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| Ultimi arrivi - Asteroids and Comets |
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.MareKromiumMag 26, 2020
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Comet_Borisov_-_GIF_3.gifFrom far away: the Comet Borisov through the Solar System (GIF-Movie)286 visiteGuardate bene! EccoVi la differenza (REALE ed IN FATTO) tra un Fly-By and uno Swing-By...E senza dimenticare "Oumuamua"!
As the first known object of its type, Oumuamua presented a unique case for the International Astronomical Union (IAU, for short), which assigns designations for astronomical objects. Originally classified as comet C/2017 U1, it was later reclassified as Asteroid A/2017 U1, due to the absence of a coma (--> "Chioma", in Italian).
Once it was unambiguously identified as coming from outside the Solar System, a new designation was created.
The name comes from the Hawaiian word "oumuamua", meaning 'scout' (from ou, meaning 'reach out for', and mua, reduplicated for emphasis, meaning 'first, in advance of', and reflects the way this object is like a scout or messenger sent from the distant past to reach out to Humanity.
It roughly translates to 'first distant messenger' (or "The First Messenger from the distance").
Before the official name was decided upon, the name "Rama" was suggested by the name given to an Alien Spacecraft discovered under similar circumstances in the 1973 science fiction novel "Rendezvous with Rama", by Sir Arthur C. Clarke.MareKromiumNov 10, 2019
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Comet_Borisov_-_GIF.gifFrom far away: Comet Borisov (GIF-Movie)119 visitenessun commentoMareKromiumNov 10, 2019
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Comet_Borisov_-_Still.pngFrom far away: Comet Borisov138 visiteDa un altro Sistema, dallo Spazio Interstellare, da "altrove".... La "Cometa" Borisov attraverserà il nostro Sistema Solare così come una Rondine attraversa il nostro campo visivo in un luminoso giorno di Primavera.
Da dove viene? Dove va?
... Ma che importa, alla fine?!?.....MareKromiumNov 10, 2019
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ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-Ultima_Thule_2-flyby.gifUltima Thule (Fly-By)69 visiteOriginal Caption:"Mission scientists created this "departure movie" from 14 different images taken by the New Horizons Long Range Reconnaissance Imager (LORRI) shortly after the spacecraft flew past the Kuiper Belt object nicknamed Ultima Thule (officially named 2014 MU69) on Jan. 1, 2019".MareKromiumOtt 19, 2019
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ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-ZZ-Ultima_Thule_-_1.jpgUltima Thule94 visiteThe New Horizons team used the Hubble Space Telescope to search for its post-Pluto, Kuiper Belt flyby target. Using observations made with Hubble on June 26, 2014, the science team (led by co-investigator Marc Buie) discovered an object that New Horizons could reach with its available fuel. The object was subsequently designated 2014 MU69, given the minor planet number 485968 and, with public input, nicknamed "Ultima Thule" (which means "beyond the known world").
MU69 is located in the Kuiper Belt, beyond the orbit of Neptune. At 12:33 a.m. (EST) on January 1, 2019, New Horizons flew just 2,200 miles (3,500) kilometers from the object's surface, when it was about 4 billion miles (6.6 billion kilometers) from the Sun -- the most distant planetary flyby in history and the first close-up look at a solar system object of this type.
Ultima Thule is the first unquestionably primordial contact binary ever explored. Approach pictures hinted at a strange, snowman-like shape, but further analysis of images, taken near closest approach, uncovered just how unusual the KBO's shape really is. At 22 miles (35 kilometers) long, the binary consists of a large, flat lobe (nicknamed "Ultima") connected to a smaller, rounder lobe (nicknamed "Thule").
This strange shape was the biggest surprise of the flyby. Nothign like it has been anywhere in the solar system -- sending the planetary science community back to the drawing board to understand how planetesimals (the building blocks of the planets) form.
Because it is so well preserved, MU69 offered our clearest look back to the era of planetesimal accretion and the earliest stages of planetary formation. Apparently the two lobes once orbited each other, like many so-called binary worlds in the Kuiper Belt, until something brought them together in a "gentle" merger.
