X-ray range. Telescope Chandra, Nebula, Pulsary, Black Holes. School encyclopedia X-ray telescopes
x-ray telescope
Device for study of the time and spectrum. SV-in sources of space. RENTH. Radiation, as well as to determine the coordinates of these sources and build their image.Existing R. t. Work in the energy range photons RENTG. Radiation from 0.1 to hundreds of keV, i.e., in the wavelength range from 10 nm to hundredths of nm. For astronomy. Observations in this area of \u200b\u200bwavelengths R. t. Raise outside the earth's atmosphere on rockets or an exercise, so on. Rentg. Radiation is very absorbed by the atmosphere. Radiation with \u003e 20 keV can be observed from the heights of ~ 30 km from the aerostat.
R. t. Allows: 1) to register with high efficiency of the RENTG. pho-
tones; 2) Separate events corresponding to photons entering the desired energy range from signals caused by the impact of charging. ch-c and gamma photons; 3) Determine the direction of the arrival of the RENTG. Radiation.
In R. t. For the range of 0.1-30 KV, the photon detector serves proportional counterfilled with a gas mixture (AR + CH4, AR + CO2 or XE + CO2). Absorption of RENTG. The photon of the gas atom is accompanied by the emission of the photoelectron (see Photoelectronic emission),auger electrons
Fig. 1. A-scheme Xage. a telescope with a slotted collimator; b & mdash; Telescope operation in scanning mode.
(cm. Auger effect)and fluorescent photons (see Fluorescence).Photoelectron and AUger-electron quickly lose their energy to gas ionization, fluorescent photons can also quickly absorb gas thanks to photo effect.In this case, the total number of generated electron-ion pairs of proportions. Energy RENTG. Photon. T. O., Pulse Current in the Anode circuit is restored by the Energy of the RENTG. Photon.
Under normal conditions, R. t. Irradiated with powerful charge streams. Ch-c and gamma photons are spoken. Energies, to-ry detector R. t. Registers with RENTG. Photons from the studied radiation source. To highlight the RENTG. Photons from the total background is used by the method of anti-trusses (see Coincidences method).Rentg arrival. Photons are also fixed in the form of an electric pulse created by them. Current because the charge. Ch -ts give signals, more tightened in time than those caused by RENTG. photons.
To determine the direction on the RENTG. The source serves a device consisting of a slotted collimator and a rigidly fixed with it on one frame of the star sensor. The collimator (set of plates) limits the field of view R. T. and skips the RENTG. Photons that are running only in a small bodily corner (~ 10-15 square degrees). RENTH. Photon, passed collimator (Fig. 1, a), the top is registered. Volume of the counter. The current pulse over the chain is top. Anode
there is a scheme of anti-trudents (since there is no prohibitive signal from the bottom. Anode) and is supplied to the analyzer to determine the time and energy. Har-to photon. Then, by telemetry, the information is transmitted to the Earth. At the same time, the information of the star sensor is transmitted about the brightest stars in his field of view. This information allows you to establish the position of the axes of R. t. In pr-ve at the time of the photon arrival.
During the operation of R. t. In the scan mode, the direction to the source is defined as the position of R. t., With a row, the score rate reaches the maximum. Corner Resolution R. t. With a slotted collimator or similar cellular collimator, several dozen angular minutes is.
Significantly better angle. resolution (~ several tens of seconds) possess R. t. from the modulus. collimators (Fig. 2, but).MODULES. The collimator is two (or more) wire one-dimensional grids installed between the detector and the slotted collimator, for which the latter rises above the height detector ~ 1 m and the observations are carried out in or scanning mode (Fig. 1, b) or rotation relative to the axis, perpendicular plane of grids. Wires in each grid of the collimator are set parallel to each other at a distance equal to the diameter of the wire. Therefore, when the source is moving through the field of view R. T. Shadows from the top. Wires slide along the bottom. The grid, falling on the wire, and then the speed of the account is maximal, then between them, and then it is minimal (background).
Corner Distribution of the R. account speed distribution. from the modulus. The collimator (F U N to C and I O T K L and K a) is shown in Fig. 2, b.For N-grid modulosity. Colimator angle between adjacent maxima 0 \u003d 2 n-1 r, where r \u003d d / L.- Corner. Resolution R. t. In most cases R. t. from the modulus. Collimators give the accuracy of the regionalization of the RENTG. Sources sufficient to identify them with celestial objects emitting in other bands of EL.-Magn. waves.
With modulus. Colimators begins to compete the method of codings. aperture that allows you to get r<1". В Р. т. с кодиров. апертурой поле зрения перекрывается экраном, обладающим неоднородным пропусканием по всей площади. Детектор излучения в таком Р. т. позиционно-чувствительный, т. е. кроме энергии рентг. фотона измеряют и координаты точки, где он был зарегистрирован. При таком экране точечный источник излучения, находящийся на бесконечности, даёт распределение скорости счёта по поверхности детектора, соответствующее функции пропускания экрана.
Fig. 2. A - RENTG device. Telescope with modulus. collimator; b - corner. Distribution of the score rate.
The position of the radiation source. radiation in the field of view R. t. Determined by the position of the maximum of the correlation. The functions between the resulting distribution of the account speed over the surface of the detector and the screenshot function.
