telescopes(1) - 1r to keep up with the reading...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1r to keep up with the reading g'tonight—weather permitting '3 tonight, we will have observing on the roof 0 ___8 building, starting at 6:00 pm. ‘ post on blackboard around 4:00pm whether we intend to go forward with the observing—it may be too cloudy. NASA, NOAO, ESAand The Hubble Heritage Team (STSCI/ Telescopes (Kulner, Ch. 4; Bennett el al. Ch. 6; see also Carroll and Osllie, Ch. 6) AST 203 (Spring 2011) Astronomical Telescopes 2 main functions of telescopes: - Increase the amount of light we collect - Resolve smaller features Light gathering is easy to understand: Amount of light collected is proportional to area. Eye pupil diameter of ~ 5 mm. Ratio of the area of a 1 m telescope compared to our pupil is: 2 2 fl : fl : 100 cm : 4 X 104 Ap dp 0.5 cm AST 203 (Spring 2011) Astronomical Telescopes Detectors are sensitive to power received. For constant power, P : ftAt : prp Take this to be the detector's (eye) sensitivity limit. Flux ratio: fl _ Aw fp * At Le. a larger telescope can detect a smaller flux. The limiting magnitude we can see with the eye is 6, so mp — mt = —2.5log : —2.5log(4 x 104) = —11.5 ft With a 1 meter telescope, our eye can see down to m = 17.5 AST 203 (Spring 2011) Refraction (Zélonyi SéndorNVikipedia) Refracting Telescope Classic type: refracting telescope. Objective lens focuses light eyepiece/camera at focal point. Larger objective lens = more light Major difficulty: lens is heavy, difficult to support. AST 203 (Spring 2011) Refracting Telescope Refracting telescopes suffer chromatic aberration Different colors come into focus at different points—image is blurred. Lens can be deformed when the telescope is moved. The long size of a refracting telescope can also provide challenges for mounting it. (Vlfikipedia) \_,-‘ Chmmrm'c‘ aberration AST 203 (Spring 2011) Reflecting Telescope Largest telescopes today: reflecting Newton—Teleskop (AltMechanic/leipedia) Cassegrain Concave primary mirrors (shaped as a parabola) focus light; (maybe) a secondary mirror redirects the light path. (G riffenjbs/Vlfikipedia) AST 203 (Spring 2011) Reflecting Telescope Secondary mirror blocks some of the incoming light. Coudé reflectors, redirect the light down the telescope mount. A mirror reflects all wavelengths the same—no chromatic aberration. 7 Mirrors are supported from behind and can be composed of multiple segments. (Molmasqo pleuoaoew) AST 203 (Spring 2011) Optical Telescope Keck telescopes in Hawaii. Two 10 m telescopes with a variety of instruments. Currently: several competing designs for 30 m or larger telescopes. (KGGK) AST 203 (Spring 2011) Largest Telescopes M' . . . . Name Aperture 4:? Nationality of Sponsors Site Built 2 X B 4 = M H} l1 l t t' I Oh I . Large Ellnocular Telescope (LBTJ m 2 x single USA. ltaly. Germany mm la am n ems Inna SENS my 2007 11 E m Arizona Southern African Large Telescope South Africa. USA. UK. Germany. Poland. South Afrlcan Astrohomlcal Observatory. 11 0 m Mosaic 2005 (SALTJ New Zealahd South Afrlca . . . . . Flo ue de los Muchachos Observator . Gran Telescopio Canaries (GTC) 10.4 rn Mosaic Spain. Mexico. USA q if 2005 Canary lslands . Keck 1 10 rn Mosaic USA Mauna Kea Observatory. Hawali 1993 Effective k _ b _ Kec 2 10 rn Mosaic USA Mauna Kea O servator .l—lawali 1996 aperture _ y N 9 m Hobby-Eberly Telescope (HET) 9.2 m Mosaic USA. Germany McDonald Observatory. Texas 1997' Subaru (MI) 8.3 m Slngle Japan Mauna Kea Observatory. Hawali 1999 VLT 1(Antu! E 2 n1 Slngle ESO Countrles (European +13hlle] Faranal Observatory. Chile .1998 VLT 2 (Kileyen) E 2 n1 Slngle ESO Countrles (European +13hlle] Faranal Observatory. Chile .1999 VLTS (Mellpall E 2 n1 Slngle ESO Countrles (European 4- Chlle] Faranal Observatory. Chile 2000 VLT I1 (Yepun) E 2 n1 