The first telescope was built in 1609 by Italian astronomer Galileo Galilei. The scientist, based on rumors about the invention of the telescope by the Dutch, unraveled its structure and made a sample, which he used for the first time for space observations. Galileo's first telescope had modest dimensions (tube length 1245 mm, lens diameter 53 mm, eyepiece 25 dioptres), imperfect optical design and 30-fold magnification. But it made it possible to make a whole series of remarkable discoveries: discovering the four satellites of the planet Jupiter, the phases of Venus, spots on The sun, mountains on the surface of the moon, the presence of appendages on the disk of Saturn at two opposite points.
More than four hundred years have passed - on earth and even in space, modern telescopes are helping earthlings look into distant cosmic worlds. The larger the diameter of the telescope mirror, the more powerful the optical system.
Multi-mirror telescope
Located on Mount Hopkins, at an altitude of 2606 meters above sea level, in the state of Arizona in the USA. The diameter of the mirror of this telescope is 6.5 meters. This telescope was built back in 1979. In 2000 it was improved. It is called multi-mirror because it consists of 6 precisely adjusted segments that make up one large mirror.
Magellan telescopes
Two telescopes, Magellan-1 and Magellan-2, are located at the Las Campanas Observatory in Chile, in the mountains, at an altitude of 2400 m, the diameter of their mirrors is 6.5 m each. The telescopes began operating in 2002.
And on March 23, 2012, construction began on another more powerful Magellan telescope - the Giant Magellan Telescope; it should go into operation in 2016. In the meantime, the top of one of the mountains was demolished by the explosion to clear a place for construction. The giant telescope will consist of seven mirrors 8.4 meters each, which is equivalent to one mirror with a diameter of 24 meters, for which it has already been nicknamed “Seven Eyes”.
Separated twins Gemini telescopes
Two brother telescopes, each of which is located in a different part of the world. One - “Gemini North” stands on the top of the extinct volcano Mauna Kea in Hawaii, at an altitude of 4200 m. The other - “Gemini South”, is located on Mount Serra Pachon (Chile) at an altitude of 2700 m.
Both telescopes are identical, the diameters of their mirrors are 8.1 meters, they were built in 2000 and belong to the Gemini Observatory. Telescopes are located on different hemispheres of the Earth so that the entire starry sky is accessible for observation. Telescope control systems are adapted to work via the Internet, so astronomers do not have to travel to different hemispheres of the Earth. Each of the mirrors of these telescopes is made up of 42 hexagonal fragments that have been soldered and polished. These telescopes are built with the most advanced technologies, making the Gemini Observatory one of the most advanced astronomical laboratories today.
Northern Gemini in Hawaii
Subaru telescope
This telescope belongs to the Japan National Astronomical Observatory. A is located in Hawaii, at an altitude of 4139 m, next to one of the Gemini telescopes. The diameter of its mirror is 8.2 meters. Subaru is equipped with the world's largest “thin” mirror: its thickness is 20 cm, its weight is 22.8 tons. This allows the use of a drive system, each of which transmits its force to the mirror, giving it an ideal surface in any position, which allows you to achieve the best image quality.
With the help of this keen telescope, the most distant galaxy known to date was discovered, located at a distance of 12.9 billion light years. years, 8 new satellites of Saturn, protoplanetary clouds photographed.
By the way, “Subaru” in Japanese means “Pleiades” - the name of this beautiful star cluster.
Japanese Subaru Telescope in Hawaii
Hobby-Eberly Telescope (NO)
Located in the USA on Mount Faulks, at an altitude of 2072 m, and belongs to the MacDonald Observatory. The diameter of its mirror is about 10 m. Despite its impressive size, Hobby-Eberle cost its creators only $13.5 million. It was possible to save the budget thanks to some design features: the mirror of this telescope is not parabolic, but spherical, not solid - it consists of 91 segments. In addition, the mirror is at a fixed angle to the horizon (55°) and can only rotate 360° around its axis. All this significantly reduces the cost of the design. This telescope specializes in spectrography and is successfully used to search for exoplanets and measure the rotation speed of space objects.
Large South African Telescope (SALT)
It belongs to the South African Astronomical Observatory and is located in South Africa, on the Karoo plateau, at an altitude of 1783 m. The dimensions of its mirror are 11x9.8 m. It is the largest in the Southern Hemisphere of our planet. And it was made in Russia, at the Lytkarino Optical Glass Plant. This telescope became an analogue of the Hobby-Eberle telescope in the USA. But it was modernized - the spherical aberration of the mirror was corrected and the field of view was increased, thanks to which, in addition to working in spectrograph mode, this telescope is capable of obtaining excellent photographs of celestial objects with high resolution.
The largest telescope in the world ()
It stands on the top of the extinct Muchachos volcano on one of the Canary Islands, at an altitude of 2396 m. Diameter of the main mirror – 10.4 m. Spain, Mexico and the USA took part in the creation of this telescope. By the way, this international project cost 176 million US dollars, of which 51% was paid by Spain.
The mirror of the Grand Canary Telescope, composed of 36 hexagonal parts, is the largest existing in the world today. Although this is the largest telescope in the world in terms of mirror size, it cannot be called the most powerful in terms of optical performance, since there are systems in the world that surpass it in their vigilance.