In color and composition, New Horizons data revealed that MU69 resembles many other objects found in its region of the Kuiper Belt. Consistent with pre-flyby observations from the Hubble Telescope, Ultima Thule is very red – redder even than Pluto, which New Horizons flew past on the inner edge of the Kuiper Belt in 2015 – and about the same color as many other so-called "cold classical" KBOs. ("Cold" referring not to temperature but to the circular, uninclined orbits of these objects; "classical" in that their orbits have changed little since forming, and represent a sample of the primordial Kuiper Belt.)
New Horizons scientists have also seen evidence for methanol, water ice and organic molecules on the surface -- a spectrum similar to some of the most extreme objects we've seen in the outer solar system.
Flyby data transmission continues, with all data expected on the ground by late summer 2020.MareKromiumOtt 08, 2019
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Comets-Comet_Churyumov-Gerasimenko-cometCG01_rosetta_2048-MF-EB-LXTT-IPF.jpgA view of Comet Churyumov-Gerasimenko224 visiteUn "piccolo" Tributo dato dalla prestigiosa rubrica quotidiana NASA "Astronomy Picture Of The Day" ai nostri Amici e Partner, Marco Faccin ed Elisabetta Bonora. Guardate su http :// apod. nasa. gov/ apod/ astropix.html di lunedì, 15 Settenbre 2014. Complimenti, di Cuore! E, sia detto per Onestà Intellettuale, qui, Lunexit, non c'entra nulla. Il nostro è solo un Omaggio a due OTTIMI Partners. Ma Lunexit, su questo Lavoro, non ha credito alcuno.MareKromiumSet 15, 2014
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Comets-Comet_ISON-4-10-2013-HST.jpgComet ISON (Hubble Space Telescope's View)60 visiteCaption originale:"Comet C/ISON was imaged with the Hubble Space telescope on April 10, 2013, using the Wide Field Camera 3, when the Comet was 394 million miles from Earth. View larger. Image via NASA, ESA, J.-Y. Li (Planetary Science Institute), and the Hubble Comet ISON Imaging Science Team".
MareKromiumOtt 17, 2013
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Comets-Comet_ISON-Nucleus.jpgComet ISON (Tian Lian 1 - Satellite's View - Controversial: possible fake)84 visiteEd ecco il Nucleo di ISON: come vedete, assomiglia TANTISSIMO a quello di Tempel-1 e Wild-2. Mia opinione? Immagine genuina. Con tutto quanto ne segue e consegue... Il punto è che, a quanto leggo (ma NON sul Sito dell'Agenzia Spaziale Cinese, sul quale non posso capirci nulla), il Satellite Geostazionario Tian-Lian 1 NON ha fotocamere! E se questo è vero (ma non so se è vero), allora è evidente che siamo davanti all'ennesima bufala...MareKromiumOtt 15, 2013
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Comets-Comet_ISON-HST-30Apr-V_I-L-800.jpgComet ISON (Hubble Space Telescope's View)148 visiteAdvanced amateur astronomers are already getting good images of Comet ISON, which currently shines at around +12th magnitude in the constellation Cancer. And although NASA’s Deep Impact/EPOXI mission is down for the count, plans are afoot for the Curiosity rover and the Mars Reconnaissance Orbiter to attempt imaging the comet when it makes its closest approach to the Red Planet on October 1st at 0.0724 Astronomical Units (A.U.) or 10,830,000 kilometres distant. If MSL is successful, it would be the first time that a comet has been observed from the surface of another world.
Currently, ISON sits about a magnitude below the projected light curve, (see below) but that isn’t all that unusual for a comet. Already, there’s been increasing talk of “ISON being a dud,” but as Universe Today’s Nancy Atkinson pointed out in a recent post, these assertions are still premature. The big question is what ISON will do leading up to perihelion, and if it will survive its passage 1.1 million kilometres above the surface of the Sun on November 28th to become a fine comet in the dawn skies in the weeks leading up to Christmas.
