This pictures covers about the size of your “pinky” finger nail held at arms length. Each speck is a galaxy – each galaxy contains 100’s of billions of stars!!

Galaxies Galaxies are collections of stars, gas, and dust held together by gravity. Scientists believe there are about 125 billion of these structures in our universe.

3 Shapes of Galaxies: Elliptical Galaxy Spiral Galaxy Irregular Galaxy

1) Spiral Galaxies From above, looks like a pin-wheel From the side, looks like a fried egg They have lots of gas, dust and young stars The “bulge” is made up of older stars, the disc is made of young stars The “glow” around galaxy is called the “halo” TOP VIEW (pinwheel) SIDE VIEW (fried egg)

Milky Way Galaxy – Home Sweet Home We live out in one of the arms of the galaxy

2) Elliptical Galaxies Looks like an ellipse (stretched out circle) Made of very little gas and dust, mostly stars Contain some of the oldest stars in the universe The largest galaxies are elliptical More than half the galaxies are elliptical

3) Irregular Galaxies These galaxies have no regular shape Made up of a mixture of old and new stars Contain lots of gas and dust

Comparing Galaxies continued… Star Clusters (#, size, mass, colour, brightness and speed they spin)

Ex. Nebula found in Sagittarius Nebulae made of different amount and type of gas & dust commonly consisting of 70% Hydrogen, 28% Helium, 2% Heavier elements 1) Diffuse Nebula - gases glow from stars within them Ex. Nebula found in Sagittarius

2) Dark Nebula nebula not near a bright star Ex. Horse Head Nebula in Orion

Nebulas Cone Nebula Ring Nebula

Nebulas IC - 1396

Nebulas Dumbell Nebula Crab Nebula

North American nebula Cat’s eye nebula ring nebula ant nebula