Imagine the Universe!
Imagine Home  |   Ask an Astrophysicist  |  
Ask an Astrophysicist

The Question

(Submitted March 17, 1998)

How large is the Milky Way?

The Answer

The disk of the Milky Way galaxy is about 100,000 light years in diameter (one light year is about 9.5 x 1015 meters), but only about 1000 light years thick.

Our Galaxy contains about 200 billion stars. Most of the stars are located in the disk of our galaxy, which is the site of most of the star formation because it contains lots of gas and dust.

The halo, which is a spherical cloud surrounding the disk, contains only about 2% as many stars as the disk. It contains old and cool stars, since it has little gas and dust.

Eric Christian and Samar Safi-Harb
for Ask an Astrophysicist

Main topic
Main
Next question
Next

If words seem to be missing from the articles, please read this.

Imagine the Universe! is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Project Leader: Dr. Barbara Mattson
Curator: Meredith Gibb
Responsible NASA Official: Phil Newman
All material on this site has been created and updated between 1997-2014.
This page last updated: Thursday, 01-Dec-2005 13:58:40 EST