Located on Mount Graham, at an altitude of 3.3 km, in Arizona (USA). This telescope belongs to the Mount Graham International Observatory and was built with money from the USA, Italy and Germany. The structure is a system of two mirrors with a diameter of 8.4 meters, which in terms of light sensitivity is equivalent to one mirror with a diameter of 11.8 m. The centers of the two mirrors are located at a distance of 14.4 meters, which makes the telescope's resolving power equivalent to 22 meters, which is almost 10 times greater than that of the famous Hubble Space Telescope. Both mirrors of the Large Binocular Telescope are part of the same optical instrument and together constitute one huge binocular - the most powerful optical instrument in the world at the moment.
Keck I and Keck II are another pair of twin telescopes. They are located next to the Subaru telescope on the top of the Hawaiian volcano Mauna Kea (height 4139 m). The diameter of the main mirror of each of the Kecks is 10 meters - each of them individually is the second largest telescope in the world after the Grand Canary. But this telescope system is superior to the Canary telescope in terms of vigilance. The parabolic mirrors of these telescopes are made up of 36 segments, each of which is equipped with a special computer-controlled support system.
The Very Large Telescope is located in the Atacama Desert in the Chilean Andes, on Mount Paranal, 2635 m above sea level. And it belongs to the European Southern Observatory (ESO), which includes 9 European countries.
A system of four 8.2-meter telescopes, and another four auxiliary 1.8-meter telescopes, is equivalent in aperture to one instrument with a mirror diameter of 16.4 meters.
Each of the four telescopes can work separately, obtaining photographs in which stars up to 30th magnitude are visible. Rarely do all telescopes work at once; it is too expensive. More often, each of the large telescopes works in tandem with its 1.8-meter assistant. Each of the auxiliary telescopes can move on rails relative to its “big brother”, occupying the most advantageous position for observing a given object. The Very Large Telescope is the most advanced astronomical system in the world. A lot of astronomical discoveries were made on it, for example, the world's first direct image of an exoplanet was obtained.
Space Hubble telescope
The Hubble Space Telescope is a joint project of NASA and the European Space Agency, an automatic observatory in Earth orbit, named after the American astronomer Edwin Hubble. The diameter of its mirror is only 2.4 m, which is smaller than the largest telescopes on Earth. But due to the lack of atmospheric influence, the resolution of the telescope is 7 - 10 times greater than a similar telescope located on Earth. Hubble is responsible for many scientific discoveries: the collision of Jupiter with a comet, images of the relief of Pluto, auroras on Jupiter and Saturn...
Hubble telescope in earth orbit
Hubble as seen from Space Shuttle Atlantis STS-125
Hubble Space Telescope ( KTH; Hubble Space Telescope, HST; observatory code "250") - in orbit around , named after Edwin Hubble. The Hubble Telescope is a joint project between NASA and the European Space Agency; it is one of NASA's Large Observatories.
Placing a telescope in space makes it possible to detect electromagnetic radiation in ranges in which the earth’s atmosphere is opaque; primarily in the infrared range. Due to the absence of atmospheric influence, the resolution of the telescope is 7-10 times greater than that of a similar telescope located on Earth.
Story
Background, concepts, early projects
The first mention of the concept of an orbital telescope occurs in the book “Rocket in Interplanetary Space” by Hermann Oberth ( Die Rakete zu den Planetenraumen ), published in 1923.
In 1946, American astrophysicist Lyman Spitzer published the article "The Astronomical Advantages of an Extraterrestrial Observatory" ( Astronomical advantages of an extra-terrestrial observatory ). The article highlights two main advantages of such a telescope. First, its angular resolution will be limited only by diffraction, and not by turbulent flows in the atmosphere; at that time, the resolution of ground-based telescopes was between 0.5 and 1.0 arcseconds, whereas the theoretical diffraction resolution limit for an orbiting telescope with a 2.5-meter mirror is about 0.1 seconds. Secondly, the space telescope could observe in the infrared and ultraviolet ranges, in which the absorption of radiation by the earth's atmosphere is very significant.
Spitzer devoted a significant portion of his scientific career to advancing the project. In 1962, a report published by the US National Academy of Sciences recommended that the development of an orbiting telescope be included in the space program, and in 1965 Spitzer was appointed head of a committee tasked with defining the scientific objectives for a large space telescope.
Space astronomy began to develop after the end of World War II. In 1946, the ultraviolet spectrum was obtained for the first time. An orbiting telescope for solar research was launched by the UK in 1962 as part of the Ariel program, and in 1966 NASA launched the first orbital observatory OAO-1 into space. The mission was unsuccessful due to battery failure three days after launch. In 1968, OAO-2 was launched, which made observations of ultraviolet radiation until 1972, significantly exceeding its design life of 1 year.
The OAO missions served as a clear demonstration of the role that orbiting telescopes could play, and in 1968 NASA approved a plan to build a reflecting telescope with a 3 m diameter mirror. The project was codenamed LST ( Large Space Telescope). The launch was planned for 1972. The program emphasized the need for regular manned expeditions to maintain the telescope in order to ensure long-term operation of the expensive instrument. The Space Shuttle program, which was developing in parallel, gave hope for obtaining corresponding opportunities.
The struggle to finance the project
Due to the success of the JSC program, there is a consensus in the astronomical community that building a large orbiting telescope should be a priority. In 1970, NASA established two committees, one to study and plan technical aspects, the second to develop a scientific research program. The next major obstacle was financing the project, the costs of which were expected to exceed the cost of any ground-based telescope. The US Congress questioned many of the proposed estimates and significantly cut the appropriations, which initially involved large-scale research into the instruments and design of the observatory. In 1974, as part of a program of budget cuts initiated by President Ford, Congress completely canceled funding for the project.
