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Multispectral Astrophysics

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Multispectral Astrophysics MULTISPECTRAL ASTROPHYSICS Dainis Dravins - Lund Observatory www.astro.lu.se/~dainis The multi-wavelength sky Lund Observatory Milky Way painting (1955) IRAS mid-infrared all-sky survey Cosmic Microwave Background All-sky map, obtained by the ESA Planck satellite PLANCK: Actually measured all-sky maps 30 – 44 – 70 -100 – 143 – 217 – 353 – 545 – 857 GHz ( 1 cm -- 0.3 mm) Sun and stars R.A.Stern, M.Ch.Zolcinski, S.K.Antiochos, J.H.Underwood: Stellar coronae in the Hyades - A soft X-ray survey with the Einstein Observatory, Astrophys.J. 249, 647 STELLAR VISUAL BRIGHTNESS STELLAR SOFT X-RAY FLUXES R.A.Stern, M.Ch.Zolcinski, S.K.Antiochos, J.H.Underwood: Stellar coronae in the Hyades - A soft X-ray survey with the Einstein Observatory, Astrophys.J. 249, 647 M16 Eagle Nebula (“Pillars of Creation”), ~5 light-years tall. Left: Visible light. Right: Near-infrared. (HST; NASA/ESA) “Coreshine” in a dark interstellar cloud Dense cloud cores shine by reflecting infrared starlight. At longer wavelengths (right) the cloud Lynds 183 is dark, but at shorter wavelengths (left) the core (1.5 light-years in size) shines, scattering light from nearby stars. Such scattering requires dust grains about 1 µm in size. (NASA Spitzer Space Telescope) Transits of exoplanets in front of, and behind their host star Observation of exoplanet atmospheres I. J. M. Crossfield: , arXiv:1507.03966 (2015) VENUS TRANSIT June 8, 2004 Swedish solar Telescope, La Palma D.Charbonneau: Astronomy: Atmosphere out of that world, Nature 422, 124 (2003); commenting on: A.Vidal-Madjar, A.Lecavelier des Etangs, J.-M.Désert, G.E.Ballester, R.Ferlet, G.Hébrard & M.Mayor An extended upper atmosphere around the extrasolar planet HD209458b Nature 422, 143 (2003) Transit curves in different spectral features Planetary transit of HD189733b, observed with Hubble Space Telescope 1.6–1.8 m (blue); 2.0–2.4 m (red) Comparison with simulated water and methane absorption M.R.Swain, G.Vasisht, G.Tinetti: The presence of methane in the atmosphere of an extrasolar planet Nature 452, 329 (2008) Occultation of exoplanet during transit of star Exoplanet transit geometry J.Winn: Measuring accurate transit parameters, IAU Symp. 253, 99, 2008 FLUX EMITTED BY A SOLAR-TYPE (G2 V) STAR, AND THOSE FROM SOLAR- SYSTEM PLANETS (J = JUPITER, V = VENUS, E = EARTH, M = MARS). Z REPRESENTS ZODIACAL LIGHT. THE TWO PEAKS CORRESPOND TO MAXIMA OF REFLECTED LIGHT, AND INTRINSIC EMISSION. INFRARED AND VISIBLE TRANSIT LIGHT CURVES L.J.Richardson, IAU Coll.200 Global temperature map of exoplanet HD189733b Left: Multiwavelength Spitzer observations through an orbit of HD189733b yield a thermal phase curve that can be used to infer properties of the planet’s atmosphere. Data at different wavelengths [µm] are plotted along with atmospheric circulation models using different amounts of metallicity: solar (solid) and 5× solar (dashed). Right: Reconstruction of the distribution of temperature across the surface of the planet suggests that supersonic winds shift the hottest gas away from the substellar point. Beichman et al.: PASP 126, 1134 (2014) Solar-system planets MAVEN (Mars Atmosphere and Volatile Evolution) entered Mars orbit on September 21, 2014 Ultraviolet spectrograph images in three wavelength bands: Blue is sunlight scattered from atomic hydrogen; Green shows atomic oxygen; Red shows the surface with bright reflections from polar ice. Oxygen is held close to the planet by gravity, while lighter hydrogen gas goes to higher altitudes. These gases derive from the breakdown of water and carbon dioxide. Such observations tell the loss rate of hydrogen and oxygen, helping to understand what amounts of water that escaped from the planet. URANUS with aurorae at a time of heightened solar activity in November 2011 Composite multispectral image combining observations of the aurorae in visible and ultraviolet light by the Hubble Space Telescope in 2011; the 1986 Voyager-2 photos of the cyan-colored disk of Uranus in visible light, and 2011 Gemini Observatory observations of the faint ring system as seen in infrared. URANUS, with its rings, prominent in near-infrared around 2 µm. Adaptive-optics image from the 8.2 m Subaru telescope on Maunakea, Hawai’i. Near-infrared images in three different filters are combined. In this color scheme, methane (dominant component of Uranus's atmosphere), shows up as blue Galaxies M31 - Left: Combining far-UV (blue) & near-UV (red); Right: Visible light Andromeda Galaxy M31 Infrared view from NASA WISE (Wide-field Infrared Survey Explorer) satellite. Four infrared channels combined: 3.4- & 4.6-µm is colored blue; 12 µm is green; 22 µm is red. Blue highlights mature stars, while yellow and red show dust heated by newborn, massive stars. Satellite galaxies are M32 (above) and M110 (below). Spiral galaxy NGC 1512 from ultraviolet to the infrared Center of our Milky Way galaxy Combined images by Hubble Space Telescope in near-infrared, Spitzer Space Telescope in long-infrared, and