Radio source
In radio astronomy, a radio source is an astronomical object that emits noticeable radio waves. The strongest astronomical radio sources are suns, exploding stars, quasars and so-called radio galaxies.
The first radio source detected in the starry sky was the diffuse radio radiation from our Milky Way (1931/32). Its discoverer, Karl Jansky , became the founder of radio astronomy, which from 1950 developed into a rapidly growing branch of celestial science.
Causes of astronomical radio emissions
Such celestial bodies are also called radio loud referred - as opposed to radio quiet objects that are (almost) do not emit radio waves. Your radio emission can arise through the following physical mechanisms:
- Thermal radiation: Due to its own temperature, a body in the cosmos emits thermal radiation .
- Synchrotron radiation: Cosmic gas nebulae are often in the state of a plasma . If a magnetic field is present at the same time, the electrons (and also the ions) are forced to spiral around the field lines and therefore emit continuous synchrotron radiation in a tangential direction . The intensity of the radio waves decreases with frequency.
- Gas clouds: When radio sources irradiate gas clouds , radio waves of certain wavelengths are absorbed according to the spectrum of the gas and are re-emitted isotropically . In "review", i.e. H. if a radio source is behind the gas cloud, absorption lines are observed, in all other directions emission lines, see spectroscopy . Important wavelengths are:
- the hydrogen line with a wavelength of 21.1 cm (1420.40575177 MHz)
- the CO line with a wavelength of 0.260 cm (115271.2 MHz)
- the OH lines with wavelengths of 92 cm, 18.0 cm and 6.29 cm (327 MHz, 1665.402 / 1667.357 MHz and 4765 MHz)
- the H 2 O line with a wavelength of 1.35 cm (22.23508 GHz)
- Maser : A cosmic maser is an interstellar gas cloud in which an external energy source brings about an inversion of occupation between two states of the gas. Similar to a laser , radio waves passing through are amplified by stimulated emission.
Classes of radio sources
- the sun : In the sunspot minimum , the calm sun shines approximately like a black body. Certain wavelength ranges are emitted more intensely when the sun is active. In addition, protuberances can also be observed very well in the radio range. With solar radio astronomy one can observe the sun and transient events on and in it.
- Moons and planets : All planets emit blackbody radiation . In addition, one can observe planetary events, see e.g. B. Jupiter bursts .
- Supernova remnants and like Cassiopeia A and pulsars in our Milky Way and in other galaxies
- Radio galaxies and active galaxy nuclei
- Quasars (made up for quasi-stellar objects )
literature
- Peter Lay: Signals from space - simple experiments on receiving extraterrestrial radio signals. Franzis, Poing 2001. ISBN 3-7723-5925-6 .
Web links
- What is a cosmic burl? from the alpha-Centauri television series(approx. 15 minutes). First broadcast on June 22, 2003.
- The strongest radio sources in the sky Max Planck Institute for Radio Astronomy, Bonn
- Radio sky with constellations
- Radio map of the entire sky at 73cm wavelength
- Have you ever heard the Sun?
- These are the "sounds of space" collected by U Iowa instruments on various spacecraft. physics.uiowa.edu
- astronews.com: A New Class of Cosmic Radio Sources October 9, 2017
Individual evidence
- ↑ Frequency ranges of radio astronomy ( Memento of the original from June 20, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. mpg.de; Radio frequencies of the astrophysically most important spectral lines ( Memento of the original from June 15, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. craf.eu
- ↑ 1970 CO astrochymist.org
- ↑ Table 1.4. & 1.6. in: Claudio Maccone: Deep space flight and communications . Springer, Berlin 2009, ISBN 978-3-540-72942-6 , pp. 12 & 13 .;
- ↑ Detection of Water in Interstellar Regions by its Microwave Radiation , bibcode : 1969Natur.221..626C