In response, astronomers launched a broad lobbying campaign. Many astronomers met personally with senators and congressmen, and several large mailings of letters were also carried out in support of the project. The National Academy of Sciences published a report emphasizing the importance of building a large orbiting telescope, and as a result, the Senate agreed to allocate half of the budget originally approved by Congress.
Financial problems led to cutbacks, chief among them the decision to reduce the diameter of the mirror from 3 to 2.4 meters to reduce costs and achieve a more compact design. The project of a telescope with a one and a half meter mirror, which was supposed to be launched for the purpose of testing and testing the systems, was also canceled, and a decision was made to cooperate with the European Space Agency. ESA agreed to participate in financing, as well as to provide a number of instruments for the observatory, in return for European astronomers to reserve at least 15% of the observing time. In 1978, Congress approved $36 million in funding, and full-scale design work began immediately thereafter. The launch date was planned for 1983. In the early 1980s, the telescope was named after Edwin Hubble.
Organization of design and construction
The work on creating the space telescope was divided among many companies and institutions. The Marshall Space Center was responsible for the development, design and construction of the telescope, the Goddard Space Flight Center was responsible for the overall management of the development of scientific instruments and was chosen as the ground control center. The Marshall Center contracted with Perkin-Elmer to design and manufacture the telescope's optical system ( Optical Telescope Assembly - OTA) and precision guidance sensors. Lockheed Corporation received the construction contract for the telescope.
Manufacturing of the optical system
Polishing the telescope's primary mirror, Perkin-Elmer Laboratory, May 1979
The mirror and the optical system as a whole were the most important parts of the telescope design, and particularly stringent requirements were placed on them. Typically, telescope mirrors are made to a tolerance of about one-tenth the wavelength of visible light, but since the space telescope was intended to observe from ultraviolet to near-infrared, and the resolution had to be ten times higher than that of ground-based instruments, the manufacturing tolerance its primary mirror was set at 1/20 the wavelength of visible light, or approximately 30 nm.
The Perkin-Elmer company intended to use new computer numerical control machines to produce a mirror of a given shape. Kodak was contracted to manufacture a replacement mirror using traditional polishing methods in case of unforeseen problems with unproven technologies (the Kodak-manufactured mirror is currently on display at the Smithsonian Institution museum). Work on the main mirror began in 1979, using glass with an ultra-low coefficient of thermal expansion. To reduce weight, the mirror consisted of two surfaces - lower and upper, connected by a lattice structure of a honeycomb structure.
Telescope backup mirror, Smithsonian Air and Space Museum, Washington DC
Work on polishing the mirror continued until May 1981, but the original deadlines were missed and the budget was significantly exceeded. NASA reports from the period expressed doubts about the competence of Perkin-Elmer's management and its ability to successfully complete a project of such importance and complexity. To save money, NASA canceled the backup mirror order and moved the launch date to October 1984. The work was finally completed by the end of 1981, after applying a reflective coating of aluminum 75 nm thick and a protective coating of magnesium fluoride 25 nm thick.
Despite this, doubts about Perkin-Elmer's competence remained as the completion date for the remaining components of the optical system was constantly pushed back and the project budget grew. NASA described the company's schedule as "uncertain and changing daily" and delayed the telescope's launch until April 1985. However, the deadlines continued to be missed, the delay grew by an average of one month every quarter, and at the final stage it grew by one day every day. NASA was forced to postpone the launch twice more, first to March and then to September 1986. By that time, the total project budget had grown to $1.175 billion.
Spacecraft
The initial stages of work on the spacecraft, 1980
Another difficult engineering problem was the creation of a carrier apparatus for the telescope and other instruments. The main requirements were protection of the equipment from constant temperature changes during heating from direct sunlight and cooling in the Earth's shadow, and particularly precise orientation of the telescope. The telescope is mounted inside a lightweight aluminum capsule, which is covered with multi-layer thermal insulation, ensuring a stable temperature. The rigidity of the capsule and the fastening of instruments is provided by an internal spatial frame made of carbon fiber.
Although the spacecraft was more successful than the optical system, Lockheed also ran somewhat behind schedule and over budget. By May 1985, cost overruns amounted to about 30% of the original volume, and the lag behind the plan was 3 months. A report prepared by the Marshall Space Center noted that the company did not show initiative in carrying out work, preferring to rely on NASA instructions.
Research coordination and flight control
In 1983, after some confrontation between NASA and the scientific community, the Space Telescope Science Institute was established. The institute is managed by the Universities Association for Astronomical Research ( Association of Universities for Research in Astronomy ) (AURA) and is located on the campus of Johns Hopkins University in Baltimore, Maryland. Hopkins University is one of 32 American universities and foreign institutions that are members of the association. The Space Telescope Science Institute is responsible for organizing scientific work and providing astronomers with access to the data obtained; NASA wanted to keep these functions under its control, but scientists preferred to transfer them to academic institutions.
The European Space Telescope Coordination Center was founded in 1984 in Garching, Germany, to provide similar facilities to European astronomers.
Flight control was entrusted to the Goddard Space Flight Center, which is located in Greenbelt, Maryland, 48 kilometers from the Space Telescope Science Institute. The functioning of the telescope is monitored round-the-clock in shifts by four groups of specialists. Technical support is provided by NASA and contracting companies through the Goddard Center.
Launch and getting started
Launch of the Discovery shuttle with the Hubble telescope on board
The telescope was originally scheduled to be launched into orbit in October 1986, but on January 28 the Space Shuttle program was suspended for several years, and the launch had to be postponed.
