Ray astronomy isX-ray(Electromagnetic radiation with a wavelength of 0.01~100 A) The study of celestial bodies.X-rays of celestial bodies are seriously hindered by the earth's atmosphere, and are mainly detected by satellites.Therefore, although X-ray detection began in the 1940s, as a disciplineArtificial earth satelliteAfter God.Early observations focused on the study of the sun.Since June 18, 1962, the MIT research team first found thatscorpioNon solar X-ray astronomy has entered a new stage of development after the direction of the powerful X-ray source.[1]
In X-ray astronomyElectron volt(eV) meansphotonThe observed object is 0.1keV to 100keV X-ray.Among them, 0.1keV-10keV X-ray is called soft X-ray, and 10keV-100keV X-ray is called hard X-ray.
Since X-ray belongs to the high energy end of the electromagnetic spectrum, X-ray astronomyGamma ray astronomyAlso referred to asHigh-energy astrophysics。
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X-ray, you must be no stranger.During the physical examination in the hospital, the doctor will use an X-ray machine to see through your heart and lungs.The X-ray of this instrument is artificially generated.Use a certain voltage to accelerate electrons in vacuum, so that electrons hit a target.When the electron suddenly decelerates, most of its kinetic energy is converted into photon energy, thus emitting X-rays.In November 1895, the German physicist W.K. Roentgen found that a certain kind of ray was emitted from the ray tube during the cathode ray experiment.At that time, little was known about the nature of this kind of ray, so he called it X-ray, which means unknown, and now it is also called Roentgen ray.1901Nobel PrizeFor the first time, Roentgen won the physics prize of the year for this discovery.[2]
Because the X-ray of celestial bodies will be seriously hindered by the earth's atmosphere, it is mainly detected by satellites.Therefore, although X-ray detection began in the 1940s, as a disciplineArtificial earth satelliteAfter God.
Early observations focused on the study of the sun.Non solar X-ray astronomy has entered a new stage of development since the MIT research team first discovered a powerful X-ray source from the direction of Scorpius on June 18, 1962.Since the 1970s, astronomical satellites specialized in X-ray have been launched, and many previously unknown cosmic X-ray sources have been observed, which has dramatically increased the number of X-ray sources from a dozen to more than 1000.
origin
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In September 1949, the United StatesNaval Research Laboratory(NRL) researchers inNew MexicoOfBaisha Missile Range, using GermanyV-2 rocketCarriedGeiger counter, observed the sun for the first timeCoronaThe X-rays emitted confirmed that the sun is a source of X-rays. In 1956, people observed the sun with a solid rocket launched from a balloonsolar flareX-rays emitted.becausemoonReflecting the light of the sun, people speculate that the moon will also emit weak X-ray fluorescence.Italian American astronomer, June 18, 1962Ricardo GiacconiThey used the Aerobee sounding rocket to reach an altitude of 150 kilometers, and began to scan the whole day in the X-ray band.The rocket is equipped with three Geiger counters, which can record the energy of photons by using the different thickness of the X-ray penetration window, and determine the direction of the X-ray source by using the rotation of the rocket itself.The purpose of this experiment was to observe the X-ray radiation of the moon, but this goal was not achieved. However, during the 6 minutes of the rocket's hovering, at about 25 degrees from the moon, a very strongX-ray source, because located atscorpio, namedScorpio X-1。It was later confirmed thatGalaxyX-ray radiation at the center.Scorpio X-1Is the first human discovery other than the sunCosmic X-ray source。This observation is considered the beginning of X-ray astronomy.Giacconi also won the award ofThe nobel prize in physics。[3]
Walter H. G., astronomer of Massachusetts Institute of TechnologyLewin andUniversity of Amsterdam Astronomer Jan Van Paradjjs commented on the quasi periodic oscillation phenomenon in the third quarter of 1986, and now the main contents of their article are published below.X-ray astronomy has recently discovered a new phenomenon called quasi periodic oscillation, which is surprising;The origin of the oscillation is still unknownTherefore, it is too early to judge its importance.About known low quality brightX-ray binaryIt is a very old celestial body (its life span is several x 10 years).In most cases, they contain a neutron star that accretes material from a nearby low-mass companion star.There is evidence that the dipole magnetic field of the neutron star weakens with its age (when the neutron star was born, its magnetic