| Piú votate - Asteroids and Comets |
Comets-Wild_2-01.jpgApproaching Wild 2 (2)57 visiteCaption NASA originale:"On January 2, 2004 NASA's Stardust spacecraft made a close flyby of comet Wild 2.
Among the equipment the spacecraft carried on board was a navigation camera.
This is the 34th of the 72 images taken by Stardust's navigation camera during close encounter. The exposure time was just 10 milliseconds". 
(7 voti)
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Comets-Wild_2-03.jpgSome surface features of Wild 252 visiteCaption NASA originale:"These images taken by NASA's Stardust spacecraft highlight the diverse features that make up the surface of comet Wild 2. The three pictures on the left side show a variety of small pinnacles and mesas seen on the limb of the comet. The picture on the right shows the location of a 2-Km (1,2-mile) series of aligned scarps, or cliffs, that are best seen in the stereo images".
(7 voti)
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EROS-PIA02492.jpgEros in true colors82 visiteAs the NEAR Shoemaker spacecraft descends into lower orbits around Eros, it continually returns higher spatial resolution images of the asteroid. The true color image at left was taken February 12, 2000, from a range of 1.748 Km and shows details only as small as 180 meters (590 feet) across. It was taken two days before orbit insertion, as part of an image sequence designed to provide moderate-resolution color mapping of Eros at a near-constant viewing geometry. The true color image inset at right was taken February 29 from a range of 283 Km and shows much smaller details only 27 meters (89 feet) across.
(7 voti)
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Comets-Comet_Hartley_2-MF-LXTT4.jpgComet "Hartley 2" (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)168 visite...Come da richiesta del nostro Amico e Socio, "AndreaGG"...MareKromium
(6 voti)
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Comets-Halley-nucleus.jpgThe Nucleus of Halley56 visiteWhat does a Comet Nucleus look like?
Formed from the primordial stuff of the Solar System, Comet Nuclei were thought to resemble to very dirty icebergs. But ground-based telescopes revealed only the surrounding cloud of gas and dust of Active Comets nearing the Sun, clearly resolving only the Comet's Coma, and the characteristic cometary tails.
In 1986, however, the European Spacecraft "Giotto" became one of the first group of spacecrafts which encountered and photographed the Nucleus of a Comet, when it passed and imaged Halley's Nucleus as it approached the Sun.
Data from Giotto's camera were used to generate this enhanced image of the potato shaped Nucleus that measures roughly 15 Km across. Some Surface Features on the dark Nucleus are on the right, while gas and dust flowing into Halley's Coma are on the left.
Every 76 years Comet Halley returns to the Inner Solar System and each time the Nucleus sheds about a 6-meter deep layer of its ice and rock into space. This debris shed from Halley's Nucleus eventually disperses into an orbiting trail responsible for the Orionids Meteor Shower, which occurs in October of every year, and the Eta Aquariids Meteor Shower, that occurs in May.MareKromium
(6 voti)
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Haumea-1.jpgHaumea: an "Egg" in the Outer Solar System...78 visitenessun commentoMareKromium
(6 voti)
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Comets-Comet_Holmes-UZ-2.jpgComet 17-P-Holmes, from Hungary54 visiteCaption NASA:"Comet Holmes refuses to fade. The unusual comet that surprisingly brightened nearly a million-fold in late October continues to remain visible to the unaided eye from dark locations. Night to night, Comet 17P/Holmes is slowly gliding through the constellation Perseus, remaining visible to northern observers during much of the night right from sunset. Pictured above, Comet Holmes was captured from Hungary last week. The remarkable snowball continues to retain a huge coma, but now shows very little of a tail. To the far right is the open cluster of stars NGC 1245.
How much longer Comet Holmes will remain visible to the unaided eye is unknown".MareKromium
(6 voti)
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Eris_Dysnomia.jpgEris and Dysnomia54 visiteNASA's HST has teamed up with the W.M. Keck Observatory to precisely measure the mass of Eris, the largest member of a new class of Dwarf Planets in our Solar System. Eris is 1,27 times the mass of Pluto, formerly the largest member of the Kuiper Belt of icy objects beyond Neptune.
Hubble observations in 2006 showed that Eris is slightly physically larger than Pluto. But the mass could only be calculated by observing the orbital motion of the moon Dysnomia around Eris. Multiple images of Dysnomia's movement along its orbit were taken by Hubble and Keck.
Astronomer Mike Brown of the California Institute of Technology in Pasadena, Calif. and colleagues also report in this week's Science Magazine that Dysnomia is in a nearly circular 16-day orbit. This favors the idea that Dysnomia was born out of a collision between Eris and another Kuiper Belt object (KBO).
