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McNaught-07.jpgComet McNaught (8)67 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".
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McNaught-08.jpgComet McNaught (9)68 visiteCaption NASA originale:"Comet McNaught, the Great Comet of 2007, has grown a long and filamentary tail. The spectacular tail spreads across the sky and is visible to Southern Hemisphere observers just after sunset. The head of the comet remains quite bright and easily visible to even city observers without any optical aide. The amazing tail is visible on long exposures and even to the unaided eye from a dark location. Reports even have the tail visible just above the horizon after sunset for many Northern observers as well. Comet McNaught, estimated at magnitude - 2 (minus two), was caught by the comet's discoverer in the above image just after sunset last Friday from Siding Spring Observatory in Australia.
Comet McNaught, the brightest comet in decades, is now fading as it moves further into Southern Skies and away from the Sun and Earth".MareKromium
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McNaught-09.jpgThe "Tail" of McNaught, at Sunset...84 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".
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McNaught-13.jpgMc Naught and its "Iron Tail"68 visiteCaption NASA:"Outstanding in planet Earth's sky early this year, Comet McNaught is captured in this view from the STEREO A spacecraft. McNaught's coma is so bright, it blooms into the long horizontal stripe at the bottom of the field. Brilliant Venus, near the top left corner, also produces a severe horizontal blemish in the digital image. But the sensitive camera does accurately record the striations in McNaught's famous dust tail along a region stretching over 30 MKM toward the top right of the field of view. A separate, fainter, arching tail just to the left of the dust tail was initially thought to be an example of a common ion tail, formed by electrically charged atoms carried away from the comet by the Solar Wind.
However, detailed modeling indicates that tail is actually due to Neutral Iron atoms pushed out by the pressure of sunlight - the first ever detected Neutral Iron tail from a comet. The Iron atoms are thought to originate in dust grains from the comet nucleus that contain the Iron-Sulfur mineral Troilite (FeS)". MareKromium
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McNaught-9.jpgComet McNaught (10)69 visiteCaption NASA:"By January 19/20, 2007, Comet McNaught's magnificent dust tail stretched for about 150 MKM (~1 AU), requiring images from both Southern and Northern Hemispheres of planet Earth to take it all in. Two such views - from Cerro Paranal in Chile (left) and the Carnic Alps in Italy - are combined in this unique graphic that also outlines a perspective view of the Comet's orbit (dotted line) and relative position of the Sun. Driven by solar radiation pressure the dust tail initially points away from the Sun, but also trails outside the comet's orbit. Astronomers try to account for the complex structure along the tail, including the pronounced striations, by considering forces acting on the dust (e.g. gravity, solar wind and radiation) as well as the release time and size of the dust grains. In the diagram, the modeled location of dust grains released at approximately the same time relative to perihelion passage, synchrones, are shown as dashed lines. The location of grains of similar size, syndynes, are shown as solid lines".
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Meteor-Wiggle.jpgWiggling Meteor86 visiteDalla Rubrica "NASA - Picture of the Day" del giorno 2 Giugno 2010:"Did this meteor take a twisting path?
No one is sure. Considered opinions are solicited.
Meteors, usually sand sized grains that originate in comets, will typically disintegrate as they enter the Earth's atmosphere. A fast moving meteor ionizes molecules in the Earth's atmosphere that subsequently glow when they reacquire electrons. Meteor paths that twist noticeably have been noted before, and even photographed, but attributing such behavior to the motion of the meteor itself and neither the wind-blown meteor train nor the observer remains somewhat controversial.
The above meteor, imaged two weeks ago streaking over the Teide Observatory in Tenerife, Canary Islands, appears to swagger as much as several minutes of arc, which the experienced astrophotographer did not think could be attributed to drifting of the resulting train or motion of the camera mount.
If truly an indication of a twisted meteor path, an underlying reason could be the pictured meteor was markedly non-spherical in shape, non-uniform in composition, or electrically charged. Non-uniform meteors, for example, may evaporate more on one side than another, causing a rotating meteor to wobble.
Understanding meteors is important partly because meteors are candidates to have seeded Earth with prebiotic molecules that allowed for the development of life". MareKromium
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Orcus-GIF.gif90482 Orcus84 visiteCaption NASA:"A newly discovered object in the Outer Solar System moves like an anti-Pluto. 90482 Orcus was first discovered in 2004 and is slightly smaller than Pluto, although still one of the largest Kuiper Belt objects known.
Orcus may one day have the same IAU designation as Pluto: a dwarf planet.
Orcus and Pluto have similar orbits: each achieves nearly the same maximum and minimum distances from the Sun, each orbits on a similarly shaped ellipse, and each orbital ellipse is tilted toward the other planets' orbital ellipse by roughly the same angle. The great mass of Neptune causes each to circle the Sun twice for every three Neptune orbits.
Orcus is like an anti-Pluto, however, because the two objects always remain across the Solar System from each other. Orcus can be found as the spot near the center of these discovery frames moving slightly down from the top.
