Astronomical telescope is the main tool for observing celestial bodies and capturing celestial information.Since Galileo made the first telescope in 1609, telescopes have been developing continuously. From optical band to full band, from ground to space, telescopes have become more and more capable of observing and capturing more and more celestial information.Human beings in the electromagnetic wave bandneutrino、Gravitational wave、cosmic raysThere are telescopes in all aspects.
Telescope originated fromglasses。People began to use glasses about 700 years ago.Around 1300 A.D,ItalyPeople start usingConvex lensmakePresbyopic glasses。Around 1450,Myopia glassesIt also appeared.In 1608,NetherlandsAn apprentice of H. Lippershey, the eyewear manufacturer, discovered by accident that when two lenses are folded together, you can clearly see things in the distance.In 1609, Italian scientist Galileo immediately made his own telescope and used it to observe the stars after he heard of the invention.Since then, the first astronomical telescope was born.Galileo observedSunspot、MoonCrater、Jupiter's satellite（Galileo satellite）, Venus' profit and loss, which strongly supported Copernicus'sHeliocentric theory。Galileo's telescopeutilizeRefraction of lightIt is made by principle, so it is called refractor.
In 1663,ScotlandAstronomer Gregory usedReflection of lightThe principle is made into GregorianreflectorHowever, it was not popular due to the immature manufacturing process.In 1667, British scientistNewtonThe idea of Gregory was slightly improved, and a Newton type reflector was made. Its aperture was only 2.5 cm, butMagnificationMore than 30 times, but also eliminatedRefracting telescopeThis makes it very practical.[1]In 1672, the French Cassegrain usedConcave mirrorandconvex mirror, designed the most commonly used Cassegrain reflector.The telescope has long focal length, short mirror body, large magnification and clear image;It can be used for small researchfieldThe objects inside can also be used to photograph large areas of objects.hubble space telescope This is what is usedReflecting telescope。
Haier telescope with aperture of 5.08 meters.
In 1781, the British astronomer Herschel brothers and sisters (W. Herschel and C. Herschel) discoveredUranus。Since then, astronomers have added many functions to the telescope, making it capable of spectral analysis.In 1862, American astronomers A. Clark and A.G. Clark made a 47 cm refractor and photographed itSiriuscompanionPicture of.1908 American astronomerHaierThe leaders built a 1.53-meter aperture reflector, which captured the spectrum of Sirius companion star.In 1948,Haier telescopeWhen completed, its 5.08 meter diameter is enough to observe and analyze the distance andApparent velocity。[2]
In 1931, it was made by German optician SchmidtSchmidt telescope, 1941Soviet RussiaAstronomer Maksutov made Maksutov Kasegrain type reentry mirror, enriching the variety of telescopes.
In modern and contemporary times, astronomical telescopes are no longer limited to optical bands.In 1932, the United StatesRadio engineerDetected fromGalactic centerOfRadio radiation, markingRadio astronomyThe birth of.1957Artificial satelliteAfter going to heaven, space telescopes have developed vigorously.Since the new century,neutrino、dark substance、Gravitational waveAnd other new telescopes are in the ascendant.Now, many messages sent by celestial bodies have become the object of astronomers' eyes, and the vision of human beings has become broader and broader.[2]
At the beginning of November 2021, after a long period of engineering development andintegration testing , expected by allJames Webb Space Telescope(James Webb Space Telescope, abbreviated as JWST) finally arrived atFrench GuyanaOfLaunch site, will be launched in the near future.[18]
The longer the focal length is, the larger the image on the focal plane is, and vice versa.
Caliber (D) Yesobjective lenseThe diameter ofopticsSystematicResolution。according toRayleigh criterionThe resolution of a telescope is related to its aperture.The larger the aperture, the stronger the resolution.Focal length (f) is the distance from the telescope objective to the focus, which determinesoptical system The size of the image on the image plane.aboutAstronomical photographyFor example,Object distance(ObservedDistance of celestial bodies）It can be regarded as infinity, soImage distanceIs equal to the focal length, so the image plane is also calledfocal plane。The longer the focal length of the telescope, the larger the image formed on the focal plane;On the contrary, it is smaller.Focal ratio (F) is the focal length of the telescope divided by the aperture of the telescope, that is, F=f/D, which determines the number of photons received per unit area per unit time on the focal plane.alsoBe treated asAn important indicator of exposure efficiency.The smaller the focal ratio, the more photons will be received per unit area on the focal plane;On the contrary, it is less.That is to say, the smaller the focal ratio, the higher the exposure efficiency of the mirror.[3]
See entry:caliber、focal length、Coke ratio、diffraction
For the imaging of a point light source in a spherically aberrated system, the second behavior is the case of no spherically aberrated light source.
