Explanation:
Grand tidal streams of stars seem to surround galaxy
NGC 5907.
The arcing structures form tenuous loops extending more than 150,000
light-years from the narrow, edge-on spiral, also known as the
Splinter
or Knife Edge Galaxy.
Recorded only in very deep exposures, the streams likely represent
the
ghostly trail of a dwarf galaxy -- debris left along the
orbit of a
smaller satellite galaxy that was gradually
torn
apart and
merged
with NGC 5907 over four billion years ago.
Ultimately this remarkable discovery image, from a small robotic
observatory in New Mexico, supports the cosmological
scenario in
which large spiral galaxies,
including
our own Milky Way, were
formed by the accretion of smaller ones.
NGC 5907 lies about 40 million light-years distant in the northern
constellation
Draco.
digg_url = 'http://apod.nasa.gov/apod/ap080619.html'; digg_skin = 'compact';
