Twinkle, twinkle, little star, how I wonder what

you are?

What are stars?And what are they made of?

Stars are huge, hot, bright balls of gas.Stars have different temperatures.Stars are of different colors.Stars are made of different elements.

Betelgeuse

Rigel

Which star is hotter?

Stars are of different colors.

Composition of StarsStars are made of different elements in the form of gases.

A star is very dense and hot.The outer layers of a star (atmosphere) are made of cooler gases (elements).

The elements emit certain wavelengths of light (fingerprints)

The Fingerprints of Elements

Emission Spectral Lines

Hydrogen

Helium

Neon

Sodium

Mercury

It is a group of billions and billions

of stars held together by gravity.

What is a Galaxy?

Top View

• Huge; contains stars, gas, and dust• Held together by gravity• Pinwheel shape/looks like a hurricane• Bulge and thin disk• Halo (glow) is present• Rich in gas and dust• Young and old stars are present

Side View

Bulge

Disk

Spiral Galaxy

Spiral Galaxy

Spiral Galaxy

Spiral Galaxy

Spiral Galaxy

Elliptical Galaxy

•Huge; contains stars, gas, and dust

•Held together by gravity•Round to oval•Bulge but no disk•Halo is present•Little cool gas and dust•Mainly OLD STARS are present

Elliptical Galaxy

Elliptical Galaxy

Elliptical Galaxy

Elliptical Galaxy

Irregular Galaxy

• Huge; contains stars, gas, and dust

• Held together by gravity• No regular shape• May show signs of a disk and/or bulge

• Halo is present• Usually rich in gas and dust• Young and old stars are present

Irregular Galaxy

Irregular Galaxy

Irregular Galaxy

Nebulae

Planetary Nebula

(death of a star)

Movie

Stellar Nebula (where stars are

born)

Stellar Nebula

Stellar Nebula

Stellar Nebula

Stellar Nebula

Planetary Nebula

Planetary Nebula

Planetary Nebula

Planetary Nebula

Colliding Galaxies

Betelgeuse

Rigel

Orion Constellation

Supernovae

Spiral Galaxy

Huge: contain stars, gas, and dust

Huge; contain stars, gas and dust

Huge; contain stars, gas, and dust

Held together by gravity

Held together by gravity

Held together by gravity

Pinwheel shape Round to oval in shape

No regular shape

Bulge and thin disk; halo is present

Bulge but no disk; halo is present

May show signs of a disk and/or bulge; halo is present

Rich in gas and dust Little cool gas and dust

Usually rich in gas and dust

Young and old stars are present

Mainly old stars are present

Young and old stars are present

Top View Side View

Elliptical Galaxy Irregular Galaxy