• Luminosity is the total power output of an object!
• Units of luminosity are energy/sec or Watt• The luminosity of the sun is
Luminosity
L! = 3.826 × 1026
W
*Compact Remnant! • White Dwarf! • Neutron Star! • Black Hole
†Ejected Remnant! • Planetary Nebula! • Supernova Remnant
ISM
Protostar
MS Star
Post MS Star
Brown Dwarf
CR* ER†
The life-cycle of stars
ISMThe interstellar medium is
mostly Hydrogen!
This radio image shows the distribution of hydrogen in center of our galaxy.
Star forming regions
Protostars are often obscured by dust.
Can “see” through dust in the infrared!
Main Sequence Stars
Main Sequence Stars
• “burn” hydrogen in their cores (PP chain)
• lifetime depends on the star’s mass
t∗ =1010 years
(M/M")2
large-mass short-lifetime stars
small-mass long-lifetime stars
Lifetime of Main Sequence Stars
τms ≈1010 years
(M/M!)2
Nuclear Binding Energy
Hydrogen Fusion (PP chaine)
Post MS evolution of star1M!
Planetary Nebula
Nuclear Binding Energy
Supernovae
Post MS
White Dwarf & Planetary Nebula
Type II Supernova
Neutron Star
Black Hole
Increasing star mass
*Compact Remnant! • White Dwarf! • Neutron Star! • Black Hole
†Ejected Remnant! • Planetary Nebula! • Supernova Remnant
ISM
Protostar
MS Star
Post MS Star
Brown Dwarf
CR* ER†
The life-cycle of stars