Aberration is an imperfect description of optical system imaging.There are spherical aberration, chromatic aberration, coma, astigmatism, field curvature, distortion, etc.Spherical aberrationExists in the spherereflectorIn the optical system, parallel tooptic axisThe incident light passes throughSpherical lensOr the reflection mirror is not strictly converged at a point, and the light far away from the optical axis will converge closer to the mirror.Use the combination lens and change the sphere toparaboloidIt can improve the ball error.Chromatic aberration is the most obvious aberration of refractive optical system, which is formed inDispersion of light, which makes the starlight appear many colors, affecting the observation.Combined by multiple lensesApochromatic aberrationThe system can reduce the degree of color difference.ComaIt's a paraboloidReflective optical systemThe most obvious aberration is due to the tilt on the optical axisincident lightThe inability to converge will make the starlight look like a comet.The coma correction lens set can eliminate the coma.AstigmatismIt is the phenomenon that the light inclined to the optical axis appears that the vertical vibration light wave and the horizontal vibration light wave do not meet at the same point.The farther awayfieldEdge, the more serious astigmatism.installFlat fieldThe correction lens group can correct astigmatism.Field musicIt refers to the phenomenon that the light far from the optical axis converges on a curved spherical surface, which will cause defocus during imaging.The object point on the distortion axis is different from the edge of the field of viewMagnificationThe phenomenon that objects and images are not completely similar.[4]
Keplerian and Galilean light path schematic diagrams.
Refracting telescopeA telescope that uses a lens as its objective lens.There are two types:Concave lensdoeyepieceGalilean refractor;fromConvex lensThe eyepiece is called Kepler type refractor.becauseSingle lensThe chromatic aberration and spherical aberration of objective lens are quite serious, and apochromatic aberration systems are commonly used in modern refractive telescopes.
The Kepler structure is commonly used in refractive telescopes.Because of the imaging of refraction telescopemass ratioReflecting telescopeGood, large field of view, easy to use, easy to maintain, small and medium-sized astronomical telescopes and many special instrumentsRefracting systemHowever, it is much more difficult to manufacture a large refracting telescope than a reflecting telescope, because it is very difficult to smelt high-quality lenses with large aperture, and the large lenses have huge quality and are inconvenient to operate.
Schematic diagram of optical path of Newton type reflector.
A reflector is a telescope that uses a reflector as its objective lens.There are mainly three types: Gregorian, Newton and Cassegrain.NewtonianPlane mirrordoSecondary mirrorCassegrain type uses convex hyperboloid mirror as secondary mirror, and Gregory type uses concave ellipsoid mirror as secondary mirror.Reflector presenceOff-axis aberrationTherefore, the field of view is limited, but because the mirror does not require the internal quality of the lens, the cost is low.Many modern telescopes useReflecting telescope。[5]
Catadioptric telescopeBoth refractors and reflectors.In 1931, German optician Schmidt used a unique piece ofaspheric surfaceThin lensAs a correction lens, it works with a spherical mirror to make aSchmidt telescopeThe telescope has strong light power, large field of view and small aberration, and is suitable for taking pictures of large areas of the sky, especially for faint nebulae.If a reflector is added in front of the focus of the Schmidt telescope and the focal plane is led out, the Schmidt Newton telescope will be formed.If you add a piece in front of the focusConvex surfaceThe secondary mirror introduces lightPrimary mirrorThe small hole of is imaged behind the main mirror, forming Schmidt-Cassegrain telescope。Schmidt Cassegrain telescope has a short lens tube and good imaging qualityAstronomical observationImportant tools.
Schematic diagram of the light path of the Maksutov Cassegrain telescope.
1941Soviet RussiaAstronomer Maksutov used a crescent shaped lens as a correction lens to create another type of catadioptric telescope, the Maksutov Kaseglin type reentrant mirror, whose two surfaces are twocurvatureDifferent spheres have little difference, but the curvature and thickness are very large.All its surfaces are spherical, which is easier to grind than the correction plate of Schmidt telescope, and the lens tube is shorter, but the field of view is smaller than Schmidt telescope, and the requirements for glass are higher.This kind of telescope is easy to carry and is often used in small and medium-sized telescopesAstronomerLove.[5]
modernastronomerStudy the universe, the most importantinformation sourceIt's from the celestial bodyelectromagnetic waveRadiation.Electromagnetic wave is the charge in the atomVariable speed movementWhen.Electromagnetic waves from the universe pass throughEarth's atmosphereMany wave bands are absorbed by atmospheric molecules.The atmospheric shielding effect isTerrestrial organismWithout these shields, life on earth will be threatened.But this is a hindrance to astronomy.Fortunately, there are two transparent windows: optics and radio, which provide necessary information for the development of human astronomyInformation channel。
The optical and radio bands are transparent to the atmosphere.