Slngle ESO Countrles (European +13hlle] Faranal Observatory. Chile 2001 USA. UK. C d .Chl .A t l l Geininl North 8 1 n1 Slngle am a is HE G ‘3 Mauna Kea Observatory. Hawali .1999 Argentlha. Brazll USA.UK.C d.Chl.A t ll Geminl South 8 1 m Slngle ma 3 ‘6 us ra ‘3 Cerro Pachon. Chlle 2001 Argentlha. Brale EABZJ’lflterlelMagflum errorTelescope '65 m Smg‘e USA :i'rezdolgwrehce Whipple Observatory. :3: Magellan 1 (Walter Elaadel 6.5 m Slngle USA Las Campanas Observatory. Chile 2000 Magellan 2 (Landon Clay] 6.5 m Slngle USA Las Campanas Observatory. Chile 2002 ETA-6 6 rn Slngle Russia Zelenchukskaya. Caucasus 1976 Large Zenlth Telescope (LZT) 6 rn Slnqle Canada. France Maple Ridge. British Columbia 2003 Hale Telescope 5 m Slnqle USA Palomar Observatory. Callfprnia 194B Willlam Herschel Telescope 4 2 n1 Slngle UK. Netherlands. Spaln Ruqua de la; MUChaChUE Observamry' .198? Canary lslancls SOAR 4 2 m Slngle USA. Brazll Cerro F‘achon. Chlle _2002 Note, all the largest telescopes are reflecting telescopes (listfromVlnkipedia) AST 203 (Spring 2011) Angular Sizes i——i QNL/d - Angular size of full moon/Sun ~ 0.5° - Angular size of your fist at arms length ~ 10° - Angular size of a finger at arms length ~ 1-2° Why do we use angular sizes and not true (physical) sizes for our measurements? Diffraction Limit Telescopes allows us to see finer WW“!WWWW detail. ‘ (Bipedixwo Diffraction: fundamental limit to resolution. Infantry . . — Light waves from different paths add together either constructively or destructively—diffraction pattern. \J (\Mkipedia) AST 203 (Spring 2011) Diffraction Limit Consider pairs of waves interfering Divide the slit into two parts upper half interferes with lower half T Consider a slit of width D. i Path difference between center of the slit compared to the edge is L (D/2) sin 0 Destructive interference occurs when this path difference is 1/2 of a wavelength. D S. 0 A _ 1n : _ 2 2 AST 203 (Spring 2011) Diffraction Limit Additional minima from destructive interference from two waves originating D/4 apart, or D/6, A general expression for the location of the minima is sinH : m% where m is an integer called the order. Circular opening more complicated Airy disk 04 m is no longer integer. . '35 Location of the first minimum is given by )1 ' l9 : 1.22— S1n D '33 1': (Wikipedia) AST 203 (Spring 2011) Diffraction Limit )1 ' 9 z 0 : 1.22— 8111 D Location of first minimum in the diffraction pattern is a fundamental limit of telescope's resolution. Want higher resolution (more detail)? Need bigger D For a 10 meter telescope observing in the visible wavelengths (550 nm), we have . 1 —7 0 = rmw = 6.7 x 10—8 rad = 0.014” 10 m AST 203 (Spring 2011) Angular Resolution Credit: National Astronomy and Ionosphere Center. Comell U., NSF Why are radio telescopes much larger than optical telescopes? Seeing We do not always attain the theoretical resolution for a telescope Atmospheric fluctuations on short Planewavesfromdistantpointsouroe timescales bends the light. This effect is called seeing. “WWW?” in atmosphere In most places, this limits the effective angular resolution to a few arcseconds. Pcrturbed wavefronts (Bob Tubbs) Very good astronomical sites (Hawaii, Chile): seeing ~ 1/3” It's important to pick the right location to build your telescope. AST 203 (Spring 2011) Good Observing Site - Minimal number of cloudy nights - Minimal atmospheric turbulence - Away from bright lights / cities - Low water vapor Such as... - High mountaintop - Airplane - Artificial satellite / spacecraft (Bob Tubbslleipedia) Keck Telescopes on Mauna Kea Clouds typically are below 10,000 ft AST 203 (Spring 2011) Light Pollution “ASNJPUGSFC Sunset on Mauna Kea — Gemini Telescope - . -:i__ Secondary Mirror _ Primary ' ' Mirror (Gemini Observatory) - Open air design reduces air turbulence in the dome AST 203 (Spring 