Quasars, Pulsars, Black Holes and HEAO's

8/8/2019 Quasars, Pulsars, Black Holes and HEAO's

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"This &ool wantsto turn the WholecArt of c4stronomyUpside fDown."Martin Luther on Copernicus

Energy in electron volts (eV)M e V )1 - 1 - " 1 0 " . p V i 4 ; ; ; >

RADIO MICROWAVES LIGHT X - R A Y S GAMMA R A Y S10 2 10-2 1CT6 10 10 10 '14

Wavelength in metersTHE ELECTROMAGNETIC SPECTRUM. Radiation at any point on this spectrummoves in a vacuum at the speed of light: 186,000 miles per second. X-rays and gammarays are no different from visible, TV, or radio radiation except for their shorterwavelengths, higher frequencies, and higher energies. The shorter thewavelength, the higher the energy.

COVER: The Crab Nebula was first observed in 1054 A.D. as a supernova, a catastrophicexplosion in which a star with a mass several times that of our sun blew up, spittingout a cloud of matter it had been making. The Crab Nebula is one of the richestobjects in the sky for today's astronomers. It emits radiation at all wavelengths fromradio to X-ray and its total output is equivalent to the power of 100,000 suns. Its corecontains a pulsar. In many ways the Crab symbolizes the new discipline of high-energyastronomy.


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Recent discoveries of startling celestial objects byhigh-energy astronomy have led to revolutionarynew theories about energy, matter, and the originof the universe. So fundamental are these discov-eries that they may well result in major revisionsto the entire structure of physics. These celestialbodies, including quasars, pulsars, and stars, arevery violent assemblages of matter; deep withintheir interiors they undergo physical processes soenergetic that they cannot be reproduced here onearth. To understand these processes, we must goto the natural laboratory of the universe.Beginning in 1977, these objects and the universewill be surveyed by a new generation of large X-ray,gamma ray, and cosmic ray instruments carriedonboard High-Energy Astronomy Observatories

(HEAD). These satellite observatories will explorethe invisible, high-energy universe which lies be-yond the range of the visible universe explored bysuch earth-based instruments as the Mount Palo-mar telescope. HEAO will study the objects de-scribed in this booklet. These energetic sourcesare destined to play an ever greater part in ourlives. If they yield the data expected, a new under-standing of astronomy and of physics will emerge.This new branch of science is appropriately calledastrophysicsthe physics of the stars. The ulti-mate benefits of such new knowledge could rangefrom the development of additional sources ofenergy to a dramatic change in our view of our-selves and our place in the universe.


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ASTRONOMYAT A TURNING POINT"In 1543, an obscure Polish priest named NicolausCopernicus set forth the shocking theory that theearth revolves around the sun. Defying the dogmathat because man was created in the image ofGod, his place must be at the center of the uni-verse, Copernicus unleashed a theological an dscientific controversy that was to last more thantw o centuries."1 On the 500th anniversary of thebirth of Copernicus, a new revolution in astronomyis underway, a revolution perhaps destined to beas far-reaching as that begun by the lowly Polishpriest 20 generations ago.

"In no scientific discipline has there beensuch an avalanche of surprising discov*eries as there has in astronomy over thepast decade."2Herbert Friedman

M 82. A violently energetic explosionthis galaxy, 10-million light years fromhas been underway for 1,500,000 yearsstillyoung. A mass of hot hydrogento the mass of five-million averageis bursting out of the galactic nucleus.great is the force of this explosion that it isup neighboring galaxy M 81, manyyears away.

A series of extraordinary observations of newastronomical phenomena made during the lastdecade are the basis for this revolution. To theclassic visible universe, the new astronomy hasadded a picture of a universe characterized by "ageneral cosmic violence, exploding galaxies andquasars, an almost universal presence of high-energy particles and magnetic fields, and eventssuggesting relativistic collapse."3

These discoveries appear to be converging to-ward a dramatic synthesis of basic ideas aboutthe cosmos. The relativistic universe which Ein-stein foresaw early in the 20th century is actuallybeing observed today. Ideas and predictions aboutth e universe made only five years ago, which astro-physicists did not expect to see confirmed withintheir lifetimes, are now being verified by excitingobservations.In these discoveries, we are looking at the life

cycles of stars, galaxies, clusters of galaxies, andperhaps the evolution of the universe itself. W eare seeing energy processes an d aspects of nu-clear and high-energy physics never previouslyobserved. Three of the very unusual objects whichhave been discovered are described here briefly:the quasar, the pulsar, and the black hole.