Optical windowIs the wave band with a wavelength of 0.35-22 μ m, includingvisible lightAnd part ofinfrared。Where 17-22 microns are translucent and 1.1-17 microns areDiscontinuityWindow, that is, a number of small slits can pass through radiation.The radio window is a radio band with a wavelength between 1mm and 30m.A portion of the 1-40mm microwave is also a translucent window.Therefore,Ground telescopeUsuallyOptical telescopeandradio telescope。[2]
adaptive optics It can effectively solve dynamic problemsStatic errorThe optical system that is too large and greatly improves the imaging quality isActive opticsOne of.In the optical system of astronomical telescopephysical propertyChange andatmospheric turbulenceThe resolution of the telescope is not very high, and the imaging is also very unsatisfactory.Since the 1970sBasic technologyThe adaptive optics system was established.Adaptive optics system is based on optical wavefrontautomatic control system, using theOptical wavePreviousreal-time measurement , control and calibration, so that the optical system can automatically adaptenvironmental change , keep goodworking condition 。wavefront sensor The optical wavefront error is measured in real time. The wavefront controller converts the error into a correction signal, and the wavefront corrector quickly changes the wavefront phase to correct distortion.This system has been widely used in astronomical telescopes. Now, the adaptive optics system can also be used in laser technologyOphthalmologyOn.[6]
Ultra long antenna array located in the United States.
Radio bandThe parabolic antenna is needed as the main mirror for astronomical observation.Because radio waves are ten thousand times longer than light waves, the resolution of radio telescopes is much lower than that of optical telescopes.The precise orientation of the radio source can not be determined by the single side radio telescope with small aperture.Radio wave imaging ratioOptical imagingIt is much more difficult because the radio wave intensity at each point can only be measured by the radio wave pickup.In the early 1950s, radio astronomer M. Ryle and others proposedSynthetic apertureTechnology, that is, the interference array of radio telescope is composed of multiple antennas,Simultaneous observationThe same sky,Comprehensive data processingThen the radio image of the celestial body can be obtained.This method has greatly expanded the total aperture of radio telescopes, greatly improved the resolution and the field of view, which is larger than optical telescopes.Modern radio interference arrays usually include cross array, T-shaped array and spiral array.Very long baseline interferometerWith the advent of the, radio telescopes anywhere on the earth can form interference arrays, greatly expanding the vision of the radio observation eye.[7]
Comparison chart of astronomical telescope aperture.
Typical telescope
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Ground telescope
optics
The European Southern Observatory Very Large Telescope.
Southern EuropeobservatoryVery large telescope(VLT), consisting of four telescopes with an aperture of 8.2 meters, and the optical system is the Richie Kletchen reflection telescope (R-C type, a variant of Cassegrain type), located in the northern part of ChileParina Observatory。The four telescopes can be observed either individually or as an optical interference array.The observatory is in the desert,Atmospheric visual acuityExcellent, many observations have been made in recent years.
The Keck Telescope in Hawaii.
Keck telescope(Keck), consisting of two telescopes with an aperture of 10 meters, located in HawaiiMauna Keamountaintop.The optical system is a R-C reflecting telescope.The two telescopes adopt thin mirror mosaic technology, which greatly reduces the quality of the main mirror. It also has an adaptive optical system.These technologies make it one of the most successful telescopes.
The Northern Gemini Telescope in Hawaii.
GeminiThe GEMINI telescope consists of two 8-meter telescopes, one located in Hawaii's Mauna Kea Mountain and the other located inChileThe desert in the north of Latin America for systematic observation throughout the day.The optical system is a R-C reflecting telescope, and its main mirror adopts active optical technology.
Hobby Eberle telescope(HET), composed of 91 pieces ofRegular hexagonIt is made of glass, with a total diameter of 11m and an equivalent diameter of 9.2m, located atTexas, USAMacDonald Observatory。The optical system is reflective.The HET telescope is a telescope for spectral sky surveyZenith angleFixed at 35 °, that is, the primary mirror cannot move up or down;The azimuth can be rotated 360 °, but it is only used to change the observation area. The telescope is fixed in one observation.The focal plane device is equipped with a spherical aberration corrector, and only a part of the main mirror is used for each observation.The observable sky area isDeclination-10° to 75 °, but the observable period for stars at different declinations is different, and the tracking time may also be different, ranging from 45 minutes to 2.5 hours.
