The Milky Way

Sum up Introduction: the Milky Way’s identity View from Earth: a few explications Size and mass Age Spiral arms Environment Velocity Some order of magnitude

Introduction The Milky Way galaxy is visible from Earth as a band of light in the night sky, and it is the appearance of this band of light which has inspired the name for our galaxy.

View from Earth

Size and mass Mass: about 5.8×10^11 Size: approximately 10×10^4 light years in diameter, and about 10×10^2 light years thick.

Age About 13.2×10^9 years

There are four major spiral arms in the Milky way.

Environment The Milky Way and the Andromeda Galaxy are a binary system of giant spiral galaxies. Together with their companion galaxies they form the Local Group, a group of some 50 closely limited galaxies. Andromeda Galaxy

velocity Many astronomers believe that the Milky Way is moving at approximately 600 km per second.

Some order of magnitude 10^23 m: 10 million light years away from the Milky Way 10^21 m: our galaxy, the Milky Way 10^20 m: stars at the rim of the Milky Way galaxy 10^19 m: stars in the Milky Way galaxy 10^18 m: 100 light years from earth and nothing but stars 10^13 m: our solar system 10^9 m: the earth and the orbit of the moon

The end Our references: Images: Google Text: Wikipédia http://www.eso.org/public/outreach/press-rel/pr-2004/pr-20-04.html. Nwnw.gsfc.nasa.gov/-5k-