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UASARSQuasars may be the same size as large stars, yetthey emit energy at all wavelengths equivalent tothat of a thousand galaxies and produce moreenergy in a given volume than any other object inth e sky. They were first called Quasi-Stellar Ob-jects when discovered in 1963 by radio astron-omers because they were point sources of radio

"A healthy quasar each year eats up asmuch energy as our sun will use in itsentire existence."4Maarten Schmidt

energy starl ike instead of diffused over largeareas of the sky like all previously discovered radiosources. To astronomers, finding a quasar is likefinding a flashlight which shines as brightly as allthe lights in the entire Los Angeles basin.5 Under-standing their energy processes could be a keylink to new theories on the structure of matteritself.Quasars are cont rovers ia l ob jects becauseobservations do not yet permit conclusive inter-pretation. They are believed to be receding at enor-mous velocit iesup to 92 percent of the speed of

l ightbecause of the huge redshifts of their spectrallines. Objects moving at this speed must be billionsof light years distant, near the limits of the observ-able universe. One newly discovered quasar, OQ172, is believed to be the most remote recordedobject in the universe. Calculated to be 10-billionlight years from earth, it started sending out itsenergy before the sun, the earth, or the moonexistedeven as stellar dust. If quasars are thatremote from us, they may be among the youngestobserved objects and may prove important to cos-mological research by revealing what the earlyuniverse was like.

3C 273. The jet extending somelightyears from the edge of the quasarhave been produced by a galacticMatter is ejected at velocities up60,000 miles per second. Quasars may beyoung galaxies.


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NP 0532. This pulsar was discoveredheart of the Crab Nebula shown one cover. Thepulsar is invisible in the topIt has flashed on in the bottomIts repetition rate is 30 pulses per

ULSARSFormed from the collapsed remnants of super-novae explosions, pulsars are extremely dense,rotating neutron stars with intense magnetic fields.

"During the collapse. . .the stellar matterpasses from the atomic regime of con-densed matter and atomic physics throughthe nuclear realm. . .to thestill mysteriousrealms of elementary particlesIn thisone collapse, the star sweeps throughmuch of modern physics."6

They are believed to generate beams of directionalenergy which sweep across space like a lighthousebeacon. According to this model, when the beamwipes across earth, it appears as a pulse.When first formed, pulsars may spin up to 1,000revolutions per second. Their diameter is typicallyabout 12 miles. When the first pulsar was discov-ered in 1967, the remarkable regularity of its pulserate was initially interpreted as a meaningful signalf rom another intelligent civilization.A very rich pulsating source fo r future investiga-tions is Hercules X-1, a binary X-ray star which

exhibits a wide variety of pulse periods an d inter-actions with its visible companion. At least one ofthe pulse periods is produced by eclipses of theX-ray star by this larger companion.Another important pulsar in the Crab Nebula ha sbeen observed in the radio, optical, X-ray, gammaray, an d infrared regions of the spectrum. This spin-ning star, like the rotor in an electrical power gen-erator, produces most of the Crab Nebula's energy.Collapse to a neutron star convertsthe gravitationalpotential energy of the particles in the original starinto kinetic energy of explosion and rotation.Squeezed by its collapse, the star explodes, blow-

ing off the matter in its outer shell or mantle. Next,continued collapse spins up the remnant star as itgrows smaller. The detailed mechanism of thisgravitational collapse is one of the major problemsbeing studied by astrophysicists.


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LACK HOLESBlack holes are former stars which, having col-lapsed to an extremely dense state, have an extra-ordinarily powerful gravitational field. This field isso strong that no object, light, radio wave s, or otherradiation can escape to reveal the presence of theblack hole.

Black holes may account for 90 percent of thecontent of our universe. Potentially, there are one-billion black holes in our galaxy. Astrophysicistsspeculate that black holes may be bridges con-necting one part of our universe to another. Simi-larly, the other violent sources which we haveobserved may be white holes through which thisenergy is surging to us.