In the region of energies \u003e 15 keV in the quality of detectors R. t. Apply Crysta. NAI scintillators (TL) (see Scintillation counter); to suppress the background of the charge. High energies and gamma photons are installed on anti-attacks with the first Crist. CSI scintillators (TL). To limit the field of view in such R. t. Apply active collimators - cylinders from scintillators included on anti-cylinders with NAI scintillators (TL).
In the energy range from 0.1 to several. KEV is the most effective R. t., In which the radiation is focused, falling at low angles to the focusing mirror (Fig. 3). The sensitivity of such R. t. At ~ 10 3 times is superior to R. t. Dr. structures due to its ability to collect radiation so much. Square and direct to the small size detector, which significantly increases the signal-to-noise ratio. R. t., Built according to such a scheme, gives a two-dimensional image of the X-ray source.
Fig. 3. Scheme of focusing RENTG. Telescope.
radiation like ordinary optch. telescope. To build an image in the focusing R. t. In the quality of detectors use positional and sensitive proportions. Cameras, microchannel detectors, as well as instruments with charging link (CCD). Corner Permission in the first case is determined by ch. arr. spaces. The camera resolution is ~ 1, microchannel detectors and CCD give 1-2 "(for the beams close to the axis). With spectrometrich. Research is used by PP detectors, Bragg Crysta. Spectrometers and diffraction. Grids with positional sensitors. detectors. Cosm RFG sources. Radiation is very diverse. RENTH. The radiation of the sun was opened in 1948 in the USA with a ricake rose Geiger countersat the top. The layers of the atmosphere. In 1962, the first source of Xage was discovered from R. Giakconi (USA) with a missile. Radiation outside the solar system - "Scorpio X-1", as well as diffuse x-ray background, apparently extragalactic. Origin. By 1966, as a result of experiments, OK was opened on rockets. 30 discrete xvents. Sources. With the conclusion in the orbit of a series of specials. Uses ("Wuora", "Ariel", "CAC-3", "Vela", "Copernicus", "Heao", etc.) with R. t. Spl. Types discovered hundreds of RENTG. sources (galactic. and extragalactic, extended and compact, stationary and variables). MN. From these sources are not yet identified with sources that manifest themselves in Optic. and other bands of EL.-Magn. Radiation. Among the identified galactic. Objects: Close double starry systems, one of the components of the to-rye - RENTG. pulsar; Single pulsary(Crab, Vela); residues supernovae stars(extended sources); Temporary (transient) sources, sharply increasing the luminosity in the RENTG. The range and newly fading during from several. minutes to several minutes months; t. n. B and R S T E R Y - powerful flashabling sources of RENTG. Radiation with a characteristic flash of the order of several. seconds. To the identified extragalactic. Objects include the nearest galaxies (Magellanovy clouds and the Andromeda Nebula), Deva-A (M87) and Centaur-A (NGC 5128), quasars (in particular, ZH 273), Seyfert and other galaxies with active nuclei; Accumulations of galaxies - the most powerful sources of RENTG. Radiation in the Universe (in them for radiation hot crossing intergalactic. Gas with pace-swarm 50 million K). The overwhelming majority of space. RENTH. Sources of Yavl. Objects that are completely dissimilar in those that were known before the start of the RENTG. Astronomy, and above all, they differ in huge energy release. Galactic luminosity. RENTH. Sources reaches 10 36 -10 38 Erg / s, which at 10 3-10 5 times the energy release of the Sun in the entire wavelength range. In extragalactic. The sources were registered with the luminosity of up to 10 45 erg / s, which indicates the unusual radiation mechanisms here. In close double starry systems, for example, in katch-vesn. The energy release mechanism consider the flow of in-to from one component (star giant) to another (Neutron Staror black hole)- Disc accretion,with a swarm, falling on the star in-in forms a disc near this star, where in-in due to friction heats up and begins to intensively emit. Among the probable hypotheses of the origin of diffuse x-ray. background, along with the assumption of thermal radiationhot intergalactic. gas is considered reverse Compton Effectel new on IR photons emitted by active galaxies, or on photons relic radiation.These observations with the ISS HEAO-B testify that a significant contribution (\u003e 35%) into diffuse RENTG. The background give distant discrete sources, ch. arr. quasars.
X-ray Astronomy, ED. R. Giacconi, H. Gursky, Dordrecht-Boston, 1974; Shklovsky I. S., Stars: their birth, life and death, 2 ed., M., 1977; K A P L A N S. A., Picelner S. B., Physics of the interior medium, M., 1979.
N. S. Yamburchenko.
Often the invention The first telescope is attributed to Gansu Lippersley from the Netherlands, 1570-1619, but almost certainly he was not the discoverer. Most likely, his merit is that he first made a new device the telescope popular and in demand. And it was also he filed in 1608 a patent application for a couple of lenses placed in the tube. He called the device with a pavement pipe. However, his patent was rejected because its device seemed too simple.
The X-ray telescope is designed to observe remote space objects in the X-ray spectrum. Usually, telescopes are placed on high-rise rockets or on artificial satellites, as the Earth's atmosphere is a very serious interference for X-rays.
American Professor Ricardo Giakconi, together with Bruno Rossi, in 1960, published the world's first scheme of a real X-ray telescope with a focusing mirror system. What is the principal difference between the X-ray telescope from other types of telescopes? The fact is that X-ray quanta due to its high energy is practically not refracted in the substance, they are absorbed by almost any corners of the fall (except the most gentle). That is why it was necessary that X-rays walked almost parallel to the reflective mirror. Such a mirror is a narrowing hollow tube with a parabolic or hyperbolic surface, which is just an X-ray ray. The Jixconi telescope and Rossi included several tube-shaped mirrors with a single central axis in order to maximize the sensitivity of the instrument. A similar scheme formed the basis of all modern X-ray telescopes.
