GALAXIES AND SUPER STRUCTURES

Hubble Deep Field

What are galaxies? Galaxies are systems made up of stars,

gas, and dust. All galaxies have a center of mass that its

stars orbit around. Galaxies can have from around ten

million stars to a hundred trillion stars. In 1999 the Hubble telescope estimated

the total number of galaxies in the visible universe at 125 billion. http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/021127a.html

Galaxy Shapes

Elliptical Galaxy M87

Elliptical Galaxy NGC 4649

http://chandra.harvard.edu/photo/category/galaxies.html

Galaxy ShapesElliptical (E0-E7)

Elliptical galaxies can range from nearly round to flatter, football-like shapes.

Elliptical galaxies are appear to be made up of older stars and have low rates of new star formation.

Whirlpool Galaxy

http://chandra.harvard.edu/photo/category/galaxies.html

Spiral Galaxy M101

http://chandra.harvard.edu/photo/category/galaxies.html

Galaxy ShapesSpiral (Sa, Sb, Sc)

• Spiral galaxies have the following characteristics:• A flat, rotating disc of (mostly newly created)

stars and interstellar matter• A central stellar bulge of mainly older stars,

which resembles an elliptical galaxy• A supermassive black hole at the very center

of the central bulge • Arms of stars radiating out from the central

bulge.

http://en.wikipedia.org/wiki/Spiral_galaxy

Barred Spiral Galaxy NGC 2903

http://en.wikipedia.org/wiki/File:NGC_2903_GALEX.jpg

Barred Spiral Galaxy NGC 1300

http://en.wikipedia.org/wiki/File:Hubble2005-01-barred-spiral-galaxy-NGC1300.jpg

Galaxy ShapesBarred Spiral (Sba, SBb, SBc)

Rather than a bulge, barred spirals have a bar shape in their centers.

The bar of barred spiral galaxies is thought to be the birthplace for new stars.

The Milky Way is a barred spiral.

Hoag’s Object (Ring Galaxy)

http://en.wikipedia.org/wiki/File:Hoag%27s_object.jpg

NGC 5866 (Lenticular Galaxy)

http://en.wikipedia.org/wiki/File:File-Ngc5866_hst_big.png

Colliding GalaxiesAntennae Galaxies

Galaxy ShapesIrregular

Although most galaxies in the universe are elliptical or spiral, some have irregular shapes.

Galaxies with irregular shapes are thought make up about ¼ of all galaxies.

These galaxies shapes are thought to be caused by gravitational forces of larger neighboring galaxies.

What are Super Structures?

Super structures are clusters and superclusters of galaxies.

Clusters and superclusters form large, orderly structures called filaments and walls.