around the Sun.
Radiation pressure from the Sun should have swept the material back and away from it. But pictures of Comet Holmes taken by Spitzer over time show the Streamers and Shell in the same configuration, and not pointing away from the Sun. The observations have left astronomers stumped.
The horizontal line seen in the contrast-enhanced picture is a trail of debris that travels along with the Comet in its orbit.
The Spitzer picture was taken with the Spacecraft's multiband imaging photometer at an infrared wavelength of 24 microns.MareKromium
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Craters-Unnamed_Crater-Deuteronilus_Mensae-PIA08472-00.jpgAlmost Buried Unnamed Crater in Deuteronilus Mensae (Original NASA/JPL/ASU b/w Frame)53 visiteCaption NASA originale:"This Unnamed Crater appears to be in the process of being covered over by downslope movement of material. These large slopes of material are common in Deuteronilus Mensae".
Image information: VIS instrument;
Latitude: 41,1° North;
Longitude: 17,8° East;
Resolution: 19 meter/pixel.
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Craters-Unnamed_Crater-Deuteronilus_Mensae-PIA08472-01.jpgAlmost Buried Unnamed Crater in Deuteronilus Mensae (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)131 visiteCaption NASA originale:"This Unnamed Crater appears to be in the process of being covered over by downslope movement of material. These large slopes of material are common in Deuteronilus Mensae".
Image information: VIS instrument;
Latitude: 41,1° North;
Longitude: 17,8° East;
Resolution: 19 meter/pixel. MareKromium
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SOL0003-ML0000090000E1_DXXX-GB-LXTT-3.jpgExtremely unusually-looking Rock: "The Helmet" - Sol 3 (Credits: NASA/JPL-Caltech; Research: Dr Gianluigi Barca - Lunexit Team/Italian Planetary Foundation)125 visite...Senza parole... Anzi, qualcuna l'abbiamo: in primo luogo, le fattezze di questa "roccia" sono DAVVERO inusuali e, in secondo luogo, se questa "roccia" l'avessero vista i Signori di Enterprise Mission (Hoagland & C.), state pur certi che ci avrebbero già costruito sopra un castello. Di stupidaggini, ovviamente.
Noi, come sempre, ci fermiamo a dire "Caspita: è davvero strana!". La NASA, invece, queste "rocce" nemmeno le vede...
Sempre GRANDI COMPLIMENTI al nostro Dr Barca!MareKromium
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