Ground-Based Astronomy A Ten-Year Program (1964) / Chapter Skim
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2 The Present Position in Ground-based Astronomy
2 The Present Position in Ground-based Astronomy
Pages 13-44
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From page 13... ...
my tional tasks now clearly foreseen, It has also considered a projection of astronomical manpower over the next ten years, to keep the facilities and the number of observing outlets ín step with the demands of a growing body of researchers, and yet not outrun the expected supply of experienced instru mentalists and observers needed to build and operate t-he new major installa tions proposed. The Panel presents here its evaluations of tìe present posi tion as a background for the recommendations tÏat follow in Sections III and IV.
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From page 14... ...
While the Panel has concentrated its attention on the facilities needed to accelerate the acquisition of new observatíonal data about tÏe universe, it also recognizes the great importance of a continuing buildup of strength on the theo¡etical side. OPTICAL ASTRONOMY Present Domínant Position of the UníteiL States The position of Ieadership that thd United States enjoys in optical astronomy has been won as a direct result of its superior observing facilities.
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From page 15... ...
astlo The insistence of tle builders of all these pioneering telescopes on the high basic est sta¡dards of optical and mechanical performance also contributed to ¡ pre: their spectacular success. The McDonald 82-inch telescope in West Texas oring in 1939, the giant 200-inch reflector on Palomar Mou¡rtain in 1949, and the etical 120-inch reflàctor at Lick Observatory in 1959 complete tìe list of tle rvolu telescopes that have continued ttre tradition.
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From page 16... ...
With onþ two major frontier telescopes operating, this means that no more than two or th¡ee astronomers in tTe entire worlil now have the opportunity to work on the most excitíng problems in any given ûeld. Competition and the obviously needed opportunity to check results are lacking.
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From page 17... ...
/ilson The inádeq-uacy of the existing large telescopes for the difficult prob:eas,) lems involving fãínt sources would be even more acute if telescopes of lesser i-20th size could ,to-'t b" used to câlry the considerable fraction of the needed rnald, observations that do not demanil such geat light-gathering power' Telet efi scopes of intermediate size can perforrn all the standard- observational tasks ms at ove-r most of the brightness range covered by obiects of a given class' For ,i thu some types of measrirement, toãh ut the study of nebulae, there is almost )
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From page 18... ...
by such foreign instuuments âs the 2l0-foot telescope in Australía, tÏe 22-meter millimeter-wave telescope near Moscow, and ttre large cross-q4) e arrays nearing completion near Sydney and Moscow.
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From page 19... ...
opes; , said teleopes: ) -foot , and r two retels o-belwefys to scope , ?
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From page 20... ...
r Fígure 2 The spiúL galaxg M31, uíth íts tüo compaìnioß, as photogruphed þith øn optícøl telescope giDíng a rcsolu tion of 1 second, of arc iJ Copyright © National Academy of Sciences. All rights reserved.
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From page 21... ...
The galarg M31 øs ít u;ould, appeu to a lelesaope 4 ¡esoluÍían ol 34' The gaünV M37 Fìgure seen tD¡th 12, resohttìon o.s L íts tØo aompaníons, ,ope eíþíng ø rcsolu 5 galatg M31 as seen aith 3' resolut¡on- 6 Th.e The galary M37 as seen @ìth ft Figurc rcsolutìon. Copyright © National Academy of Sciences.
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From page 22... ...
8 The spiîol golLxg M87 os seen Ðilh 7' rcsolutíon' Fìs|iîe galarg M87 as seen aíth an optícal 7 The l) 71n, tio" tttot pott¡ble Øíth er'islìñg rcilìo relescopes spìto¿ Fìeu¡e telescope gioíng 7" tesolution The uhbþool galary as seen 1þith 7' resohiìon' The whi pool ¿alaxg,M51' as seen þith an optí' 9 Figure gioìn!
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From page 23... ...
seen tDíth 7' xs ting tad,io t el¿sc opes. 12 Thé bared spi¡al gala*
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From page 24... ...
