We live on a small planet near a small star in a giant galaxy, which nevertheless itself is lost in the incredible vastness of the Universe. Almost everything that is in space is very far from us, and some objects are separated from us by an unimaginable distance.
But we are very curious and want to know what surrounds us. We are lucky - the universe is not silent. All processes occurring in space are accompanied by phenomena, the consequences of which in various forms, and primarily in the form of electromagnetic waves, reach us. By capturing them, we get to know the essence of the events taking place in the Universe, learn new things about the worlds into which we will never be able to get. And tools that are simply called telescopes help us in this.
Today we will tell you about some of them that seemed interesting to us, and those that you may not know. And on their example, we will show how telescopes of different types differ from each other. You will also learn about the goals scientists set for them.
Since ancient times, people have been watching the sky. Even before the advent of telescopes, the first stellar maps were compiled, all fixed stars were combined into constellations, and those that changed their position relative to other stars were marked as "wandering" - this is how the ancient astronomers discovered the planets.
The first planet discovered with a telescope was Uranus. It was discovered by the English astronomer William Herschel in 1781. Although the planet is sometimes visible to the naked eye, earlier observers mistook it for a dim star. But Herschel was not the first to point the telescope into the sky. For the first time, the Italian astronomer Galileo Galilei used a telescope to observe space objects at the beginning of the 17th century. The discovery of the four moons of Jupiter in 1610 was one of the most important events of that time.
Since then, astronomy has changed. The Milky Way has disintegrated into separate stars. A huge number of new stars were discovered in the sky. There are mountains and craters on the moon, and spots on the sun. And all this thanks to an optical telescope, or an optical telescope. But more precisely, the telescope in the visible range, since for most of the history of astronomy, only visible light was observed with these devices. Detection of waves in the infrared and ultraviolet ranges was not yet available at that time.
In such telescopes, a magnified image of a celestial body is observed with the eye, our natural detector of electromagnetic waves, or photographed. We still use optical telescopes everywhere.
One of the largest telescopes on the planet is the Very Large Telescope. Its name is translated as “Very large telescope”. Indeed, this is not even one telescope, but a whole complex of four main and the same number of auxiliary ones. These telescopes are located in the Paranal Observatory - one of the most famous astronomical observatories in the world. It was built at the very end of the last century and is operated by the European Southern Observatory (ESO). Despite the fact that the observatory is European, it is located in South America - in Chile. Here, at the top of Cerro Paranal, in the Atacama Desert, there are excellent conditions for observing the sky, a high transparency of the atmosphere and a large number of clear days.
Very large telescope
In addition to the VLT “family”, there are also survey telescopes VISTA and VLT Survey Telescope. And nearby, on Mount Armasones, construction of the European Extremely Large Telescope (EELT) began in 2017. The diameter of its segmented mirror will be 39.3 meters.
The first of the four main VLT telescopes entered service in 1998, and became the world's largest monolithic mirror in diameter, ahead of the Russian BTA (Large Azimuth Telescope) telescope located in the village of Nizhny Arkhyz. The diameter of the mirror of the largest Russian telescope and the largest in Eurasia is 6 m.
The remaining three telescopes were completed by 2000. They all have the same mirrors with a diameter of 8, 2 meters. In January 2012, for the first time, it was possible to combine them into an interferometer mode - the so-called VLTI. This made it possible to obtain a telescope equivalent in area to a telescope with a single mirror 16.4 m in diameter.
Four more auxiliary telescopes have mirror diameters of 1.8 meters. They can travel on rails around major telescopes and are designed for interferometric observations. VLT allows observation in a wide range of electromagnetic waves: both in the visible range and near ultraviolet, as well as in the near and middle infrared. In some respects, the Very Large Telescope even surpasses the Hubble - perhaps one of the most famous telescopes of our time.
The Hubble Telescope is a joint US-European project. It is the first of four NASA Large Space Observatories, each dedicated to space exploration in its own region of the electromagnetic spectrum. Hubble "sees" the sky in ultraviolet, visible and near infrared spectra.
