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Kepler's
Supernova Remnant: A Star's Death Comes to Life
01/09/07
Using
NASA's Chandra X-ray Observatory, scientists have created a
stunning new image of one of the youngest supernova remnants in
the galaxy. This new view of the debris of an exploded star helps
astronomers solve a long-standing mystery, with implications for
understanding how a star's life can end catastrophically and for
gauging the expansion of the universe.
Over 400 years ago,
sky watchers -- including the famous astronomer Johannes Kepler
-- noticed a bright new object in the night sky. Since the
telescope had not yet been invented, only the unaided eye could
be used to watch as a new star that was initially brighter than
Jupiter dimmed over the following weeks.
Chandra's latest
image marks a new phase in understanding the object now known as
Kepler's supernova remnant. By combining nearly nine days of
Chandra observations, astronomers have generated an X-ray image
with unprecedented detail of one of the brightest recorded
supernovas in the Milky Way galaxy.
The explosion of the
star that created the Kepler remnant blasted the stellar remains
into space, heating the gases to millions of degrees and
generating highly energized particles. Copious X-ray light, like
that shining from many supernova remnants, was produced.
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Chandra
X-ray Image & DSS Optical Image of Kepler's SNR
More
Information ROLLOVER
Credit:
X-ray: NASA/CXC/NCSU/S.Reynolds et al; Optical: DSS
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Astronomers have studied
Kepler intensively over the past three decades with radio,
optical and X-ray telescopes, but its origin has remained a
puzzle. On the one hand, the presence of large amounts of iron
and the absence of a detectable neutron star points toward a
so-called Type Ia supernova. These events occur when a white
dwarf star pulls material from an orbiting companion until the
white dwarf becomes unstable and is destroyed by a thermonuclear
explosion.
On the other hand, when viewed
in optical light, the supernova remnant appears to be expanding
into dense material that is rich in nitrogen. This would suggest
Kepler belongs to a different type of supernova (known as "Type
II") that is created from the collapse of a single massive
star that sheds material before exploding. Type Ia supernovas do
not normally have such surroundings.
A team of
astronomers, led by Stephen Reynolds of North Carolina State
University in Raleigh, N.C., was able to use the Chandra dataset
to address this mystery. By comparing the relative amounts of
oxygen and iron atoms in the supernova, the scientists were able
to determine that Kepler resulted from a Type Ia supernova.
In
solving the mystery of Kepler's identity, Reynolds and his team
have also given an explanation for the dense material in the
remnant. Kepler could be the nearest example of a relatively rare
"prompt" Type Ia explosion, which occur in more massive
progenitors only about 100 million years after the star formed
rather than several billion years. If that is the case, Kepler
could teach astronomers more about all Type Ia supernovas and the
ways in which prompt explosions from massive stars differ from
their more common cousins associated with lower mass stars. This
information is essential to improve the reliability of the use of
Type Ia stars as "standard candles" for cosmological
studies of dark energy as well as to understand their role as the
source of most of the iron in the universe.
In the new
Chandra Kepler image, red represents low-energy X-rays and shows
material around the star -- dominated by oxygen -- that has been
heated up by a blast wave from the star's explosion. The yellow
color shows slightly higher energy X-rays, mostly iron formed in
the supernova, while green (medium-energy X-rays) shows other
elements from the exploded star. The blue color represents the
highest energy X-rays and shows a shock front generated by the
explosion.
Source
/ Credit: NASA / Chandra X- Ray
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Chandra's
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Credit:
NASA/CXC/NCSU/S.Reynolds et al.
