• 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