Modern X-ray telescopes operate in the energy range of X-ray photons from 0.1 to hundreds of CEV. Mirrors of similar telescopes are made of ceramics or metal foils (gold and radium are often used). The critical reflection angle will depend on the energy of photons.
The main problem of registering x-ray rays is related to the fact that the X-ray telescope is irradiated with powerful flows of charged particles and gamma photons of various energies that are registered by them on a par with X-ray photons. To solve this problem, use the method of anti-attachment. In order to accurately determine the direction on the X-ray source, the device is used, which consists of a slotted collimator (a set of plates that limit the field of view) and the star sensor (registers the X-ray photon consolimator). The current pulse passes the anti-sampling scheme, after which the energy characteristics of the photon are determined using a special analyzer.
The angular resolution of a similar telescope with a slotted collimator is several dozen angular minutes. Also, the so-called modulation (swinging) collimators can also be used in X-ray telescopes (the angle of permission is several tens of seconds). A similar collimator consists of two or more wire one-dimensional grids, which are installed between the detector and the slotted collimator. Observation is performed either in scanning mode, or either rotation relative to the axis perpendicular to the mesh plane.
One more More advanced technology is a method encoding aperture method for obtaining images. When using this technology, a mask in the form of a lattice with an inhomogeneous transmission over the entire area is established before the matrix detector (due to the alternation of transparent and opaque elements). This design weighs much less and allows you to get an angular resolution of less than 1. An example of X-ray telescope is the Candra Space X-ray Observatory, launched NASA in 1999.
X-rays - a range of electromagnetic radiation with a wavelength from 0.01 to 10 nm, intermediate between the ultraviolet range and gamma rays. Since the photons of this range have high energy, they are characterized by a high ionizing and permeability, which determines the scope of their practical use. The same properties make them very dangerous for living organisms. From X-rays coming from space, we are protected by the earth's atmosphere. However, from the point of view of astronomers, they are of particular interest, as they carry important information about the substance, heated to ultra-high temperatures (about millions of Kelvin), and processes leading to such a heating.
As in the case of the UV band, the first attempts to take pictures of the celestial sphere in the X-ray spectrum were made by equipment installed on high-altitude geophysical rockets. The main problem here was that "ordinary" methods of focusing - with the help of lenses or concave mirrors - for high-energy rays are unacceptable, so it is necessary to apply the complex "moving fall" technology. Such focusing systems have significantly large masses and dimensions than optical tools, and sufficiently powerful carrier missiles should appear so that X-ray telescopes finally entered the near-earth orbits.
The first such successful attempt was the American satellite Uhuru (Explorer 42), which worked from 1970 to 1973, also deserve mention of the first Dutch spacecraft ANS (Astronomical Netherlands Satellite), launched in August 1974, and two NASA Space Observatory (NASA) - The second of them, bred in orbit on November 13, 1978, received the name of Albert Einstein. Japan on February 21, 1979 launched the Hakucho (CORSA-B) apparatus, who observed the "X-ray sky" until 1985. Over eight years - from 1993 to 2001 - operated the second Japanese high-energy ASCA (ASTRO-D) telescope. The European Space Agency "noted" in this direction by satellites EXOSAT (European X-Ray Observatory Satellite, 1983-1986) and Bepposax (1996-2003). In early 2012, the operation of one of the "cosmic long-livers" - the orbital telescope Rossi X-Ray Timing Explorer, launched on December 30, 1995
The third of the "Big Four"
CHANDRA X-ray telescope, delivered in orbit July 23, 1999 on board the COLUMBIA Reusable Ship (Mission STS-93), became the third of the four large NASA Observatory, launched from 1990 to 2003. The name he received in honor of American Physics and Astrophysics Indian origin subramanyan chandrasen.
Geocentric orbit with a height of Appoge 139 thousand km and the perichem about 16 thousand km allows continuous observation sessions to 55 hours, which is significantly more compared to the same indicator for low-bit Earth satellites. The choice of orbits also is also associated with the fact that X-ray radiation is notably absorbed even with sparse gases contained in the topmost layers of the earth's atmosphere - at altitudes where most artificial satellites work. The circulation period is 64.2 hours, with 85% of this time Chandra spends out of the limits of the radiation belts of the Earth. The disadvantage of such an orbit is, in particular, the impossibility of sending to the telescope of the repair brigade (as it was repeatedly done in the case of the Hubble Observatory).
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Technical characteristics of the Chandra telescope
\u003e Mass: 4620 kg Basic scientific tasks: \u003e Study of black holes in galaxic centers |
| Space telescopes |
The X-ray telescope has a rather narrow specialization. It is intended for observing the radiation of very hot objects of the Universe - such as exploding stars, galactic clusters, a substance in the vicinity of black holes. However, it can register high-energy radiation, arising in one way or another in the atmospheres and on the surfaces of various bodies of the solar system. It was originally planned that Chandra would work in space for 5 years, but taking into account the good state of the on-board systems, its operation has been extended several times (last time - in 2012).
