The sun is simple. Part One: Research Tools
I introduce myself first. I am a 4th year student of the Faculty of Computational Mathematics and Cybernetics of Nizhny Novgorod State University. From the 10th grade began to get involved in solar astronomy. Subsequently, this hobby led me to the department of solar radio astronomy of the Nizhny Novgorod Radio Physics Research Institute. I would like to acquaint Habr's readers with what we know about the Sun and how research is going. Several parts are planned, in them I will try to tell everything quite accessible and make this reading matter fascinating.
The sky of the earth in the radio band
')
Studies are conducted in the range of radio frequencies, since they very well "see" the Sun from the Earth, also used the gamma range with receivers located in Earth orbit.
The image of Jupiter in the radio
I think that most of the readers of Habr from the school course of astronomy imagine the device of a simple telescope, but briefly we’ll dwell on this.
The radio telescope consists of the antenna itself and the receiver. The antenna focuses the received signals and transmits them to the receiver, from where they already arrive at the handler and subsequently stored on the hard disk.
A radio telescope is characterized by a radiation pattern directly proportional to the wavelength and inversely proportional to the diameter of the mirror (for a parabolic telescope). On the image you can see the "side lobes" of the radiation pattern - a feature arising from diffraction, respectively, the telescope, in addition to its main direction, can receive radiation from the side and even behind.
1. Green Bank Telescope (GBT) - the world's largest full-turn parabolic radio telescope with a mirror size of 100x110 meters. Located in the USA.
2. Arecibo is the world's largest parabolic radio telescope, the mirror diameter is 306 meters, the collecting area is an unimaginable 73,000 square meters. The telescope is located in a natural karst funnel in Puerto Rico. The Arecibo Observatory is the US National Astronomy and Ionosphere Center.
3. Ratan-600 is a Russian telescope located in the North Caucasus at a height of almost 1 km above sea level. Consists of 895 rectangular reflecting elements of 11.4 by 2 meters in size, arranged in a circle with a diameter of 576 meters.
Photo of the telescope and a diagram describing the principle of its operation.
1. With the advent of new approaches to image synthesis (Fourier transform), it became possible to build images of the Sun with a large spatial (~ 1 '') and temporal (1ms) resolution.
2. Satellites are launched into Earth's orbit, allowing to investigate the Sun in gamma and X-rays (TRACE, HESSI), as well as to receive maps of the magnetic field on the surface of the Sun.
3. Radiointerferometers (SSRT, Nobeyama, etc.) appear. I will dwell on them in more detail.
First, let's talk about the principles of the interferometer.
The interferometer consists of several (from 2 to infinity) antennas that transmit data to a single processing center. Acts on the principle of interference. An interferometer allows you to replace a single antenna with a large aperture, which allows you to get a high resolution. Accordingly, an increase in the number of antennas in the interferocenter leads to an increase in the resolution of the resulting image. The main problem of creating interferometers is the synchronization of signals received from different antennas. Currently, the problem is solved mainly by laying the same length of cables.
The angular resolution of such an interferometer will be equal to the ratio of the wavelength to the base length (that is, the distance between the telescopes themselves). Accordingly, it is possible to improve the results not only by increasing the number of receivers, but also by increasing the distance between them. However, there is an acute issue of signal synchronization.
Well, a few interferometers:
1. VLA (Very Large Array / Very Large Array, Extra Large Array) - an interferometer in the shape of the letter Y, consisting of 27 antennas, each of which is 25 meters in diameter. The overall sensitivity is similar to a conventional radio telescope with a diameter of more than 36 kilometers. Currently used mainly for research stars.
2. Siberian Solar Radio Telescope (SSRT) . Cross-shaped interferometer: antenna lines 622.3 m long in the E – W and N – S directions, has 128 x 128 parabolic antenna elements, each of which is 2.5 m in diameter. Currently, restructuring and an increase in the number of antenna elements are planned.
3. Nobeyamsky radio heliograph . This interferometer receives radiation from the Sun at two frequencies: 17 GHz and 34 GHz, which corresponds to wavelengths of 17.6 mm and 8.8 mm. It consists of 84 antennas with a diameter of 80 cm each. All antennas are located from north to south and from west to east in a T-shape. The interferometer has the maximum temporal and spatial resolution today: 10 ms, 5 ”(34 GHz) and 10” (17 GHz), respectively. The radiation intensity at 17 and 34 GHz is measured, as well as the polarization of radiation only at 17 GHz. This is our main tool for research.
1. ATA (Allen Telescope Array) . The interferometer consists of 350 antennas, each of which is 6.1 m in diameter. The frequencies of observations are 0.5–11.5 GHz. The construction needs about 40 million. dollars. Currently there are a little over 30 million. The main investor is Paul Allen, a former partner of Bill Gates, who has invested more than 10 million. It is planned that with the help of this interferometer it will be possible to observe several times more stars than now.
2. Radio Interferometer with Ultra Long Baselines (VLBI) is a project in which it is planned to use several telescopes spaced around the globe and synchronized with each other. The scheme is presented below:
It is also planned to increase the base of the obtained interferometer several times using the Radioastron radio telescope, which is being put into Earth orbit.
PS This article has only a small relation directly to the Sun, an in-depth story about it is planned further, there will actually be more science and slightly less visibility there.
PPS The materials for this article are taken from open sources and from official sites.
