DSST Astronomy notes 1

Highest metallic content aiii sun is population i

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Highest metallic content a.iii) Sun is Population I star b) Population II – oldest stars found in the universe b.i)Have very low metal content, around .1% b.ii) Tend to be found in globular clusters and in halos of galaxies b.iii) Less luminous and cooler c) Population III – are stars with the lowest metallicity (no metallicity) c.i) One composed entirely of Hydrogen and Helium c.ii) none have been observed 119) Hydrogen and Helium the most abundant elements in stars in the solar system 120) Vast majority of stars and the sun are in a steady state, neither expanding or contracting 121) Hydrostatic Equilibrium – balance between the weights of various layers and the pressures that support them a) Surface and internal temperatures of stable stars is balanced 122) The Perfect Gas Law – states that the pressure is proportional to the density and temperature of the gas 123) Stellar thermal Energy – energy associated with the motions of the molecules in a star a) Internal heat, stored in a gas is the energy of the motion of the particles 124) Gravitational Energy – a star is bound together by gravity 125) Theoretical Approach – the study of stellar evolution a) Calculations are made from theory about how stars should change as they contract gravitationally or age 126) Observational Approach – stars and groups of stars are observed in their evolution 127) Giant – a star of large luminosity and radius a) Supergiant is a star of very high luminosity a.i) Less than 1% of the stars on the H-R diagram are giant or supergiant 128) Absolute Magnitude – the indicator of the star’s luminosity a) Which is the brightness of a star seen from a distance of 10 parsecs, or 33 light years 129) Albedo – the fraction of incident light that is reflected by a body a) Moon albedo is .07, which means that it reflects only about 7% of the light from the sun, and absorbs most of the sunlight 130) 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)
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Highest metallic content aiii Sun is Population I star b...

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