"At first glance any theory that talks ofa hole in space, where time stands still sothat a fraction of a second becomes eter*nity and where all things simply disap*pear from sight, would seem to belong tothe more fantastic realms of science fic-tion. But to astronomers it is far fromfantasy."7David Brand

X-1. This black hole model is basedcalculations performed by Kip Thome ofCalifornia Institute of Technology and wasby Lois Cohen of the GriffithHot, radiating gas glows red as

Cygnus X-1,believed to be the f irst identif iableblack hole, was discovered by the Uhuru satellitein 1972. This b lack hole is the invisible but do mi-nant component of a binary pair of stars and isshown sucking the material of its visible compan-ion into a rotating disk. The black hole is at thecenter of the disk. The violence of the transfer an dshredding action heats the atoms of gas into emit-ting X-rays at the edge of the black hole. TheseX-rays indirectly reveal its presence.The total energy of the particles and radiationnear a black hole is enormous. This energy is pro-duced by the conversion of gravitational energyinto radiation energy as the matter falls inw ard,accelerating into the hole. This mechanism is manytimes more eff ic ient than nuclear fusion, whichproduces stellar and solar energy. A black holeconverts mass to energy m ore eff ic ien tly than an yother mechanism known in physicsexcept fo rmatter-antimatter annihilation. Accordingly, blackholes have been called an "ultimate" source ofcosmic energy.


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I G H - E N E R G Y ASTRONOMYA KEY TOOLMany of the most exciting discoveries have beenmade in a new field called high-energy astro-physics, of which X-ray astronomy is an importantpart. Astrophysicists study the physics of the starsby observing their X, gamma, and other radiationas well as charged-particle cosmic rays speed-ing particles of atomic matter from the sun andsources outside our solar system.

Measurements of this invisible radiation are asmeaningful to the high-energy astronomer as visi-ble light is to the classical astronomer. Until the1950's, except fo r meteorites, most of what weknew about the universe came to us by light theastronomer's bridge. Optical astronomy has en-

"They have had a greater influence onastronomy in the first few years than the200'inch telescope on Mount Palomardid!"* A scientist, commenting on the immenseimpact of satellite X-ray astronomy experiments

E X - R A Y SKY. These high-energy objectsbeen seen by the Uhuru satellite. Sincelaunch in December 1970, this satellite haswell over a hundred new X-ray

joyed about 3,000 years of instrumented observa-tion. This optical picture was suddenly expandedby 20 years of radio astronomy, and now, by 10years of X-ray astronomyof which only the lastfe w have been conducted from spacecraft.Although light and radio waves pass throughto ground-based instruments, high-energy radia-tion is absorbed by the atmosphere. Therefore itcan only be observed by instruments carried abovethe atmosphere either by short-lived rockets andballoons or by much longer-life orbiting satellites.Already, X-ray astronomy has discovered well overa hundred new sources in the X-ray sky, largelybecause of the spectacular success of the smallUhuru X-ray satellite. The larger and heavier satel-lites of the future such as HEAO will offer muchimproved observations of this radiation.The data from high-energy astrophysics provideimpor tant additional information about some of thesame stellar objects that had been previously ob-served by optical astronomers. For example, X-raydata yield precise information about orbit size,object diameter, and rotation rates. These data inturn are used by theorists to propose new and im-proved models of the observed objects and theuniverse.In this way, sharing new discoveries and per-spectives, astronomers and astrophysicists work-ing in various regions of the electromagneticspectrum are preparing th e basis for the coming

synthesis of ideas about the cosmos.


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HERE THIS LEADS USX, gamma, an d cosmic rays streaming to us acrossthe universe contain messages about the structure,composition, and energy processes of the stellarand galactic objects which produced them. "Lightfrom the atomic processes in the stars and galax-ies tells us what is going on in their outer atmos-phere," says physicist and gamma-ray astronomerRobert Hofstadter. "X-rays tell us what happensdeeper within the surfaces and gamma rays willtell us what goes on at even greater depths. Theimportance of the greater depths of observationcan be understood particularly in the recently dis-covered binary star systems which emit X-rays "As the matter is transferred between the binarymembers "perhaps in clouds streaming betweenthe stars, we have a thrilling opportunity to lookinto this gigantic funnel and see the X-rays andgamma rays arising from th e fundamental atomic,

NEBULA. Th e creation of newis believed to be underway in such regionsthis bubble 100 light-years in diameter.e luminous glow comes f rom clouds ofatoms heated by the absorption ofstars embedded deepclouds. This local spectacle is dwarfedth e primeval fireball, which, accordingbig-bang cosmology, created th e cosmosa hot, ultradense droplet containingmatter an d radiation in the universemore than 10-billion years ago.