field intensity was as high as 1013 gauss). The weaker the magnetic field becomes, the closer the accretion disk will be to the neutron star, and the faster the neutron star rotates (as a result of accretion torque, it rotates and accelerates).For a very weak magnetic field (such as Shi 1 Ding Gauss), the neutron star can reach the shortest period of about 1 millisecond, which is comparable to the Kepler period of the matter near the surface of the neutron star.Generally speaking, in X-ray binaries, the rotation of neutron stars can be regarded as coherenceX-ray pulseIt is detected that this is the result of funnel shaped accretion of the magnetic pole of the neutron star.For many years, coherent X-ray pulses have been observed in high-quality X-ray binaries, with typical periods ranging from 1 second to several hundred seconds.[4]
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Solar X-ray astronomy
X-ray flare
The detection of solar X-rays has mainly clarified its three components: the continuous radiation of the coronal high-temperature plasma and other spectral line radiation constitute the quiet component of X-radiation;The radiation generated by the super hot plasma in the coronal condensation area with a temperature of more than one million degrees constitutes the slowly changing component of X radiation, which appears as bright X-ray spots on the solar surface.The X-ray bursts generated by the solar active regions constitute the mutation components of X-ray radiation.They appear as X-ray flares on the solar surface.
In the past few years, an important aspect of solar X-ray measurement is to detect the energy spectrum and polarization of X-ray bursts.It focuses on studying high-energy astrophysical processes in the flare pulse stage, such asHigh-energy particleThe origin, transmission, transformation of energy and the nature of emission.At present, the model of X-ray radiation source has been preliminarily established, which is of great value to the research of flare physics.In addition, it has been clearly studied that the solar X-ray is formingEarth's ionospherePlay an important role in the process.
X-ray telescopeIt has high resolution power of angular second order, which creates conditions for in-depth study of solar phenomena.The discovery of X-ray flares and X-ray bright spots has greatly enhanced the research and understanding of solar active regions.The discovery of X-ray coronal holes is a major achievement in solar physics.It has been identified that the X-ray coronal hole is the wind source of the high-speed solar wind, that is, the M region that has not been clarified for a long time in the study of the solar terrestrial relationship.The coronal hole physics has raised many valuable topics, such as the formation of coronal holes, the causes of high-speed solar wind sources, and so on.
Non solar X-ray astronomy
Over the past decade, non solar X-ray astronomy has developed particularly rapidly and made major breakthroughs.Among the discovered X-ray sources, there are many different types of objects, and only a small number of them have been confirmed by optical methods.Strong in galaxies and clustersRadio galaxy(such as Virgo A) and activeSeyfert galaxies Are famous X-ray sources.As the source of Hanoi,Supernova remnant(e.gCrab NebulaCassiopeia A) is also an important X-ray source.Some X-ray sources are optically proved to be members of binary stars, such asCentaurX-3、Hercules X-1, Scorpio X-1Cygnus X-1Wait, one of their members is an X-ray star.According to the modern X-ray binary theory, it is supposed that such X-ray stars are neutron stars or black holes.
of large numberRadio pulsarTo induce people to exploreX-ray pulsarThe exists of.With the development of new detection technology, it is possible to find the latter pulsar.Discovered in 1969Crab NebulaOf pulsar PSR0532X-ray pulseRadiation, which has almost the same period as the corresponding optical pulse.Later, other types of X-ray pulsars were discovered.These findings are valuable for the study of the evolution process of binary stars.
Another kind of subject of X-ray astronomical observation is aboutDiffuse X-ray backgroundMeasurement.Almost isotropicCosmic X-ray backgroundThe discovery of radiation is considered one of the major achievements of X-ray astronomy in the 1960s.
In the years after 1974, the British Antelope 5 and other satellites discoveredCosmic X-ray burstAnd a batchTemporary X-ray source, thus revealing a number of previously unknown phenomena and new X-ray sources in the universe, which is recognized as a major discovery of astronomy in the 1970s.The large amount of energy released by these processes, the fast speed of energy release, the high energy storage density and the strange reproduction cycle are still modernHigh-energy astrophysicsThe major research topic of.
