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| Piú viste - Asteroids and Comets |
Tempel1-ZZ-ZJ-Stardust_1024-PIA13860-PCF-LXTT.jpgComet Tempel-1 from Stardust NeXT Spacecraft (Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team) 118 visiteCaption NASA:"This image mosaic shows 4 different views of comet Tempel-1 as seen by NASA's Stardust Spacecraft as it flew by it on February 14, 2011.
The images progress in time beginning at upper left, moving to upper right, then proceeding from lower left to lower right. When the Spacecraft first approached, it got a clear look at the same Surface that was imaged previously by NASA's Deep Impact Spacecraft in 2005. Deep Impact sent a projectile into the Comet, creating a crater that is located in the upper left image, but is difficult to see at this particular contrast level.
As Stardust flew closer to the Comet, it began to see New Territory that had not been imaged before. The New Territory appears on the left side of the upper right image. The Deep Impact Crater is also located in this view, on the right side.
Both the upper right and lower left images are the Closest Approach images for Stardust, taken at 3" before, and 3" after it. The images were taken from a distance of about 185 Km (approx. 115 miles). In the lower left image, the vast majority of Terrain pictured had not been seen until now. The fourth image, at lower right, shows Stardust's view as the Spacecraft was on the way out.
The image at upper left was taken 15" before the Encounter (or Closest Approach) from a distance of approx. 244 Km (about 152 miles); the image at lower right was taken 15" after the Encounter, from a distance of approx. 245 Km (about 152 miles)".MareKromium
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Comet_Oumuamua-1.jpgOumuamua113 visiteQuesta immagine profonda mostra, al centro, l'asteroide interstellare "Oumuamua", circondato dalle tracce di stelle deboli prodotte poichè il telescopio insegue l'asteroide in movimento (rispetto alla stelle cosiddette "fisse"). L'immagine è ottenuta combinando numerose immagini del VLT (Very Large Telescope) dell'ESO e del telescopio Gemini South. L'oggetto è indicato con un cerchio blu e appare come una sorgente puntiforme, senza polvere diffusa.MareKromium
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Asteroids-3753-Cruithne-1.gifAsteroid 3753 Cruithne - Horseshoe orbit of Cruithne from the Earth's perspective (Credits: Wikipedia)112 visitenessun commentoMareKromium
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Comets-Wesley-Jupiter_Impact-1.jpgCometary Impact on Jupiter 108 visitenessun commentoMareKromium
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Planet_9-b.jpgPlanet Nine (2)108 visiteAd esempio, come spiegava l’INAF, le linee degli apsidi, “ossia quelle su cui si trova l’asse maggiore della loro orbita, puntano tutte in una stessa porzione di cielo. Inoltre le loro orbite sono disposte attorno ad un piano orbitale comune”.
Così cinque anni fa Mike Brown, il ricercatore che nel 2005 spinse per declassificare Plutone a pianeta nano, e Konstantin Batygin hanno ipotizzato la presenza di una super-Terra, il nono pianeta appunto, in grado di allinearsi così bene con le orbite di cinque altri oggetti trans-nettuniani senza che questo fenomeno potesse dirsi casuale né frutto di un improbabile incidente statistico.
In particolare nel 2018 l’oggetto trans-nettuniano 2015 BP519 si ritrovò su una traiettoria inusuale, tale da poter essere proprio influenzata da un oggetto con una massa simile, da cinque a dieci volte quella terrestre.
Prova ulteriore di come Planet Nine, con la sua solo ipotizzata presenza, sia in grado di orchestrare le orbite dei molti oggetti sotto osservazione.MareKromium
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Asteroids-3753-Cruithne-2.gifAsteroid 3753 Cruithne - Orbits of Cruithne and Earth (Credits: Wikipedia)106 visitenessun commentoMareKromium
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Asteroids.jpgAsteroids (an Image-Mosaic by Emily Lakdawalla - Planetary Society - & Ted Stryk)104 visiteDalla Rubrica "NASA - Picture of the Day" del giorno 26 Luglio 2010:"As humans explore the Universe, the record for largest Asteroid visited by a Spacecraft has increased yet again. Earlier this month, ESA's robotic Rosetta Spacecraft zipped past the asteroid 21 Lutetia taking data and snapping images in an effort to better determine the history of the Asteroid and the origin of its unusual colors.
Although of unknown composition, Lutetia is not massive enough for gravity to pull it into a sphere.
Pictured above on the upper right, the 100-Km across Lutetia is shown in comparison with the other nine Asteroids and four Comets that have been visited, so far, by human-launched spacecraft. Orbiting in the Main Asteroid Belt, Lutetia shows itself to be a heavily cratered remnant of the early Solar System.
The Rosetta Spacecraft is now continuing onto comet Churyumov-Gerasimenko where a landing is planned for the AD 2014".MareKromium
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Tempel1-ZZ-ZJ-Stardust_1024-PCF-LXTT.jpgComet Tempel-1 from Stardust NeXT Spacecraft (Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)104 visiteCaption NASA:"No Comet has ever been visited twice before. Therefore, the unprecedented pass of the Stardust-NeXT Spacecraft near Comet Tempel-1 in February 2011 gave Humanity a unique opportunity to see how the Nucleus of a Comet changes over time.