Figr.ue 14 The model skg of Figure 13 as it Lþoul¿' be 13 A s(nlple of si,mulated' sk{ populated @ith tun FígØe seen at a rcsohttion oÍ 7', or about th&t possìbtø @ilh a d,ontfu d.ístrtbuted. radìo soØces of a consíderøble tunge ol 300-foot tudio telescope üorkiltg at 2f cm.
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From page 25... ...
Fl,gurc 16 Th,e modd skg oÍ Figure 13 at a îesoh.ttt'n of ít toould, be The model skg of Fi,gute 73 at a resohttioí of 3' aà oossíble üíth a 7', begond, the capabllitv of ang eíìsting rudia telescopes. Copyright © National Academy of Sciences.
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From page 26... ...
Theory anil preliminary experiments have indicated that the ultimate aknospheric limitations on radio-telescope resolution will be about the same as tltose for optical tele scopes-a fraction of a second of arc. Thus, there is no natural barrier that prevents building radio telescopes on the ground witl an angular resolution far beyonrl tlìat yet achieved, and thus to go beyond an all-important threshold of information.
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From page 27... ...
:ï $ tì Resolution and the Cosmologi'cal Problem ,$ The important role of resolution in radio astronomy is nowhere more clearly Ì demonstrated than in radio observations associated with problems of cosmol 20 i:i -81 Copyright © National Academy of Sciences. All rights reserved.
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From page 28... ...
radio sources'throughout the universe can be obtained until ¡esolution of the sial order of seconds of arc is available to radio astronomers' Melhods of Achíeoing High Angulat Resolution of the Increased resolution can be obtained only by increasing the linear size trly to build a single antenna that Fortunateþ, it is unnecessary 101 "ri"nr",y.t"-. 2L iì Ë 8,, Copyright © National Academy of Sciences.
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From page 29... ...
pl"t"íy ffIlecl aperture of greai dimension- can be imitated' or ;;; ;.yott interfeiometer expedments have brought great atten "ri""d."-fhesehat any distribution of radio sources, or radío "bright tiáo to tttu concept t be represented as an infinite Fourier series of intensities ,r"r." in th" tþ, í"u"I".tgth, projected on the sþ' An interferometer' at âny ""n "iïUlp"i* f ;J;f; recording oã" of thlt" Fourier components' Given time' ynthesis enough ;;;;;;;" can b""obtuio"d to allow a combination in.a Fourier s th"i ."p.od.t"", with good accuracy the appearance of tle raclio sþ' It now tÏe o this technique õp""i aft"r, if sufficiãnt care is tafenrwith mapsbservations' The procedure of tÏe sky' froa,r""'"""*
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From page 30... ...
This problem is particularþ acute when only a two or very few antenna elements occupy the space between tihe extreme x- separation requireil for speciffed resolution; hence the need to reduce the nt so-called grating response by adding the many Fourier components previET ously mentioned. One solution is to ffll Ín the area between the two extremities completely.
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From page 31... ...
A balanced anil fully efiective program of radio telescopes wlll include fully steerable single paraboloids of the largest feasible aperture' There is a class of problems, as in the stucly of variable radio sources, galactic shucture, and Lhe polarization of railiation, tÏat tlo not require the highest resolution. Studies of the 21-cm line of hydrogen and other spectral lines, or any problems that require frequency scanning, are extremely difficult with arrays.
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From page 32... ...
Soon the NRAO 140-foot telescope will be finished; it will achieve resolutions of the o¡der of a few minutes of arc at best. There also exist in the Unite¿l States more than a half-tlozen 85-foot class paraboloids at various institutions' Àlthorrgh these serve well for certain classes of problems, they are too small to provide adequate resolving power and collecting area.
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From page 33... ...
THE DILEMMA OF THE ASTRONOMY GRADUATE SCHOOL IN 1964 Equally as serious as the problems arising from tle lack of large frontier telescopes is the cur¡ent situation conceming the instrumentation at gradu ate schools throughout the country. The demand for grailuate astlonoÍìers is very high.
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From page 34... ...