First observation telescope
Galactic remnants of supernova outbreaks are the source of the most most valuable information about the universe, which may be the results of analyzing the monitoring of the Chandra telescope. In particular, the structure of the remainder of Cassiopheus A was detailed, a map of all incoming and outgoing flows of substance and shock waves was created, spatially separated the expirations of interstellar and near-road matter until the explosion of supernovae, localized space rays acceleration areas. No less important result was the reliable registration of strong wide emission lines of the residue in the mode of high-speed spatial resolution spectroscopy mode and mapping the distribution of elements from carbon to iron in the emissions of the substance. The remainder determined from these observations is approximately 140 years, which almost coincides with the estimates made by other methods. Comparison of the ages and linear dimensions of other supernovae demonstrated the ability of the Chandra telescope's ability to measure the speed of their radial expansion in almost the microscopabas: For example, in 22 years, the size of a supernova SN 1987A remains in a large magtel cloud6 has changed only on 4 angular seconds.
Nebula, "fed" with a pulsar
Many astronomers note that one of the most impressive advantages of the Chandra telescope is its ability to explore the subtle structure of the so-called plants (Pulsar Wind Nebulae - Pwn) - nebulae, "feeding" substance of the pulsar, whose feature of which are extremely small sizes - about several angular seconds. Chandra especially succeeded in the study of such an object in the constellation of Sail - Pulsar Vela. At the moment it is the most studied Pleurion.
A snapshot of a compact nebula around the pulsar in the constellation of the sail made by the Chandra telescope demonstrates an interesting structure consisting of two arcuate shock waves. They were formed in the collision of the cloud of gas surrounding the pulsar, with a substance of nebulae when it moves through it. Jets emitted by the pulsar are visible as bright straight segments, perpendicular to the arcs. Their direction practically coincides with the direction of movement of the super-proportion object. It is believed that they arise due to its rotation, as well as the interaction of a substance with powerful electrical and magnetic fields in its surroundings.
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| Changes in shape and brightness of jets. |
| Space telescopes |
Re-photographing the pulsar VELA X-ray Observatory CHANDRA revealed noticeable changes in the shape and brightness of the jets on relatively short sections of time. Here are four of the 13 of its images obtained over two and a half years. The length of the Jetov reaches half the light year (about 5 trillion km), and their width remains almost constant all over and does not exceed 200 billion km, which can be explained by the presence of a "holding" magnetic field. The rate of the substance thrown by the pulsar is almost half the speed of light. In such relativistic flows of charged particles, instability should occur, already observed in experiments on special accelerators. Now they managed to register on the example of a real astrophysical object. X-ray radiation in this case occurs when the interaction of ultrafast electrons and positrons with magnetic power lines.
Similar instability scientists expect to discover from jets emitted by supermassive black holes in galaxic centers, but its temporary scale should be much more (about hundreds and thousands of years).
Crab Nebula (ML) - the residue of one of the brightest outbreaks in the history of mankind, observed in 1054. Information about it is contained in Japanese, Chinese, as well as some Arabic chronicles.
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1. Young sun-like stars. Long observations of star clusters in the Orion nebulae (M42) showed that the young stars of the solar masses, having age from 1 to 10 million, demonstrate large-scale flashing activity, especially noticeable in the X-ray range, while the frequency of outbreaks and their energy is almost an order of magnitude exceeds the processes Such a kind, observed in our sun, whose age is close to 4.6 billion years. It can significantly affect the formation of planets and habitability areas around such stars. 2. Supernovae and supernova residues. The images and spectra of the supernovae obtained by the Chandra telescope made it possible to study the dynamics of shock waves generated by the explosions of massive stars as well as the mechanisms of acceleration of electrons and protons to the near-velocity, determine the amount and distribution of heavy elements formed during flashes, and explore the mechanisms of the flashes themselves. 3. Rings around the pulsars and Jeta. The images obtained by the Crabovoid nebula and other supernova residues demonstrate the amazing beauty of the ring and jets - emissions of high-energy particles emitted by fast-growing neutron stars. This indicates that they can serve as powerful generators of such particles. 4. Black holes of star masses. The discovery of two black holes (CH) whose masses exceed 15 of the Sun, served as a starting point for revising the ideas about the possible mechanisms of their evolution. 5. Sagittarius A * - Black hole in the center of the Milky Way. The Chandra telescope measured the energy output and the rate of decrease in the amount of substance in the Sagittarius radio source radio source and the supermassive black hole located in the center of our galaxy (in the directions of the Sagittarius constellation). These data allowed astronomers to conclude that the modern low level of its activity is not a direct consequence of the lack of stocks of "fuel" in its surroundings. 6. Double black holes. In the same Galaxy Chandra opened two supermassive black holes, which, according to calculations, soon merge. It is possible that it is thus growing the CHA in the centers of galaxies. 7. Black holes emitting substance. The image obtained by the chandra telescope galaxies provide monitoring of dramatic evidence of long-term repeating explosive activity associated with rotating supermassive CH. This activity has a consequence of a highly efficient conversion of the gravitational energy of the substances falling on the CH in the flows of high-energy particles. Thus, black holes from "absorbers" become powerful sources of energy, due to which they play a key role in the evolution of massive galaxies. 8. "Census" of black holes. When processing the results of observations under the Chandra Deep Field program, hundreds of supermassive CHA were opened, accretion disks in the vicinity of which X-rays are emitted during rotation. The existence of these sources can be explained by almost all diffuse x-ray "radiance" of the sky, which was detected more than 40 years ago and only today received an adequate explanation. The "census" of supermassive CHA gives an idea of \u200b\u200bthe time of the formation of these objects and about their evolution. Experts also talk about the possible opening of the so-called "black holes of intermediate masses" - in fact, the new category of objects of this class. 