It was launched into low-earth orbit (569 km) in 1990 by the Discovery shuttle. In 27 years of operation, NASA astronauts visited the observatory five times for maintenance. Actually, the Hubble has already arrived in orbit with a defect in the main mirror. It was only during the first maintenance mission, in 1993, that the COSTAR spherical aberration correction system was installed on the telescope to correct the lack of a mirror. For this, the previously installed high-speed photometer had to be sacrificed. The diameter of the main mirror of the Hubble is 2.4 m, the focal length of the telescope is 57.6 m. The telescope itself is a reflector of the Ritchie-Chretien system.
Our country is not yet building giant telescopes and launching optical observatories into space. Russia today is taking a slightly different path. Since the beginning of 2002, Lomonosov Moscow State University has been developing a global network of robotic telescopes MASTER (Mobile Astronomical System of Robotic Telescopes). Eight telescopes of this network are already operating in Russia, Argentina, South Africa and Spain (on the Canary Islands). Their tasks include a continuous survey of the sky in automatic mode. They reveal new objects, many of which are then observed in more detail in other astronomical observatories in the world.
Each observatory is equipped with powerful data processing servers and special software. All actions, from opening the dome, which is carried out by cloud sensors, and up to processing the received information, are carried out in automatic mode. The robots themselves determine the direction of the sky survey. Information is transmitted via the Network to the MSU data center.
Global space monitoring network MASTER MSU
The telescopes are equipped with ultra-fast pointing devices and are connected to an alert system. They can turn in a few tens of seconds to a given point in the sky after receiving target designation (alert).
The network, scattered across different continents, consists of small double telescopes-robots of the Hamilton system with a mirror diameter of 0.4 meters, a focal length of 1 meter and a field of view of 4 square degrees. The global MASTER network is the leader in early observations of optical emission of gamma-ray bursts. Among her discoveries are potentially dangerous asteroids, comets and supernovae of various types.
More than two hundred years have passed since the moment when the English astronomer William Herschel in 1800 discovered radiation invisible to the eye, which he called calorific, that is, thermal (later renamed infrared). Having decomposed sunlight into a spectrum, Herschel found that the zone illuminated by violet light was the least heated in the rainbow, and most of all - red. But the dark area near the red area warmed up even more.
However, truly infrared astronomy began to develop in the 50s of the last century, when, after the first advances in radio astronomy, scientists realized that there is a large amount of information outside the visible wavelength range.
But observations from the Earth in the infrared range have a number of difficulties. The atmosphere of the planet is not conducive to high-quality reception of infrared radiation. Nitrogen and oxygen dissipate it, and carbon dioxide, ozone and, first of all, water vapor absorb it. Therefore, infrared observatories are located in high-altitude regions, or they are lifted into the stratosphere and into orbit.
The most powerful infrared observation telescope in the world, located at an altitude of 2518 m above sea level, is located in the Chilean Atacama Desert in the Paranal Observatory, which we already know. This telescope is VISTA (Visible and Infrared Survey Telescope for Astronomy). It works in the near infrared region of the spectrum.
Vista InfraRed CAMera
Its main mirror has a diameter of 4.1 meters. And it was made in Russia, in the Moscow region, at the Lytkarinsky optical glass plant. It took 2 years to polish it. The focal length of the telescope is 12.1 m, the angular resolution is 0.34 arc seconds.
The telescope has only one detector instrument - VIRCAM (Vista InfraRed CAMera), a three-ton camera containing 16 special detectors sensitive to infrared light, with a total resolution of 67 million pixels. This telescope, like the VLT, is operated by the European Southern Observatory. Its head office is located away from telescopes, in the small German scientific town of Garching, 16 kilometers north of Munich.
The telescope was commissioned in December 2009. Its purpose is the systematic mapping of the southern hemisphere of the sky. VISTA generates 300 gigabytes of information every night. Its main task is to search for interesting objects for their further, more detailed study with the help of other telescopes. For example, using the adjacent VLT.
Water vapor in the atmosphere absorbs most of the infrared waves as they travel to the Earth's surface. To see the sky not only in the near-infrared range, you need to go higher. In the 50s and 70s of the last century in the USA, for such observations, they used the Stratoscope-1 and Stratoscope-2 telescopes placed on balloons and controlled by radio. Rising to a height of 24 kilometers, they made it possible to study the infrared spectrum of planets and stars. Now such telescopes are placed on airplanes.
