VisualVisualVisualVisualVisualVisualTarantula NebulaLarge
Magellanic
CloudNGC 2207 and IC 2163Small
Magellanic
CloudG. J. Jacoby, M. J. Pierce/AURA/NOAO, NSFCopyright R. J. Dufour, Rice UniversityRudolph E. Schild
NASA/ESA/Hubble Heritage Team/STScI/AURAAURA/NOAO/NSFNASA/ESA/Hubble Heritage Team/STScI/AUDust visible in spiral
arm crossing in front
of more distant galaxy.3 Irregular galaxies (classified Irr) are a chaotic mix of gas, dust, and
stars with no obvious nuclear bulge or spiral arms. The Large and Small
Magellanic Clouds are visible to the unaided eye as hazy patches in the
southern hemisphere sky. Telescopic images show that they are irregular
galaxies that are interacting gravitationally with our own much larger galaxy.
Star formation is dramatic in the Magellanic Clouds. The bright pink regions
are emission nebulae excited by newborn O and B stars. The brightest
nebula in the Large Magellanic Cloud is called the Tarantula Nebula.Some disk galaxies are rich in dust, which
is concentrated along their spiral arms.
NGC 4013, shown below, is a galaxy much like
ours, but seen edge-on, its dust is dramatically
apparent.2bGalaxies with an
obvious disk and
nuclear bulge but no visible
gas and dust and few or no
hot bright stars are classified
as S0 (pronounced “Ess
Zero”). Compare this galaxy
with the edge-on spiral
above.2cThe galaxy IC 4182 is a
dwarf irregular galaxy
only about 4 million
parsecs from our galaxy.Dust in spiral galaxies is most common in the
spiral arms. Here the spiral arms of one galaxy
are silhouetted in front of a more distant galaxy.