| Piú viste - The Universe Inside |
TwentythreeBC.jpg23 Million Years B.C.84 visiteMareKromium
|
|
Voyagers-00.gifTowards the "Terra Incognita" (1)84 visiteInterstellar Mission - Mission Objective
The mission objective of the Voyager Interstellar Mission (VIM) is to extend the NASA exploration of the Solar System beyond the neighborhood of the outer planets to the outer limits of the Sun's sphere of influence, and possibly beyond. This extended mission is continuing to characterize the outer Solar System environment and search for the heliopause boundary, the outer limits of the Sun's magnetic field and outward flow of the solar wind. Penetration of the heliopause boundary between the solar wind and the interstellar medium will allow measurements to be made of the interstellar fields, particles and waves unaffected by the solar wind.
The VIM is an extension of the Voyager primary mission that was completed in 1989 with the close flyby of Neptune by the Voyager 2 spacecraft. Neptune was the final outer planet visited by a Voyager spacecraft. Voyager 1 completed its planned close flybys of the Jupiter and Saturn planetary systems while Voyager 2, in addition to its own close flybys of Jupiter and Saturn, completed close flybys of the remaining two gas giants, Uranus and Neptune.
At the start of the VIM, the two Voyager spacecraft had been in flight for over 12 years having been launched in August (Voyager 2) and September (Voyager 1), 1977. Voyager 1 was at a distance of approximately 40 AU (Astronomical Unit - mean distance of Earth from the Sun, 150 million kilometers) from the Sun, and Voyager 2 was at a distance of approximately 31 AU.
As of July 2007, Voyager 1 was at a distance of 15.4 Billion Kilometers (103 AU) from the sun and Voyager 2 at a distance of 12.4 Billion kilometers (83 AU).
Voyager 1 is escaping the solar system at a speed of about 3.6 AU per year, 35 degrees out of the ecliptic plane to the north, in the general direction of the Solar Apex (the direction of the Sun's motion relative to nearby stars). Voyager 2 is also escaping the solar system at a speed of about 3.3 AU per year, 48 degrees out of the ecliptic plane to the south.
Both Voyagers are headed towards the outer boundary of the solar system in search of the heliopause, the region where the Sun's influence wanes and the beginning of interstellar space can be sensed. The heliopause has never been reached by any spacecraft; the Voyagers may be the first to pass through this region, which is thought to exist somewhere from 8 to 14 billion miles from the Sun. In December 2004 Voyager 1 crossed an area known as the termination shock. This is where the million-mile-per-hour solar winds slows to about 250,000 miles per hour—the first indication that the wind is nearing the heliopause. Voyager 2 is currently observing preshock phenomena, indicating that it is close to the termination shock. The Voyagers should cross the heliopause 10 to 20 years after reaching the termination shock. The Voyagers have enough electrical power and thruster fuel to operate at least until 2020. By that time, Voyager 1 will be 12.4 billion miles (19.9 billion KM) from the Sun and Voyager 2 will be 10.5 billion miles (16.9 billion KM) away. Eventually, the Voyagers will pass other stars. In about 40,000 years, Voyager 1 will drift within 1.6 light years (9.3 trillion miles) of AC+79 3888, a star in the constellation of Ophiucius. In some 296,000 years, Voyager 2 will pass 4.3 light years (25 trillion miles) from Sirius, the brightest star in the sky . The Voyagers are destined—perhaps eternally—to wander the Milky Way. For current distances, check: Mission Weekly Reports
MareKromium
|
|
NoctilucentClouds.jpgNoctilucent Clouds over Sweden84 visiteCaption NASA:"Sometimes it's night on the ground but day in the air. As the Earth rotates to eclipse the Sun, sunset rises up from the ground.
Therefore, at sunset on the ground, sunlight still shines on clouds above. Under usual circumstances, a pretty sunset might be visible, but unusual noctilucent clouds float so high up they can be seen well after dark.
Pictured above last month (September 2007), a network of noctilucent clouds cast a colorful but eerie glow after dusk near Vallentuna, Sweden.
Although noctilucent clouds are thought to be composed of small ice-coated particles, much remains unknown about them. Satellites launched to help study these clouds includes Sweden's Odin and NASA's AIM.
Recent evidence indicates that at least some noctilucent clouds result from freezing water exhaust from Space Shuttles".MareKromium
|
|
Venus_and_the_Moon.jpgNight Lovers'...84 visitenessun commentoMareKromium
|
|
Metis_and_Jupiter.jpgMetis and Jupiter84 visitenessun commentoMareKromium
|
|
StarBirth-PIA12008.jpgStar-Birth84 visitenessun commentoMareKromium
|
|
Sun-Halo.jpg...E Finchè 'l Sole splenderà...84 visitenessun commentoMareKromium
|
|
Aurora_Borealis-Coronal_Aurora-1.jpg"Auroral Corona" from l'Observatoire de la Découverte in Val Belair near Quebec - Canada83 visiteDa "NASA - Picture of the Day" del 9 Novembre 2004: "...This fisheye picture captures a particularly active and colorful 'Auroral Corona' that occurred on November 7, 2004 (...) The above aurora has an unusually high degree of detail, range of colors and breadth across the sky. The vivid green, red, and blue auroral colors are likely caused by high atmospheric oxygen and hydrogen reacting to incoming electrons. The trigger events were magnetically induced explosions on the Sun from sunspot region 696 over the past few days. Continued activity from this active solar region could mean more auroras visible to northern observers over the next few days. Early in the morning but far in the background, planets, stars and the Moon will be simultaneously putting on their own show".
Una piccola (nostra) nota di commento: dietro la vivace bellezza dell'immagine ed i "romantici" commenti, c'è un nuovo incremento dell'attività solare in un periodo in cui, invece, il nostro Sole è usualmente calmo.
|
|
Sunrise.jpgCrepuscular Rays Over Utah83 visiteDa "NASA - Picture of the Day", del 31 Agosto 2005:"What could cause such rays of dark? Dark sky rays were caught in spectacular fashion earlier this month above Utah, USA. The cause is something surprisingly familiar: shadows. Clouds near the horizon can block sunlight from reflecting off air, making columns outward from the Sun appear unusually dark. Cloud shadows can be thought of the complement of the more commonly highlighted crepuscular rays, also visible above, where sunlight pours though cloud holes. Sometimes, on the opposite side of the sky, anticrepuscular rays can also be seen".
|
|
Never Alone.jpgNever Alone...83 visitenessun commento
|
|
SettingSun.jpgA Day of the Sun83 visite"...Peace I leave with you; my Peace I give to you..."
- John 14:27
nota: "A Day of the Sun" è anche il titolo di una serie di opere dedicate al Sole, realizzate dal Pittore Tetsuro Sawada.
|
|
Perseid-1.jpgShooting Star (1)83 visiteL'immagine è sicuramente bella, ma quello che vorremmo farVi notare è la tessitura della striscia lasciata dalla "stella cadente" la quale, come ben si vede (anche senza operare ingrandimenti), contiene "nodi" (modesti rigonfiamenti dovuti, probabilmente, a perdita/consunzione di materiale a seguito dell'attrito durante la caduta del frammento di Corpo Celeste attraverso l'atmosfera) e "brillamenti" (delle vere e proprie "fiammate" che si avviano, di regola, in corrispondenza dei "nodi" e che indicano cambi di temperatura - ergo di luminosità - del Corpo in questione).
|
|
| 476 immagini su 40 pagina(e) |
 |
|
|
|
|
26 | |
|
|
|
|
