| Piú votate - Asteroids and Comets |
Asteroid_DD-45-a.gifAsteroid 2009 DD-45 (GIF-Movie)77 visiteUn bellissimo GIF-Movie; da notare ed apprezzare il movimento irregolare dell'asteroide il quale, più che "ruotare" su se stesso, sembra "rotolare" (come fa la Luna Saturniana Iperione).
Il movimento (se non altro apparentemente) caotico dell'asteroide DD-45 attorno al proprio asse di rotazione può essere spiegato non solo dalla forma irregolare ("a tubero") posseduta da questo minuscolo Corpo Celeste, ma anche dalla marcata influenza mareale (---> gravitazionale) su di esso esercitata dalla "vicina" Terra (distante circa 70.000 Km).MareKromium
(8 voti)
|
|
Comets-Comet_Lulin-01.jpgStill Comet Lulin57 visiteDa "NASA - Picture of the Day" del giorno 7 Febbraio 2009:"Sweeping through the Inner Solar System, Comet Lulin is easily visible in both Northern and Southern Hemispheres with binoculars or a small telescope. Recent changes in Lulin's lovely greenish Coma and Tails are featured in this two panel comparison of images taken on January 31st (top) and February 4th, 2009.
Taken from dark New Mexico Skies, the images span over 2°. In both views the comet sports an apparent Anti-Tail at the left - the comet's Dust Tail appearing almost edge on from an earth-based perspective as it trails behind in Lulin's orbit.
Extending to the right of the coma, away from the Sun, is the beautiful Ion Tail. Remarkably, as captured in the bottom panel, Comet Lulin's Ion Tail became disconnected on February 4, likely buffeted and torn away by magnetic fields in the Solar Wind.
In 2007 NASA satellites recorded a similar disconnection event for Comet Encke. Don't worry, though: comet tails can grow back".MareKromium
(8 voti)
|
|
Comets-Comet_Holmes-UZ_PIA11228-2.jpgComet 17-P Holmes now in the Outer Solar System57 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
(8 voti)
|
|
Asteroids-Asteroid_2007-TU24.jpgAsteroid 2007 TU24 (Radar View)57 visiteAsteroid 2007 TU24 passed by the Earth yesterday, posing no danger. The space rock, estimated to be about 250 mt across, coasted by just outside the orbit of Earth's Moon. The passing was not very unusual - small rocks strike Earth daily, and in 2003 a rock the size of a bus passed inside the orbit of the Moon, being detected only after passing. TU24 was notable partly because it was so large. Were TU24 to have struck land, it might have caused a magnitude 7 earthquake and left a city-sized crater. A perhaps larger danger would have occurred were TU24 to have struck the ocean and raised a large tsunami.
This radar image was taken 2 days ago. The Arecibo Radio Telescope in Puerto Rico broadcast radar that was reflected by the asteroid and then recorded by the Byrd Radio Telescope in Green Bank, West Virginia. The resulting image shows TU24 to have an oblong and irregular shape. TU24 was discovered only three months ago, indicating that other potentially hazardous asteroids might lurk in our Solar System currently undetected. Objects like TU24 are hard to detect because they are so faint and move so fast. Humanity's ability to scan the sky to detect, catalog, and analyze such objects has increased notably in recent years.
MareKromium
(8 voti)
|
|
Comets-Comet_Holmes-UZ-0.jpgComet 17-P-Holmes, from HST58 visiteCaption NASA:"These images taken by NASA's Hubble Space Telescope reveal Comet Holmes's bright core. The images show that the coma, the cloud of dust and gas encircling the comet, is getting fainter over time. The coma was brightest in the Oct. 29 image. It is two times fainter on Oct. 31 and nine times dimmer on Nov. 4 than during the Oct. 29 observation.
The coma is getting fainter because it is expanding. A huge number of small dust particles was created during the Oct. 23 outburst. Since then those particles have been moving away from the nucleus and filling interplanetary space.
The coma therefore is becoming more diffuse over time.