ISON is already starting to show a short, spikey tail in amateur images. Tsutomu Seki estimated it to be shining at about magnitude +11.1 on September 16th. Keep in mind, a caveat is in order when talking about the magnitudes of comets. Unlike stars, which are essentially a point source, the brightness of a comet is spread out over a large surface area. Thus, a comet may appear visually fainter than the quoted magnitude, much like a diffuse nebula. Although +6th magnitude is usually the limit for naked eye visibility, I’ll bet that most folks won’t pick up ISON with the unaided eye from typical suburban sites until it breaks +4th magnitude or so.
The forward scattering of light also plays a key role in the predicted brightness of a comet. The November issue of Astronomy Magazine has a great article on this phenomenon. It’s interesting to note that ISON stacks up as a “9” on their accumulated point scale, right at the lower threshold of comet “greatness,” versus a 15 for sungrazing Comet C/1965 S1 Ikeya-Seki. Another famous “9” was Comet C/1996 B2 Hyakutake, which passed 0.1018 A.U. or 15.8 million kilometres from Earth on March 25, 1996.
ISON will pass 0.429 A.U. or 64.2 million kilometres from Earth the day after Christmas. Bruce Willis can stay home for this one.
Here is a blow-by-blow breakdown of some key dates to watch for as ISON makes its plunge into the inner solar system:
-September 25th: ISON crosses the border from the astronomical constellation of Cancer into Leo.
-September 27th: ISON passes 2 degrees north of the planet Mars.
-October 1st: The 12% illuminated waning crescent Moon passes 10 degrees south of Mars & ISON.
-Early October: ISON may break +10th magnitude and become visible with binoculars or a small telescope.
-October 4th: New Moon occurs. The Moon then exits the dawn sky, making for two weeks of prime viewing.
-October 10th: ISON enters view of NASA’s STEREO/SECCHI HI-2A CAMERA:
-October 16th: ISON passes just 2 degrees NNE of the bright star Regulus, making a great “guidepost” to pin it down with binoculars.
-October 18th: The Full Moon occurs, after which the Moon enters the morning sky.
-October 26th: A great photo-op for astro-imagers occurs, as ISON passes within three degrees the Leo galaxy trio of M95, M96, & M105.
-October 30th: The 17% illuminated Moon passes 6 degrees south of ISON.
-Early November: Comet ISON may make its naked eye debut for observers based at dark sky sites.
-November 3rd: A hybrid (annular-total) solar eclipse occurs, spanning the Atlantic and Central Africa. It may just be possible for well placed observers to catch sight of ISON in the daytime during totality, depending on how quickly it brightens up. The Moon reaching New phase also means that the next two weeks will be prime view time for ISON at dawn.
-November 5th: ISON crosses the border from the astronomical constellation of Leo into Virgo.
-November 7th: ISON passes less than a degree from the +3.6 magnitude star Zavijava (Beta Virginis).
-November 8th: ISON passes through the equinoctial point in Virgo around 16:00 EDT/20:00 UT, passing into the southern celestial hemisphere and south of the ecliptic.
-November 14th: ISON passes less than a degree from the 10th magnitude galaxy NGC 4697.
-November 17th: The Moon reaches Full, passing into the morning sky.
-November 18th: ISON passes just 0.38 degrees north of the bright star Spica.
-November 22nd: ISON crosses into the astronomical constellation of Libra.
-November 23rd: ISON sits 4.7 degrees SSW of the planet Mercury and 4.9 SSW of Saturn, respectively.
-November 25th: ISON pays a visit to another famous comet, passing just 1.2 degrees south of short period comet 2P/Encke which may shine at +8th magnitude.
-November 27th: ISON enters the field of view of SOHO’s LASCO C3 coronagraph.
-November 28th: ISON reaches perihelion at ~18:00 PM EST/ 23:00 UT.
