ASTR 1020 1st Edition Lecture 7 Outline of Last Lecture I. The Sun: Our StarA. NeutrinosB. Solar AtmosphereC. Sun SpotsD. CoronaOutline of Current Lecture I. Surveying the StarsA. PropertiesB. DistancesC. LuminositiesD. TemperatureCurrent LectureI. Surveying the StarsA. Properties- Distances- Luminosities- Temperatures- Radii- MassesB. Distance- Use radar in Solar System, but stars are so far we use parallax, an apparentshift of a nearby object against a background of more distant objects- Parallax and distance:d(¿ parsecs)=1p(¿ arcseconds)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.P = parallax angle- Nearest star: Alpha Centauri at 1.3 parsecs- Works well out to 200 parsecs (pc)C. Luminosity- Power radiated by a star= surface area xRate/unit area ¿4 π r2x σ T4Where R = radiusT = temperatureσ = Stefan-Boltzmann constant- Apparent brightness: Amount of starlight that reaches Earth- With increasing distance, luminosity is spread over a larger areaArea of sphere = 4 π(distance)2- Divide luminosity by area to get brightness- Inverse-Square Law: brightness proportional to 1distanc e2D. Temperature- Thermal Radiation1. Hotter objects emit more light per unit area at all frequencies.2. Hotter objects emit photons with a higher average energy.- The color of a star is indicative of its temperature - Red stars are relatively cool, while blue ones are hotter.- Pioneers of Spectral Classification: Annie Jump Cannon and the “calculators” at Harvard laid the foundation of modern stellar classification- Stellar spectra are much more informative than the blackbody curves.- There are seven (ten) general categories corresponding to different temperatures.- From highest to lowest, those categories are:O B A F G K M (L T
View Full Document
Unlocking...