"Up to the twentieth century, 'reality'waseverything humans could touch, smell,see, and hear. Since the initialpublicationof the chart of the electromagnetic spec-trum ... humans have learned that whatthey can touch, smell, see, and hear isless than one^millionthof reality. Ninety*nine percent of all that is going to affectour tomorrows is being developed by hu-mans using instruments and working inranges of reality that are nonhumanlysensible."9

R. Buckminster Fuller

nuclear, and elementary particle reactions occur-ring in that enormously hot region. The more ener-getic the quanta [of radiation] we measure, thedeeper we can observe, and thereby we can ob-serve the most fundamental processes of nature inaction. This is a wonderfully exciting thing tocontemplate . . . ."10The time is ripe for research based upon high-energy astronomy observations to yield a revolu-t ionary new understanding of physics, relativity,an d cosmology. The physics of stars provides a newinsight into states of matter and energy processes.Einstein's general relativity field equations arebeing tested and observed by high-energy obser-vations. And we may be very close to determiningif the universe is a steady-state cosmos or if itoriginated in a hot big-bang or even, possibly, acold big-bang.


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Copernicus


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LTIM ATE BENEFITSThe data gathered by this new astronomy may welllead to new theories about energy production andhigh-density nuclear matter. "In looking to ourlocal energy resources," says physicist FreemanDyson, "it is well to consider how we fit into thelarger scheme of things. Ultimately what we cando here on earth will be limited by the same lawsthat govern the economy of astronomical energysources."11 Stars exhibit much m ore efficient waysof producing energy than the primitive burningwhich prevails on earth today. Our sun is a smallstar. Yet one second of its output is equivalent toall the energy ever consumed by men.

In addition to the economic benefits of energy,the cultural benefits of an enlarged consciousnessseem likely. This new knowledge of the cosmosmight dramatically change our view of ourselves,

". . .astronomy ranks w ith molecular biol-ogy in its po ten t ia l impact on man's phi l*osophical conception of himself and hisplace in the universe."12Harvey Brooks

E BREAKOUT. Theearly astronomer in thisd woodcut is an emblem of the dawningcosmic consciousness. His curious mindleft the tidy and familiar green garden ofbehind. Like astronauts poking theirabove the protective atmosphere intorealm of space, he gazes outward intoe unknown, observing the workings of themachinery. Hewill return from hisof the mind to the garden with aand a keenerand appreciation of the valuethis "blue planet."

just as men's minds were changed by Copernicus'work. "The revolution in man's view of himself an dhis place in nature, when he realized that he wasnot at the center of the universe, but a speckwhirled through a gigantic space, was far greaterthan the mere technical change in astronomy. Itbrought all things under question. It underminedastrology, and helped man to take a more de-tached view of himself and nature. It enabledobjective sciences of physiology, psychology, andsociety to be conceived, and medicine to be put ona rational basis. Few men could stomach the revo-lutionary new view."13 An equally dramatic changeof consciousness in man's near future cannot beruled out.In the mid-19th century when electricity wasmerely a curiosity, who could have predicted its20th-century promise of power and electronics?Fifty years ago, who could have foreseen theadvent of nuclear energy or believed that experi-mental and theoretical research in nuclear fissionwould make it possible to transform the world soswiftly and irrevocably? Similarly, today's astro-physical frontier portends the dawning of the 21stcentury and perhaps a glimpse of man's cosmicdestiny.


