Agenda: galaxies

Agenda: galaxies

The Milky Way Types of galaxies Finding distances to galaxies

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Hydrogen Gas

CO: MolecularClouds

Interstellar Dust

hot gas bubbles

Stars: no blocking

Seeing the Milky Way

NASA

Is it like this?

AATB

Or this?

NOAO

Or this?

What we see:

Another galaxy…

NASA

Compare

Compare to this one

Harlow Shapley (1885-1972)

Looked at many globular clusters

Determined their distance from us

We are not at the center of the galaxy!

We live in a spiral galaxy!

Globular clusters

Our galaxy iscentered about

here

Stars we can see

Our solar system

Shape of our galaxy

ESA

Our black hole

CHANDRA

Crazy x-ray bursts!

Our black hole

NRAO

Radio waves

Hubble rocks!!!

Edwin Hubble1889-1953

Our neighborAndromeda

R. Gendler

Spiral galaxy

Spiral galaxy on edge

NOAO

Dusty!!

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Barred Spiral

Spiral arms start atthe end of the bar.

hubble space telescope

Caltech

Types of spiralgalaxies

Types of barred spiral galaxies

Caltech

David Malin

Ellipticalgalaxy

Globular clusters

Contain mainly

older stars

Types of ellipticalgalaxies

Rotation not uniform

Caltech

NOAO

Irregulargalaxy

Irregulargalaxy

Some galaxies have asymmetric shapes, often because they are interacting with their neighbors.

HSTNGC4676, the “mice”

Consider Hubble’s hypothesis: Do galaxies evolve from elliptical to

spiral?A. Yes B. No C. Cannot conclude

Increasing age?

Do galaxies evolve? Ellipticals contain mainly older stars Spirals contain much dust and gas

Increasing age?

Calculating distances to other galaxies

Cepheid variables Type I supernovae Hubble’s law

Cepheid variables

Gene Smith, UCSD/CASS

Cepheids are a standard candle.

Discovered by Henrietta Leavitt. (photo: AAVSO)

Harvard

Supernovaein 4 galaxies

All Type I supernovae reach same maximum luminosity.Another standard candle!

Summary Our galaxy—the Milky Way

Spiral shape (mapped using clusters)! We have our own black hole!

Galaxies classified by Hubble Elliptical Spiral Barred spiral Irregular

Measuring distance to galaxies Cepheid variable stars Type I supernovae

Team activity #8

Stellar evolutionMake sure you label all LINES!