Galaxies

  • Hubble’s galaxy classification
  • Distribution in space
    • Tully-Fisher relationship
    • Type Ia supernovae
    • Hubble’s law
  • Active galactic nuclei
    • Galactic radiation
    • Seyfert galaxies
    • Radio galaxies
    • Quasars
  • Supermassive black holes

 

 

M81 type Sa

(Messier)

M51 type Sb

irregular galaxy APOD NGC 4449: Close-Up of a Small Galaxy Credit: NASA, ESA, A. Aloisi (STScI / ESA), Hubble Heritage (STScI / AURA) - ESA/Hubble Collaboration Explanation: Grand spiral galaxies often seem to get all the glory. Their newly formed, bright, blue star clusters along beautiful, symmetric spiral arms are guaranteed to attract attention. But small irregular galaxies form stars too, like NGC 4449, located about 12 million light-years away. In fact, this sharp Hubble Space Telescope close-up of the well-studied galaxy clearly demonstrates that reddish star forming regions and young blue star clusters are widespread. Less than 20,000 light-years across, the small island universe is similar in size, and often compared to our Milky Way's satellite galaxy, the Large Magellanic Cloud. NGC 4449 is a member of a group of galaxies found in the constellation Canes Venatici.

 

Hubble’s galaxy classification

ellipticals

Hubble’s galaxy classification

EO

E4

ellipticals

E7

Hubble’s galaxy classification

EO

E4

ellipticals

E7

Sa

Sb

spirals

Sc

Hubble’s galaxy classification

EO

E4

ellipticals

E7

Sa

Sb

spirals

Sc

SBa

SBb

barred spirals

SBc

Hubble’s galaxy classification

EO

E4

ellipticals

E7

spirals

Sa

Sb

Sc

SBa

SBb

barred spirals

SBc

lenticular

irregular

Tully – Fisher Law relates galaxy rotation speed with its luminosity

 

Higher mass galaxies spin faster – stronger gravity holds them together

Doppler shift

interactive

Tully -- Fisher relationship

Relate rotational speed of galaxy and luminosity

Use luminosity and apparent brightness to calculate distance

Type I supernovae

Narrowly defined luminosities

Bright enough to be seen over large distances

Standard candles

Novae and type la supernovae

  • Nova
    • Starts with a white dwarf in a binary system with a red giant
    • White dwarf accretes matter from the red giant
    • Accreted matter builds up and heats up enough for fusion
    • May be repeated
  • Type Ia supernova
    • Starts with same situation as a nova (above)
    • White dwarf builds up more mass over time
    • Mass exceeds the Chandrasekhar limit
    • Gravity overtakes electron degeneracy pressure
    • Core collapses and heats up
    • Carbon fusion begins and detonates star

Cosmic Distance Ladder

The local group

Virgo Supercluster