Huge star explosions give clues to life’s origins

(page 2 of 3)

Teraflops computers, meanwhile, already are enabling physicists to peel away secrets hidden in the onion-like layers of core-collapse supernovae.

The dying process

Only massive stars become core-collapse supernovae.  Smaller stars can die as thermonuclear supernovae, like thermonuclear bombs on a stellar scale, leaving little behind.

Core-collapse supernovae, the type the Oak Ridge group studies, are different.  Such stars die when their cores collapse.

What’s often left is a relatively small, extremely dense, rapidly rotating object that shoots out radio waves in a swiftly pulsating pattern.  These rotating neutron stars are called pulsars.

A core-collapse supernova’s death stems from the star’s relatively short life cycle of some millions of years.  Smaller stars, like the sun, live for billions of years.

“More massive stars evolve more quickly because of their increased gravitational pull,” Mezzacappa says.  “Gravity is always pulling inward and their nuclear fuel burns more quickly as a result.”

These massive stars have onion-like layers as they approach the ends of their lives.  A silicon layer surrounds an iron core.  An oxygen layer surrounds that, then carbon and helium layers.  A hydrogen envelope is on the outside.

The iron core, at 1.25 billion degrees Fahrenheit, eventually can’t support itself against the pull of gravity and collapses, causing the supernova.

The collapsing core splits into inner and outer layers and eventually cannot compress any further.  Like a rubber ball, it springs back, creating a gigantic shock wave that obliterates the other layers in a cataclysmic explosion.

On a cosmic scale, all of this takes place in the blink of an eye, Mezzacappa says.  The core collapses in about a tenth of a second, it rebounds in about a second, and the outer layers that took millions of years to form are destroyed within a few hours.

What remains of the core is no longer iron, but a material so densely packed with neutrons that a sugar cube-sized chunk would weigh as much as Earth’s entire human population.  Such a material cannot exist here on Earth, either naturally or in a laboratory.

In fact, the density of this material is such that these neutron stars weigh more than our sun within a radius of only about six to 12 miles.  Our sun’s radius is 434,000 miles.

« Previous       1   |   2   |   3   |   Print       Next »