2011) Adaptive Optics Remove atmospheric blurring through adaptive optics. Laser guide star is monitored and a deformable mirror is adjusted to remove the perturbations in the light blooming ()mgoi ng perlurbed corrected wavefronts wmgfiunu Deformable I minor AST 203 (Spring 2011) (Wimpedia) Neptune We and WIth AO (CfAO) Space Telescopes ;.v.:. ‘..I - 3 l: : I INVSS I 1 < 3 : “ALBA:— ‘ ; WIMP - I SWAS I l msnwrapI-Im _ : E : Planck ‘ i Hirscnel IRAS MSX - I Spllm _ I ISO “ l 3 mass l I l 3 CORE _ I Im's * 3 Hi I'ch I l “gum 1 GAsz 5 HST IUE : FUSE I 1 Perhaps the most famous is emu:— the Hubble Space XMM- Newlun _ I Telesco e c mm?“ —E—' 5 D (“B I p ' as“ — i E Afilru 1 W : Uhuru _ 3 u ‘ Elnstllrl — z i Swm — 3 RITE “ I Buppn»Sl-K m HETEAZ — 3 Gina — Get rid of the atmosphere— put the telescope in space. SAVH' VWNVB SAVH' X Astm—Ez _ Vela EB — 1 HEAD 1 —§ INTEGRAL _ 3 i L. OIUVH CGPO W AGILE 1 I I I l I 3 I nm1o‘3 10'5 1a“ IIII‘2 1I:I° 110253110 GEHVHflNI EAVMOEOIW a_ a on o. m 3 3 entgl‘ 1:19 107 195 "193 101 All? 19.“ mst AsT 203 (Spring 2011) Atmospheric Windows For certain wavelengths, there is no choice but to go above the atmosphere Atmnspheric 0 pacéty 0.1m" 1m" IDnm ‘lDClIIm Ium 101ml 100w" 1mm 1cm ‘Ucm 1m 10m WOUm ‘lkm Wavelength agar w. bun-n. I'M“ " °" W Gum-u Ravi, many- mt mimqu I ° n 53:31::- Llnfllbbom by lil- ullpIr muth (butch-wanton 3m}. AST 203 (Spring 2011) The large window in the radio frequencies allows for ground based radio astronomy. Radio wavelengths are long, so a very large dish is needed to get good angular resolution. Dishes as large as 300 m exist. (SETI) The Milky Way at 21 cm (NRAOIAUI) AST 203 (Spring 2011) (NRAO) Interferometry Resolution of radio telescopes can be increased by using multiple dishes separated by a baseline, d. Angular resolution now depends on the separation between the dishes (VLA/Wikipedia) AST 2031$p|ing 2011i Telescope Functions - Imaging — Non-visible light is given a false color representation — Sometimes filters are used - Spectroscopy - Timing — Make lightcurves 100/) l l l l l 500 7 so!) 7 'm PCA 0 ADD, 345 350 355 350 355 370 375 BED 7 Frequency (Hz) 200 7 I) l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l D 5 1D l5 20 25 30 _ Time (51.25 ms ms) Flattened Envelope around L'l 1 57 Prntostar Spitzer Space Telescope I IRAC X-ray burst curve NASA/’JDLVCaIterzh/ L Lnnney [University of Illinuis) 55620077152! (Slrohmayer el al., 1996, ApJ, 469:L9) Data Handling One of the most popular types of detectors is a charge-coupled- device (CCD). Very high efficiencies (up to 90%)—sensitive observations. Since the data is in electronic form, it makes for analysis and manipulation of the resulting images relatively easy. AST 203 (Spring 2011) Spectrographs Spectrographs allow individual spectral lines to be observed. SOU roe a grating _ mirrors Diffraction grating disperses the light. / Adjacent grooves ~ double slit detectofi/ (Kkmurray/Wikipedia) asinfi = mA Resolving power: A : — : N R AA m where N is the number of lines in the a grating. (Dirk HEInniger/Wikipedia) AST 203 (Spring 2011) S ectro ra hs (ov0N) l iiiI 1 iilLii' 1‘ T 1i rd I '1' Li. “ht, ‘ I ' , i i lilu'" ,1 ,1- ilt ! tiff, , [1% J11 , i"!l y“: To get a detailed spectra like this, you need a spectrograph with a high resolving power/lots of gratings AST 203 (Spring 2011) Hubble Space Telescope HST: 2.4 m telescope in low earth orbi Sensitive to visual and UV. Hubble has an array of instruments, including cameras (imagers), photometers, and spectrographs. After launch, it was found that the primary mirror was ground incorrectly (too spherical), making light of different colors to come into focus at different places. This was fixed in a servicing mission. (NASNESA) AST 203 (Spring 2011) Hubble Sace Telescoe Orbit Low Earth orbit— many sources blocked by Earth. (NASA) Hubble