Exploding stars found to be source of why we stand up

A COSMIC link to the calcium in people's bones has been discovered by astronomers.

Scientists have identified a new type of supernova they believe may be the chief source of calcium in the universe and on Earth.

The mineral provides vital strength to bones, so humans and other animals may owe their ability to stand upright to violent explosions far away in space.

The discovery came as scientists observed the supernova labelled SN2005E.

Scientists believe its energy source is helium "stolen" from a companion star. Increasing pressure and temperature eventually caused the helium to ignite in an H-bomb-like thermonuclear blast.

High levels of calcium and radioactive titanium were detected during observations of the exploding star, both of which are products of nuclear reactions involving helium.

So much calcium was present that it accounted for half the material thrown out by the explosion. Two such supernovae occurring every 100 years would be enough to produce the high abundance of calcium seen in our galaxy, the Milky Way, and in all life on Earth, say the scientists.

The astronomers believe seven other previously identified supernovae may belong to the same "family".

Professor Alex Filippenko, of the University of California at Berkeley, one of the scientists whose findings appear today in the journal Nature, said: "It's a confusing, muddy situation. But we hope that, by finding more examples of this and other unusual supernovae and observing them in greater detail, we will get a better understanding of the physics that's actually going on."

The Liverpool Observatory in the UK was among those involved in obtaining the supernova data.