9. Dark matter. The results of the observation of the accumulation of the "bullet" and a number of other galactic clusters conducted by the Chandra telescope together with several optical telescopes became indisputable evidence that most of the substance in the universe remains in the form of dark matter. Its presence is manifested by gravitational influence on "normal" matter - electrons, protons and neutrons, of which are "familiar" atoms. However, direct detection of this component of the universe is not possible (at least in our time). The survey studies of many clusters of galaxies confirmed that the universe contains five times more dark matter than "ordinary". 10. Dark energy. The observational data obtained by the chandra telescope was shown that the expansion of the universe accelerates - mainly due to the predominance of the substance in the space of the substance called "Dark Energy". This independent confirmation of the discovery made by analyzing the optical observations of remote supernovae eliminates any alternatives to the general theory of relativity and tightens restrictions on the nature of the dark energy. From other scientific achievements of the most successful X-ray telescope, it is necessary to note the conduct of detailed spectral studies of the activity of supermaissive black holes in the centers of galaxies (including the detection of supermassive CH, twice as more active compared to earlier estimates), new data on the processes of formation of galaxies and their evolution. as well as the creation of a common CHANDRA Source Catalog (CSC) directory containing over 250 thousand X-ray sources per 1% of the total sky area and using the data of 10 thousand individual observations of a set of sources of various types (stars in close proximity to the center of the Milky Way, Galactic and Othergalactic X-ray double, cores of active galaxies, etc.). |
| Top 10 Scientific Achievements Chandra |
After 900 years after the outbreak of a bright supernova in the Constellation of the Taurus, an expanding gas nebula is visible in its place, in the center of which is a superlit neutron star - Pulsar. It continues to emit energy and emit streams of high-energy particles. Despite the fact that you can only see it in large telescopes, the total energy release of this object is 100 thousand times higher than the power of the radiation of the Sun.
High-energy electrons emitting X-rays lose energy faster and do not have time to "fly away" away from the center of the nebula, from where they were thrown away, therefore the visible size of the region emitting in a longer-wave range is significantly larger than the playrion photographed by the Chandra telescope.
The monitoring of the crab ebbing ground and space instruments is carried out almost constantly, with the exception of periods of time, when the sun is not far from it in the sky. This object without exaggeration can be called one of the most studied celestial "attractions."
We have already reviewed the main X-ray detectors: proportional meters for energies below and scintillation counters for energies to the problem is to eliminate the cosmic rays, which also cause ionization within the meters. For this purpose, three methods apply.
The first method is to use anti-bearing detectors. In this case, X-ray counters are surrounded by a scintillating substance (plastic scintillator, or a scintillating liquid) and any events forcing and the counter, and the scintillating substance, are discarded as caused by a charged particle (Fig. 7.10, a).
The second method is to analyze the form of an electron pulse as a function of time. Fast particle, be it a low-energic particle of cosmic rays or a fast electron, knocked out of the meter walls by such a particle, creates an ionized trail, which causes a wide impulse at the output. On the other hand, a photon with energy about leads to local ionization, and the impulse as a result of this turns out short, especially its front front. The mileage of electrons escaped by cosmic X-rays from argon atoms, for example, is usually less than 0.132 cm. This method of distinguishing cosmic rays and X-ray radiation is called discrimination in time of increasing or in the form of a pulse (Fig. 7.10, b and c).
The third method used for hard x-ray and soft-quantas includes detectors that have called layered phosphors. They consist of layers of various scintillating materials that have different efficacy of photon registration and charged particles. As one component, a detector made from iodide cesium that is sensitive to photons and is used as a standard scintillation photon counter, and another component can be made from a plastic coinyllator, which is not sensitive to photons. Consequently, photons will give a signal only in the first detector, while charged deseps passing through
Fig. 7.10. Disagreement of X-ray radiation (b) and cosmic rays (B) in terms of increase time (or in the form of an impulse).
detector, cause light outbreaks in both materials. The scintillators used in layered phosphors are selected in this way, they had different highlight times, so the charged particle, permeating the device, gives two light flashes, the photon time interval calls only one flash, so light flashes can be recorded by one photomultiplier connected to the electronic system, able to recognize cosmic rays according to characteristic features and exclude them. According to the intensity of the light outbreak caused by the photon, its energy is determined, and it is possible to achieve an energy resolution of about 10% and better for energies characteristic of-emission.
It is necessary to limit the field of view of the X-ray telescope, which is often carried out using a mechanical collimator. In the simplest case, the collimator consists of hollow tubes of rectangular cross section. The radiation diagram of such a collimator has a type of triangle, since it can be considered that X-ray radiation spreads straightforwardly, i.e. In accordance with the laws of geometric optics. The only exception is the case when the bundle falls at a large angle to normal on the surface of a high electrical conductivity substance, such as copper. Then it may be reflected with a sliding drop. For photons with energy less - the reflection is observed when the angle between the direction of the beam and the surface of the material is not
Fig. 7.11. Scheme of a simple X-ray telescope. Telescopes of this type were installed on the satellites "Wuorah" and "Ariel-5".
exceeds several degrees. This reflection process is similar to a deviation of radio waves in an ionized plasma in which the plasma frequency increases with depth. Although the reflection occurs only at very small angles, it is enough to develop telescopes with mirrors of oblique fall, giving an image of the sky in the focal plane (clause 7.3.2).
