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| Ultimi arrivi - SOLAR SYSTEM |
Voyagers-Heliosphere7d.pngInterstellar Space for the "Voyagers"!206 visiteAffascinante. Notizia vecchiotta (quasi di due anni), ma sempre interessante da leggere ed osservare.MareKromiumGiu 26, 2020
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ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-Arrokoth.pngArrokoth ("Sky" - ex "Ultima Thule")114 visiteOver a year ago, the New Horizons spacecraft flew by a strange object at the edge of our solar system. Just a hazy form resembling a snowman on the day of the spacecraft’s closest approach, Arrokoth is now taking shape to be a fascinating and revelatory member of the region of the solar system beyond Neptune's orbit known as the Kuiper Belt. Untouched by the usual turmoil and impacts of most small objects, this pristinely preserved world could tell us about the earliest years of our solar system's formation.
New research published in a series of papers in Science begins to reveal Arrokoth's mysteries, including its formation, geography, composition, various basic properties and more. Scientists from NASA's Ames Research Center in California's Silicon Valley worked alongside researchers from across the world to provide a comprehensive first look at this object.
Also known as MU69, the object consists of two lobes connected by a thin "neck" and has days that run almost 16 hours, while a full orbit around the solar system takes 298 years. Its orbit lies 44 times further away from the Sun than our own Earth, and based on the craters we see across its surface, Arrokoth is estimated to be about 4 billion years old.
"Arrokoth is a time capsule for our solar system's origins," said Orkan Umurhan, a research scientist at Ames and collaborator on the three Science papers. "MU69, and objects like it, can give us a look four billion years into the past and insight into where our cosmic home came from."
A Cold, Red and Smooth Surface
The images from the New Horizon's flyby reveal a complex world, rich not only in its geology, but in color and temperature as well.
The surface of Arrokoth is all red, but new analysis shows there's more variation in the color than originally thought, with the smaller lobe slightly redder than the larger one. That red coloring is often an indicator of a type of chemical compound known as tholins – organics seen on many objects in the outer solar system, including Pluto and Saturn’s moon Titan. Though we don't know if this is the case for certain on Arrokoth, Titan-like tholins would match the data we do have on the object.
Though we can't measure the object's temperature as we traditionally think of it, we can find a value for the temperature based on the object's radiation by looking at its brightness. This "brightness temperature" varies around the object, with the poles of each lobe reaching temperatures below -350 degrees Fahrenheit, decreasing further about each lobe’s equator. The neck connecting the lobes is relatively warmer than the rest of the object by up to 6 degrees Fahrenheit.
Arrokoth is a world with complex geological features across its surface, and no rings or other smaller objects in its orbit. Though littered with light craters, each about half a mile or less across, the object's surface is mostly smooth – with the exception of a larger crater nicknamed Maryland on the smaller lobe.
Maryland is most likely an impact crater, with its rim stretching more than four miles across and less than half a mile deep. Between the crater and the neck connecting the two lobes is a series of troughs, similar to those found on the asteroid Eros or Mars’ moon Phobos.
The larger lobe is even flatter than its counterpart. Besides a section marked off by a chain of pits, there are no large craters at all. That so much of Arrokoth's surface is very lightly disturbed or not at all tells a story about its formation – one not filled with collisions and violence, but gentler and slower impacts.
The Origins of Arrokoth
Arrokoth's two lobes appear to have once been separate objects, orbiting each other in synchronicity until merging together at a very slow speed – no more than a couple meters per second, perhaps even slower.
Those objects were likely formed in the very early years of our solar system, over four billion years ago. Then, the solar system was a nebulous swirl of gas and dust. Microscopic dust particles began to stick together into larger and larger chunks. Soon, those chunks become pebble-sized clouds that continue to collapse together, creating larger objects. In some cases, such as Arrokoth's, those objects formed in pairs, leading to a binary system.
This could also explain certain aspects of Arrokoth's chemical compositions, with possible methanol ices and complex organics that were also present in the early solar system nebula seen on the object as well. However, those organics could have emerged after Arrokoth had formed through chemical processes spurred on by cosmic radiation affecting methane on its surface. Unlike many similar objects, there is an absence of water ice, which appears to have been depleted or is obscured from our view.
Because Arrokoth's formation was so benign, with no major collisions or aberrations apparent on its surface, the object can give us insight into this early phase of the solar system when planets and other objects were still forming. Its interior is likely preserved as well, leaving the same mixture of ices, organics and dust from the nebula of materials that created our solar system.