The American Stratospheric Observatory SOFIA (Stratospheric Observatory for Infrared Astronomy) is located aboard a Boeing 747SP wide-body aircraft. Flights take place at altitudes of 12-14 km. About 85% of the entire infrared spectrum is already available here. This makes it possible to bring the quality of the resulting "picture" closer to the level of space observatories. The reflector telescope is located at the rear of the aircraft fuselage. Its main mirror has an effective diameter of 2.5 meters. Scientists have at their disposal seven scientific instruments, which include cameras, spectrometers and photometers operating in the near, middle and far infrared ranges. Some of them are designed to observe specific phenomena, others - for a wide range of tasks. The project is a partnership between NASA and the German Aerospace Center (DLR). The aerial observatory is based at the Armstrong Research Center in Palmdale, California (USA). The SOFIA telescope saw its first light on May 26, 2010.
American Stratospheric Observatory SOFIA
The undoubted advantage of the aerial observatory is that the plane can fly to almost any point on the planet, thereby making it possible to conduct observations in both the northern and southern hemispheres of the sky. The most recent observation of this aircraft was the Kuiper belt asteroid 2014 MU69. As you know, this is a new target chosen by NASA for research by the New Horizons spacecraft. The probe is due to fly past it on January 1, 2019. Therefore, the agency set out to check the vicinity of the asteroid in order to make the flight of the probe past the object more safe. This year turned out to be an opportunity. A possible candidate for dwarf planets must traverse the disk of a distant star. Observations have shown that 2014 MU69 is most likely a unique double object, and not a single one, as previously assumed. In order to observe this phenomenon, SOFIA went to the skies over the Pacific Ocean.
Even higher, already in orbit, and by no means near-Earth, but heliocentric, the Herschel telescope has fruitfully worked its 4 years. It became the first space observatory to fully study infrared radiation in orbit. And, in addition, the largest infrared observatory to date, taking the palm from the fourth NASA Large Observatory - the Spitzer telescope with a mirror diameter of 0.85 meters and a focal length of 10.2 meters.
Similar parameters of "Herschel" are much larger. His mirror, "glued" of 12 elements, has a diameter of 3.5 meters. The focal length of the telescope is 28.5 meters. It also outperforms its predecessor in the width of the available spectrum, its wavelength range is from 60 to 670 µm versus 3–180 µm for Spitzer.
Herschel officially completed its scientific mission in June 2013. During four years of operation, the space observatory was located 1.5 million kilometers from our planet, near the second Lagrange point (L2) of the Earth-Sun system.
The observatory carries three scientific instruments: a camera with a low-resolution spectrometer (PACS), a spectral and photometric image receiver (SPIRE) and a heterodyne sensor for detecting far infrared radiation (HIFI).
The goal of the Herschel telescope was to study the infrared part of the radiation from objects in the solar system and the Milky Way, as well as objects outside our Galaxy, up to those that are billions of light years away.
The James Webb Space Telescope is expected to be launched into orbit next October. It is considered a replacement for the Hubble telescope, but unlike it, Webb is primarily an infrared space observatory. The diameter of the main mirror of the new observatory is 6.5 meters. This is the smallest mirror size that allows you to see light from the most distant galaxies.
James Webb Space Telescope
As you know, excess ultraviolet radiation is harmful to living organisms. Ultraviolet lamps are used to disinfect water, air and various surfaces. But the earth's atmosphere also protects us from cosmic ultraviolet radiation. And it also prevents astronomers from observing in this range. All this is primarily due to the ozone layer located at altitudes of 20–70 km. Therefore, observations in the ultraviolet range have to be carried out from the upper atmosphere or from space.
Ultraviolet radiation beyond the violet edge of the rainbow was discovered by the German physicist Johann Ritter in 1801. And the history of ultraviolet astronomy began in 1947. In the United States, the first observations were made using captured German FAU-2 missiles. Research continued using high-altitude geophysical rockets.
