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While the visual impact of this image remains in the eye of the beholder-
the impact of the appearence of Cassiopeia A in 1572 cannot be overstated.
This Type Ia supernova explosion forever shattered man's perception of an
immutable universe. The idea that stars were not permanent denizens of the
celestial sphere was almost unimaginable during time period before this event.
Tycho Brahe's (astronomer, 1546-1601) meticulous measurements of this
"new star" in Cassiopeia tell us that it was visible for 18
months and at its peak luminosity it was brighter than Venus and could be
seen in the daytime sky! A Type Ia supernova is generated by the collapse of
a white dwarf star. White dwarves are small and exceptionally
dense stars- they are the cores of stars that have shed their outer envelopes
of gas in pretty
Planetary Nebulae fashion. If left alone, these white dwarves would cool
(after billions of years) and become the dark kernels of former sunlike stars.
However, should a white dwarf have a nearby star from which it could
accrete gas (and add mass)- the extra matter pushes the white dwarf beyond the
limit of stable existence and it explodes in dramatic fashion.
Re-discovered in 1952 by radio astronomy, the remains of this star still
glow in many wavelengths of light. Later the 200in Palomar telescope detected
the dim remains of this star in optical wavelengths. Interestingly this
image with amatuer equipment far exceeds images in optical light from
the telescopic giants of yesteryear. This gas is expanding at velocities
of millions of miles per hour. Currently the shell of gas is around 10
light years in diameter and has a temperature of around 50 million degrees.
Like the Crab
Nebula, these kinds of star deaths infuse heavy elements of matter into
the galaxy... elements that may later coalesce to become planets and people.
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