Portal:Jupiter/Radiation astronomy/7
Radios edit
In 1955, Bernard Burke and Kenneth Franklin detected bursts of radio signals coming from Jupiter at 22.2 MHz.[1] The period of these bursts matched the rotation of the planet, and they were also able to use this information to refine the rotation rate. Radio bursts from Jupiter were found to come in two forms: long bursts (or L-bursts) lasting up to several seconds, and short bursts (or S-bursts) that had a duration of less than a hundredth of a second.[2]
Forms of decametric radio signals from Jupiter:
- bursts (with a wavelength of tens of meters) vary with the rotation of Jupiter, and are influenced by interaction of Io with Jupiter's magnetic field.[3]
- emission (with wavelengths measured in centimeters) was first observed by Frank Drake and Hein Hvatum in 1959.[1] The origin of this signal was from a torus-shaped belt around Jupiter's equator. This signal is caused by cyclotron radiation from electrons that are accelerated in Jupiter's magnetic field.[4]
Between September and November 23, 1963, Jupiter is detected by radar astronomy.[5]
"The dense atmosphere makes a penetration to a hard surface (if indeed one exists at all) very unlikely. In fact, the JPL results imply a correlation of the echo with Jupiter ... which corresponds to the upper (visible) atmosphere. ... Further observations will be needed to clarify the current uncertainties surrounding radar observations of Jupiter."[5]
"Although in 1963 some claimed to have detected echoes from Jupiter, these were quite weak and have not been verified by later experiments."[6]
"A search for radar echoes from Jupiter at 430 MHz during the oppositions of 1964 and 1965 failed to yield positive results, despite a sensitivity several orders of magnitude better than employed by other groups in earlier (1963) attempts at higher frequencies. ... [I]t might be suspected that meteorological disturbances of a random nature were involved, and that the echoes might be returned only in exceptional circumstances. Further support for this point of view may be gleaned from the fact that JPL found positive results for only 1 (centered at 32° System I longitude) of the 8 longitude regions investigated in 1963 (Goldstein 1964) and, in fact, had no success during their observations in 1964 (see comment by Goldstein following Dyce 1965)."[7]
"This VLA image of Jupiter [at right] doesn't look like a planetary disk at all. Most of the radio emission is synchrotron radiation from electrons in Jupiter's magnetic field."[8]
References edit
- ↑ 1.0 1.1 Linda T. Elkins-Tanton (2006). Jupiter and Saturn. New York: Chelsea House. ISBN 0-8160-5196-8.
- ↑ Weintraub, Rachel A. (26 September 2005). How One Night in a Field Changed Astronomy. NASA. http://www.nasa.gov/vision/universe/solarsystem/radio_jupiter.html. Retrieved 18 February 2007.
- ↑ Garcia, Leonard N. The Jovian Decametric Radio Emission. NASA. http://radiojove.gsfc.nasa.gov/library/sci_briefs/decametric.htm. Retrieved 18 February 2007.
- ↑ Klein, M. J.; Gulkis, S.; Bolton, S. J. (1996). Jupiter's Synchrotron Radiation: Observed Variations Before, During and After the Impacts of Comet SL9. NASA. http://deepspace.jpl.nasa.gov/technology/TMOT_News/AUG97/jupsrado.html. Retrieved 18 February 2007.
- ↑ 5.0 5.1 Gordon H. Pettengill & Irwin I. Shapiro (1965). "Radar Astronomy". Annual Review of Astronomy and Astrophysics 3: 377-410.
- ↑ Irwin I. Shapiro (March 1968). "Planetary radar astronomy". Spectrum, IEEE 5 (3): 70-9. doi:10.1109/MSPEC.1968.5214821. http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5214821. Retrieved 2012-12-25.
- ↑ R. B. Dyce and G. H. Pettengill, and A. D. Sanchez (August 1967). "Radar Observations of Mars and Jupiter at 70 cm". The Astronomical Journal 72 (4): 771-7. doi:10.1086/110307. http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1967AJ.....72..771D&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf. Retrieved 2012-12-25.
- ↑ S.G. Djorgovski (16 March 2016). A Tour of the Radio Universe. National Radio Astronomy Observatory. http://www.cv.nrao.edu/course/astr534/Tour.html. Retrieved 16 March 2014.