The sun once had rings – just like Saturn, according to new research.
And without them life might never have begun, say scientists.
They claim that the star was encircled by giant circles of dust that fuelled life on our planet.
The rings prevented our Earth getting too big and developing massive gravitational pull which would have stunted the growth of organisms and made asteroid impacts more frequent.
Without them life might never have got off the ground.
Lead author Dr Andre Izidoro said: ‘In the solar system, something happened to prevent the Earth from growing to become a much larger type of terrestrial planet called a super-Earth.’
They are rocky planets between about two and ten times the mass – seen around at least 30 percent of sun-like stars in the Milky Way.
The findings in Nature Astronomy are based on hundreds of super computer simulations of the solar system’s formation.
It produced rings like those seen around many distant, young stars. It also accurately identified an asteroid belt between Mars and Jupiter.
The locations and stable, almost circular orbits of Earth, Mars, Venus and Mercury were faithfully drawn.
It calculated the masses of the inner planets – including Mars – which previous attempts have overestimated.
The Kuiper belt of comets, asteroids and small bodies beyond the orbit of Neptune was also predicted.
The model assumes three bands of high pressure arose within the young sun’s disk of gas and dust.
Such ‘bumps’ have been observed in ringed stellar disks around distant stars.
Dr Izidoro, an astrophysicist at Rice University in Houston, said: ‘If super-Earths are super-common, why don’t we have one in the solar system?
‘We propose pressure bumps produced disconnected reservoirs of disk material in the inner and outer solar system and regulated how much material was available to grow planets in the inner solar system.’
For decades, scientists believed gas and dust in protoplanetary disks gradually became less dense.
But previous computer simulations show planets are unlikely to form under those scenarios.
Co-author Professor Andrea Isella, also from Rice, said: ‘In a smooth disk, all solid particles – dust grains or boulders – should be drawn inward very quickly and lost in the star.
‘One needs something to stop them in order to give them time to grow into planets.’
When particles move faster than the gas around them, they ‘feel a headwind and drift very quickly toward the star,’ Dr Izidoro explained.
At pressure bumps, gas pressure increases, gas molecules move faster and solid particles stop feeling the headwind.
He said: ‘That’s what allows dust particles to accumulate at pressure bumps.’
The phenomenon has been observed by ALMA, an enormous 66-dish radio telescope in Chile’s Atacama Desert.
Prof Isella said: ‘ALMA is capable of taking very sharp images of young planetary systems that are still forming.
‘We have discovered that a lot of the protoplanetary disks in these systems are characterised by rings.
‘The effect of the pressure bump is it collects dust particles, and that’s why we see rings.
‘These rings are regions where you have more dust particles than in the gaps between rings.’
Many previous solar system simulations produced versions of Mars as much as 10 times more massive than Earth.
The model correctly predicts Mars having about 10% of Earth’s mass. Dr Izidoro said: ‘Mars was born in a low-mass region of the disk.’
The delayed appearance of the sun’s middle ring in some simulations led to the formation of super-Earths – which points to the importance of timing.
Dr Izidoro said: ‘By the time the pressure bump formed in those cases, a lot of mass had already invaded the inner system and was available to make super-Earths.
‘So the time when this middle pressure bump formed might be a key aspect of the solar system.’
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