New Horizons has given us not only a new in-depth look into Arrokoth, but that of other Kuiper Belt objects and the larger solar system as well. This small and oddly shaped world contains aspects of our own history that can be uncovered almost nowhere else. It is a rare and pristine record of the early solar system, a time capsule of our origins that has many truths yet to unveil.MareKromiumMag 26, 2020
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101955-Bennu-011.png101955 Bennu - Just like Itokawa (Natural Colors; credits for the additional process. and color.: E. Bonora & Marco Faccin)221 visiteNotate la posizione "anomala" e "sporgente" dei mega-boulders (mega-macigni) visibili. Bizzarro, vero?!? La "causa" della nascita di 101955 Bennu? Aggregazione Gravitazionale di detriti. Così come Itokawa. Asteroidi fragili, polverosi e senza crateri. Ere di "lavoro" (miliardi di anni terrestri) e questo ne é un (altro esempio di) risultato.MareKromiumApr 15, 2020
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Jupiter-PIA22936.jpgThe "Giant" from Earth158 visiteThis Earth-based observation of Jupiter and the South Tropical Disturbance approaching the Great Red Spot was captured on January, 26, 2018 by the Amateur Astronomer Christopher Go, who also processed the image.MareKromiumApr 04, 2020
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Jupiter-PIA22948.jpgJupiter Abyss...192 visiteCaption NASA Originale:"NASA's Juno spacecraft captured this view of an area within a Jovian jet stream showing a vortex that has an intensely dark center. Nearby, other features display bright, high altitude clouds that have puffed up into the sunlight.
The color-enhanced image was taken at 12:55 a.m. PDT (3:55 a.m. EDT) on May 29, 2019, as the spacecraft performed its 20th science fly-by of Jupiter. At the time, Juno was about 9.200 miles (approx. 14.805,96 Km) from the Planet's cloud tops, above approximately 52° North Latitude.
Citizen scientists Gerald Eichstädt and Seán Doran created and named this image using data from the spacecraft's JunoCam imager".MareKromiumApr 04, 2020
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Jupiter-White_Storm-PIA23445.jpgWhite Storm on Jupiter154 visiteCaption NASA Originale:"This view of Jupiter's Upper Atmosphere from NASA's Juno Spacecraft includes something remarkable: two storms caught in the act of merging.
The two white ovals seen within the orange-colored band left of center are Anticyclonic Storms — that is, storms that rotate counter-clockwise. The larger of the two ovals has been tracked for many years, as it grew in size through mergers with other Anticyclonic white ovals.
JunoCam was fortunate to capture this new merger, which typically takes place over the course of only a few days.
The event interests scientists because the ovals had approached each other months earlier, only to move apart again.
This merger may be the result of perturbations due to the proximity of Oval BA, which is the larger storm just to the North of the two merging, white ovals. Oval BA is the second largest Anticyclonic Vortex in Jupiter's Atmosphere (second only to the famous Great Red Spot). During this pass over Jupiter, Juno gave scientists their best views of Oval BA to date.
Citizen scientist Tanya Oleksuik created this color-enhanced image using data from the JunoCam camera. The original image was taken on December, 26, 2019, at 10:28 a.m. PST (1:28 p.m. EST) as the Juno Spacecraft performed its 24th close fly-by of the Planet. At the time, the Spacecraft was about 44.900 miles (such as approx. 72.259,54 Km) from the tops of Jupiter's clouds, at a latitude of about 60° South".MareKromiumApr 04, 2020
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Europa-PIA23166.jpgRhadamanthys Linea (Enhanced Natural Color Version)151 visiteCaption NASA Originale:"Europa's Surface is covered with a vast network of Linear Features such as cracks, ridges, and bands, as well as other smaller circular features that include pits, spots, domes, and microchaos.
This image, created from clear-filter images taken on the Galileo spacecraft's 17th orbit around Jupiter and colorized with lower-resolution images taken on Galileo's first orbit around Jupiter, shows a huge variety of these feature types.
Of particular note is the prominent ridge at the center of the image, called Rhadamanthys Linea.
While most ridges have a reddish appearance in colorized images such as this enhanced color version, Rhadamanthys appears to have uneven blotches of darker, redder material which are more prominent in some locations than in others.
Some scientists have interpreted the appearance of Rhadamanthys to indicate that it is a recently, or perhaps currently, active feature on Europa's Surface".MareKromiumApr 04, 2020
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Jupiter-PIA21974.jpgWhat a View!189 visitenessun commentoMareKromiumApr 04, 2020
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Jupiter-PIA23442.jpgOn the Limb...160 visiteCaption NASA Originale:"NASA's Juno spacecraft captured this impressive image revealing a band of swirling clouds in Jupiter's Northern Latitudes during Juno's close fly-by occurred on November, 3, 2019. Small pop-up storms can also be seen rising above the lighter areas of the clouds, most noticeably on the right side of the image.
