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Observing the Universe

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Observing the Universe ObservingObserving thethe UniverseUniverse :: aa TravelTravel ThroughThrough SpaceSpace andand TimeTime Enrico Flamini Agenzia Spaziale Italiana Tokyo 2009 When you rise your head to the night sky, what your eyes are observing may be astonishing. However it is only a small portion of the electromagnetic spectrum of the Universe: the visible . But any electromagnetic signal, indipendently from its frequency, travels at the speed of light. When we observe a star or a galaxy we see the photons produced at the moment of their production, their travel could have been incredibly long: it may be lasted millions or billions of years. Looking at the sky at frequencies much higher then visible, like in the X-ray or gamma-ray energy range, we can observe the so called “violent sky” where extremely energetic fenoena occurs.like Pulsar, quasars, AGN, Supernova CosmicCosmic RaysRays:: messengersmessengers fromfrom thethe extremeextreme universeuniverse We cannot see the deep universe at E > few TeV, since photons are attenuated through →e± on the CMB + IR backgrounds. But using cosmic rays we should be able to ‘see’ up to ~ 6 x 1010 GeV before they get attenuated by other interaction. Sources Sources → Primordial origin Primordial 7 Redshift z = 0 (t = 13.7 Gyr = now ! ) Going to a frequency lower then the visible light, and cooling down the instrument nearby absolute zero, it’s possible to observe signals produced millions or billions of years ago: we may travel near the instant of the formation of our universe: 13.7 By. Redshift z = 1.4 (t = 4.7 Gyr) Credits A. Cimatti Univ. Bologna Redshift z = 5.7 (t = 1 Gyr) Credits A. Cimatti Univ. Bologna Redshift z = 18.3 (t = 0.21 Gyr) Credits A. Cimatti Univ. Bologna Herschel and Planck launch with Ariane V – May 2009 Planck first light yields promising results Just above the atmosphere Our Solar System The man made spacecraft at the edge of our Solar System Voyager 1 OurOur LimitsLimits :age:age andand speedspeed CassiniCassini--HuygensHuygens NASANASA-- ESAESA-- ASIASI • Antenna SaturnSaturn beforebefore andand afterafter CassiniCassini Before Cassini arrival 18 moons were Known, to date, 52 moons have been officially named. In alphabetic order, they are: Aegir, Albiorix, Anthe, Atlas, Bebhionn, Bergelmir, Bestla, Calypso, Daphnis, Dione, Enceladus, Epimetheus, Erriapus, Farbauti, Fenrir, Fornjot, Greip, Hati, Helene, Hyperion, Hyrokkin, Iapetus, Ijiraq, Janus, Jarnsaxa, Kari, Kiviuq, Loge, Methone, Mimas, Mundilfari, Narvi, Paaliaq, Pallene, Pan, Pandora, Phoebe, Polydeuces, Prometheus, Rhea, Siarnaq, Skadi, Skoll, Surtur, Suttung, Tarqeq, Tarvos, Telesto, Tethys, Thrym, Titan and Ymir. EnceladusEnceladus EnceladusEnceladus The Huygens descent on Titan NorthNorth PolarPolar RegionRegion Mosaic:Mosaic: EthaneEthane andand MethaneMethane LakesLakes Jupiter EUROPAEUROPA Mars For Robots Now….. tomorrow? Viking Lander 1 Impact of dust on atmospheric temperatures: -can reach 80 K during dust storm ! - can produce temperature inversionE. Flamini near surface E. Flamini Formation of water ice frost on the surface (Viking lander 2) E. Flamini PhoenixPhoenix MarsMars 3328 - 2202 2202 flight dir. 3328 flight dir. Exomars the European Mars Explorer The Sample return No future without imagination ! Thanks for you attention.
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  • Arxiv:1912.09192V2 [Astro-Ph.EP] 24 Feb 2020
    Draft version February 25, 2020 Typeset using LATEX preprint style in AASTeX62 Photometric analyses of Saturn's small moons: Aegaeon, Methone and Pallene are dark; Helene and Calypso are bright. M. M. Hedman,1 P. Helfenstein,2 R. O. Chancia,1, 3 P. Thomas,2 E. Roussos,4 C. Paranicas,5 and A. J. Verbiscer6 1Department of Physics, University of Idaho, Moscow, ID 83844 2Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca NY 14853 3Center for Imaging Science, Rochester Institute of Technology, Rochester NY 14623 4Max Planck Institute for Solar System Research, G¨ottingen,Germany 37077 5APL, John Hopkins University, Laurel MD 20723 6Department of Astronomy, University of Virginia, Charlottesville, VA 22904 ABSTRACT We examine the surface brightnesses of Saturn's smaller satellites using a photometric model that explicitly accounts for their elongated shapes and thus facilitates compar- isons among different moons. Analyses of Cassini imaging data with this model reveals that the moons Aegaeon, Methone and Pallene are darker than one would expect given trends previously observed among the nearby mid-sized satellites. On the other hand, the trojan moons Calypso and Helene have substantially brighter surfaces than their co-orbital companions Tethys and Dione. These observations are inconsistent with the moons' surface brightnesses being entirely controlled by the local flux of E-ring par- ticles, and therefore strongly imply that other phenomena are affecting their surface properties. The darkness of Aegaeon, Methone and Pallene is correlated with the fluxes of high-energy protons, implying that high-energy radiation is responsible for darkening these small moons. Meanwhile, Prometheus and Pandora appear to be brightened by their interactions with nearby dusty F ring, implying that enhanced dust fluxes are most likely responsible for Calypso's and Helene's excess brightness.
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