So, you can collect a simple X-ray telescope according to the scheme shown in Fig. 7.11. Once again, we note that modern electronic schemes of amplitude analyzers, discriminimizers and anti-rose schemes that should be included in such telescopes play a significant role. This type of telescopes with great success worked aboard the orbital X-ray observatory "Wurau".
7.3.1. X-ray satellite "Wuorah". Wuoru's X-ray satellite was launched from the coast of Kenya in December 1970. Scientific equipment installed on the satellite included two proportional counter with beryllium windows, the useful area of \u200b\u200beach of them was the one of them were directed in opposite sides perpendicular to the axis of rotation and were equipped with mechanical collimators. which limited the field of view (full width in half height) (Fig. 7.12). The period of rotation of the satellite around its axis was 10 minutes. Proportional counters were sensitive in the area
Sensitivity telescope. The sensitivity limit of the telescope was determined by the background radiation. There are two types of background radiation.
1. The number of samples per second is associated with insufficient exception - quanta and cosmic rays. This value varies from the telescope to the telescope and for detectors on board "Wuora" it was about
2. Space X-ray background radiation whose brightness is very high this background radiation isotropic; It is assumed that it has cosmological origin. The dimension in the energy range of the telescope. The sensitivity limit of the telescope is determined statistically. If you take as a criterion for detecting a discrete x-ray source, a signal at least three times
Fig. 7.12. X-ray satellite "Wuorah". a - location of the instruments; B - orientation of the X-ray telescope.
more than a standard deviation associated with noise (in this case, statistical noise), it can be shown that the weaker point X-ray source, affordable detection, should have a flux density
where a body angle equal to the angle of view of the telescope, the surveillance time of the source. The X-ray background radiation in the energy region is equal to the intensity spectrum approximately described by the relation where it is measured in can use this data to show that for the collimator, the background radiation of both types is approximately the same, while only the background due to charged particles is important for a smaller field of view. Space X-ray background radiation, as a source of noise, becomes insignificant if the field of view is less than several degrees.
In the usual mode, satellite scans one sky strip over many turns. Try to calculate the weakest detectable source in one day of observations and compare it with the actual Wuorah limit on the flow density taken from the Wurai catalogs, "Wuorau" in the range how much time had to scan all the sky to achieve this level of sensitivity?
Temporary variations. The most outstanding discovery made with the help of "Wurau" were pulsating X-ray sources. Telescope
Fig. 7.13. Data registration fragment for the source of the histogram shows the number of samples in successive - second bins. The continuous line is a harmonious curve, the best approximating results of observations, taking into account the changing sensitivity of the telescope when scanning the source.
with the collimator registered and every 0.096 s passed the data on the X-ray stream to earth. The average flux density from the source is equal to a period of 1.24 s. How much does the source exceed the noise level when its ripples were detected? It turns out that during the period, the source signal did not greatly exceed the noise level, but the use of Fourier analysis methods (or power spectrum), if it is applied to data processing for a longer time, allows you to open the ripples of significantly lower intensity. The record fragment is shown in Fig. 7.13.
7.3.2. Einstein X-ray observatory. The most significant achievements after the observations of "Wurau", which caused a coup in X-ray astronomy, are associated with the flight of the X-ray satellite called the Einstein X-ray Observatory. On board this observatory there were many unique equipment, including a skewed drop telescope building a high angular resolution image.
X-ray rays are reflected only from the surface of conductive materials at large angles of fall. At the energies of reflections occurs if the angle between the surface and the direction of the radiation drop of the order of several degrees; The greater the photon energy, the smaller the same angle should be. Therefore, to focus X-rays from the heavenly source, you need a parabolic reflector with
Fig. 7.14. Focusing the X-ray beam using a combination of parabolic and hyperbolic mirrors of oblique fall. This combination is used on Einstein X-ray observatory.
a very large focal length, and the central part of the reflector may not be used. The focal length of the telescope can be reduced due to the area of \u200b\u200bthe collecting surface, if you enter another collecting mirror, with a preferred configuration - a combination of a paraboloid and hyperboloid (Fig. 7.14.) Such a system focuses X-ray rays that have fallen only on the annular area shown in the figure. To increase the collecting area, you can use a combination of several mirrors. Such a system was used in the HRI high destruction telescope installed on board Einstein Observatory. It allowed to obtain an image of the heavenly sphere in a field of view with a diameter of 25, and the angular destruction was better within 5 from the center of the field of view.
In the focal plane, you should put a two-coordinate detector with the same angular resolution, like a telescope. In HRI, it consists of two microchannel plates set by each other. These detectors are a set of very thin tubes, along which a high potential difference is maintained. The electron, which came to one end of the tube, begins to accelerate and, constructing with the walls, knocks out additional electrons, which in turn accelerate and also knock out electrons, etc. As in the proportional meter, the purpose of this process is to obtain an intense electronic flash from a single electron. In HRI, the front surface of the first microchannel plate is covered with an X-ray photon, which fell on the front surface, knocks out an electron, which leads to the emergence of electrons registered at the output of the second plate. This flash of electrons is registered with a charged detector with mutually perpendicular grids, which allows you to accurately measure the coordinates of the X-ray quantum.