Chandra in X-rays. Imaging in optical & IR Sunset view of ESO VLT on Cerro Paranal, Chile; with VISTA in the background 8.2 m Kueyen telescope of the European Southern Observatory Very Large Telescope on Cerro Paranal, Chile FORS 1 at the 8.2 m ANTU telescope on Cerro Paranal MegaCam on the Canada-France-Hawaii-Telescope MegaCam CCD mosaic (40 CCD’s @ 2048 4612; total 377 megapixels) Star clusters M35 & NGC 2158 Canada-France-Hawaii Telescope CFHT MegaPrime / MegaCam (central 36 CCDs – 18K x 18K pixels) Field: 60'x60‘ (1 square degree) Filters: u', g', i' (semi true-colors) Exposures: 5 minutes per filter A perspective effect captures two open clusters in the same image, M35 (upper left) and NGC 2158. NGC 2158 is four times more distant and some 10 times older. M35 , 2,800 ly away, is a fairly young cluster of some 100 My. Some leftover material from the star forming process is still present. Silicate particles of interstellar dust scatter light from bright blue stars to produce a diffuse blue fog. 8.4 m Large Synoptic Survey Telescope being built on Cerro Pachón, Chile LSST focal plane array model. (diameter 64 cm) Mosaic of 189 CCDs provide > 3 Gigapixels per image. Image of the Moon (30 arcminutes) indicates image scale. Diffraction of light Diffraction pattern in ideal telescope, with signature of Earth-type planet Core of globular cluster NGC 6397 - Hubble Space Telescope Core of globular cluster NGC 6397, with a few white dwarfs - Hubble Space Telescope Project 1640: Extreme AO hyperspectral imaging Project 1640 is a high-contrast spectral-imaging effort using massive adaptive optics on the Palomar 5-m Hale telescope, an apodized-pupil Lyot coronagraph, an integral field spectrograph, and an interferometric calibration wavefront sensor. Its aim is to image planetary systems, breaking the speckle-noise barrier. The goal is a contrast of 107 at 1 arcsecond separation. Image slices at = 1120, 1550 and 1670 nm of the star Alcor with its M-dwarf companion at lower right. Field of view shown is 3.0 arcsec. Speckles (and four calibration spots) change position as a function of wavelength, while the companion star does not. This wavelength dependence permits discrimination between speckles and real celestial objects. B.Oppenheimer et al., Proc SPIE 8447, 844720-1 Imaging planets around HR 8799 (i) Raw telescope image; black spot in center is occulter in the coronagraph. (ii) Adaptive optics on! (iii) 5-min exposure with star behínd the occulter. Only little starlight remains but speckles abound due to optical defects. (iv) Calibration wave front sensor on makes speckles dimmer. (v) Processed data reveal the exoplanets. Spectra can be extracted once the planet locations are determined. http://www.amnh.org/our-research/physical-sciences/astrophysics/research/project-1640 Project 1640: Extreme AO hyperspectral imaging Left: Planets of HR8799: The star is at the center; the four spots b-c-d-e are the planets. This composite image using 30 wavelengths was obtained on June 14/15, 2012. Right: Spectra of four planets orbiting HR 8799. Spectral features are identified at top, B.Oppenheimer et al.: Reconnaissance of the HR 8799 Exosolar System. I. Near-infrared Spectroscopy, Astrophys.J. 768:24 (2013) Planets orbiting the young star HR8799 (~A5V) Direct imaging of HR8799 planets over 7 years. Planets seem to be in 1:2:4:8 orbital resonance with periods ranging between ~40-400 years. (Nexus for Exoplanet System Science, NExSS, collaboration, Keck Observatory) Diffraction of light in different telescope apertures Optics and starlight suppression technology Ball Aerospace: Terrestrial Planet Finder Architecture Study External occulters (“starshades”) A starshade blocks most starlight outside the telescope. It creates a shadow much like the Moon does during a solar eclipse. It must be designed to minimize diffracted light. A small and deep shadow requires very great distances. New Worlds Observer concept (Amy S. Lo et al.: Starshade Technology Development , Astro2010 Technology Development White Paper) External occulters (“starshades”) If the shade is sufficiently distant, it will subtend a small angle to enable imaging terrestrial exoplanets. A starshade with effective diameter 50 m, operating ~80,000 km from a 4 m telescope is capable of suppressing the starlight by a factor 1010 within 50 milliarcseconds.. R.G.Lyon et al.; Externally Occulted Terrestrial Planet Finder Coronagraph: Simulations and Sensitivities, SPIE 6687, 668719 (2007) External occulters (“starshades”) Testing starshades in the dark skies of the high-altitude desert at Smith Creek, Nevada. (Northrop Grumman Corporation) Energy-resolving detectors Superconducting tunnel junction S-Cam 3 detector array: 1012 pixels, each 3333 μm2, with 4 μm gaps (ESA/ESTEC) STJs consist of two superconductors separated by a thin layer of insulating material. An absorbed photon creates Cooper pairs and quasiparticles which tunnel across the junction. The binding energy between Cooper-pair electrons is on order a few meV: an optical photon (some eV) releases hundreds of these.
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