Lab 1: Scope and Nature of Matter, Galaxy

 

The Milky Way

 

Our galaxy is named the Milky Way, because on a clear night the billions of stars within it shine as a kind of milky belt across the sky. The Milky Way is a spiral galaxy, with arms spiraling out from the center:

 

 

Artist's rendition of the Milky Way Galaxy , CREDIT: R. Hurt (SSC), JPL-Caltech, NASA

 

The Milky Way is actually a barred spiral galaxy: recent work indicates the presence of a bar of ancient reddish stars in the center. Our Sun is located out on one of the arms, about 1/3 of the way in from the outer edge. Our sun moves along with its spiral arm in an orbit around the galactic center. Each orbit takes about 250 million years.

 

Estimates for the number of stars in the Milky Way Galaxy range up to several hundred billion.

 

We can't see our own galaxy from afar, because we are in it, but we can see other similar galaxies well, such as NGC 7331 :

 

NGC 7331 Galaxy, CREDIT: NASA/JPL-Caltech; produced by: M. Regan (STScI), and the SINGS Team

 

In addition to the barred spiral type of galaxy, other shapes include simple spiral, elliptical, and irregular. Galaxies are old, almost as old as the Universe itself. Our own galaxy has been estimated to be 13.6 billion years old.

 

Web Sources

The 13.6 billion year age of our Milky Way galaxy was estimated by looking at the abundance of the element beryllium in a globular cluster .