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

bottom

• right: longer life, small mass

• small stars

• increase in radius approaching top right

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