Since the end of the 60s, specialized artificial earth satellites have been used. In 1972, the United States launched the Copernicus Space Observatory (OJSC-3), and in 1983, the domestic Astron flew with an 80-centimeter ultraviolet telescope on board. Devices for shooting and studying objects in the ultraviolet range are also installed on the Hubble telescope. Thanks to the latter, it was possible for the first time to observe ultraviolet auroras on Saturn, Jupiter and its moon Ganymede. A small far ultraviolet telescope (Far Ultraviolet Camera / Spectrograph, UVC) was also taken to the moon by NASA astronauts.
Astron Astrophysical Observatory
The Swift spacecraft is one of the modern observatories on which an ultraviolet telescope UVOT (UltraViolet / Optical Telescope) is installed, designed for observations in the wavelength range from 170 to 650 nm and having a mirror diameter of 0.3 m. This is standard for space observatories of this type telescope of the Ritchie – Chretien system.
However, the Swift orbital observatory, launched into space in 2004, has a special purpose. Equipped with three scientific instruments, the multiwavelength space observatory is designed to study gamma-ray bursts. UVOT is only one of its three tools needed to detect the optical (ultraviolet) afterglow of gamma-ray bursts.
Cosmic gamma-ray bursts are large-scale short-term bursts of energy that are observed in distant galaxies. The initial gamma burst is usually followed by a long-lived "afterglow" emitted at longer wavelengths, including UV. Most of the observed GRBs are emitted during supernova explosions. Thanks to Swift tools, it was possible for the first time to observe such a flash from the very beginning. The supernova SN 2008D, which erupted on February 9, 2008, is located about 88 million light years away in the galaxy NGC 2770 (the Lynx constellation).
One of the most successful projects in the field of ultraviolet astronomy was the orbiting ultraviolet space telescope GALEX (Galaxy Evolution Explorer), launched into orbit in 2003 from the L-1011 Stargazer spaceport aircraft using a Pegasus-XL launch vehicle.
Initially, it was assumed that the observatory will operate in orbit for two and a half years, but in fact the mission stretched out for nine years. The spacecraft was in a near-earth orbit with an altitude of 697 km. A Ritchie-Chretien telescope with a mirror diameter of 0.5 meters and a focal length of 3 meters was installed on board. The telescope's field of view is 1.2 degrees.
One of the most surprising discoveries of the GALEX telescope is a gigantic tail of dust and gas discovered near the star Mira in the constellation Cetus. This double star, located at a distance of 417 sv. years, the attention of astronomers attracted as early as 1596, but until 2007 it was never observed in the ultraviolet range. The comet-like tail is 13 light-years long, three times the distance from the Sun to the nearest star, Proxima Centauri.
The Star of the World in the constellation Cetus, image from the GALEX telescope
X-ray sources - quasars, neutron stars, black holes - are also inaccessible for observation from Earth. The latter do not emit X-rays themselves, but force the material that falls into them to emit. The closest to us bright source of cosmic X-ray radiation is the Sun.
And since the Earth's atmosphere is opaque for X-rays, for the first observations in this range, X-ray detectors were placed on high-altitude rockets and balloons. Then it was possible to find out that the Sun is also a source of X-ray radiation. True, it emits only one millionth of its energy in the X-ray range.
The first spacecraft with an X-ray detector on board was the Uhuru satellite, launched by the United States in 1970. The unusual name is due to the fact that the launch was carried out on December 12, on the 7th anniversary of Kenya's independence. And the Italian sea space center "San Marco", from which the satellite was sent into orbit, was located off the coast of this country. In Swahili, the official language of Kenya, the satellite's name means "freedom." Its design name is the X-Ray Explorer spacecraft. But as soon as it was in orbit, it was immediately renamed.
The work of the satellite has resulted in a whole series of fundamental discoveries in astrophysics. Thanks to the observatory, X-ray pulsars, sources of variable X-rays, have been discovered. For the first time, they compiled a map of the entire sky in the X-ray range. The catalog created based on the results of Uhuru's work includes 339 X-ray sources.
But Uhuru is hardly a telescope. The spacecraft did not have an optical system designed to collect and focus radiation passing through the aperture. Here you need to understand that X-ray quanta have very high energy. This means that they practically do not refract in matter and are almost always absorbed by it. It is very difficult to create an X-ray mirror, especially lenses.
