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Electromagnetic radiation visible light detectable by

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Electromagnetic Radiation – visible light detectable by the human eye a) Energy emitted as particles or waves 131) Radio Telescopes – used for observing stars in 1930 a) The sun and most stars release most of their radiation in the visible light spectrum 132) Radio Waves – the longest form of electromagnetic radiation that exists 133) Gamma Rays – have the shortest wavelength on the electromagnetic spectrum
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a) Could not be observed in the universe until the 1960s because most gamma rays are absorbed by the Earths’ atmosphere b) Have the shortest wavelength and the highest frequency, c) They are the most Energetic d) Are typically released by the more high-energy events that occur d.i)Supernovae d.ii) Neutron stars d.iii) Solar flares d.iv) Etc. 134) X-Rays – are right below gamma rays on the electromagnetic spectrum a) Have a slightly lower wavelength b) Also released by high energy sources c) Have been detected coming from comets d) Are mostly absorbed by the Earth’s atmosphere e) Need to be observed from high in the atmosphere or from satellites in space 135) Infrared Rays – are just below the visible light a) Have a slightly longer wavelength b) Are heavily absorbed by the earth’s atmosphere (specifically by water vapor) c) Most efficiently observed by telescopes in space c.i) Reasons for astronomers to turn to the infrared portion of the spectrum (c.i.1) To find planets (stars do not emit energy in this section (c.i.2) Very distant galaxies with high red shift can be visible in infrared 136) Electroscope – a very simple device for detecting the presence of charged particles 137) Geiger Counter – more sophisticated instrument that counts radiation levels a) When a high energy charged particle enters the chamber it ionizes some of the gas contained so that the gas becomes momentarily conducting 138) Cloud Chamber – a device for detecting particles of radiation, is a chamber filled with a gas that is saturated with the vapor of water or other liquid 139) Cosmic Rays – atomic nuclei that are observed to strike the Earth’s atmosphere with high energy a) 1912, physicist Victor Hess carried an electroscope up in a balloon a.i) The conductivity of the air increased with altitude b) Cosmic rays are affected only slightly by the sun expect during violent solar flares c) Majority of cosmic rays approach the Earth in equal amounts from all directions, not primarily from the sun d) Most astronomers are of the hypothesis that cosmic rays originate within the Galaxy d.i)Seems unlikely as these particles would spread thinly over the vast distance e) Many astronomers feel that the most promising candidate for the cosmic rays are Supernovae e.i) Supernovae are rare e.ii) Possibly the primary cosmic ray particles that now bombard the Earth are tiny fragments of stars that exploded millions of years ago 140) Charles Messier – a comet hunter who placed on record 103 objects that might be mistaken for comets 141) By 1908, 15,000 Nebulae had been catalogued and described, with some identified as star clusters and
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