The Big StuffGalaxies

The Universe

and The Big Bang

Galaxies…Millions or billions of stars, made of gas and dust

The Universe…Everything

Three Types of Galaxies

•Spiral -shaped like pinwheels; have huge spiral arms Ex:Milky WayElliptical - Vary in shape from nearly spherical to flat discs; contain very little gas & dustIrregular - does not have an orderly or definite shape; much less common

What kind of galaxy?

Andromeda galaxy and The Milky Way

What kind of galaxy?

No spiral arms -

What kind of galaxy?

Large Magellanic Cloud – within our galactic neighborhood

The Milky Way… …Our Galaxy• A huge pinwheel-shaped disc with a bulge

in the middle.• 200 Billion+ Stars.• Most older stars found near the nucleus.

Stars here are crowded together 1000’s of times more densely than in spiral arms.

• 200 million years to rotate once.• 100,000 light years in diameter• Sun is 26,000 light years from center

Andromeda Galaxy

• The closest galaxy to the Milky Way

(2.5 Million Light Years!!!) • The other spots of light in the picture are other galaxies, not other stars!

Active GalaxiesHuge Black Hole in Center?

NEBULA

• A large cloud of dust and gas in interstellar space – a region in space where stars are born or where stars explode at the end of their lives.

• NEW STARS can form in regions of nebulas

• SPIRAL GALAXIES usually contain nebulas, but ELLIPTICAL GALAXIES contain very few

GLOBULAR CLUSTER• A tight group of stars that looks

like a ball and contains up to 1 million stars

• They are located in a spherical HALO that surrounds spiral galaxies such as the Milky Way.

OPEN CLUSTERS

• Groups of closely grouped stars that are usually located along the spiral disk of a galaxy

nebula, globular clusters and open clusters

Quasars – discovered in the 1960’s

• QUASi-StellAR Radio Source• Looked like stars, but strong radio

emitters• Brightest objects in Universe• Highly Energetic Galaxies?• Most Distant Objects in Universe (12

Billion Light years)• Black Hole at center?• May be caused by BLACK HOLES

SO, WHERE DID WE ALL COME FROM?

•COSMOLOGY – The study of the origin, structure, and future of the universe.

•Measurements have shown that galaxies are moving apart

• Raisin bread model

The Big Bang

• Scientists’ theory about what they think happened starting less than a second after universe formed.

• About 10-20 (14?) Billion Years ago• Everything started in a small hot

dense object: The Singularity• Singularity exploded and

everything have been moving apart since.

Evidence for The Big Bang

•Cosmic Background Radiation- The “echo” of the Bang, static in space, comes from all directions.

•Red Shift of All galaxies•Galaxies (Quasars) that are

further away are more red shifted

How to calculate the age of the universe

•Measure distance from Earth to various galaxies – can estimate the age of the universe and predict its rate of expansion

• Calculate the ages of old, nearby stars. Universe must be as old as the oldest stars it contains.

What’s next?

•Open Universe - Everything will continue to expand and will eventually cool off.

•Closed Universe - Gravity will overcome expansion and, expansion will stop, the universe will start to contract, leading to a “Big Crunch”