A gravitationally captured object would be expected to be in a more elliptical orbit.
The satellites of Pluto, as well as the Earth-Moon system are also believed to have been born out of a collision process where debris from the smashup goes into orbit and coalesces into a satellite.
By comparing the mass and diameter, Brown has calculated a density for Eris of 2.3 grams per cubic centimeter. This is very similar to the density of Pluto, the large Kuiper Belt object 2003 EL61, and Neptune's moon Triton which is likely a captured KBO. These higher densities imply that these bodies are not pure ice but must have a significant rocky composition.
The discovery of Eris in 2005 (originally nicknamed Xena, and officially cataloged 2003 UB313) prompted a debate over the planetary status of Pluto because astronomers realized they would have to call it the "10th" planet if Pluto retained its own planetary status, which was already under debate. This led the International Astronomical Union, in 2006, to make a new class of solar system object called dwarf planets. These are spherical bodies in hydrostatic equilibrium (objects that have sufficient gravity to overcome their own rigidity and form a spherical shape) like the planets, but unlike the major planets in the solar system, they have not gravitationally cleared out the neighborhood of particles and small debris along their orbits.
MareKromium
(6 voti)
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Man-Made_Nebula.gifMan-Made Nebula, such as: a warning sign of the Kessler Syndrome (GIF Movie)75 visiteCaption NASA:"What's that cloud drifting in space? It's not an astronomical nebula because...those appear to stay put.
Atmospheric clouds don't look like this.
The answer to last week's sky mystery turned out to be orbiting and expanding debris from the upper stage of a failed Russian rocket that exploded unexpectedly. The cloud became visible to unaided southern hemisphere observers, and its cause was initially unknown. The above time lapse movie shows the cloud drifting as seen from Australia. Streaks in and near the cloud are likely large pieces of debris. The debris cloud is more than an astronomical curiosity -- particles from this cloud and others could become projectiles damaging existing satellites. As the cloud disperses, many particles will fall to Earth, but many more may help make low Earth orbit an increasingly hostile environment".MareKromium
(6 voti)
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McNaught-09.jpgThe "Tail" of McNaught, at Sunset...60 visiteCaption NASA originale:"What's happening over the horizon? Many a sky enthusiast who thought they had seen it all had never seen anything like this. To the surprise of many Northern Hemisphere observers, the tail of Comet McNaught remained visible even after the comet's head set ahead of the Sun. What's more, visible were bright but extremely rare filamentary striae from the comet's expansive dust tail. The cause of dust tail striae are not known for sure, but are possibly related to fragmentation of comet's nucleus. The last comet to show prominent striae was Comet Hale-Bopp in 1997.
Pictured above, the tail of Comet McNaught was caught just after Sunset last Friday above the Carnic Alps of Northern Italy".
(6 voti)
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McNaught-07.jpgComet McNaught (8)54 visiteCaption NASA:"Comets grow bright when they're close to the Sun, basking in the intense solar radiation. Of course, they're also usually impossible to see against the overwhelming scattered Sunlight. But surprising Comet McNaught - whose January 12, 2007, closest approach to the Sun (perihelion passage) was well inside the orbit of Mercury - gave an enjoyable performance in bright blue daytime skies. In fact, comet expert David Levy captured this remarkable inset (upper left) telescopic view of McNaught within an hour of perihelion, with the comet in broad daylight only about 7° away from the Sun's position.
Stefan Seip's wider daytime view of the comet and fluffy clouds was recorded approximately a day later. Seip used a polarizing filter and a telescope/camera set up near Stuttgart, Germany.
No longer visible in broad daylight, Comet McNaught is now touring twilight Southern Skies".
(6 voti)
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McNaught-00.jpgComet McNaught (1)53 visiteCaption NASA:"Early morning risers with a clear and unobstructed eastern horizon can enjoy the sight of Comet McNaught (C/2006 P1) in dawn skies over the next few days. Discovered in August by R. H. McNaught (Siding Spring Survey) the comet has grown bright enough to see with the unaided eye but will soon be lost in the glare of the Sun. Still, by January 11 sun-staring spacecraft SOHO should be able to offer web-based views as the comet heads toward a perihelion passage inside the orbit of Mercury. This image captures the new naked-eye comet at about 2nd magnitude in twilight skies near sunset on January 3rd. After rounding the Sun and emerging from the solar glare later this month, Comet McNaught could be even brighter".
(6 voti)
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