Lo strano anello di Saturno

Di Space Telescope Science Institute1 aprile 2023

Un astronomo veterano ha scoperto che il vasto sistema di anelli di Saturno sta riscaldando l'atmosfera superiore del pianeta, un fenomeno mai osservato prima nel nostro sistema solare. Analizzando 40 anni di dati ultravioletti provenienti da molteplici missioni spaziali, tra cui il telescopio spaziale Hubble della NASA, la sonda Cassini, Voyager 1 e 2 e l'International Ultraviolet Explorer, il ricercatore ha scoperto che le particelle dell'anello ghiacciato piovono sull'atmosfera di Saturno, provocandone il riscaldamento. Questa scoperta rivoluzionaria non solo evidenzia un’interazione inaspettata tra il pianeta e i suoi anelli, ma apre anche la possibilità di utilizzare queste informazioni per prevedere l’esistenza di sistemi di anelli simili a Saturno attorno agli esopianeti.

The planet SaturnSaturn is the sixth planet from the sun and has the second-largest mass in the Solar System. It has a much lower density than Earth but has a much greater volume. Saturn's name comes from the Roman god of wealth and agriculture." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]">Saturn is easily recognizable for its opulent ring system that can easily be seen through a small telescope. Astronomers have now found that the rings are not as placid as they look. The icy rings particles are raining down onto Saturn's atmosphere. This is heating the upper atmosphere. It took a collection of 40 years’ worth of Saturn observations, gleaned from four NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]">NASA planetary missions to come to this conclusion. Hubble Space TelescopeThe Hubble Space Telescope (often referred to as Hubble or HST) is one of NASA's Great Observatories and was launched into low Earth orbit in 1990. It is one of the largest and most versatile space telescopes in use and features a 2.4-meter mirror and four main instruments that observe in the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum. It was named after astronomer Edwin Hubble." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]"> Le osservazioni del telescopio spaziale Hubble sono state utilizzate per collegare tutte le prove, raccolte alla luce ultravioletta. Questi risultati possono essere applicati per determinare se sistemi di anelli simili circondano pianeti che orbitano attorno ad altre stelle. I loro anelli sarebbero troppo lontani per essere visti, ma la spettroscopia della luce ultravioletta dei pianeti potrebbe fornire indizi.

Lo sguardo di Hubble su Saturno il 12 settembre 2021, mostra cambiamenti di colore rapidi ed estremi delle bande nell'emisfero settentrionale del pianeta, dove era l'inizio dell'autunno. Le bande sono variate nel corso delle osservazioni di Hubble sia nel 2019 che nel 2020. In particolare, l'iconica tempesta esagonale di Saturno, scoperta per la prima volta nel 1981 dalla sonda spaziale Voyager 2, era difficile da distinguere nel 2020, ma è di nuovo chiaramente evidente nel 2021. L'immagine di Saturno di Hubble cattura il pianeta segue l'inverno dell'emisfero meridionale, evidente nella persistente tonalità bluastra del polo sud. Crediti: NASA, ESA, A. Simon (NASA-GSFC) e MH Wong (UC Berkeley); Elaborazione delle immagini: A. Pagan (STScI)

The most feasible explanation is that icy ring particles raining down onto Saturn's atmosphere cause this heating. This could be due to the impact of micrometeorites, solar wind particle bombardment, solar ultraviolet radiation, or electromagnetic forces picking up electrically charged dust. All this happens under the influence of Saturn's gravitational field pulling particles into the planet. When NASA's CassiniThe Cassini–Huygens Mission, generally called Cassini, was a joint mission between NASA, the European Space Agency and the Italian Space Agency to study the Saturn system. Launched in 1997, Cassin provided astronomers with a massive amount of data about Saturn and its rings, its magnetosphere, and its moons. Cassini reached the end of its journey in 2017 when it deliberately dived into Saturn's atmosphere, where it disintegrated like a meteor." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]"Cassini probe plunged into Saturn's atmosphere at the end of its mission in 2017, it measured the atmospheric constituents and confirmed that many particles are falling in from the rings./p>

Ben-Jaffel's conclusion required pulling together archival ultraviolet-light (UV) observations from four space missions that studied Saturn. This includes observations from the two NASA Voyager probes that flew by Saturn in the 1980s and measured the UV excess. At the time, astronomers dismissed the measurements as noise in the detectors. The Cassini mission, which arrived at Saturn in 2004, also collected UV data on the atmosphere (over several years). Additional data came from Hubble and the International Ultraviolet Explorer, which launched in 1978, and was an international collaboration between NASA, ESA (European Space AgencyThe European Space Agency (ESA) is an intergovernmental organization dedicated to the exploration and study of space. ESA was established in 1975 and has 22 member states, with its headquarters located in Paris, France. ESA is responsible for the development and coordination of Europe's space activities, including the design, construction, and launch of spacecraft and satellites for scientific research and Earth observation. Some of ESA's flagship missions have included the Rosetta mission to study a comet, the Gaia mission to create a 3D map of the Milky Way, and the ExoMars mission to search for evidence of past or present life on Mars." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]"European Space Agency), and the United Kingdom's Science and Engineering Research Council./p>

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