This view provides scientists with high-resolution details — the spacecraft skimmed approximately 3.200 miles (such as about 5.149,9 Km) above Jupiter's cloud tops at the time it was taken.
Citizen scientist Björn Jónsson created this enhanced color image using data from the JunoCam camera. The picture, as we wrote above, was taken on November, 3, 2019 at 2:13 p.m. PST (5:13 p.m. EST) at a Latitude of about 38° North".MareKromiumApr 04, 2020
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Jupiter-PIA23606.jpgThe "Eye" of Jupiter180 visiteCaption NASA Originale:"Swirling in Jupiter's Atmosphere for hundreds of years, the Great Red Spot is captured in this pair of close-up images from Juno's JunoCam Camera. The giant storm churns through Jupiter's Atmosphere, creating the turbulent flows to its West. On the West-side of the Great Red Spot itself, a sliver of red material is being pulled off the periphery. This is a recent, frequent, phenomenon first observed in ground-based data in 2017.
Two images have been mosaicked together by citizen scientist Kevin M. Gill to create this enhanced color composite. When they were taken on Feb. 12, 2019 at 10:24 a.m. PDT (1:24 p.m. EDT) and 10:29 a.m. PDT (1:29 p.m. EDT), Juno was about 43.500 miles (such as about 70.006,464 Km) above Jupiter's cloud tops. Features as small as 31 miles (approx. 49,889 Km) can be resolved in the images, allowing us to see structure in the interior of the Great Red Spot, as well as the fine texture of the white clouds in the South Tropical Zone below".MareKromiumApr 04, 2020
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Jupiter-PIA23437.jpgIo's Shadow173 visiteCaption NASA Originale:"Jupiter's volcanically active moon Io casts its shadow on the planet in this dramatic image from NASA's Juno Spacecraft. As with solar eclipses on the Earth, within the dark circle racing across Jupiter's cloud tops one would witness a full solar eclipse as Io passes in front of the Sun.
Such events occur frequently on Jupiter because it is a large planet with many moons. In addition, unlike most other planets in our solar system, Jupiter's axis is not highly tilted relative to its orbit, so the Sun never strays far from Jupiter's equatorial plane (+/- 3°). This means Jupiter's moons regularly cast their shadows on the planet throughout its year.
Juno's close proximity to Jupiter provides an exceptional fish-eye view, showing a small fraction near the planet's Equator. The shadow is about 2.200 miles (such as approx. 3.540,55 Km) wide, approximately the same width as Io, but appears much larger relative to Jupiter.
A little larger than Earth's Moon, Io is perhaps most famous for its many active volcanoes, often caught lofting fountains of ejecta well above its thin (?) Atmosphere.
Citizen scientist Kevin M. Gill created this enhanced-color image using data from the spacecraft's JunoCam imager. The raw image was taken on Sept. 11, 2019 at 8:41 p.m. PDT (11:41 p.m. EDT) as the Juno spacecraft performed its 22nd close fly-by of Jupiter. At the time the image was taken, the spacecraft was about 4.885 miles (approx. 7.861,64 Km) from the cloud tops at a Latitude of 21° North".
Nota: e per chi ha visto il famoso "2010 Odissea Due: l'Anno del Contatto", questa immagine dovrà "ricordare" qualcosa...MareKromiumApr 04, 2020
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Titan-PIA21890.jpgTitan126 visiteCaption NASA Originale:"As it glanced around the Saturn system one final time, NASA's Cassini Spacecraft captured this view of the planet's giant moon Titan. Interest in mysterious Titan was a major motivating factor to return to Saturn with Cassini-Huygens following the Voyager mission fly-bys of the early 1980s. Cassini and its Huygens probe, supplied by the ESA (European Space Agency), revealed the moon to be every bit as fascinating as scientists had hoped.
These views were obtained by Cassini's Narrow-Angle Camera on Sept. 13, 2017. They are among the last images Cassini sent back to Earth.
This natural color view, made from images taken using red, green and blue spectral filters, shows Titan much as Voyager saw it - a mostly featureless golden orb, swathed in a dense Atmospheric Haze. An enhanced-color view (such as this one) adds to this color a separate view taken using a spectral filter (centered at 938 nanometers) that can partially see through the haze.
The views were acquired at a distance of about 481.000 miles (such as approx. 774.094,464 Km) from Titan. The image scale is about 3 miles (roughly 4,828 Km) per pixel".MareKromiumMar 12, 2020
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