Space Telescope The Hubble Ultra Deep Field—the deepest visual wavelength image ever taken. The light from the most distant galaxies shown here has traveled for 13 billion years to reach us. (NASNESA) AST 203 (Spring 2011) Fermi Gamma-Ray Space Telescope The CGRO was launched in June 2008 Large Area Telescope sensitive to photons with energies between 30 MeV to 300 GeV—4 decades of the electromagnetic spectrum! Also has a gamma-ray burst monitor Fermi data reveal giant gamma—ray bubbles A giant gamma-ray structure was discovered by processing Fermi all- sky data at energies from 1 to 10 billion electron volts, shown here. The dumbbell-shaped feature (center) emerges from the galactic center and extends 50 degrees north and south from the plane of the Milky Way http://www.nasa.govlmission_pageslGLAST/newslnew-slmcture.hlml AST 203 (Spring 2011) Credit: NASA/DOEIFenni LAT/D. Finkbeiner el al. Spitzer Space Telescope Spitzer is an infrared telescope currently in space. Its follows earth in its orbit around the Sun, lagging behind by a few tenths of an AU. Spitzer has an infrared camera, spectrograph, and photometer. (NASNJPL.C...ech, (uomos 'wuoeuao-HNVSVN) AST 203 (Spring 2011) Chandra is an X-ray Observatory launched in Chandra X-Ray Observatory 1999. It contains imagers and spectrographs, and can observe thermal emission from hot gas surrounding blackholes, neutron stars, white dwarfs, and supernovae remnants. 400 x 900 ly image of the center of the Milky Way showing white dwarfs, neutron stars and the galactic black hole as well as million K gas AST 203 (Spring 2011) AST 20 (NASA/U. Mass/D. wang) James Webb Space Telescope “successor to Hubble”, launch date: 2014-15 Will operate in the IR: 0.6 to 28 um Study first galaxies and stars, galaxy formation and evolution (high redshift), study star/planet formation (dust obscuration), study extrasolar planets Will orbit in the Sun-Earth L2 point—4x Earth-Moon distance'fl—not serviceable (EnEdC/Wikipedia)| JWSTprimary, / \ 7 \_ mirror ,/ / > \\\ H bbl ' x ‘\ r/ u eprlmary t 4,» 7. ' ,‘ mirror < I \3' \\ glow, ,H x, Qt I ASA; mirro ' Large Synoptic Survey Telescope - Survey telescope to be built in Chile - First light later this decade - 8—m class mirror - 3.5 degree field of view (several full moons across!) - 3.2 gigapixel camera - 1.3 PB of data/yr AST 203 (Spring 2011) Crab Nebula: Remnant of an Exploded Star (Supernova) Ftadio wave (VLA) ll'lfrared radiation (Spitzer) Visible light (Hubble) Pixel Size —_—— Ultraviolet radiation (Astra—1) Low—energy X—ray (Chandra) High—energy X—ray (HEFI') *** 15 min exposure *** CM Hubert Chen, Fiona A. Harrison, Principal Investigator, Caltech Charles J. Hailey, Columbia Principal, _ Columbia, Finn E. Christensen, DSRI Principal, DSRI, William W. Craig, Optics Scientist, LLNL, Stephen M. AST 203 (Spr'ng 2°11) Schindler, Project Manager, Caltech Heliopause‘ ' ' " voyage“ is \ the most distantman-made object in spacee‘lOT AU or 9 billion miles from the Sun. Eventually,- it will reach interstellar space. ' Galactic Cosmic Rays I No comrn’urfiiation '_ '- >. ' SularWind ' since '95 '{ \ lg. \\ Pioneer10 ‘3 _ l i ' . ,- o’I‘Voyager 1 I \ I V » ' / / \\ ' \ a‘ Pioneer 11 F ‘ / “A. J No communication since 2995» Termination Shock ' Bow Shock‘ ~ .(NASA) Space Probes The Voyager spacecraft just flew by the mum cum-m lNSI-‘rmox IJLJ 200.1 outer planets ZEWEEESB" L y | VENUS2 FLVBY ', _ 24m" 1999 Sometimes, a space probe is inserted into an orbit around a planet. VENUS ‘. 'lflFIGE‘ITMG '--‘ MANEUVEFl 3 DEC 1998 The Galileo probe orbited Jupiter from 1995 to 2003. ‘\ Lnuncu 15 OCT 1997 -' JuPn‘LH EARTH FLVBV ?I.‘.-'EIV 1a AUG1999 30 Marcus The Cassini probe is currently orbiting Saturn. (All images from NASA/JPL) AST 203 (Spring 2011) ...
View Full Document

Ask a homework question - tutors are online