Until the end of next week, the discoverers of Orcus ask for your help in naming its newly discovered moon".MareKromium
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P-2010-A2-HST.jpgP/2010-A2: Extremely unusually-looking Asteroid77 visiteFirst discovered on ground based LINEAR images on January 6, 2010, the object appeared unusual enough to investigate further with the Hubble Space Telescope last week.
Pictured above, what Hubble saw indicates that P/2010 A2 is unlike any object ever seen before.
At first glance, the object appears to have the tail of a comet. Close inspection, however, shows an about 140-meter Nucleus offset from the tail center, very unusual structure near the Nucleus, and no discernable gas in the Tail. Knowing that the object orbits in the Asteroid Belt between Mars and Jupiter, a preliminary hypothesis that appears to explain all of the known clues is that P/2010 A2 is the debris left over from a recent collision between two small asteroids.
If true, the collision likely occurred at over 15.000 Km-per-hour (five times the speed of a rifle bullet) and liberated energy in excess of a nuclear bomb. Pressure from Sunlight would then spread out the debris into a trailing tail.
Future study of P/2010 A2 may better indicate the nature of the progenitor collision and may help humanity better understand the early years of our Solar System, when many similar collisions occurred. MareKromium
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Planet_9-a.jpgPlanet Nine (1)125 visiteChe cos il Pianeta 9? Spesso ci si riferisce a questo misterioso pianeta anche con letichetta Planet X.
Si tratta di un oggetto del tutto ipotetico e massiccio in orbita ellittica ben oltre Plutone, all'incirca a una distanza che impiegherebbe dai 10mila ai 20mila anni terrestri per completare un singolo giro intorno al Sole.
Su questo pianeta non abbiamo osservazioni dirette, ovviamente: se ne ipotizza lesistenza osservando alcuni pattern inaspettati nelle orbite di altri oggetti cosmici pi piccoli nelle gelide regioni esterne del Sistema Solare. Variazioni che, appunto, potrebbero spiegarsi con lattrazione gravitazionale di un corpo come questo.
In particolare nella fascia di Kuiper estrema la regione esterna del Sistema Solare che si estende da oltre l'orbita di Nettuno fino a 50 Unit Astronomiche (U.A.) dal Sole alcuni oggetti, per la precisione quattordici, sfoggiano comportamenti bizzarri: anzich avere orbite casuali e indipendenti, presentano alcune caratteristiche comuni.MareKromium
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Planet_9-b.jpgPlanet Nine (2)128 visiteAd esempio, come spiegava lINAF, le linee degli apsidi, ossia quelle su cui si trova lasse maggiore della loro orbita, puntano tutte in una stessa porzione di cielo. Inoltre le loro orbite sono disposte attorno ad un piano orbitale comune.
Cos 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 cos bene con le orbite di cinque altri oggetti trans-nettuniani senza che questo fenomeno potesse dirsi casuale n frutto di un improbabile incidente statistico.
In particolare nel 2018 loggetto trans-nettuniano 2015 BP519 si ritrov 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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Planet_9-c.jpgPlanet Nine (3)113 visiteAd oggi - spiega Science Alert la migliore prova di un pianeta sconosciuto nei confini pi remoti del nostro Sistema Solare rimane questo raggruppamento, insieme a una strana inclinazione delle loro orbite e all'orbita di 90377 Sedna che non pu essere spiegata dalla presenza di Nettuno.
Eppure non tutto sembrerebbe tanto scontato, visto che successive analisi effettuate dall'Outer Solar System Origins Survey, cos come diversi altri risultati dell'indagine, non hanno trovato alcun segno di raggruppamento tra altri oggetti trans-nettuniani rilevanti, rendendo l'esistenza del Pianeta Nove per ora estremamente controversa.
Ma come sarebbe questo pianeta?
Come detto, sarebbe dotato di una massa fino a dieci volte quella terrestre, con una circonferenza che si avvicina a quella di uno dei nostri giganti di ghiaccio, cio Urano e Nettuno, originatosi fra le orbite di Giove e Nettuno.
Con la differenza che prima di poter assumere la massa attuale, Planet Nine avrebbe ricevuto un calcio dal pozzo gravitazionale di uno dei due giganti gassosi e si sarebbe ritrovato tra le distese ghiacciate.
Altre ipotesi, meno probabili, lo inquadrerebbero invece come un frammento di una stella di passaggio davvero molto tempo fa.
Se il pianeta Nove esiste, la sua estrema lontananza - da qualche parte circa 10 volte pi lontano di Nettuno - limita la quantit di luce solare che si riflette dalla sua superficie conclude Science Alert individuarlo sarebbe reso pi difficile proprio dalla sua lontananza. Non solo per la sua oscurit, ma anche per il suo relativo calo della velocit orbitale sarebbe poi pi difficile identificare le differenze di posizione.
Se per ora il nostro Sistema Solare rimane una famiglia di otto pianeti, la ricerca di un nono, ipotetico membro potrebbe essere giustificata anche dai molti segreti che saremmo in grado di ricavare nel corso della caccia, a prescindere dal risultato.MareKromium
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Pompeja.jpgPompeja (imagination)119 visitenessun commentoMareKromium
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