Ultra long baseline array(VLBA) consists of 10 radio telescopes with a diameter of 25 meters, spanning from Virgin Island in the east of the United States to Hawaii in the west. The longest baseline is 8600 kilometers, and the shortest baseline is 200 kilometers. Its precision is HubbleSpace telescope500 times that of the human eye, 600000 times that of the human eye.
Green Bay Radio Astronomical Telescope(GBT), one of the largest mobile radio telescopes in the world.Its parabolic antenna is 100 m x 110 m in size, and its asymmetric shape can prevent the support structure from blurring the mirror inlaid with more than 2000 aluminum panels.The Green Coast Telescope weighs 7300 tons and is 148 meters high, but it is very flexible. It can track targets in real time and zoom quickly to adapt to different observation objects.[2]
The International Low Frequency Radio Telescope Array (LOFAR) is the largest low frequency radio telescope array, which consists of a large number of (about 20000) individual antennas scattered in several European countries.These antennas use high-speed network and "COBALT", one of the most powerful supercomputers in EuropeCorrelatorA radio telescope covering an area of 300000 square meters will be formed.[8]
Atacama large millimeter wave/submillimeter wave array(ALMA), consisting of 54 radio telescopes with a diameter of 12 meters and 12 radio telescopes with a diameter of 7 meters, is located in northern ChileAtacama Desert。66 antenna canCollaboration, can also be observed separately.All antennas acquire signals via dedicatedSupercomputerhandle.These antennas can be used in differentCollocation methodArrayed in an array, the distance between antennas varies from 150 meters to 16 kilometers.
Arecibo Observatory(ART), consisting of a spherical radio telescope with an aperture of 300 meters, located in the United StatesPuerto RicoFree State.It used to be the largest single aperture radio telescope in the world. It can not only receive radio waves, but also transmit radio waves.Scientists around the world have been usingArecibo telescopeStudy distant planets and discover potential dangersasteroidAnd look for possibleExtraterrestrial life。fromSmall objects in the solar systemArresibo telescope has witnessed many "human first discoveries" to pulsars in the deep space.[11]On December 1, 2020, the Arecibo Radio Telescope collapsed because all three support towers were broken, and the 900 ton receiving platform fell directly onto the reflecting disk of the telescope.The antenna was damaged, and the telescope has no possibility of repair.[12]
neutrinoIt is one of the most basic particles in nature.It's smalldead , can pass through the earth freely, with very light mass, moving at the speed of lightInteractionVery weak, known as the "invisible man" in the universe.It took more than 20 years for the scientific community to predict its existence and discover it.Neutrinos contain a lot of information about celestial bodies.Because the interaction with matter is very weak, neutrino observatories are usually very large and built underground.
Super Kamioka detector, consisting of about 10000 neutrino detectors, located in an abandoned building in Shinoka, JapanArseniteMedium.The main structure -- the water tank with a height of 41 meters and a diameter of 39 meters -- holds 50000 tons ofUltra pure water, tens of thousands are installed on the inner wallPhotomultiplier tube, used to observe Cherenkov radiation.It is acceptableSolar neutrinoAnd solved the problem of neutrino loss, and made many scientific achievements.
JiangmenUnderground neutrinoObservation station(JUNO)Jiangmen CityA comprehensive experimental observation station with multiple physical targets built.Jiangmen neutrino experimentIn addition to the availabilityreactorNeutrinos can determine the quality order of neutrinos and accurately measure the neutrino mixing parameters, and can also detect solar neutrinosGalaxyAnd adjacentGalaxyOfSupernova explosionProduced neutrinos andSupernovaBackground neutrinos are of great significance to the study of stellar evolution and supernova explosion mechanism.On the other hand, supernovae andAstrophysicsandcosmologyThe basic problems of are closely related, such asHigh qualityThe evolution of starsneutron starAnd the formation of black holesHeavy nucleusComposition of elementsGamma ray burstAnd high energycosmic rayThe origin of.[13]
Laser Interferometric Gravitational Wave Observatory(LIGO), consisting of twoInterferometerEach is equipped with two 4km long arms and forms an L-shape, respectively located in the United States, 3000 km awayWashington StateAnd Louisiana.Each arm is composed of a vacuum steel pipe with a diameter of 1.2 meters. Once the gravitational wave enters the earth, causing space-time oscillation, the distance of the interference arm will change, which willinterference fringeChange, and then determine the strength of gravitational wave.[14]On August 17, 2017, it first found thatNeutron star amalgamationGravitational wave events.[15]
cosmic raysIs from outsideSpaceCharged high energySubatomic particle。They may produceSecondary particleEarth penetratingatmosphereAnd surfaces.majorPrimary cosmic ray(Particles from deep space impacting the atmosphere) The components on the earth are generally stable particles, such as protonsNucleus, or electronic.However, there are very few stable proportionsAntimatterParticles, likepositronorAntiprotonThe remaining small part is an active field of research.
