Could an exploding star have been responsible for the death of the dinosaurs? This
idea has become popular again as an explanation for the disappearance of the
dinosaurs. An exploding star can blast material enormous distances into space. If
this material reached Earth?s atmosphere, changes may have occurred that were
harmful to life.
We call an exploding star a supernova. Nova is the Latin word for new, and in
ancient times, when an exploding star was observed, people often thought a new
star was being born. The plural form of nova is novae. So when we talk of more than
one supernova, we say supernovae.
When a star has used all it?s nuclear fuel, the gravitational force that pulls
the star?s material towards it?s center no longer has an opposing force to act
against it. As a result the star collapses. A star that once had eight times as much
matter as our sun and was 1,000,000 miles across, becomes a sphere only ten to
fifteen miles across. As the star collapses, very small particles (called neutrinos)
escape into space. After the star becomes a very small sphere, it explodes like a
giant nuclear bomb and becomes a billion times as bright as our own sun. All kinds
of matter and radiation are blasted into space. This matter and radiation travels
through space at nearly the speed of light (186,000 miles per second)
Now, if one of these supernovae were to occur within about 130 light years
of Earth, some scientists feel that life on earth would be drastically affected.
Since a light year is the distance light travels in one year, 130 light years is about
760,000,000,000,000 (760 quadrillion miles!).
So, suppose a supernova had occurred sixty-five million years ago within 130
light years of Earth, how exactly would it cause the death of the dinosaurs? Some
scientists think neutrinos and galactic cosmic rays would cause extremely high
rates of deadly cancer among the animals. Others believe neutrinos and radiation
caused reaction within the Earth?s atmosphere that resulted in destruction of the
ozone layer. Without the ozone layer to filter out dangerous radiation, high rates
of cancer would occur. Only small animals and plants, whose homes were sheltered
from the harmful radiation would survive. An identical result would occur if no
ozone layer existed to filter out radiation coming from our own Sun.