exam 2

blackbodies

* idealized that absorbs all radiation that falls onto it
* perfect emitters of radiation

wien’s law

* Λ : b / T
* relates the temperature of an celestial object by analyzing light color
* short wavelength = blue, hot
* long wavelength = red, cold

how hot is the sun

5800 K

spectral class

O B A F G K M

* O = bigger, hot, blue
* M = small, cool, red

brown dwarfs

* failed stars
* don’t sustain fusion in core due to lack of sufficient mass
* lower limit: 80 jupiters OR 8% of suns mass

luminosity

relies on surface temp and size

most important property of a star

mass

HR Diagram

top

* left: shorter life, larger mass
* big stars

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bottom

* right: longer life, small mass
* small stars

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* increase in radius approaching top right

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left

* hot stars

\
right

* cool stars

stefan - boltzmann law

* AT^4 = total energy
* a = area
* t = temperature
* relationship b/w temp & radiation emitted
* increase temp = increase radiation emission

variable stars