Supernova Explosion Rich With Calcium : Discovery News

A new type of supernova explosion could explain the origin of the calcium in our teeth and bones.

THE GIST

A new, third type of supernova explosion that is rich in calcium has been discovered.

The discovery may explain why some galaxies are richer in calcium than would be expected.

Calcium, which form teeth and bone, are in all living organisms.

The discovery of a new type of supernova explosion could explain why the Milky Way and other galaxies are so rich in calcium, an element that found its way into our teeth and bones.

Chemical analysis of an object known as SN 2005E shows an unusual abundance of calcium, a finding that suggested scientists had discovered a third type of supernovae, the exploded remains of stars.

"It was clear that we were seeing a new type," said Hagai Perets, with the Harvard-Smithsonian Center for Astrophysics.

Previously, supernova explosions fell into two general categories. One type stem from giant young stars -- 15 to 20 times the mass of the sun -- which build up an iron core and eventually collapse under their own weight, forming neutron stars whose outer layers rebound and then explode. The other type of explosion results from the dense remains of sun-like stars that pick up extra matter from a nearby companion, triggering a final thermonuclear explosion.

SN 2005E, located in spiral galaxy NGC 1032 about 117 million light-years away in the constellation Cetus, fits neither category. Its chemistry more resembles the collapsed massive star type, though it has significantly more calcium. It also resides in a sparsely populated area of space, while typical supernova explosions of massive stars occur in more crowded regions of galaxies.

Astronomers believe SN 2005E did have one key companion, identity unknown. It was a dysfunctional relationship, with the supernova's progenitor making regular raids on its partner's helium. That would explain some puzzling aspects SN 2005E's chemistry, including vast concentrations of calcium and titanium, elements that result from nuclear reactions of helium.

More importantly, SN 2005E does not appear to be one of a kind.

"This one, 2005E is the best studied example, but we have seven additional members that we know of. It's not just one mutant that we've only seen one," astronomer Alex Filippenko, with the University of California at Berkeley, told Discovery News.

The extra calcium distributed by these types of supernovae could explain why our galaxy and others have more calcium than computer models predict.

"If just a few percent of the supernovae are this type, that could help account for the excess," Filippenko said.

"All the atoms in your body -- other than hydrogen and helium -- were cooked up by nuclear reactions billions of years ago inside stars. Some of those stars exploded and eventually became our solar system, which formed from a cloud of hydrogen and helium that was chemically enriched by previous generations of exploded stars," Filippenko added. "That's why we have a rocky, Earth-like planet, carbon in our cells, oxygen we breathe, iron in our blood, not to speak of the silver, platinum and gold in our jewelry. It was all cooked up in the stars."

Several papers about SN2005E, written by scientists from the United States, Israel, Germany, Italy, Canada, Chile and the United Kingdom, appear in this week's Nature.