Detecting instrument
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X-ray astronomyDetecting instrumentIt varies with the energy of X-ray photons.Thin window for soft X-ray detectionProportional counter, commonberylliumMake window materials,platingThe sealing performance of the window is good, which can ensure the stability of the instrument, but the thickness of the plated window still limits the sensitivity of the counter to lower energy X-ray.To detect extremely soft X-ray, the counter of organic film window should be used, but the gas tightness of organic film window is not good.In recent years, an automatic gas flow technology has been developed in space exploration to ensure that a certain air pressure is maintained in the counter tube and the response of the instrument is stable and reliable. However, its manufacturing process and use conditions are complex.
In the detection of non solar X-ray sources, in order to improve the sensitivity, a large area of thin earth is often neededProportional counter。The manufacturing technology of this instrument has developed rapidly in recent years.U.S.ASmall astronomical satelliteFreedom once used a beryllium window proportional counter with an area of 840 square centimeters and a thickness of only 50 microns.With the increase of X-ray energy, the proportional counter will lose its function, and its upper detection limit is about 60KV.For higher energy detectionScintillation counter。
The proportional counter and scintillation counter do not have any imaging and orientation functions.In order to identify various X-ray sources and accurately determine their position in the air, a collimator must be added to the front of the counter.This kind of collimation technology has developed rapidly in recent years.At present, the widely used types of collimators include wire grid collimator, slat collimator and honeycomb collimator.The former is mostly used in soft X-ray band, and the latter two are used in hard X-ray band.In addition, there are active collimators composed of scintillators.
One of the outstanding achievements of experimental X-ray astronomy is the application of grazing optics to X-ray astronomy, which makes the large-area X-ray focusing imaging technology a reality and makes it a truly valuable high-resolutionX-ray telescope。It offers the possibility of expanding the detection area of X - rays to the deeper reaches of the universe.
Since its birth, X-ray astronomy has discovered a series of previously unknown new objects in a short period of time in the past 20 years, and obtained celestial information that cannot be obtained by optical astronomy and radio astronomy, greatly expanding the research field of astronomy.The unique power of X-ray astronomy makes itSpace astronomyIs particularly important.
Observation content
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X-ray coronal hole
Radiated bywavelength0.001~10 urnastronomyThe way.The resulting astronomy is called x-ray astronomy.becauseearthThe atmosphere strongly absorbs the X-ray radiation of celestial bodies, so the detectioncelestial bodiesX ray ofradiationOnly inatmosphereOutside.Since the first discovery of non solar strong X-ray sources in the direction of Scorpius by rocket in 1962, astronomers have successively observed more than 1000 cosmic X-ray sources.The research scope of x-ray astronomy includes solar x-ray sourcesthe galaxyX-ray source, extragalactic x-ray source and cosmic diffuse x-ray background radiation.
ObserveduniverseX-ray source is different fromvisible lightObservation aids are mostly giant hot gas clouds containing many stars. For example, cosmic X-ray sources from tens of billions of light years can contain hundreds of trillions of stars.X-ray astronomical observationdetectorThin window proportional counter with soft x-ray detection and hard x-ray detectionScintillation counter。Applying the principle of glancing optics, large area x-rayfocusingImaging, which can greatly improve the detector resolution.Through X-ray astronomical observation, a series of previously unknown strange processes of celestial bodies releasing high energy have been revealedopticsandRadio astronomyUnavailableinformationThus greatly expanding the research field of astronomy.[5]
achievement
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One of the outstanding achievements of X-ray astronomy is the application of grazing optics principle to X-ray astronomy, which makes the large-area X-ray focusing imaging technology a reality and makes X-ray telescopes with high resolution that are really valuable for research.It offers the possibility of expanding the detection area of X - rays to the deeper reaches of the universe.
Since its birth, X-ray astronomy has discovered a series of previously unknown new celestial bodies in a short period of time, obtained celestial information that cannot be obtained by optical astronomy and radio astronomy, and greatly expandedastronomyResearch field of.The unique power of X-ray astronomy makes it play a particularly important role in contemporary space astronomy.
