Uncovering the Veil Nebula
NASA’s Hubble Space Telescope photographed
three magnificent sections of the Veil Nebula –
the shattered remains of a supernova that exploded
thousands of years ago. This series of images provides
beautifully detailed views of the delicate, wispy
structure resulting from this cosmic explosion.
The Veil Nebula is one of the most spectacular supernova
remnants in the sky. The entire shell spans about
3 degrees, corresponding to about 6 full moons.
The Veil Nebula is a prototypical middle-aged supernova
remnant, and is an ideal laboratory for studying
the physics of supernova remnants because of its
unobscured location in our galaxy, its relative
closeness, and its large size. Also known as the
Cygnus Loop, the Veil Nebula is located in the constellation
of Cygnus, the Swan. It is about 1,500 light-years
away from Earth.
Stars in our galaxy, and in other galaxies, are
constantly in the process of being born and dying.
How long a star lives depends on how big and heavy
it is. The bigger the star, the shorter its life.
When a star significantly heavier than our Sun runs
out of fuel, it collapses and blows itself apart
in a catastrophic supernova explosion. A supernova
releases so much light that it can outshine a whole
galaxy of stars put together. The exploding star
sweeps out a huge bubble in its surroundings, fringed
with actual stellar debris along with material swept
up by the blast wave. This glowing, brightly-colored
shell of gas forms a nebula that astronomers call
a “supernova remnant.”
Such a remnant can remain visible long after the
initial explosion fades away. Scientists estimate
that the Veil supernova explosion occurred some
5,000 to 10,000 years ago and could have been witnessed
and recorded by ancient civilizations. These early
viewers would have seen a star increase in brightness
to roughly the brightness of the crescent Moon.
The small regions captured in these Hubble images
provide stunning close-ups of the Veil. Fascinating
smoke-like wisps of gas are all that remain visible
of what was once a star in our Milky Way galaxy.
The intertwined rope-like filaments of gas in the
Veil Nebula result from the enormous amounts of
energy released as the fast-moving debris from the
explosion plows into its surroundings and creates
shock fronts. These shocks, driven by debris moving
at 600,000 kilometers per hour, heat the gas to
millions of degrees. It is the subsequent cooling
of this material that produces the brilliant glowing
colors.
The Hubble images of the Veil Nebula are striking
examples of how processes that take place hundreds
of light-years away can sometimes resemble effects
we see around us in our daily life. Although caused
by different forces, the structures show similarities
to the patterns formed by the interplay of light
and shadow on the bottom of a swimming pool, rising
smoke, or a ragged cirrus cloud.
Although only a few stars per century in our galaxy
will end their lives in this spectacular way, these
explosions are responsible for making all chemical
elements heavier than iron in the universe. Elements
such as copper, mercury, gold, and lead are forged
in these violent events. The expanding shells of
supernova remnants mix with other clouds in the
Milky Way and become the raw material for new generations
of stars and planets. The chemical elements that
constitute Earth, and indeed those of which we ourselves
are made, were formed deep inside ancient stars
and distributed by supernova explosions in nebulae
like the one we see here.
The images were taken with Hubble’s Wide
Field Planetary Camera 2 (WFPC2) in November 1994
and August 1997. The color is produced by creating
a composite of three different images. The colors
indicate emission from different kinds of atoms
excited by the shock: blue shows oxygen, green shows
sulfur, and red shows hydrogen.
Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble
Collaboration
Acknowledgment: J. Hester (Arizona State University) |
