February 15, 2010 at 17:59The sun is simple. Part One: Research Tools
First introduce myself. I am a 4th year student at the Faculty of Computational Mathematics and Cybernetics of Nizhny Novgorod State University. From the 10th grade I began to get involved in solar astronomy. Subsequently, this hobby led me to the department of solar radio astronomy of the Nizhny Novgorod Research Radiophysical Institute. I would like to acquaint readers of the Habr 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 it readable fascinating.
The sky of the Earth in the radio range
Studies are carried out in the range of radio frequencies, since they “see” the Sun very well from the Earth, and the gamma range with receivers located in the Earth’s orbit was also used.
Jupiter image in the radio range
I think that most readers of the habr from the school course of astronomy imagine a simple telescope device, but briefly still dwell on this.
The radio telescope consists of the antenna itself and the receiver. The antenna focuses the received signals and transfers them to the receiver, from where they are already received by the processor and subsequently stored on the hard disk.
A radio telescope is characterized by a radiation pattern that is directly proportional to the wavelength and inversely proportional to the diameter of the mirror (for a parabolic telescope). In the image you can see the "side lobes" of the radiation pattern - a feature that arises due to diffraction, respectively, the telescope, in addition to its main direction, can receive radiation coming from the side and even from behind.
1. Green Bank Telescope (GBT) - the world's largest full-rotary parabolic radio telescope with a mirror size of 100x110 meters. Located in the USA.
2. Arecibo - the world's largest parabolic radio telescope, mirror diameter 306 meters, collecting area - unimaginable 73,000 sq.m. The telescope is located in a natural karst funnel in Puerto Rico. Arecibo Observatory is the US National Center for Astronomy and Ionosphere.
3. Ratan-600 - the Russian telescope located in the North Caucasus at an altitude of almost 1 km above sea level. It consists of 895 rectangular reflective elements measuring 11.4 by 2 meters, arranged in a circle with a diameter of 576 meters.
A photograph of a 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 construct images of the Sun with large spatial (~ 1 '') and time (1ms) resolution.
2. Satellites are launched into the Earth’s orbit, allowing them to study the Sun in gamma and X-ray radiation (TRACE, HESSI), as well as to obtain magnetic field maps on the surface of the Sun.
3. Radio interferometers appear (SSRT, Nobeyama, etc.). I will dwell on them in more detail.
First, let's talk about the principles of action of the interferometer.
An interferometer consists of several (from 2 to infinity) antennas that transmit data to a single processing center. It operates on the principle of interference. The interferometer allows you to replace one antenna with a large aperture, which allows you to get a high resolution. Accordingly, the increase in the number of antennas in the interferometer leads to an increase in the resolution of the resulting image. The main problem in 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 length of the base (i.e., to 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 question of signal synchronization.
Well, a few interferometers:
1. VLA (Very Large Array / Extra Large Array) - a Y-shaped interferometer 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 star research.
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, it is planned to rebuild and increase the number of antenna elements.
3. The Nobeyama 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 is measured at 17 and 34 GHz, as well as the polarization of radiation at only 17 GHz. This is our main research tool.
1. ATA (Allen Telescope Array) . The interferometer consists of 350 antennas, each of which is 6.1 m in diameter. Observation frequencies 0.5 - 11.5 GHz. The construction needs about 40 million. dollars. Currently, there is 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. A radio interferometer with extra-long bases (VLBI) is a project in the work of 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 with the help of the Radioastron radio telescope, put into orbit of the Earth.
PS This article has only a small relationship directly with the Sun, an in-depth story about it is planned further, in fact there will be more science and a little less visibility.
PPS Materials for this article are taken from open sources and from official sites.