All this time, the telescope was stored in a room with an artificially purified atmosphere, its on-board systems were partially turned on. Storage costs were approximately $6 million per month, which further increased the cost of the project.
The forced delay allowed for a number of improvements: solar panels were replaced with more efficient ones, the on-board computer complex and communication systems were modernized, and the design of the aft protective casing was changed in order to facilitate the maintenance of the telescope in orbit. In addition, the software for controlling the telescope was not ready in 1986 and was actually only finalized by the time of its launch in 1990.
After the resumption of shuttle flights in 1988, the launch was finally scheduled for 1990. Before launch, dust accumulated on the mirror was removed using compressed nitrogen, and all systems were thoroughly tested.
In July 1923, the Oldenburg publishing house in Munich published the book “Rocket into Outer Space.” Its author was Hermann Julius Oberth, who became famous decades later and was even promoted to the “founding fathers” of rocketry. The main provisions of his work can be briefly formulated as follows:
1. With the current state of science and technology, it is possible to create an apparatus capable of going beyond the Earth’s atmosphere.
2. In the future, such devices will be able to develop such a speed that they will overcome gravity and go into interplanetary space.
3. It is possible to create devices that can perform similar tasks with a person on board, and without serious damage to his health.
4. Under certain conditions, the creation of such devices may become quite feasible. Such conditions may arise in the coming decades.
In the final, ascertaining phrases of the last part of the book, there is a discussion of distant prospects - the possibility of seeing the far side of the Moon, launching artificial Earth satellites, their widespread use for various purposes, creating orbital stations, carrying out certain types of activities with their help, including scientific research and astronomical observations. This allows us to consider July 1923 as the “starting point” of space astronomy.
To commemorate the 90th anniversary of this event, the editors of our journal have prepared a series of articles about ongoing (or recently completed) projects to explore the Universe, based on astronomical instruments beyond the Earth's atmosphere. The complete chronicle of this most interesting and actively developing branch of astronomy deserves a separate book, which, undoubtedly, will be written soon.
Visible space telescopes
In the course of evolution, the human eye has acquired the greatest sensitivity to that part of the electromagnetic spectrum that is best transmitted by the earth's atmosphere. Therefore, astronomical observations since ancient times have been carried out mainly in the visible range. However, already at the end of the 19th century, it became clear to astronomers that the “ocean of air” with its inhomogeneities and unpredictable currents created too many obstacles for the further development of observational technology. If, when measuring the positions of stars in the sky, all these errors were mainly eliminated by statistical methods, then attempts to obtain high-resolution images of celestial bodies were unsuccessful even in places with the best astroclimate. When observing from the Earth's surface, the most advanced telescopes could provide a standard resolution of about half an arcsecond, in ideal cases up to a quarter of a second. Theoretical calculations showed that moving the telescope outside the atmosphere would improve its capabilities by an order of magnitude (in the ultraviolet part of the spectrum it was possible to achieve almost 20 times higher resolution).
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CHARACTERISTICS OF THE SPACE VEHICLE:
> Length - 13.3 m, diameter - 4.3 m, weight - 11 tons (with installed instruments - about 12.5 tons); two solar panels measure 2.6 x 7.1 m. INSTRUMENTS THAT WORKED OR ARE WORKING AT THE HUBBLE OBSERVATORY: > Wide Field and Planetary Camera. Equipped with a set of 48 light filters to highlight areas of the spectrum that are of particular interest for astrophysical observations. The cameras contain 8 CCD matrices (2 sections of 4 matrices each). A wide-angle camera has a larger viewing angle, while a planetary camera has a larger equivalent focal length, allowing for greater magnifications. |
| > Wide Field Camera 3 (WFC 3) - a camera for observations in a wide spectral range (visible, near-infrared, near and mid-ultraviolet sections of the electromagnetic spectrum). |
> A corrective optical system (COSTAR) was installed during the first service mission to compensate for manufacturing inaccuracies in the primary mirror
In 1968, the US National Aerospace Administration (NASA) approved a plan for the construction of a reflecting telescope with a mirror diameter of 3 m. The project received the code name LST (Large Space Telescope). The launch was planned for 1972. But the struggle now continued in the financial “plane”: funds were then allocated, then the next government and Congress reduced funding, until the program was completely curtailed. The diameter of the telescope lens was reduced to 2.4 m, but a new participant in the project appeared - the European Space Agency (ESA), which agreed “in exchange” for 15% of the observation time to partially finance the program and participate in the manufacture of individual instruments.
In 1979, the NASA report “Strategy for Space Astronomy and Astrophysics for the 1980s” was published, which proposed the implementation of the “Large Observatories” program. Already funded by Congress in 1978, the LST became one of the four elements of the project - it was assigned the role of “observer” in the visible, as well as near-infrared and ultraviolet ranges. The Compton Observatory (CGRO) was responsible for research in the hard X-ray and gamma-ray range,2 the Chandra telescope (CHO) was supposed to study soft X-rays, and the Spitzer (SST) - the mid- and far-infrared region of the spectrum.
Hubble Space Telescope
Work on the creation of LST moved most quickly. Initially, its launch into orbit was planned for 1983. However, it was not possible to launch it then, but it was decided to name the orbital observatory after Edwin Hubble. On April 24, 1990, the Discovery shuttle launched the telescope into its intended orbit. From the beginning of design to launch, $2.5 billion was spent on this project - with an initial budget of $400 million.
Hubble is currently the oldest and most prolific astronomical instrument operating outside the atmosphere. To keep it in working order, NASA organized 4 repair missions, the last of which was carried out by the crew of the Atlantis shuttle in May 2009. The total cost of operating the orbital observatory on the American side amounted to more than 6 billion dollars; another 593 million euros were allocated by the ESA.
