The Milky Way. The Milky Way Galaxy A broad, faintly glowing band stretching across the night sky.

The Milky Way

The Milky Way Galaxy

• A broad, faintly glowing band stretching across the night sky.

Composed of billions of stars in our galaxy too faint to be seen individually.

It’s invisible when the sky is lit up by artificial light or bright moonlight.

Galaxies

Galaxies

• Galaxies are systems of stars, gas and dust

• They exist in a wide variety of shapes and sizes

• 4 basic types - elliptical, spiral, barred spiral, and irregular

Elliptical Galaxies

• About 60% of the galaxies

• Are round to oval in shape

Spiral galaxies

• have a central nucleus surrounded by a flattened disc with the stars, gas, and dust organized into a pattern of spiral arms.

• Greater concentration of stars near their centers

Barred Spiral

Has a bar through the center with arms extending through the bar

Irregular Galaxy

These galaxies have little symmetry in their structureAbout 10% of the galaxies