To determine the sensitivity of the telescope, you need to know its effective area and the level of background signals of the detector. Since the reflection when the sliding drop is the function of photon energy and since the absorption in the material of the detector window, effective
Fig. 7.15. Effective telescope area building a high resolution image as a function of energy. Curves show the effect of the installation before the detector of beryllium and aluminum filters.
the area is highly dependent on energy (Fig. 7.15). As expected, the maximum efficient area corresponds to the energies around and is equal to about the response of the detector can be changed by entering the filter telescope in the field of view (Fig. 7.15), thus ensures a coarse energy resolution.
The noise level in the detector, mainly due to charged particles, reaches this means that the source of the Wurai catalog at the limit of sensitivity, i.e. A point source with a flux density of the order of units "Uuuru" in the range can be detected at 5 o on exposure of 50,000 s.
To fully use the high quality of the telescope mirrors, the spacecraft would have to stabilize with accuracy - however, such attempts were not taken. The telescope is much more rude, but at any time it is precisely defined by its instant orientation relative to standard bright stars. Therefore, as soon as observations end, the sky map is restored with a complete angular resolution, which has a telescope. An example of the quality of images obtained by HRI is shown in Fig. 7.16.
The following tools were also installed on Einstein Observatory.
Fig. 7.16. (See Skan) X-ray Picture of a supernova residue obtained using a high-resolution telescope Eistein Observatory. Each image element has dimensions of the exposure time is 32,519 s.
Fig. 7.17. General scheme of the location of the devices on board Einstein X-ray observatory.
1 - Visor, 2 - Front Precolematimator, 3 - System Mirrors, 4 - Rear Plug, 5 - Diffraction Spectrometer, 6 - Broadband Spectrometer with Filters, 7 - Focal Crystal Spectrometer, 8 - Displays high voltage detector, 9 - Rear insulating support, 10 - solid-state spectrometer, 11 -Mnogocannal proportional counter, 12 - blocks of electronic equipment, 13 - optical bench, 14 - front insulating support, 15 - control proportional counter, 16 - thermal collimator of the control proportional counter, 17 - Blends of orientation sensors.
a positive number, in the angle of falling, the distance between reflective crystallographic planes. X-rays pass through the focus and, forming a consigning beam, fall on the crystal. The crystal is twisted in such a way that reflected X-ray radiation focuses on a positional sensitive proportional detector. At energies, its energy resolution of its order is 100-1000, and the effective area is near the observatory in one paragraph. The main achievements of the first year of observations are as follows: X-ray detection in stars of all luminosity classes, including all stars of the main sequence, supergiant and white dwarfs; Opening more than 80 sources in the nebula of Andromeda and the same number in Magellan clouds; images with high resolution in the X-ray range of galaxies, detecting an extensive range of various processes leading to X-ray emission; detection of X-ray radiation from many quasars and active galaxies; Registration of sources with a flow density is 1000 times weaker than the weaker sources of the Wurahu catalog. Observations conducted with the Einstein Observatory have significantly affected all areas of astronomy. (A significant part of the first results of the observations of the Einstein Observatory was published in Astrophys. J., 234, No. 1, Pt. 2, 1979.)
Flights of spacecraft opened before astronomers unprecedented opportunities that terrestrial astronomy never had had, and could not have to be placed. To explore the heavenly bodies of the solar system, our galaxy and numerous extragalactic facilities are now launched specialized astronomical observatory stations equipped with the latest physical devices. They capture invisible radiation, which are absorbed by the atmosphere and do not reach the earth's surface. As a result, all types of electromagnetic radiation coming from cosmic depths became available for studies. Figuratively speaking, if before we observed the universe as it were in one, black and white color, today it seems to us in all the "colors" of the electromagnetic spectrum. But to take invisible radiation, we need special telescopes. What way and with the help of which you can catch and explore the rays of invisible?
With the word "telescope", each has an idea of \u200b\u200ban astronomical tube with lenses or mirrors, that is, an idea of \u200b\u200boptics. After all, until recently, the celestial objects studied exclusively using optical instruments. But to capture invisible radiation, which are very different from the eye visible, need special receiving devices. And it is not necessary at all that they resemble the telescope's usual to us with their appearance.
Receivers of short-wave radiation are completely similar to optical telescopes. And if we say, for example, "X-ray telescope" or "gamma telescope", Under such names should be understood: X-ray receiver or gamma quanta receiver.
The whole difficulty of receiving short-wave radiation is that for electromagnetic radiation with a wavelength, less than 0.2 microns, conventional refractive (lens) and reflective (mirror) systems are absolutely not suitable.
Thus, X-rays and especially gamma quanta are so energetic that they easily "break through" lenses made from any materials: the initial direction of the movement of these rays and quanta does not change. In other words, they cannot be focused! But how then to explore them? How to construct a telescope for them?
In the language of physicists, shortwave radiation - hard radiation! This means that photons of x-ray and gamma rays in their properties are similar to high-power particles of cosmic rays (alpha particles, protons) coming to the ground from the depths of the cosmos. But then, for registering hard quanta, perhaps, particle counters will be suitable, what are used to explore the cosmic rays? It is similar counters that are used as a receiving device in X-ray and gamma telescopes. To find out where X-ray comes from, the meter concludes a massive metal tube. And if the counter is still films with films of different composition, then different counters will take quanta of different stiffness. A peculiar X-ray spectrograph is obtained, which allows to identify the composition of X-ray radiation.