Flight control, data reception and primary processing are carried out by the Goddard Space Flight Center. Within 24 hours, the data is transferred to the Space Telescope Science Institute (STScI), which is responsible for its main processing and publication for use by the scientific community. The Hubble telescope operates as an international research laboratory. Projects from all over the world are considered, although competition for observation time is fierce, so on average one in 10 projects is implemented.
Scientific achievements of the Hubble telescope. Despite the fact that after the start of work, deviations in the shape of the telescope’s main mirror from the calculated ones were discovered (which did not allow it to be used “at full strength”), Hubble almost immediately began to produce valuable scientific results. When creating this instrument, it was stated that its main task was “to direct your gaze into the depths of the Universe.” He had, first of all, to work off the “advance payment” - to continue the research begun by his “godfather” Edwin Hubble: to clarify the constant and verify the law of his name, to confirm the interpretation of the red shift as the Doppler effect and the reality of the expansion of the Universe. The now legendary space telescope successfully completed these tasks.
Astronomers have long ceased to need evidence that our Galaxy is not the only such system in the Universe. There is also no doubt that all these “stellar islands” (more precisely, their gravitationally bound groups) are constantly moving away from each other. The speed of mutual removal is directly proportional to the distance between objects, and the proportionality coefficient is called the “Hubble constant” (H0). Its first estimates, made by Hubble itself, gave a value of about five hundred kilometers per second per megaparsec. Over the next 90 years, they were repeatedly revised, being the subject of heated debate: after all, in fact, this constant, reduced to system units, is the reciprocal - neither more nor less - of the age of the Universe. Its last, most accurate value is 70.4 (km/s)/Mpc (H0 = 2.28x10 -18 s -1), and measurements made by the Hubble telescope made a significant contribution to its establishment. This is precisely what is considered to be his main “scientific feat”.
Having established the fact of the expansion of the Universe, Edwin Hubble limited himself to this, but his “cosmic namesake” went further and managed not only to confirm this at a new technical level, but also to prove the unevenness of this expansion (more precisely, its acceleration). Such a discovery required measurements of the spectral characteristics of objects at extremely large distances - and only Hubble was “strong” in this. It was possible to make several thousand estimates of the brightness of type 1a supernovae, the peculiarity of which is that at the maximum of the outburst they release approximately the same amount of energy, which means that the observed brightness of the outburst depends only on the distance to its source.6 More than a dozen people participated in this research program ground and space telescopes. The fruits of such cooperation were very successful, and the degree of importance of the results obtained for science was sufficient to award the Nobel Prize in physics to the team of authors of the discovery.
To test the “range” of the telescope, several so-called deep surveys of the Universe were carried out. To do this, a site in the sky was selected where there were no nearby galaxies and stars of our Galaxy, and photography was carried out with the longest possible exposures. At the same time, it was possible to capture very distant objects of various types, sizes, luminosities and ages. Among them were young star clusters that are just preparing to become “familiar” galaxies, and already fully formed star systems. Deep surveys of the Universe - the Hubble Deep Field (HDF), jokingly called by astronomers “Deep Punctures of the Universe” - are a look through billions of years into the ancient history of our world.
During one of the “punctures”, Hubble focused its attention on an area the size of one thirty-millionth of the celestial sphere and discovered more than 3,000 dim—at the limit of visibility—galaxies there. A detailed photograph of another similar area of the sky showed the same picture, from which it was concluded that the Universe is isotropic - its homogeneity in all directions on large scales. Since such observations require very long exposures (during one of the sessions the “exposure” reached 11.3 days), they were rare. Astronomers were able to see protogalaxies - the first clumps of matter that formed less than a billion years after the Big Bang and later merged into modern star systems.
Of particular note is the unique Great Observatories Origins Deep Survey (GOODS) experiment, carried out by the coordinated efforts of the Hubble, Spitzer, Chandra space telescopes, the XMM-Newton orbital X-ray telescope and a number of the largest ground-based instruments. The objects of observation were two sites from the Hubble Deep Field program. At redshift Z=6, a spatial resolution of the order of a kiloparsec has been achieved, and photometric redshifts have been determined for 60 thousand galaxies in the field. Participants in this project claim that they looked 13 billion years ago, into the era of reionization, when the radiation of the first stars caused the decay of some interstellar hydrogen atoms into electrons and protons.
The record so far is the “dive” into the depths of the Universe, announced in September 2012 (Hubble extreme Deep Field). For 10 years, a section of the sky in the Fornax constellation was exposed with a total exposure of 2 million seconds. Astronomers claim that in this case they saw the Universe at a completely “childish” age - no more than half a billion years. The dimmest galaxies in the image (there are about 5,500 of them in total) have a brightness 10 billion times lower than the sensitivity limit of human vision.
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ASC FIAN Astrospace Center of the Physical Institute of the Academy of Sciences, Russia ESA European Space Agency NASA National Aerospace Administration, USA CNES National Center for Space Research, France CSA Canadian Space Agency A.S.I. Italian Space Agency JAXA Japan Aerospace Exploration Agency SSC Swedish Space Corporation |
| > Wide Field Camera 3 (WFC 3) - a camera for observations in a wide spectral range (visible, near-infrared, near and mid-ultraviolet sections of the electromagnetic spectrum). |
| Below the names of the telescopes are the orbital parameters, operator and launch date. |
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For a long time, theoretical astrophysicists tried to convince the scientific community that supermassive black holes must necessarily be present in the central regions of galaxies, but there was no observational evidence of this. As soon as the Hubble telescope “intervened in the dispute,” everything fell into place: now a galaxy without a central black hole is more exotic. Now the scientists’ arguments look very convincing: systematic observations of a large number of stellar systems have revealed a correlation between the size of the bulge (the central condensation of the galaxy) and the mass of superdense objects in their centers, determined from the radial velocities of the stars.
