Explanation:
Spiral galaxy NGC 4651 is a mere 35 million light-years distant,
toward the well-groomed constellation
Coma Berenices.
About 50 thousand light-years across, this galaxy is seen to have
a faint umbrella-shaped structure (right) that
seems to extend some 50 thousand light-years farther,
beyond the bright galactic disk.
The
giant cosmic umbrella is now known to be composed of
tidal star streams.
The streams themselves are
extensive trails of stars
gravitationally
stripped
from a smaller satellite galaxy that was eventually
torn apart.
Placing your cursor over the image will superimpose a simulation of
the satellite galaxy's path as it was disrupted and
absorbed into NGC 4651.
Recent work by a remarkable collaboration of amateur and professional
astronomers to image faint structures around bright galaxies
suggests that
even in nearby galaxies,
such tidal star streams
are common.
The result is
predicted by models
of galaxy formation,
including
the formation of our Milky Way.
