Flashcards
Stellar Astrophysics
Cards in this deck (15)
- 1What 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 - 2What is Bolometric Luminosity?The total power emitted.
The integral of the luminosity with respect to the wavelength. - 3What 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" - 4What equation relates luminosity and temperature?The surface area * the Stefan Boltzman
- 5What is the mass of the sun?2E30 kg
- 6What is the range of mass of a star0.08 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 - 7How 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. - 8How to you calculate the mass of a single star?Measure the effective temperature and luminosity and fit to the stellar model.
- 9How 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.
- 10What is the Sun's radius?7E8m
- 11What is a WD and RG radius?10E-2 SR and 10E3 SR.
- 12How 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. - 13What is spectroscopy?As stars are not perfect BBs, the cooler layers of their atmospheres imprint absorption lines onto their spectra.
- 14What is spectral classification? Included hottest, coolest and the Sun.OBAFGKM
O is hottest
M is coolest
The Sun is G - 15What is Wein's displacement law?A way to calculate the max wavelength.
Max Wavelength=2..9E-3/Effective Temp
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- Masters Physics Flashcards on Stellar Astrophysics, created by emmalmillar on 06/12/2015.
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- emmalmillar
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