Even mo¡e serious is the fact that most of tle newly created grailuate depart' ments have virtually no instrumental legacy from the past. This problem was recognized about ten years ago when the discussions leading tJ setting up tÏe Kitt Peak National Observatory anil the National Radio Astronomy Observatory were begun.
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From page 35... ...
There remains the important question of the balance l¡e t* e"o tie creation of facilities and tìe number of astronomers that wiII be demanding observing time when the facilíties are completed' The a-nswer to this question cannot be given in hard bookkeeping terms' because the availability of facilities afiects the choice that young scientists l, make on whether to g; into tÌìeoretical or into observational astronomy' The for evidence we have cit-ed earlier in this discussion-the unsatisûed demand centeï and the desire of many univer the telescope time at maior observing sity graduate departments for modern, locaþ based observing equipment poLis to tlte current severe limitations in facilities' Fine new instmments ^o.rdonbt"dly do attract and inspire imaginative use by outstanding young 28 ,i tn Þ -,..
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From page 36... ...
Truiníng of As'tronnmers Comparcd to Ttainíng of Other Phgsical Scíenfists Astronomy is one of the smallest disciplines among the engineering, mathematical, and physical sciences. The annual proiluction of Ph.D.'s has been widely used as an index of the growth rate in these Êelils, The following studies contain material relevant to the present discussion: Doctorate Productíon in tJni,teiJ Statas Uniqersitíes.
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From page 37... ...
tl:l 'i ,l;l il rl i,. .t r970 1960 1950 r940 1930 1920 Fígure 77 sciences ùt the fJnitect States' Annual Ph.D, 11ro¿uctìott itu attÍonony and other Ttlrysical t i &_ I 1,u..
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From page 38... ...
from 1923 to 1955. The-tlree points {rom (The íSSS ìo fSO¿ Jrow a sharp ltptorn to a doubling time of nine years 1964 point is an estimate from the U
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From page 39... ...
Since a good part of the university-based space efiort is in special institutes separate from astronomy departments-often dominated by physicists, geophysicists, and engineersthJ rapidly growing student population in the departmental tâbülation of Table ì reprãsents a broad spectrum o{ interests, and something like the traditional pioportion of tlre students may be expecteil to go ínto ground-based observational astronomy. The new astronomy students irndoubtedly lepresent a shift in interest Copyright © National Academy of Sciences.
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From page 40... ...
. This percentage has remained stable over many years, as has the over-all fractíon of abdut one sixth of total doctorate production going into all the physical sciences' The shift diil not need to b; a hrge one to produce the drastic increase in astronomy alone, since astronomy plt.¡.t irr the years 1957-62 were only 3 per cent o{ t'hose in physics, rising to just over 4 per cent in 1962.
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From page 41... ...
UNIFORÀ{ CROWTI¡ / , :¡ÀPERED GROWTII NUIIIER OF ASTRONOI4ENS GB¡.DUATE STI'DE\TTS I] NIFOR}I CNOWTII , 19ø PER YE,lû TÀPERED GÂOWTII 7 ¡¡n va¿¡ n¡ 1973 Fígurc 19 Ninnbet of gra.Iuate st¿(lents í'n asftonontg, the number of PhD"s 1954-1962, and Prcìecte¿ Ph.D.
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From page 42... ...
õiah; i aì" nf..i"¡ * ià""át i" genåral by the enil oI theSociety on Janu "ä".tråã " r,36^0 itmbets ãf the Ãmerican'Astronomical hold doctorates or professorships' "-, I laR4 620 have U
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From page 43... ...
L Koltun of the National Science Foundation, ,tl,ì il :t,l which maintains tle Register, estimates that tÏe listing, basecl on responses ii to a questionnairg is only 80 per cent complete.
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From page 44... ...
Conclusían The surge of students into the graduate departments of astronomy has fol no sign lowed aiteaily upward course for at least six years, and as yet shows from the cur-rent enrollment are àf ,ou.rding oif. If only the Ph.D.'s expecteil in the countetl, a"sharp increase in growth rate of the number of ast¡onomers in the count yis ioevitable.
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