The Chandra Space Observatory is one of the most famous X-ray telescopes. The third of the four NASA Large Observatories. Together with the IUS upper stage, the observatory was launched into orbit in the cargo hold of the Columbia shuttle in 1999.
Space Observatory "Chandra"
The telescope is one of the most distant satellites of the Earth. The upper stage lifted the observatory into a highly elliptical orbit with an apogee of 134,527.6 km and a perigee of 14,307.9 km. Such an orbit allows continuous observations for 55 hours out of the 65-hour period of the spacecraft's orbit. At the apogee, the orbit goes beyond the orbits of geostationary satellites and radiation belts. The observatory was named in honor of the American scientist of Indian origin Subrahmanyan Chandrasekhar, one of the greatest astrophysicists of the 20th century.
Conventional mirrors, and even more so lenses, are not suitable for X-ray astronomy. Therefore, in X-ray telescopes, optical systems are used that use only oblique incidence mirrors. In them, the X-ray beam "slides" along the surface of the mirror (Voltaire's system). The maximum diameter of the Chandra multilayer X-ray mirror is 1.2 m. The angular resolution is 0.5 arc seconds. The focal length is 10 meters.
The X-ray instrument is also installed aboard the Swift space observatory. XRT (X-ray Telescope) is used to measure the flux, spectrum and luminosity curves of gamma-ray bursts, as well as their persistence in a wide dynamic range. Its diameter is 0.51 meters, and the focal length is 3.5 meters. Like the Chandra telescope, XRT is a Voltaire telescope.
Gamma radiation is adjacent to X-rays, but gamma rays have even more energy. It is the most energetic form of electromagnetic radiation with photon energies above 100 keV. Radiation below 100 keV is considered X-ray and is the subject of X-ray astronomy. Emission of gamma rays requires colossal energy, therefore, as in X-ray astronomy, rather “exotic” objects become objects of study: pulsars, supernova remnants, active galactic nuclei, etc.
Most of the gamma rays emanating from space are absorbed by the earth's atmosphere, so gamma astronomy could not develop until it was possible to raise gamma detectors over all or at least most of the atmosphere using balloons and spacecraft.
The Compton Space Observatory was launched into orbit by the Atlantis shuttle on April 5, 1991 and operated until June 4, 2000. After that, the satellite was de-orbited in a controlled manner, and its remnants, which had not been burnt in the atmosphere, fell into the Pacific Ocean.
Space Observatory "Compton"
Unlike the Chandra observatory, Compton, in order to avoid the influence of radiation belts, was placed in a near-earth orbit with an altitude of 450 km. That is, under the belts. The Compton Observatory was also part of the Grand Observatory series, the second after the Hubble Space Telescope. Named after Arthur Holly Compton, American scientist, Nobel Prize winner in physics for his work related to the physics of gamma radiation.
The four main instruments of the observatory covered together the energy range from 20 keV to 30 GeV.
Among the most significant results of the Compton mission is the compilation of a high-quality map of the sky in gamma rays with energies above 100 MeV. During its operation, the telescope has registered more than 3000 gamma-ray bursts. Found short gamma-ray bursts from thunderclouds in the earth's atmosphere.
The Fermi gamma-ray space telescope is considered one of the successors to Compton. The observatory was launched into orbit on June 11, 2008 aboard a Delta II 7920-H rocket. This is a joint project of the USA, France, Germany, Italy, Japan and Sweden. The satellite's orbital altitude is 550 km. Until August 26, 2008, the device was called GLAST (Gamma-ray Large Area Space Telescope) and was renamed in honor of the Italian physicist Enrico Fermi, pioneer of high energy physics, Nobel Prize laureate in physics in 1938 and one of the "fathers" of the atomic bomb.
Its main instrument is the Large Area Telescope (LAT), a gamma-ray telescope designed for observations in the energy range from several tens of MeV to hundreds of GeV. In his field of view is about one fifth of the sky. Another instrument, Fermi GBM, is a gamma-ray burst recording instrument that it can detect throughout the sky, with the exception of the part that our planet has hidden from it.