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IGH-ENERGY ASTRONOMYOBSERVATORIES [HEAO]Based on recommendations of the scientif ic com-munity and the National Academy of Sciences thathigh-energy astrophysics research should receivevery high national priority, th e National Aeronauticsan d Space Administration has undertaken a pro-gram called HEA O. To manage this program, NASAnamed the Marshall Space Flight Center who, inturn, contracted w ith TR W Systems to design andbuild observatories into which experiments fromleading scientif ic and educational institutions willbe integrated. The first observatory, HEAO-A, willbe launched in 1977 to perform a detailed X-raysurvey of the celestial sphere. The experiments car-ried by this m ission w ill study the spectra and mea-sure precise positions and time-variabilities of theX-and gamma radiations from as many objects aspossible. These m easurements are similar to thosemade by ground-based telescopes. HEAO-B will

"These clues have been gained almostentirely withfirst'generation tools. Futureinstruments of far greater power are inpreparation and the prospectsfor impor-tant advances in knowledge and under"standing are immense."14

IN CYGNUS. Among theobjects which HEAO is expected towith its large and heavy advancedare such sources as this remnantthe expanded and cooled gas shell fromprehistoric supernova which has evolvedfurther than the Crab on the cover. Inway, some stars return to space all thethey have been manufacturing befored during their blow-up. This enrichedbecomes available to create new stars.

carry a focusing X-ray telescope with a variety ofinstruments to obtain precise measurements, in -cluding X-ray photographs, of the most interestingcelestial objects. It is scheduled to be launched in1978. HEA O-C will be launched in 1979 to performcosmic ray and gamma ray observations. Follow-onHEAO payloads will be carried by the SpaceShuttle.

The initial HEAO observa tories will be launchedinto a 225-nautical-mile orbit f rom th e NASA Ken-nedy Space Center byAtlas-Centaur boosters. Each18-foot long observatory will weigh 6,000-7,000pounds, provide electrical power from solar arrays,an d carry over 11/2 ons of experiments. Th e observ-atory design implements th e objectives of NASA toconduct space research at low cost by using a highpercentage of off- the-shelf hardware, high safetymargins to minim ize testing, and a standard space-craft equipment module to which th e experimentcomplements can be readily attached for each mis-sion. This spacecraft module will also be easilyadaptable to many other future missions launchedby both Shuttle and conventional boosters.The HEAO observatories will be national scien-tific facilities dedicated to furthering th e under-standing of the high-energy universe.

HEAO-A. To be launched in 1977. (Left)HEAO-B. To be launched in 1978. (Right)


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EFERENCES

NOTE: These diagrams appearing on previouspages are the classification of galaxies madeby astronomer Edwin Hubble who firstdiscovered other galaxies lying beyond ourMilky Way Galaxy only 50 years ago.

1. "Light-Years Past Copernicus," Newsweek, May 7,1973, p. 62.2. Herbert Friedman, "High-Energy Astronomy," Dry-den Lecture, A I A A 11th Aerospace Sciences Meet-ting, Washington, D.C., January 10-12, 1973, AIAA

Paper No. 73-197, p. 9.3. Astronomy & Astrophysics for the 1970's, Vol. 1,Report of the As trono my Survey Com mittee, JesseGreenstein, Chairman. National Academy of Sci-ences, W ashing ton, D.C., 1972, p. 4.4. "Light-Years," op. cit., p. 62.5. George Ale xand er, "Quasars the Key. The U niverse:Is the Edge of It Now in Sight?", Los Angeles Times,January 29, 1973, p. 3.6. Phy s ic s S urv e y Com m i t t ee , D. A l l en B rom ley ,Chairman, Physics in Perspective, Vol. 1. NationalAcademy of Sciences, Washington, D.C., 1972, p.

345.7. David Brand, "Where's the Matter?", Wall StreetJournal, June 16, 1972, p. 1.8. Will iam D. Metz, "Astronomy from an X-ray Satell ite:Measuring the Mass of a Neutron Star," Science,March 2, 1973, p. 884.9. R. Buckminster Fuller, "Heartbeats and Illions,"World, March 27, 1973, p. 23.

10. Robert Hofstadter, "Statement to Subcommit tee onSpace Science and Appl icat ions on the Subject ofNASA's Physics and Astronomy Program," March14, 1973, p. 9.11. Freeman J. Dyson, "Energy in the Universe," Scien-tific American, September 1971, p. 51.12. Astronomy & Astrophysics, op. cit., p. vi.13. J. G. Crowther, "The Copernican Revolution," NewScientist, February 15, 1973, p. 381.14. Friedman, op. cit., p. 9.

