A galaxy is a system of stars and gas held together by gravity. In this image we can see the galaxy Messier 81 taken from NASA’s Spitzer Space Telescope. This galaxy is 12 million light years away and is easily seen with binoculars or a small telescope. Both M81 and our own Milky Way galaxy are spiral shaped galaxies. Galaxies can come in many different shapes. Our galaxy is 100,000 light years across (1 light year = 5.8 trillion miles) and contains 100 billion stars. In the Northern Hemisphere, the only other galaxy we can see with the unaided eye is the Andromeda Galaxy.
Useful Links:
http://www.nasa.gov/worldbook/galaxy_worldbook.html
http://hubblesite.org/gallery/
http://www.lpi.usra.edu/education/resources/stars_galaxies/stars.shtml
Thought Questions:
How large is our galaxy in miles?
What professions are related to studying the stars?
How do scientists measure the distances between stars, planets and galaxies?
In what galaxy is earth located? How are the milky way and M81 similar?
Watch NASA building the next outer space telescope The Webb Space Telescope:
http://www.jwst.nasa.gov/webcam.html
Image Credit: Hubble data: NASA, ESA, and A. Zezas (Harvard-Smithsonian Center for Astrophysics); GALEX data: NASA, JPL-Caltech, GALEX Team, J. Huchra et al. (Harvard-Smithsonian Center for Astrophysics); Spitzer data: NASA/JPL/Caltech/Harvard-Smithsonian Center for Astrophysics)
Monday, April 12, 2010
Word of the Week: Galaxy
