# Stellar Astrophysics

Flashcards by emmalmillar, updated more than 1 year ago
 Created by emmalmillar almost 5 years ago
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### Description

Masters Physics Flashcards on Stellar Astrophysics, created by emmalmillar on 12/06/2015.

## Resource summary

 Question Answer What is Luminosity? The power emitted by the star. The amount of energy emitted over time. L=-dE/dt The total light emitted over a specified wavelength intensity What is Bolometric Luminosity? The total power emitted. The integral of the luminosity with respect to the wavelength. What is the effective temperature? The temperature the star would have if it was a perfect black body. The temperature of a star is different all over. "The temperature a BB would have if it was a sphere with the same radius and luminosity of the star" What equation relates luminosity and temperature? The surface area * the Stefan Boltzman What is the mass of the sun? 2E30 kg What is the range of mass of a star 0.08 SM - 100 SM Stars with core less than 0.08 SM never get hot enough for nuclear reaction. stars greater than 30 SM are unstable How do you directly measure the mass of a star? By observing the star in a binary system. Measure the orbital velocity from Doppler Shift and use Kepler's laws. How to you calculate the mass of a single star? Measure the effective temperature and luminosity and fit to the stellar model. How is the radii of a star defined? As the radius at which most photons escape (the photosphere), which is wavelength dependent. It is not normally used as the photosphere can appear very fuzzy. What is the Sun's radius? 7E8m What is a WD and RG radius? 10E-2 SR and 10E3 SR. How are radii measured? Very few stars are spatially resolvable. Can measure L&T but this is model dependent. For direct measurements use lunar occulations, binary eclipses or inetrferometry. What is spectroscopy? As stars are not perfect BBs, the cooler layers of their atmospheres imprint absorption lines onto their spectra. What is spectral classification? Included hottest, coolest and the Sun. OBAFGKM O is hottest M is coolest The Sun is G What is Wein's displacement law? A way to calculate the max wavelength. Max Wavelength=2..9E-3/Effective Temp

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