4186527
Description
Flashcards by emmalmillar, updated more than 1 year ago
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Created by emmalmillar
about 9 years ago
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| 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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