Supernova conception: Chemical evidence from meteorites suggests that the explosion of a truly massive star triggered the formation of our Solar System.

Credit: NASA

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SYDNEY: New evidence backs up the idea that a shockwave from the explosion of massive star triggered the collapse of a dense, dusty gas cloud to form our Sun and its retinue of planets.

For many decades astronomers have postulated that the after effects of this violent supernova led to the birth of the Solar System.

But detailed models of this formation process have only produced the right results under the simplifying – and likely wrong – assumption that the temperatures during the violent events remained constant.

Devil in the details

Now, U.S. astrophysicists at the Carnegie Institution, in Washington DC, have shown for the first time that a supernova could indeed have triggered the Solar System's formation under the more likely conditions of rapid heating and cooling.

They argue that their results, published last month in the Astrophysical Journal, resolve a long-standing debate.

"We've had chemical evidence from meteorites that points to a supernova triggering our Solar System's formation since the 1970s," said Alan Boss, lead author of the study.

"But the devil has been in the details," he said. "Until this study, scientists have not been able to work out a self-consistent scenario, where collapse is triggered at the same time that newly created isotopes from the supernova are injected into the collapsing cloud."

Short-lived radioactive isotopes – versions of elements with the same number of protons, but a different number of neutrons – found in very old meteorites decay on time scales of millions of years and turn into different 'daughter' elements.

Hewn in the furnace of massive stars

Finding these daughter elements in primitive meteorites is helpful, in that it implies that the short-lived radioisotopes they were formed from must have been created only a million or so years before the meteorites themselves were formed.

"One of these parent isotopes, iron-60, can be made in significant amounts only in the potent nuclear furnaces of massive or evolved stars," explained Boss. "Iron-60 decays into nickel-60, and nickel-60 has been found in primitive meteorites. So we've known where and when the parent isotope was made, but not how it got here."

Previous models by Boss and former Carnegie colleague Prudence Foster showed that the isotopes could be deposited into a 'pre-solar cloud' if a shock wave from a supernova explosion was simplistically slow and cool.