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Q&A: Supernova Remnants and Neutron Stars
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Q:
Where in the galaxy would you expect to find Type I and Type II
supernovas?
A:
The two basic types of supernovas are Type Ia and Type II. Other
types, such as Types Ib and Ic, are unusual supernovas that have
most of the properties of type II supernovas.
Type Ia are believed to be triggered by a large transfer of mass
from a companion star onto a white dwarf that pushes the white
dwarf over the Chandrasekhar limit. A thermonuclear explosion
follows, blowing the entire star apart, and sending material
rich in iron and other products of the explosion rushing out
into space. Since a white dwarf is involved, Type Ia supernovas
are expected to be found among old star systems, such as
globular clusters, the central bulges of galaxies and elliptical
galaxies.
Type II supernovas are thought to result from the collapse of a
massive star (ten or more times as massive as the Sun) that has
reached the end of the red giant stage of evolution, and formed
an iron core. The core collapses under the weight of the outer
layers of the star. A neutron star is formed, lots of neutrinos
and other radiation is emitted, and everything except the
neutron star is blown away. Since massive stars are involved,
Type II supernovas are found in the spiral arms and other
star-forming regions of spiral and disk galaxies, which have
lots of gas and dust for the formation of new stars.
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