But such a telescope is still very imperfect. The main drawback is too small allowing. The meter marks radiation falling into a tube. And it comes from several square degrees of the sky, where thousands of stars are visible in a regular telescope. Which of them emit X-rays? You do not always know. And yet, with the help of X-ray and gamma telescopes working in space orbital stations, there are already many interesting information about the sources of invisible short-wave radiation.
One of these sources is our sun. Back in 1948, with the help of photoflaxes raised by the Fau-2 rocket, about 160 km (USA, the marine laboratory), the X-ray radiation of the Great Luminage was opened. And in 1962, replacing the photoplastic meter of Geiger, astronomers discovered the second X-ray source is already far outside the solar system. This is the brightest X-ray source in the constellation of Scorpio, called Scorpion X-1. In 1963, the third object of X-ray astronomy became the famous crab nebula in the constellation Taurus - Taurus X-1.
The most important stage in the development of X-ray astronomy was the launches of the world's first American Xuuru X-ray satellite in 1970 and the first X-ray telescope-Einstein reflector in 1978. With their help, X-ray double stars were discovered, X-ray pulsars, active kernels of galaxies and other X-ray sources.
To date, thousands of X-ray sources are known in the Star Sky. In general, the X-ray telescopes are available about a million such sources, that is, as much as the best radio telescope. How does the X-ray sky look like?
In the X-ray rays, the universe seems completely different than it is visible to optical telescopes. On the one hand, an increase in the concentration of bright radiation sources is observed as it approaches the middle plane of the Milky Way - they belong to our galaxy. On the other hand, the uniform distribution of numerous extragalactic X-ray sources throughout the sky. Many celestial bodies adorning the sky of the Earth - the Moon and the Planet - are not visible in X-rays.
Gamma Astronomy Also born along with rocket technology. As is known, the cosmic gamma radiation arises due to the physical processes in which particles of high energies are involved, the processes occurring inside the atomic nuclei. However, the most intense source of gamma quanta is the process of annihilation, that is, the interactions of particles and antiparticles (for example, electrons and positrons), accompanied by the transformation of matter (particles) into rigid radiation. Consequently, studying gamma quanta, astrophysicist can be once a witness to interaction with the bodies of our ordinary world of bodies theoretically possible antimiraconsisting exclusively antiTuracy.
In our galaxy, the diffuse (scattered) gamma radiation is focused mainly in the galactic disk; It is enhanced towards the center of the Galaxy. In addition, discrete (point) gamma sources were found, such as crab (crab nebula in Taurus), Hercules X-1, Geming (in the constellation of twins) and some others. Hundreds of discrete sources of extragalactic gamma radiation are scattered literally throughout the sky. It was possible to take gamma radiation emanating from the active areas of the Sun during solar flares.
On the border with a visible spectrum, to the left of the purple rays, is invisible ultraviolet radiation. Starting with a wave 0.29 micron, the earth's atmosphere completely absorbs the cosmic ultraviolet, perhaps, "in the most interesting place" ...
With the beginning of space studies, observations were also carried out in the ultraviolet wavelength interval. On March 23, 1983, in our country, an astronomer astronomer station "Astronom" was launched in our country on the high-elliptical near-earth orbit (height in perigaire 2000 km. It was the first domestic station equipped with equipment for X-ray and ultraviolet observations.
Now appliances fixing ultraviolet rays are installed on many spacecraft. And if we could look at the starry sky through "ultraviolet glasses", it would be completely unrecognizable for us, as, however, in other invisible rays of the spectrum. For example, for residents of the northern hemisphere of the Earth, the star of the Orion Zeta Orion would be especially highlighted in the sky - the leftmost shone in his "belt". Some other stars would be unusually bright, especially hot.
It is surprising that at the ultraviolet sky there are many huge, shrinking nebulaes. The famous Orion Nebula, which in the form of a tiny foggy spot with difficulty distinguishes his eyes, would take all the constellations of the "heavenly hunter". Golyanish ultraviolet nebula envelops the main star of the constellation of the Virgin - shining sprike. This nebula is very bright and almost round. Its visible diameter is approximately 50 times the visible diameter of the full moon. But the spoke itself is not visible by a simple eye: its ultraviolet radiation turned out to be very weak.
In the range of waves from 22 microns up to 1 mm (to the right of the red rays of the visible spectrum) the earth's atmosphere absorbs infrared (thermal) radiationheavenly bodies. In addition, the air itself is a source of thermal rays, which prevents observations in the infrared wavelength interval. Obtaining these obstacles succeeded only when infrared radiation receivers began to place outside the atmosphere - on spacecraft.
Infrared technique made it possible to get the most accurate data on the relief of the planets, opened the core of our galaxy, who had hidden the core of our galaxy in front of the researchers, helped astrophysics to look into the star "cradles" - gas-pepped nebulae and "touch" to the secrets of the birth of stars.
Thus, the removal of astrophysical instruments into space has opened new horizons before Astronomy: ultraviolet, X-ray and infrared astronomy began to be created, and in the 70s, observations began in the gamma range. Today, the universe researchers have the opportunity to make an overview of the sky in almost the entire range of electromagnetic spectrum - from ultrashort gamma rays to super-long radio waves. Astronomy became the science of Mesvolovna. The rich scientific "harvest" collected from cosmic "fields" caused a real coup in astrophysics and rethinking our ideas about the large universe.