Not all of the space telescope's results required complex long-term observations. Among his photographs there are many that in themselves already represent solved astrophysical problems. He demonstrated the birth of stars in the “Tripartite Nebula” M20 extremely clearly. Planetary nebula NGC 7027 is the final stage of evolution of a star similar to our Sun. The “Pillars of Creation” in the Eagle Nebula have become classic...
At the time of preparing the “flight mission” of the observatory, some problems were not only not a priority, but astronomers only guessed that they would arise. Such tasks, first of all, should include the search for planets of other stars (exoplanets). Thanks to the high sensitivity of its detectors and the absence of the influence of the Earth's atmosphere, Hubble is able to detect an insignificant change in the brightness of the observed star caused by the passage of a planetary-sized satellite in front of its disk. In observational technology, this method of searching for exoplanets is called the “transit method.” It is applicable only for objects whose orbital plane is slightly inclined towards the direction of the Earth, but it allows one to immediately determine many of their characteristics - in particular, size, mass, and sometimes the composition of the atmosphere (by spectral analysis of the star’s radiation during an “eclipse”). A breakthrough discovery should be recognized as the first detection of an organic molecule - methane CH4 - in the gaseous shell of the giant planet HD 189733b using one of the most important instruments of the Hubble telescope - the NICMOS spectrometer (Near Infrared Camera and Multi-Object Spectrometer), installed on board the observatory seven years after launch during the second repair mission.
In addition to planet-like bodies, the space telescope confirmed the existence of numerous protoplanetary disks in star-forming regions (the Eagle Nebula, the Great Orion Nebula) and near some stars. These discoveries initiated the emergence of a very promising scientific direction - the search and study of exocomets and exoasteroid belts. It is now obvious that the process of planet formation in our Galaxy occurs constantly. Hubble has collected a lot of evidence for the recently generally accepted conclusion that exoplanets should be a completely ordinary and widespread phenomenon in the Universe.
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| The Hubble Space Telescope gave us a stunning image of the bright ring of star formation surrounding the heart of a barred spiral galaxy, designated NGC 1097. This galaxy is approximately 45 million light-years away and visible in the southern constellation Fornax. It belongs to the class of Seyfert galaxies; the fact that its main plane is almost perpendicular to the direction towards Earth makes it a particularly tasty object for astronomers. Hidden in the very center of the galaxy, a supermassive black hole (BH) with a mass of about 100 million solar masses is gradually absorbing matter from the surrounding space. This matter, falling into a black hole, “spins” into an accretion disk, heats up and begins to emit in a wide range of electromagnetic waves. The contours of the disk are clearly outlined by relatively recently “born” stars, the material for which is the matter of the central bar (bridge) of the galaxy falling onto the BH. These star-forming regions glow brightly due to emission from clouds of ionized hydrogen. The diameter of the ring is about 5 thousand light years, and the spiral arms of NGC 1097 extend tens of thousands of light years beyond. |
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| > Wide Field Camera 3 (WFC 3) - a camera for observations in a wide spectral range (visible, near-infrared, near and mid-ultraviolet sections of the electromagnetic spectrum). |
The main “field of activity” of a powerful space telescope, of course, was considered to be deep space exploration. Therefore, when studying our Solar System, its potential was used rather limitedly. But the list of his achievements within its boundaries is also impressive. First of all, it should be noted that, unprecedented in the history of astronomy, the fall of fragments of comet Shoemaker-Levy 9 (D/1993 F2 Shoemaker-Levy 9) onto Jupiter in July 1994. This incident was the first observed collision of two bodies in the Solar System.
The Hubble telescope has finally photographed the surface of Pluto with such resolution that it has become possible to talk about mapping it. In images taken by the space observatory, experts distinguish polar caps, bright moving spots and mysterious lines. Also impressive was the discovery at Pluto, in addition to the already known satellite Charon, of four more small moons - Nix, Hydra, PIV, PV.
When observing the asteroid Vesta (4 Vesta), planetary scientists were struck by the high resolution and clear detail of the surface (of course, one should not compare the images taken a decade and a half ago from a distance of more than 110 million km with those obtained by the Dawn spacecraft in 2011-12 gg., while in orbit around Vesta). After Hubble's 2006 study of 2003 UB313, initially considered the 10th planet in the solar system and later named Eris (136199 Eris), the celestial body was deemed too small to be considered a planet. There is no doubt about the importance of the discovery of polar (auroral) lights on the giant planets Jupiter and Saturn, as well as on the Jovian moons Io and Ganymede.