Information wiki on the article:
1. The directivity diagram is the solid angle from which the telescope can receive data
2. The radio heliograph is a radio telescope / radio interference that studies the Sun
3. The Fourier transform is Wikipedia
4. The base is the distance between antenna elements in the interferometer
Related books:
1. S.A. Kaplan “Elementary Radio Astronomy”
2. Haye J. “Radio Universe”
Thematic Sites:
1. SSRT
2. Nobei Radio Heliograph
3. ATA
The sky of the Earth in the radio range
Studies are carried out in the range of radio frequencies, since they “see” the Sun very well from the Earth, and the gamma range with receivers located in the Earth’s orbit was also used.
Jupiter image in the radio range
Telescopes
I think that most readers of the habr from the school course of astronomy imagine a simple telescope device, but briefly still dwell on this.
The radio telescope consists of the antenna itself and the receiver. The antenna focuses the received signals and transfers them to the receiver, from where they are already received by the processor and subsequently stored on the hard disk.
A radio telescope is characterized by a radiation pattern that is directly proportional to the wavelength and inversely proportional to the diameter of the mirror (for a parabolic telescope). In the image you can see the "side lobes" of the radiation pattern - a feature that arises due to diffraction, respectively, the telescope, in addition to its main direction, can receive radiation coming from the side and even from behind.
The largest radio telescopes in the world
1. Green Bank Telescope (GBT) - the world's largest full-rotary parabolic radio telescope with a mirror size of 100x110 meters. Located in the USA.
2. Arecibo - the world's largest parabolic radio telescope, mirror diameter 306 meters, collecting area - unimaginable 73,000 sq.m. The telescope is located in a natural karst funnel in Puerto Rico. Arecibo Observatory is the US National Center for Astronomy and Ionosphere.
3. Ratan-600 - the Russian telescope located in the North Caucasus at an altitude of almost 1 km above sea level. It consists of 895 rectangular reflective elements measuring 11.4 by 2 meters, arranged in a circle with a diameter of 576 meters.
A photograph of a 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 construct images of the Sun with large spatial (~ 1 '') and time (1ms) resolution.
2. Satellites are launched into the Earth’s orbit, allowing them to study the Sun in gamma and X-ray radiation (TRACE, HESSI), as well as to obtain magnetic field maps on the surface of the Sun.
3. Radio interferometers appear (SSRT, Nobeyama, etc.). I will dwell on them in more detail.
Interferometers
First, let's talk about the principles of action of the interferometer.
An interferometer consists of several (from 2 to infinity) antennas that transmit data to a single processing center. It operates on the principle of interference. The interferometer allows you to replace one antenna with a large aperture, which allows you to get a high resolution. Accordingly, the increase in the number of antennas in the interferometer leads to an increase in the resolution of the resulting image. The main problem in 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 length of the base (i.e., to 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 question of signal synchronization.
Well, a few interferometers:
1. VLA (Very Large Array / Extra Large Array) - a Y-shaped interferometer 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 star research.
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, it is planned to rebuild and increase the number of antenna elements.
3. The Nobeyama 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 is measured at 17 and 34 GHz, as well as the polarization of radiation at only 17 GHz. This is our main research tool.
Promising projects
1. ATA (Allen Telescope Array) . The interferometer consists of 350 antennas, each of which is 6.1 m in diameter. Observation frequencies 0.5 - 11.5 GHz. The construction needs about 40 million. dollars. Currently, there is 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. A radio interferometer with extra-long bases (VLBI) is a project in the work of 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 with the help of the Radioastron radio telescope, put into orbit of the Earth.
PS This article has only a small relationship directly with the Sun, an in-depth story about it is planned further, in fact there will be more science and a little less visibility.
PPS Materials for this article are taken from open sources and from official sites.
Information wiki on the article:
1. The directivity diagram is the solid angle from which the telescope can receive data
2. The radio heliograph is a radio telescope / radio interference that studies the Sun
3. The Fourier transform is Wikipedia
4. The base is the distance between antenna elements in the interferometer
Related books:
1. S.A. Kaplan “Elementary Radio Astronomy”
2. Haye J. “Radio Universe”
Thematic Sites:
1. SSRT
2. Nobei Radio Heliograph
3. ATA