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Does our sun have any brothers and sisters and, if so, where are they?

That's a question that has puzzled astronomers, who think that our sun most likely formed in a molecular cloud along with other stars.

But now a simulation has predicted that we should be able to find such siblings, because all stars born from the same cloud have a similar chemical 'fingerprint'.

Scroll down for animations showing the simulation

Astrophysicists at the University of California have simulated star formation. They show that stars born of the same cloud have similar 'fingerprints'. This information could be used to find stars that were born from the same molecular cloud as our sun (shown) - even if they are the other side of the galaxy

The simulation was devised by astrophysicists at the University of California, Santa Cruz.

Their results, published in Nature, show that stars born from the same cluster will share a chemical fingerprint with each other.

This can then be used to trace them to the same birthplace.

'We can see that stars that are part of the same star cluster today are chemically identical,' said Dr Mark Krumholz, professor of astronomy and astrophysics at UC Santa Cruz.

'But we had no good reason to think that this would also be true of stars that were born together and then dispersed immediately rather than forming a long-lived cluster.'

For example it's thought that our sun and its siblings probably went their own separate ways within a few million years after they were born.

But the study suggests that, even if the long-lost siblings are now the other side of the galaxy, they could be found.

To make the findings Dr Krumholz and UC Santa Cruz graduate student Yi Feng used supercomputers to simulate two streams of interstellar gas coming together to form a cloud that, over the course of a few million years, collapses under its own gravity to make a cluster of stars.

This face-on view of the simulation shows interstellar giant molecular cloud gas streams mixing before collapsing to form stars. The numbers rapidly increasing at the upper left show the passage of time in millions of years. The left panel shows the density of interstellar gas and right panel shows red and blue 'tracer dyes'

The results showed extreme turbulence as the two streams came together, and this turbulence effectively mixed together the tracer dyes.

'We put red dye in one stream and blue dye in the other, and by the time the cloud started to collapse and form stars, everything was purple,' said Dr Krumholz. 

'The resulting stars were purple as well.

'This explains why stars that are born together wind up having the same abundances: as the cloud that forms them is assembled, it gets thoroughly mixed. 

'This was actually a bit of a surprise. I didn't expect the turbulence to be as violent as it was, so I didn't expect the mixing to be as rapid or efficient. I thought we'd get some blue stars and some red stars, instead of getting all purple stars.'

This edge-on view shows a cross section through the two streams as they meet. In both animations the circles outlined in black are stars; stars are shown as white in the left panel, and in the right panel their color reflects the amount of the two tracer dyes in each star

The simulations also showed that the mixing happens very fast, before much of the gas has turned into stars. 

This is encouraging for the prospects of finding the sun's siblings, because the distinguishing characteristic of stellar families that don't stay together is that they probably disperse before much of their parent cloud has been converted to stars. 

If the mixing didn't happen quickly enough, then the chemical uniformity of star clusters would be the exception rather than the rule. 

Instead, the simulations indicate that even clouds that don't turn much of their gas into stars produce stars with nearly identical chemical signatures.

'The idea of finding the siblings of the sun through chemical tagging is not new, but no one had any idea if it would work," Dr Krumholz said. 

'The underlying problem was that we didn't really know why stars in clusters are chemically homogeneous, and so we couldn't make any sensible predictions about what would happen in the environment where the sun formed, which must have been quite different from the environments that give rise to long-lived star clusters. 

'This study puts the idea on much firmer footing and will hopefully spur greater efforts toward making use of this technique.'

In the simulation the researchers found that chemicals in interstellar clouds, represented by a purple trace dye (shown), mixed more than thought in the turbulent event. The research could ultimately lead to find brothers and sisters of our sun elsewhere in the Milky Way