Changes in the Nucleus of Comet Tempel-1 were of particular interest because the Comet was hit with an impactor from the passing Deep Impact Spacecraft in 2005. Here is one digitally sharpened image of Comet Tempel-1 near the closest approach of Stardust-NeXT.
Visible are many features already imaged in 2005, including Craters, Ridges and seemingly smoother areas. Few firm conclusions are yet available, but over the next few years astronomers who specialize in Comets and the understanding the early Solar System will be poring over these images looking for new clues as to how Comet Tempel-1 is composed, how the 2005 Impact Site now appears, and how general features of the Comet have evolved".MareKromium
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Asteroid-2022_WJ1.jpgAsteroid 2022 WJ1104 visiteDi solito riusciamo a studiare gli Asteroidi quando passano a milioni di Km o quando sono ormai caduti da qualche parte sulla Terra. Non è semplice osservare uno di questi oggetti poco prima dell'impatto e, nella storia, ci siamo riusciti solo 6 volte; questa è l'ultima, fino ad oggi. Si tratta di 2022 WJ1, un Asteroide scoperto in traiettoria di entrata il 19 novembre 2022, quasi 4 ore prima dell'impatto. L'oggetto era troppo piccolo per essere preoccupante o pericoloso, ma quello che importa è che i nostri sistemi di rilevamento stanno diventando sempre più sofisticati e veloci.
In questo caso la scoperta è stata fatta dal Catalina Sky Survey (un insieme di telescopi) in Arizona, il quale ha immediatamente allertato una rete di altri osservatori che hanno calcolato in poco tempo dove sarebbe caduto. La roccia aveva circa il 20% di possibilità di cadere da qualche parte nel continente Nord-Americano e le osservazioni di follow-up hanno permesso agli scienziati di perfezionare le loro misurazioni fino a ottenere precisamente l'ora e il luogo di impatto.
Un bolide infuocato infatti ha illuminato il cielo sopra la regione del Golden Horseshoe nel sud dell'Ontario, in Canada. Misurava circa un metro di diametro quando è entrato nell'atmosfera terrestre, rendendolo l'asteroide più piccolo mai osservato prima dell'ingresso nell'atmosfera fino ad oggi.
"Questa palla di fuoco è particolarmente significativa in quanto il meteoroide genitore è stato osservato telescopicamente prima che colpisse l'Atmosfera. Ciò rende una rara opportunità di collegare i dati telescopici di un asteroide con il suo comportamento di rottura nell'Atmosfera per poi poter raccogliere informazioni sulla sua struttura interna", ha affermato l'astronomo e fisico Peter Brown della University of Western Ontario.
Nota: ora Vi sentite più tranquilli? Io no. Stiamo "tessendo" troppe lodi circa la nostra capacità di intercettare la rotta di Asteroidi "alla svelta" e calcolarne la traiettoria, le dimensioni ed il possibile luogo di impatto. Secondo me questi Fenomeni solo cercando "fondi" (soldi, USD, insomma) e nulla di più... Scusate il cinismo.MareKromium
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Comets-Comet_Mach_Holz.jpgThe C/2004 Q2 Comet103 visiteScoperta solo pochi mesi fa, la Cometa C/2004 Q2 (Machholz) è già chiaramente visibile (a magn. 5 o superiore) nei Cieli del Sud. Ma nessuna paura, non occorrerà viaggiare per vederla: essa si sta rapidamente portando verso i nostri Cieli e, nel frattempo, continuerà ad aumentare il suo splendore (probabilmente sino alla prima metà di Gennaio 2005). La luminosità massima che C/2004 Q2 potrà raggiungere non ci è ancora nota; ciò che sappiamo, invece, è che essa resterà nei "nostri" Cieli per buona parte del 2005 e la potremo anche vedere in prossimità della Stella Polare nei primi giorni di Marzo. L'immagine che Vi proponiamo (da "NASA - Picture of the Day" del 13.12.2004) è stata ripresa ai primi di Dicembre e, come potete vedere, la cometa già ci mostra una consistente "chioma", un'abbondante coda di polveri e detriti (di colore bianco e verde) ed un'abbastanza intricata "coda ionica" (andante verso la Dx dell'Osservatore), che presenta delle increspature verso la fine.
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ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-Arrokoth.pngArrokoth ("Sky" - ex "Ultima Thule")103 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.MareKromium
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Didymos_and_Dimorphos.jpeg65803 Didymos and 65803-1 Dimorphos101 visiteAsteroid Didymos and its small moonlet Dimorphos make up what’s called a "Binary Asteroid System" – meaning the small moon (Dimorphos) orbits the larger body (Didymos).
The two asteroids are not a threat to Earth, but because they do pass relatively close to Earth, they were chosen as the target for NASA’s Double Asteroid Redirection Test (DART) mission – the agency's first mission to test planetary defense technology. This technology could one day be used to deflect hazardous asteroids on a collision course with Earth.MareKromium
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