The nucleus, however, is still active and is producing a significant amount of new dust. So the region around the nucleus is still much brighter (at least 10 times brighter) than it usually is at this point in the comet's orbit.MareKromium
(8 voti)
|
|
Comets-Comet_Holmes-UY.jpgComet 17-P-Holmes, from Hungary56 visiteCaption NASA:"A beautiful blue ion tail has become visible in deep telescopic images of Comet Holmes. Pointing generally away from the Sun and also planet Earth, the comet's ion tail is seriously foreshortened by our extreme viewing angle.
Still, enthusiastic comet watchers have remarked that on the whole, the compact but tentacled appearance suggests a jellyfish or even a "cosmic calamaro".
This stunning view of the comet's greenish coma and blue tail was recorded on November 4, 2007, in clear skies near Budapest, Hungary.
The colors are caused by molecules in the tenuous gas, like C2 (green) and CO+ (blue), fluorescing in sunlight". MareKromium
(8 voti)
|
|
Comets-Comet_Holmes-UX.jpgComet 17-P-Holmes and its - now - Green Coma57 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
(8 voti)
|
|
Comets-Comet_SWAN-2.jpgComet SWAN57 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".
(8 voti)
|
|
Comets-Comet_SWAN-3.jpgComet "SWAN"59 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".
(8 voti)
|
|
Comets-Schwassmann_Wachmann_1-03.jpgComet Schwassmann-Wachmann 3: fragment "B"54 visitePeriodic comet 73P/Schwassmann-Wachmann 3 has fallen apart before. A cosmic souffle of ice and dust left over from the early Solar System, this comet was seen to split into several large pieces during the close-in part of its orbit in 1995. However, this time the comet seems to be rapidly disintegrating with over 3 dozen fragments, named alphabetically, now stretching several degrees across the sky. Since comets are relatively fragile, stresses from heat and gravity and outgassing, for example, could be responsible for their tendency to breakup in such a spectacular fashion. On April 18th, 2006, HST recorded this sharp view of prolific Fragment B, itself trailing dozens of smaller pieces, each with its own cometary coma and tail. The picture spans over 3000 Km at the comet's April 18 distance of 32 MKM from planet Earth. With its brightest fragment presently too faint to be seen with the naked eye, comet Schwassmann-Wachmann 3 will pass closest to Earth on May 13 at a distance of about 11 MKM.
(8 voti)
|
|
Comets-Schwassmann_Wachmann_1-02.jpgComet Schwassmann-Wachmann 3 from HST54 visiteHubble Space Telescope is providing astronomers with extraordinary views of Comet 73P/Schwassmann-Wachmann 3. The fragile comet is rapidly disintegrating as it approaches the Sun. Hubble images have uncovered many more fragments than have been reported by ground-based observers. These observations provide an unprecedented opportunity to study the demise of a comet nucleus. The comet is currently a chain of over three dozen separate fragments, named alphabetically, stretching across the sky by several times the angular diameter of the Moon. Hubble caught two of the fragments (B and G) shortly after large outbursts in activity.
HST shows several dozen of "mini-comets" trailing behind each main fragment and probably associated with the ejection of house-sized chunks of surface material.
(8 voti)
|
|
Comets-Schwassmann_Wachmann_1-01.jpgComet Schwassmann-Wachmann 3: incoming Space debris!55 visiteDa "NASA - Picture of the Day" del 26 Aprile 2006:"A crumbling comet will soon pass near the Earth. Comet 73P/Schwassmann-Wachmann 3 is brightening and may even be visible to the unaided eye when the fragmented comet zooms past Earth during the middle of next month. Still, the small comet poses no Earth hazard, since it will pass the Earth at about 25 times the distance of the Moon. Exactly how bright Comet Schwassman-Wachmann 3 will get is unknown. It is even possible, althought unlikely, that debris from the comet will have spread out enough to cause a notable meteor shower. Pictured above, Fragment B of Comet Schwassman-Wachmann 3 was photographed two nights ago by a 8.2-meter Very Large Telescope in Chile. Visible to the lower right of the large B Fragment are many mini-comets that have broken off and now orbit the Sun separately. Each mini-comet itself sheds gas and dust and so appears to have its own hazy coma.
The comet will pass closest to the Sun on June 7, 2006".
(8 voti)
|
|
| 282 immagini su 24 pagina(e) |
 |
|
|
|
6 | |
|
|
|
|
|