One of the most interesting discoveries made by the telescope was the discovery in 2010 of Fermi bubbles - giant formations extending in both directions from the plane of the Milky Way disk for a distance of about 25 thousand light years in each direction. Both bubbles are a source of high-energy radiation.
Another significant discovery came shortly after the first detection of gravitational waves by the LIGO observatory. Astrophysicists working with the Fermi telescope said they were able to roughly identify the area of the sky where there were two black holes, the merger of which has generated recently found gravitational waves. The Fermi GBM detector recorded a high energy burst coinciding with the time of the gravitational wave registration. The approximate area covers the constellations Cetus and Pisces.
An instrument for gamma astronomy is also installed aboard the Swift Observatory. The BAT (Burst Alert Telescope) gamma-ray burst monitor is its third instrument and is designed to detect and determine the coordinates of gamma-ray bursts. It operates in the 15–150 keV range.
Almost all space objects are objects of study of radio astronomy. For the first time, radio waves of astronomical origin were discovered by the American physicist and radio engineer Karl Jansky in 1932. Studying atmospheric radio interference in the meter wavelength range, the scientist recorded constant radio noise of unknown origin. The noise correlated with sidereal days, and therefore, its source was unambiguously in space. The "stellar noise" had the greatest intensity when the radio antenna was directed towards the central part of our Galaxy. Since that time, many radio telescopes, both large and small, have appeared on Earth and in space.
In 2016, China completed the construction of the telescope, which is called the largest radio telescope in the world. FAST (Five hundred meter Aperture Spherical Telescope), as the name suggests, has a reflective surface (reflector) of 500 meters in diameter. It is only worth noting that radio telescopes are different. The Russian RATAN-600, located in Karachay-Cherkessia, near the village of Zelenchukskaya, has a diameter of 576 m. But, unlike its Chinese counterpart, it is a radio telescope with an empty aperture. Simply put, its antenna is a ring. RATAN-600 is the largest ring radio telescope with a variable profile antenna. It was commissioned back in 1974.
The gathering area of the FAST telescope is 70,000 m2, and the focal length is 140 m. It took the palm among the filled aperture radio telescopes from the American radio telescope installed in Arecibo (diameter 304, 8 m). FAST is located in the south of China in Guizhou province. It was built in a natural depression. And during its construction, about 9,000 people had to be resettled from the surrounding areas.
The operating frequency range of the radio telescope is from 70 MHz to 3.0 GHz, which corresponds to electromagnetic radiation with a wavelength of 0.1 to –4.3 m. and the evolution of galaxies and solve many other scientific problems.
Currently still under construction, the SKA (Square Kilometer Array) radio telescope is one of the most ambitious projects in radio astronomy of this century. The name can be translated as “square kilometer of collecting surface”. But this, of course, does not mean that it will have a mirror of such an area and will be ahead of FAST in this regard. No, this telescope will be designed differently.
SKA radio telescope
SKA is an interferometer, that is, it will consist of several radio telescopes located at a distance from each other. More precisely, from thousands of small radio telescopes-antennas located at a distance from tens of meters to thousands of kilometers. Moreover, this one of the world's largest radio interferometers will be located on two continents at once: in Africa (South Africa) and Australia. At the same time, the Australian part will be partially located in neighboring New Zealand. The headquarters of the project is based at the Jodrell Bank Observatory in the UK. The choice of the Southern Hemisphere and, in particular, the indicated countries for the placement of the telescope antennas is not accidental, since it is in this part of the planet that the best view of the Galaxy is provided, and the level of radio interference is less.
Initial observations are planned for 2020, and completion of construction by 2030. SKA will allow continuous observations from 50 MHz to 30 GHz. To provide such a wide range of received radio frequencies, various types of antenna elements are used in the telescope. Its sensitivity is expected to be more than 50 times that of any other radio telescope in existence today.
SKA capabilities will be designed to address a wide range of issues in astrophysics, cosmology and particle astrophysics. The telescope will expand the range of the observable universe. With its help, it is assumed, it will be possible to look into its early past and obtain data about it at the age of only a few million years after the Big Bang, that is, at the moment when the first stars and galaxies had just begun to form.