About 89% of cosmic rays are pure protons, and 10% are pure protonsHelium nuclei (i.eαparticle）And 1%Heavy element。These nuclei make up 99% of cosmic rays.Lonely electrons (likeβparticle, although the source is still unclear), constituting the majority of the remaining 1%;γradialAnd ultrahigh energy neutrinos account for only a tiny part.These particles may come from the sun (or other stars) or from distantVisible universe, produced by some unknown physical mechanisms.The energy of cosmic rays can exceed 10twentyeV, far more than on earthParticle acceleratorAttainable 10twelveTo 10thirteeneV。
LHAASO completed muon detector array.[16]
High altitude cosmic ray observatory(LHAASO) is the world's highest (4410 meters), largest (2040 mu) and most sensitive cosmic ray detection device under construction, located in ChinaSichuanprovinceDaocheng CountyHaizi Mountain。The observation station is divided into four parts: electromagneticParticle detectionArray, muon detector array, water Cerenkov detector array and wide-angle Cerenkov detector array.Infrastructure construction began in July 2016, and Muzi detector array was completed on December 6, 2020.
Space telescope
Space is a good place for astronomical observation.Because there is noEarth's atmosphereShielding and interference of many types of astronomytelescopeAre located in space.these ones hereObserverMost of them are well designed and have complete functions. Some of them have the functions of telescope and detector.
The Hubble Space Telescope.
hubble space telescope AstronomersEdwin HubbleIn the name ofEarth orbitA telescope.Because it is located above the earth's atmosphereGround-based telescopeBenefits not available: the image is not disturbed by atmospheric turbulenceVisual acuityIt is excellent, and there is no background light caused by atmospheric scattering. It can also be observed thatozone layerAbsorbedultraviolet rays。Launched in 1990, it has become the most important instrument in the history of astronomy.It successfully made up forGround observationThe deficiency of the new theory has helped astronomers solve many basic problems in astronomy, and made people have more understanding of astrophysics.In addition, Hubble's superdeep spaceThe field of view is the deepest and most sensitive space optical image that astronomers can obtain.
Kepler space telescope yesNASASpace telescopes designed to discover planets around other stars and the likeKeplerNaming.It usesTransitTo observe the star to check whether it has planets.In the whole life cycle (2009-2018), more than 2000 candidate planets were found, 48 of which are located inLivable zoneThe planet of.
Gaia Telescope released photos of stars in the Milky Way.
Gaia Space TelescopeIt is a stellar telescope designed by ESA, which is used to observe the position andMotion dataTo solve the origin and evolution of the Milky Way.Gaia telescope has got a lot of data about stars.
Transsolar extraplanetary survey satellite(TESS, also known as Tess) is a planetary telescope designed by NASA, which was launched in April 2018 to take over the Kepler Space Telescope and become a new generation of NASA's main exoplanet detector.Tess passed the testStellar brightnessThe light curve changes with time to find the planet.Once the "transit" phenomenon occurs, that is, when the planet passesStellar surfaceThe brightness of the star will appearsolar eclipseThere is also a decline.Tess carries the most sophisticatedDetecting instrumentIf you lock the rocky planet similar to the earth, it can be launched by NASAJames Webb Telescope observationatmospheric environment , looking for the characteristics of biological existence.[17]
Parker Solar Probe(PSP), which is based onsolar windNamed by scientist Yuri ParkerspacecraftIs the first NASA spacecraft named after a living person.It was the first to fly into the sunCoronaThe aircraft is only 9 above the surface of the sunSolar radiusAt.Solar detectorOur instruments detect what they encounterPlasma, magnetic field and waveHigh-energy particleAnd dust.They also image the structure of the corona near the orbit of the solar detector and the dipole structure at the bottom of the corona.