Wiki reference for the article:
1. The radiation pattern is the solid angle from which the telescope can receive data
2. Radio heliograph - a radio telescope / radio interferometer that studies the sun
3. Fourier Transform - Wikipedia
4. Base - the distance between the antenna elements in the interferometer
Books on the subject:
1. S.A. Kaplan "Elementary radio astronomy"
2. Hey J. Radio Universe
Thematic sites:
1. SSRT
2. Nobeyamsky radio heliograph
3. ATA
The sky of the earth in the radio band
')
Studies are conducted in the range of radio frequencies, since they very well "see" the Sun from the Earth, also used the gamma range with receivers located in Earth orbit.
The image of Jupiter in the radio
Telescopes
I think that most of the readers of Habr from the school course of astronomy imagine the device of a simple telescope, but briefly we’ll dwell on this.
The radio telescope consists of the antenna itself and the receiver. The antenna focuses the received signals and transmits them to the receiver, from where they already arrive at the handler and subsequently stored on the hard disk.
A radio telescope is characterized by a radiation pattern directly proportional to the wavelength and inversely proportional to the diameter of the mirror (for a parabolic telescope). On the image you can see the "side lobes" of the radiation pattern - a feature arising from diffraction, respectively, the telescope, in addition to its main direction, can receive radiation from the side and even behind.
The largest radio telescopes of the world
1. Green Bank Telescope (GBT) - the world's largest full-turn parabolic radio telescope with a mirror size of 100x110 meters. Located in the USA.
2. Arecibo is the world's largest parabolic radio telescope, the mirror diameter is 306 meters, the collecting area is an unimaginable 73,000 square meters. The telescope is located in a natural karst funnel in Puerto Rico. The Arecibo Observatory is the US National Astronomy and Ionosphere Center.
3. Ratan-600 is a Russian telescope located in the North Caucasus at a height of almost 1 km above sea level. Consists of 895 rectangular reflecting elements of 11.4 by 2 meters in size, arranged in a circle with a diameter of 576 meters.
Photo of the telescope and a diagram describing the principle of its operation.
New research methods.
1. With the advent of new approaches to image synthesis (Fourier transform), it became possible to build images of the Sun with a large spatial (~ 1 '') and temporal (1ms) resolution.
2. Satellites are launched into Earth's orbit, allowing to investigate the Sun in gamma and X-rays (TRACE, HESSI), as well as to receive maps of the magnetic field on the surface of the Sun.
3. Radiointerferometers (SSRT, Nobeyama, etc.) appear. I will dwell on them in more detail.
Interferometers
First, let's talk about the principles of the interferometer.
The interferometer consists of several (from 2 to infinity) antennas that transmit data to a single processing center. Acts on the principle of interference. An interferometer allows you to replace a single antenna with a large aperture, which allows you to get a high resolution. Accordingly, an increase in the number of antennas in the interferocenter leads to an increase in the resolution of the resulting image. The main problem of creating interferometers is the synchronization of signals received from different antennas. Currently, the problem is solved mainly by laying the same length of cables.
The angular resolution of such an interferometer will be equal to the ratio of the wavelength to the base length (that is, the distance between the telescopes themselves). Accordingly, it is possible to improve the results not only by increasing the number of receivers, but also by increasing the distance between them. However, there is an acute issue of signal synchronization.
Well, a few interferometers:
1. VLA (Very Large Array / Very Large Array, Extra Large Array) - an interferometer in the shape of the letter Y, consisting of 27 antennas, each of which is 25 meters in diameter. The overall sensitivity is similar to a conventional radio telescope with a diameter of more than 36 kilometers. Currently used mainly for research stars.
2. Siberian Solar Radio Telescope (SSRT) . Cross-shaped interferometer: antenna lines 622.3 m long in the E – W and N – S directions, has 128 x 128 parabolic antenna elements, each of which is 2.5 m in diameter. Currently, restructuring and an increase in the number of antenna elements are planned.
3. Nobeyamsky radio heliograph . This interferometer receives radiation from the Sun at two frequencies: 17 GHz and 34 GHz, which corresponds to wavelengths of 17.6 mm and 8.8 mm. It consists of 84 antennas with a diameter of 80 cm each. All antennas are located from north to south and from west to east in a T-shape. The interferometer has the maximum temporal and spatial resolution today: 10 ms, 5 ”(34 GHz) and 10” (17 GHz), respectively. The radiation intensity at 17 and 34 GHz is measured, as well as the polarization of radiation only at 17 GHz. This is our main tool for research.
Perspective projects
1. ATA (Allen Telescope Array) . The interferometer consists of 350 antennas, each of which is 6.1 m in diameter. The frequencies of observations are 0.5–11.5 GHz. The construction needs about 40 million. dollars. Currently there are a little over 30 million. The main investor is Paul Allen, a former partner of Bill Gates, who has invested more than 10 million. It is planned that with the help of this interferometer it will be possible to observe several times more stars than now.
2. Radio Interferometer with Ultra Long Baselines (VLBI) is a project in which it is planned to use several telescopes spaced around the globe and synchronized with each other. The scheme is presented below:
It is also planned to increase the base of the obtained interferometer several times using the Radioastron radio telescope, which is being put into Earth orbit.
PS This article has only a small relation directly to the Sun, an in-depth story about it is planned further, there will actually be more science and slightly less visibility there.
PPS The materials for this article are taken from open sources and from official sites.
Wiki reference for the article:
1. The radiation pattern is the solid angle from which the telescope can receive data
2. Radio heliograph - a radio telescope / radio interferometer that studies the sun
3. Fourier Transform - Wikipedia
4. Base - the distance between the antenna elements in the interferometer
Books on the subject:
1. S.A. Kaplan "Elementary radio astronomy"
2. Hey J. Radio Universe
Thematic sites:
1. SSRT
2. Nobeyamsky radio heliograph
3. ATA
Source: https://habr.com/ru/post/84318/
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