There are also radio telescopes in orbit. The world's first space radio telescope was installed in July 1978 at the Soviet orbital station Salyut-6. It was "KRT-10" (Space Radio Telescope with antenna mirror 10 meters in diameter). It was delivered to the station by the Progress-7 cargo spacecraft and worked for two months.
Today, its actual successor, the Spektr-R space observatory, also known as Radioastron, is in orbit. The spacecraft was launched into low-earth orbit on July 18, 2011 by the Zenit rocket. It orbits in an elliptical orbit with a perigee of 10 651.6 km and an apogee of 338 541.5 km. At its apogee, it practically reaches the orbit of the Moon and uses its gravity to rotate the plane of its orbit.
Space Observatory "Spectrum-R"
The diameter of the Spectra-R antenna is 10 meters, the focal length is 4.22 m. As for the resolution, the Radioastron project allows obtaining the highest angular resolution in the entire history of the Universe observations. A very high angular resolution is achieved when an orbiting radio telescope is used in conjunction with ground-based and interferometric methods. These almost 340,000 kilometers are the maximum diameter of the conventional "dish" of the radio telescope, or, as scientists say, the base. Extra long base. Many of the planet's largest radio telescopes are already working in tandem with the Russian space observatory. The main scientific task of the project is to study astronomical objects with an angular resolution of up to several millionths of a second. There are four frequency ranges available for astronomical observations: 92 cm, 18 cm, 6, 2 cm and 1, 19–1, 63 cm.
The telescope is intended for radioastrophysical observations of extragalactic objects with ultra-high resolution, as well as for studying the characteristics of near-Earth and interplanetary plasmas.
It is possible to obtain information about the processes occurring in the Universe by registering not only electromagnetic waves. There is one more way. Fluxes of neutrinos pass through the entire Universe without encountering practically any obstacles on their way. Neutrino is a subatomic particle, it is electrically neutral, and its mass is so small that only recently it was possible to establish that the particle does exist. Neutrino fluxes are born in the course of nuclear reactions and carry unique information about physical processes in the interiors of stars. Neutrino interacts extremely weakly with matter and is very difficult to detect. But nevertheless it succeeds.
Located at the South Pole, IceCube is the largest neutrino observatory in the world. It is located at the American Antarctic station Amundsen-Scott. IceCube is a giant neutrino detector placed deep beneath the surface. Deep holes were made in the thickness of the Antarctic ice, where vertical garlands of strong cables with optical detectors (photomultipliers) fixed to them were lowered to a depth of 1450 to 2450 meters. Each such garland consists of 60 detectors.
Thousands of sensors are spread over one cubic kilometer of clear Antarctic ice. And ice plays a primary role in detecting neutrinos.
A particle that practically does not interact with matter can be detected only by trapping muons - secondary particles that are born when neutrinos collide with oxygen atoms in a water molecule (in this case, frozen water). In turn, muons, moving in a sufficiently dense medium, give rise to photons of visible Cherenkov radiation - flashes of blue light. It is in the thickness of the transparent Arctic ice that IceCube optical detectors register them. Despite the fact that IceCube is located at the South Pole, its task is to register astrophysical neutrinos that came through the Earth from the northern hemisphere of the sky.
And although it is believed that neutrino astronomy is only at the beginning of its journey, it cannot be said that no one has previously done such research. The name of the world's oldest neutrino observatory is the Baksan neutrino observatory located in Kabardino-Balkaria under the slope of Mount Andyrchi. It has been operating since the 1970s and is under the jurisdiction of the Russian Academy of Sciences. But here, instead of water and ice, about 50 tons of molten metallic gallium, which is located in 7 chemical reactors, is used as a target.
The presence of a large observatory in the Southern Hemisphere required the creation of a neutrino observatory of similar power in the Northern Hemisphere. This will allow the observation of high-energy neutrino sources throughout the entire celestial sphere. And such an observatory will be built in our country. And the most suitable place for this is Lake Baikal, known for its clear water and depth.
Since 2015, the Dubna deep-sea multi-megaton-scale neutrino telescope has already started operating at the bottom of Lake Baikal. It is the first cluster of the Baikal-GVD (Gigaton Volume Detector) cubic-kilometer-scale neutrino telescope under construction.
