Now, a big bubble theory

Solar system was born in a shell made of material flung off a giant star, says study

December 26, 2017 10:00 pm | Updated 10:00 pm IST - New York

A Wolf-Rayet star sparkles in the centre of a distinctive blue bubble made of a cloud of dust, hydrogen, helium and other gases. The material expelled from the star can later nourish a new generation of stars and planets.

A Wolf-Rayet star sparkles in the centre of a distinctive blue bubble made of a cloud of dust, hydrogen, helium and other gases. The material expelled from the star can later nourish a new generation of stars and planets.

Scientists have said that the solar system could have formed in the bubbles produced by a giant, long-dead star, which was 40 to 50 times the size of the sun.

Despite the many impressive discoveries humans have made about the universe, scientists are yet to come to a consensus about the birth story of the solar system.

The prevailing theory is that the solar system formed billions of years ago near a supernova.

But the new scenario, explained in a paper in the Astrophysical Journal , begins with a giant type of star called a Wolf-Rayet star.

They burn the hottest of all stars, producing tonnes of elements which are flung off the surface in an intense stellar wind.

As the Wolf-Rayet star sheds its mass, the stellar wind ploughs through the material around it, forming a bubble structure with a dense shell.

“The shell of such a bubble is a good place to produce stars,” because dust and gas become trapped inside where they can condense into stars, said study co-author Nicolas Dauphas, Professor at University of Chicago in the U.S.

The researchers estimate that 1% to 16% of all sun-like stars could be formed in such stellar nurseries.

The study addresses a nagging cosmic mystery about the presence of two elements in our solar system compared to the rest of the galaxy.

Meteorites left over from the early solar system suggests there was a lot of aluminium-26. In addition, studies increasingly suggest the solar system had less of the isotope iron-60.

This brings scientists up short, because supernovae produce both isotopes.

“It begs the question of why one was injected into the solar system and the other was not,” said co-author Vikram Dwarkadas from the University of Chicago.

This brought the scientists to Wolf-Rayet stars, which release lots of aluminium-26, but no iron-60.

As for the fate of the giant Wolf-Rayet star, the researchers believe that its life ended long ago, likely in a supernova explosion or a direct collapse to a black hole.

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