Spiral Galaxy M74
When most of us think of a galaxy we think of a beautiful
spiral shaped entity. Astronomers have been studying these spiral galaxies for
quite some time now, and have noticed that most of the stars seem be located
within the arms. To form a star, you need a giant cloud of molecular hydrogen,
and other gaseous materials. The cloud will eventually collapse due to gravity
and form stars, and some of those stars may even host planetary systems. Most
of the material in a galaxy (gas, dust, rocks, etc.) sits in the spiral arms in
the plane of the galaxy. So it makes sense that stars tend to form here; it’s
where all the stuff is! Because the
spiral arms contain millions of stars, they glow very brightly in optical light.
This allows Hubble, and other telescopes, to image the structure of the galaxy.
M74, pictured above, is a perfect example of a spiral galaxy whose structure is
illuminated by the light from many stars within its spiral arms.
Image Credit: NASA, ESA, Hubble Heritage(STScI/AURA)-ESA/Hubble Collaboration
