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.