ASTR 124 Ch 1

# ASTR 124 Ch 1 - ASTR 124 Ch 1 A solar system consists of a...

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ASTR 124 Ch 1 A solar system consists of a sun, its planets (if any), and some smaller bodies like moons and comets. A star is a self luminous ball of hot gas that generates it’s own energy. Our sun is 109 times larger in diameter than earth. The average distance from the earth to the sun is called the astronomical unit (AU ), and measures out at 1.5x1011 m. One light year (ly) is 1013 km, or ~63k AU. A galaxy is a vast cloud of stars, gas and dust bound together by the combined gravity of all the matter within. They range in size from 1500ly to 300k ly in diameter and can contain >100b stars. A supercluster is believed to be the largest structure in the universe (except that one big gas one you read about…find it). They are huge clusters of clusters of galaxies. ASTR 124 Ch. 6 Light and Telescopes Light is electromagnetic radiation. c, the speed of radiation in a vacuum, is ~300k km/s. λ signifies wavelength, the distance from peak to peak. Frequency is the number of wave cycles that pass in one second. λ = c/f shows the relationship between wavelength and frequency. A nanometer (nm) is 10-9 m. Visible light has wavelengths that range from ~400nm to ~700nm An angstrom (Å) is 10-10 m. Visible light has wavelengths that range from ~4000Å to 7000Å. A micrometer (µm) is 10-6 meters. A photon is a “particle of light” exhibit wave/particle duality. Think of it as a bundle of waves. The amount of energy a photon carries depends on its wavelength, the relationship can be described as: E= hc/ λ Where h is the Planck constant (6.6262 x 10-34 joules), c is the speed of light (3 x 108 m/s),

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and λ is wavelength in meters. The electromagnetic spectrum Infrared radiation is beyond the red end of the spectrum. Wavelengths range from 700nm to 0.1cm Beyond the infrared lie radio waves, with wavelengths from 1mm to >1cm VHF and UHF have longer wavelengths, and FM, military, gov’t, HAM signals have wavelengths up to a few meters, and AM waves have wavelengths up to a few km. Gamma ray < X ray < Ultra violet < visual spectrum < infrared < microwave <
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ASTR 124 Ch 1 - ASTR 124 Ch 1 A solar system consists of a...

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