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| An important object of research for the Hubble telescope has become planetary nebulae - the post-mortem stage of the evolution of stars like our Sun. As thermonuclear fuel reserves are depleted, they begin to periodically eject their matter into the surrounding space, turning into the state of a white dwarf - a super-dense object that releases energy due to slow gravitational compression. The ejected shells, illuminated by the radiation of the stellar remnant, form complex structures in which the dynamics of the process of emission of matter can be seen. A striking example of such structures are the gaseous filaments of the nebula NGC 5189, located in the southern constellation Muca at a distance of 1800 light years (it has the unofficial name “Spiral”). It can be assumed that the nebula was formed through the interaction of two independent expanding structures inclined towards each other. Such double bipolar structuring is usually explained by the presence of a massive satellite in the “burnt out” star, which, with its attraction, influences the direction of the “rivers” of outflowing gas. Although this explanation is very plausible, it was not possible to visually detect such a companion in this case. The bright golden rings consist of a large number of radial filaments and comet-like nodes. They are usually formed by the combined effects of ionizing radiation and stellar wind. The photograph was taken on July 6, 2012 with a Wide Field Camera 3 through narrow-band filters centered on the main emission lines of ionized sulfur, hydrogen and oxygen atoms. Broadband filters were used to determine the star's color in the visible and near-infrared. |
| > Wide Field Camera 3 (WFC 3) - a camera for observations in a wide spectral range (visible, near-infrared, near and mid-ultraviolet sections of the electromagnetic spectrum). |
Since service missions to the Hubble Observatory are no longer possible (due to the cessation of flights of American reusable spacecraft), its technical capabilities will only decrease over time, and its equipment will become obsolete. NASA guarantees full operation of the telescope until at least 2015. Its proposed “replacement”, named after the former director of the US space agency James Webb (James Webb Space Telescope - JWST), will be focused mainly on the near-infrared range. This is due to the fact that as a result of the development of adaptive optics technology, which compensates for the influence of atmospheric inhomogeneities, ground-based observatories will soon be able to take photographs of celestial objects with “Hubble” resolution, spending much less money and effort than is required for launching into orbit and operating a tool of comparable size.
The James Webb Telescope is an orbital infrared observatory that should replace the famous Hubble Space Telescope.
This is a very complex mechanism. Work on it has been going on for about 20 years! The James Webb will have a composite mirror 6.5 meters in diameter and cost about $6.8 billion. For comparison, the diameter of the Hubble mirror is “only” 2.4 meters.
Let's see?
1. The James Webb telescope should be placed in a halo orbit at the Lagrange point L2 of the Sun-Earth system. And it's cold in space. Shown here are tests conducted on March 30, 2012, to examine the ability to withstand the cold temperatures of the space. (Photo by Chris Gunn | NASA):
2. The James Webb will have a composite mirror 6.5 meters in diameter with a collecting surface area of 25 m². Is this a lot or a little? (Photo by Chris Gunn):
3. Compare with Hubble. Hubble (left) and Webb (right) mirrors on the same scale:
4. Full-scale model of the James Webb Space Telescope in Austin, Texas, March 8, 2013. (Photo by Chris Gunn):
5. The telescope project is an international collaboration of 17 countries, led by NASA, with significant contributions from the European and Canadian Space Agencies. (Photo by Chris Gunn):
6. Initially, the launch was planned for 2007, but was later postponed to 2014 and 2015. However, the first segment of the mirror was installed on the telescope only at the end of 2015, and the main composite mirror was not fully assembled until February 2016. (Photo by Chris Gunn):
7. The sensitivity of a telescope and its resolution are directly related to the size of the mirror area that collects light from objects. Scientists and engineers have determined that the minimum diameter of the primary mirror must be 6.5 meters in order to measure light from the most distant galaxies.
Simply making a mirror similar to that of the Hubble telescope, but larger, was unacceptable, since its mass would be too large to launch the telescope into space. The team of scientists and engineers needed to find a solution so that the new mirror would have 1/10 the mass of the Hubble telescope mirror per unit area. (Photo by Chris Gunn):
8. Not only here everything becomes more expensive from the initial estimate. Thus, the cost of the James Webb telescope exceeded the original estimates by at least 4 times. The telescope was planned to cost $1.6 billion and be launched in 2011, but according to new estimates, the cost could be $6.8 billion, with the launch not taking place earlier than 2018. (Photo by Chris Gunn):
9. This is a near-infrared spectrograph. It will analyze a range of sources, which will provide information about both the physical properties of the objects under study (for example, temperature and mass) and their chemical composition. (Photo by Chris Gunn):
The telescope will make it possible to detect relatively cold exoplanets with a surface temperature of up to 300 K (which is almost equal to the temperature of the Earth’s surface), located further than 12 AU. that is, from their stars, and distant from Earth at a distance of up to 15 light years. More than two dozen stars closest to the Sun will fall into the detailed observation zone. Thanks to James Webb, a real breakthrough in exoplanetology is expected - the capabilities of the telescope will be sufficient not only to detect the exoplanets themselves, but even the satellites and spectral lines of these planets.