"Dubna" contains 192 optical sensors immersed in the transparent water of Lake Baikal to a depth of 1300 meters. Today this telescope is already one of the three largest neutrino detectors on the planet. The next step in the development of the project will be a gradual increase in the volume of the telescope by adding new clusters. As a result, by 2020 it is planned to create an installation consisting of 10-12 clusters with a total volume of about 0.5 cubic meters. km.
Gravitational Wave Observatories
At the beginning of this summer, the international collaboration LIGO-Virgo again announced the registration of a gravitational wave burst. And this is the third time in history when we manage to catch such a signal. It originated about three billion years ago as a result of the approach in a spiral and the subsequent merger of two black holes, about 19 and 31 solar masses. They merged into one large black hole, losing about two solar masses in the process. Such a merger is an explosion of immense power. But only all its energy goes not into electromagnetic radiation, not into particles, but into oscillations of space and time - gravitational waves. The merger process took less than a second, and at the time of the merger, the speed of black holes reached 60% of the speed of light.
Gravitational wave astronomy is a growing branch of observational astronomy. And at the moment we have only two laboratories in the world designed to detect gravitational waves.
The American project LIGO (Laser Interferometer Gravitational-Wave Observatory) includes two identical detectors. One is in the southeastern United States in Livingston, Louisiana, and the other is in the northwest in Hanford, Washington. The distance between the detectors is 3002 kilometers. Because of this, two detectors register the signal with a small interval. And this allows you to determine the approximate direction where this signal came from.
LIGO detector (Livingston)
Each unit is an L-shaped system, consisting of two four-kilometer high vacuum hoses inside. A modified Michelson interferometer is installed inside such a system.
There is another reason why it is important to have two detectors. Only if the signal is registered by all detectors will it be considered that it really was, and the visible burst on the monitor is not an error of the devices. But when the Franco-Italian Virgo detector finally goes into operation, then there will be even less reason to doubt, and the detection accuracy will noticeably increase.
The Virgo detector is located at the European Gravity Observatory (EGO) in the commune of Cashina near the Italian city of Pisa. It is slightly smaller than the LIGO detectors: each of its arms is 3 kilometers long.
Virgo is sensitive to gravitational waves over a wide frequency range from 10 to 10,000 Hz. This should make it possible to detect gravitational waves caused by the merger of binary systems (stars, black holes, pulsars), as well as waves that accompany supernova explosions. Moreover, both in the Milky Way and in other galaxies, for example, in the galaxies of the nearest Virgo cluster. Hence the name of the project.
Gravitational wave astronomy is just at the beginning. Several more similar observatories will appear on the planet soon. One of them is already under construction in Japan (KAGRA), and India is planning to launch the LIGO-India detector by 2022.
And, naturally, sooner or later gravitational-wave instruments will appear in space. On July 18 this year, the LISA Pathfinder satellite mission ended. Launched by ESA in 2015, the spacecraft tested the technologies needed to build the Evolved Laser Interferometer Space Antenna (eLISA) gravitational-wave observatory. Its European Space Agency plans to launch it by 2034.
The project involves sending three spacecraft into space, which will be located at the tops of an equilateral triangle with sides of 2.5 million kilometers each. Like ground-based gravitational-wave observatories, eLISA uses laser interferometry. Its three satellites form a giant Michelson interferometer, in which two dependent satellites act as reflectors, and one, the main satellite, acts as a source of a laser beam and a detector. As the gravitational wave travels through the interferometer, the lengths of the two eLISA arms change due to space-time distortion.
Astronomy is constantly evolving. Several decades later, today's telescopes will be complemented by even more sophisticated observation instruments.
Astronomy has already gone through several revolutions during its existence. At the beginning of the 17th century, thanks to Galileo, a man first looked at the sky with an armed eye. In the last century, the "optical monopoly" was eliminated, and astronomy became universal - the sky "lit up" in the entire spectrum of electromagnetic radiation. Today we are on the cusp of a new revolution involving neutrinos and gravitational waves. And this breakthrough will not be the last.
The future of astronomy promises to be interesting. We will find answers to many riddles of the Universe and, like good students, we will receive a portion of new ones from it. And we will already look for answers with the help of new telescopes, the principle of operation of which we today, perhaps, cannot even imagine.