A DDITIONAL READINGRichard A. Condon, "HEAO Con versation Piece: It TakesA Very Big Thing To Make A Very Smal l Thing," ScienceNews, November 4, 1972, p. 304.Robert Jastrow, Red Giants and White Dwarfs: Man'sDescent from the Stars. New American Library, NewYork, 1969.Will iam J. Kaufmann, III, Relativity and Cosmology.Harper & R ow, Ne w Yo rk, 1973.Charles W. Misner, Kip S. Thorne, and John ArchibaldWheeler, Gravitation. W. H. Freeman and Comp any, SanFrancisco, 1973.Patrick Moore, The Atlas of the Universe. Rand McNallyand Company, New York, 1970. In association withMitchell Beazley Ltd. London.


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LOSSARYBINARY STAR A pair of stars orbiting abouteach other under mutual gravitational attraction.BLACK HOLES Objects resulting from completegravitational collapse beyond that of a neutronstar. The accompanying gravitational field is sointense that no radiation can escape.COSMIC-RAYS High-energy atomic nuclei andelectrons originating in stellar sources and inter-s te l la r s p a c e and o b s e r v e d in the n e a r - e a r t he n v i r o n m e n t .COSMOLOGY The study of the origin, evolution,an d structure of the universe.DIFFUSE BACKGROUND - The microwave radia-tion that pervades all of space and is believed tobe a remnant of the initial big-bang which markedth e birth of the universe.EXPLODING GALAXIES - Violent, energetic ex-plosions centered in certain galactic nuclei wherethe total mass of ejected material is comparableto 5-million average stars. Jets of gas 1000 light-years long are typical.GALAXY A large system of stars held togetherby mutual gravitational attraction.G A MMA -RA Y Electromagnetic radiation with en-ergies in excess of 100,000 electron volts.GENERAL RELATIVITY - The theory of gravity andthe nature of gravitational forces as expounded byAlbert Einstein.

NEBULA A cloudlike, luminous mass of gas anddust.NEUTRON STARS Remnants of supernovae ex-plosions. They consist of ultra-dense matter com-posed almost entirely of neutrons which have beensqueezed together by the force of gravity exertedby the collapsing matter.PULSARS Believed to be rotating neutron stars.The intensity of their radiation in the electromag-netic spectrum is modulated by the period of ro-ta t ion . Add i t iona l per io d ic i t ies have a lso beenobserved.Q UA S A RS Q uasi-Stellar Objects. Very controver-sial. Quasars seem to be the size of large stars,ye t they emit energy at all wavelengths compar-able to that of a thousand g alaxies. Ch aracte rizedby very large redshif ts.SEYFERT GALAXIES-Unusual spiral galaxiescharacterized by small, extremely bright nucleicontaining one to ten billion stars. They are ordersof magnitude brighter in the X-ray than in thevisible part of the spectrum.SUPERNOVA A catastrophic stellar explosionoccurring near the end of a star's l i fe in which th estar collapses and explodes, manufacturing th eheavy elements which it spews ou t into space.Visible luminosity may reach 100-million times thatof the sun.X - R A Y Electromagnetic radiation typically in therange of 100 to 100,000 electro n v olts of energy.

Reprinted by NASA with permission of TRW, Inc. AUTHORS:D R. F. DoolittleD Ken MoritzDR. D. C. Whilden

DESIGNER:D R.E. S hepard

ICTURE CREDITS 3C 273 courtesy Hale Observatories.NP 0532 courtesy Lick Observatory.The X-ray S ky courtesy Riccardo Giacconi, Smith-sonian Observatory.COLOR PLATESCrab Nebula, M 82, Rosette Nebula, Veil Nebulain Cygnus, an d Trif id Nebula: Copyright by theCalifornia Institute of Technology and the Car negieInstitution of Washington.Cygnus X -1 painting courtesy Wil l iam J. Kaufmann,Griff ith Observatory.

F or sale by the S u p e r i n t e n d e n t of Documents /U.S. Gove r nmen t P r in t i n g Office/Washington, D.C., 20402/Pr ice 80 cents/Stock Number 3300-00542fr U.S. GOVERNMENT PRINTING OFFICE : 1974O-532-I08


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National Aeronautics and Space AdministrationWashington, D.C. 20546