After that, all bets are off. The days leading up to perihelion will be tense ones, as ISON then rounds the Sun on a date with astronomical destiny. Will it join the ranks of the great comets of the past? Will it stay intact, or shatter in a spectacular fashion? Watch this space for ISON updates… we’ll be back in late November with our post-perihelion guide!
Be sure to also enjoy recently discovered Comet C/2013 R1 Lovejoy later the year.
(source: http://www.universetoday.com/104818/comet-ison-a-viewing-guide-from-now-to-perihelion/#ixzz2fpLTKJwD)
Read more: http://www.universetoday.com/104818/comet-ison-a-viewing-guide-from-now-to-perihelion/#ixzz2fpLG75usMareKromiumSet 24, 2013
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Comets-Comet_ISON-Nucleus_Crop_Chumack.jpgComet ISON92 visite"Comet ISON is probably at least twice as big as Comet Lovejoy and will pass a bit farther from the sun’s surface" notes Knight. “This would seem to favor Comet ISON surviving and ultimately putting on a good show.
One of the most exciting possibilities would be a partial break-up. "If Comet ISON splits, it might appear as a 'string of pearls' when viewed through a telescope," speculates Battams. “It might even resemble the famous Comet Shoemaker-Levy 9 that hit Jupiter in 1994.”
A break-up would pose no threat to Earth, assures Yeomans. "Comet ISON is not on a collision course. If it breaks up, the fragments would continue along the same safe trajectory as the original comet."
Whatever happens, northern sky watchers will get a good view. For months after it swings by the sun, Comet ISON will be well placed for observers in the northern hemisphere. It will pass almost directly over the North Pole, making it a circumpolar object visible all night long.
Will Comet ISON fizzle ... or sizzle? Stay tuned to Science@NASA for updates.MareKromiumSet 24, 2013
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Lutetia-05-CTX-EDM-PCF-LXTT-IPF.jpgAsteroid 21-Lutetia (CTX Frame and EDM - Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)152 visite21 Lutetia is a relatively large Main-Belt Asteroid, measuring about 100 Km in diameter (approx. 120 km along its Major Axis). It was discovered in the AD 1852 by the French-German Astronomer Hermann Goldschmidt, and is named after Lutetia, such as the Latin name of the city that stood where Paris was later built. The Asteroid 21 Lutetia has an irregular shape and is heavily cratered, with the largest Impact Crater reaching about 45 Km in diameter.
The Surface of this Asteroid is geologically heterogeneous and it is intersected by a system of Grooves and Scarps, which are thought to be the external manifestation of deep, internal, Fractures; it also possess an high Average Density, which could have meant that is (likely) made of Iron and Nickel rich Rock (even though, as we shall better see later on, this - however logical - claim, is still unproven). The ESA - Rosetta Probe passed as close as about 3162 Km (approx. 1965 miles) from 21 Lutetia in July 2010 and, at the time of Rosetta's Fly-By, it was the largest Asteroid ever visited by a Spacecraft (that, until the NASA - Dawn Spaceraft arrived at 4 Vesta, in July 2011).
The composition of 21 Lutetia has puzzled astronomers for some time, and that is because, while classified among the M-type Asteroids, most of which are Metallic (better yet: rich of Metallic Minerals/Elements), 21 Lutetia must be one of the so-called Anomalous Members of this classification, since it does not display much evidence of Metallic Minerals on its Surface. As a matter of fact, after most part of the data received from the Rosetta Probe were analyzed, several indications of a NON-Metallic Surface of this Asteroid were found, like, for instance, a flat, Low Frequency Spectrum (similar to that of Carbonaceous Chondrites and C-type Asteroids - which is, of course, deeply different from the one of the so-called Metallic Meteorites, such as those Meteorites which are logically believed to derive from a Metallic - such as, we repeat, Iron and Nickel-rich - Celestial Body), a low Radar Albedo (unlike the high Albedoes of Strongly Metallic Asteroids, like 16 Psyche), evidence of Hydrated Materials on its Surface, abundant Silicates, and a thicker layer of Regolith than most of the other known (as far as their composition is concerned) Asteroids.MareKromiumApr 26, 2012
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