Artist’s impression of the protoplanetary disk (right) during the dawn of our Solar System. A nearby dying star (on the left) sheds material into space (reddish gas).
Credit: Gabriel Pérez Díaz, Servicio MultiMedia, Instituto de Astrofísica de Canarias, Spain
SYDNEY: Strong winds from a nearby dying star may have injected radioactive material into the early Solar System, according to a new model of star death.
The findings challenge the theory that radioactive isotopes trapped in meteorites from the dawn of our Solar System originated in a supernova. They also shed light on the origins of water on Earth, says a study in the journal Meteoritics and Planetary Science, and may help astronomers predict how common water is on other planets.
"In the past, most people have been convinced that the radioactive isotopes present in the young Solar System must have come from a supernova," said co-author Maria Lugaro, an astrophysicist from Monash University in Melbourne.
Stellar winds
"What we have shown is that dying stars of lower masses, shedding material into their surroundings via strong winds, actually better match the meteoritic signature of these radioactive nuclei," she said.
Scientists have known for over 40 years that meteorites – made of rocks formed during the birth of the Solar System – contained radioactive material. Commonly thought to have been spewed into space by a spectacular cosmic explosion known as a supernova, this material polluted the gas from which these rocks formed.
The supernova theory is problematic though, say some experts.
Firstly, stars that die as supernovae are very rare and massive – at least 10 times the size of our own Sun. Secondly, models of the types of radioactive isotopes produced by supernovae don't quite match the types of isotopes found in the meteorites.
Red giants
Although closely matching the meteoritic levels of aluminium-26 and iron-60, supernovae are predicted to produce too much manganese-55.
Lugaro and colleagues suspected this is because a different kind of dying star, known as a red giant, is responsible for the radioactive material. Red giants are much smaller – sometimes with less mass than our Sun – and are much more common than the massive stars that create supernovae.
To test their theory, telescopes were used to record the emissions from red giants as they were dying. Spectral measurements from these telescopes were then used to validate a theoretical computer model of star evolution, composition and death.