11. Engineers test in the chamber. telescope lift system, September 9, 2014. (Photo by Chris Gunn):
12. Research of mirrors, September 29, 2014. The hexagonal shape of the segments was not chosen by chance. It has a high fill factor and has sixth order symmetry. A high fill factor means that the segments fit together without gaps. Thanks to symmetry, the 18 mirror segments can be divided into three groups, in each of which the segment settings are identical. Finally, it is desirable that the mirror has a shape close to circular - to focus the light on the detectors as compactly as possible. An oval mirror, for example, would produce an elongated image, while a square one would send a lot of light from the central area. (Photo by Chris Gunn):
13. Cleaning the mirror with carbon dioxide dry ice. Nobody rubs with rags here. (Photo by Chris Gunn):
14. Chamber A is a giant vacuum test chamber that will simulate outer space during testing of the James Webb Telescope, May 20, 2015. (Photo by Chris Gunn):
17. The size of each of the 18 hexagonal segments of the mirror is 1.32 meters from edge to edge. (Photo by Chris Gunn):
18. The mass of the mirror itself in each segment is 20 kg, and the mass of the entire assembled segment is 40 kg. (Photo by Chris Gunn):
19. A special type of beryllium is used for the mirror of the James Webb telescope. It is a fine powder. The powder is placed in a stainless steel container and pressed into a flat shape. Once the steel container is removed, the beryllium piece is cut in half to make two mirror blanks about 1.3 meters across. Each mirror blank is used to create one segment. (Photo by Chris Gunn):
20. Then the surface of each mirror is ground down to give it a shape close to the calculated one. After this, the mirror is carefully smoothed and polished. This process is repeated until the shape of the mirror segment is close to ideal. Next, the segment is cooled to a temperature of −240 °C, and the dimensions of the segment are measured using a laser interferometer. Then the mirror, taking into account the information received, undergoes final polishing. (Photo by Chris Gunn):
21. Once the segment is processed, the front of the mirror is coated with a thin layer of gold to better reflect infrared radiation in the range of 0.6-29 microns, and the finished segment is re-tested at cryogenic temperatures. (Photo by Chris Gunn):
22. Work on the telescope in November 2016. (Photo by Chris Gunn):
23. NASA completed assembly of the James Webb Space Telescope in 2016 and began testing it. This is a photo from March 5, 2017. At long exposures, the techniques look like ghosts. (Photo by Chris Gunn):
26. The door to the same chamber A from the 14th photograph, in which outer space is simulated. (Photo by Chris Gunn):
28. Current plans call for the telescope to be launched on an Ariane 5 rocket in the spring of 2019. When asked what scientists expect to learn from the new telescope, project lead scientist John Mather said, "Hopefully we'll find something that no one knows anything about." UPD. The James Webb Telescope's launch has been postponed to 2020.(Photo by Chris Gunn).
Man has always been interested in the mysteries of the universe. When did our universe appear? How long ago? Are there other planets similar to Earth? There are a huge number of questions, and astronomers, with the help of their instruments, have always tried to see more, further and more clearly in space.
Observing from the surface of our planet is generally quite convenient. You just need to choose a place with an atmosphere that is not polluted by various emissions. The telescope lens can be made as large as available technology allows. All that remains is to automate the process of observing and recording results. And, it would seem, that’s it, get ready to learn all the secrets of the world. However, researchers face a big problem associated with the absorption of infrared and ultraviolet radiation coming from space by the earth's atmosphere. Meanwhile, this wave range, invisible to the human eye, contains a huge amount of information that helps to understand the essence of the processes taking place.
Lyman Spitzer
The idea of creating an observation device, the image of which is not subject to distortion by the earth's atmosphere, was first put forward by Hermann Oberth in 1923. At that time, such prospects seemed very distant in the future. However, already in 1946, in the work of astrophysicist Lyman Spitzer, the basic principles of the functioning of an extraterrestrial observatory were formulated. It was proposed to use as the main working element not a system of lenses, as in conventional terrestrial telescopes, but a huge mirror that would collect flows of outgoing radiation on its surface. In this case, the accuracy of observation will be affected only by the evenness of the mirror surface without any introduced distortions caused by turbulent flows of the earth’s atmosphere. And of course, such a telescope could operate in all ranges of interest.
The period from the formulation of the idea to its implementation was more than 40 years. After all, first it was necessary to work out in detail the procedure for launching the telescope into low-Earth orbit, and tools that made it possible to polish the surface of the mirror with great precision appeared only in the 60s of the last century.
The American corporation NASA is rightfully considered a pioneer in the field of creating large space telescopes. Since 1962, she has been closely involved in the creation of universal surveillance equipment. The first orbital astronomical observatories (OAO) were quite cumbersome and did not have stable communication channels with the control center for transmitting accumulated information. But even this imperfect technique made it possible to make a number of scientific discoveries. For example, the ultraviolet spectrogram of the Sun was photographed and studied for the first time.
Hubble Telescope
The next step was to develop a telescope with a large mirror that could be used to study distant galaxies and planets. Its construction took about 15 years, and the cost was so high that NASA had to turn to the European Space Agency for help. As a result, it was launched into orbit only in 1990. The telescope was named after the American scientist Edwin Hubble, who developed the concept of the expanding Universe.
The first results of the new space telescope were simply stunning. The previously impossible resolution, which makes it possible to obtain a clear image of distant planets without any distortion, created a real sensation in the scientific community. With the help of Hubble, it was possible to examine in detail the process of the collision of comet Shoemaker-Levy with Jupiter, obtain clear images of the surface of Pluto, and discover previously unknown planets located outside the solar system.
Fragment of the Carina Nebula photographed by the Hubble telescope in 2010
The Hubble Space Telescope ends its lifespan in 2014. It should be replaced by a new device, the construction of which is already in full swing by NASA and the European Space Agency. Russian scientists also participate in the development. It is planned that the new telescope will be named after James Webb, a talented American scientist who made a huge contribution to the study of the theory of the origin of our world.
The diameter of the new telescope's mirror will be 6.5 meters (Hubble's is 2.5 m). To protect it from solar radiation, it is planned to deploy a huge reflective screen, the purpose of which will be to remove excess heat from the measuring sensors. The telescope will be able to look even further into the universe, catching the radiation of the most distant stars. Therefore, it is no coincidence that the main purpose of launching it into orbit is considered to be to conduct a whole set of observations in relation to planetary systems outside our galaxy, study their physicochemical parameters and determine the possibility of the existence of organic life on them. With the help of a new telescope, scientists will aim to prove that we are not alone in the universe.