Old flames

Chilean telescope discovers solar-twin and sees Sun’s future

Through studying a star almost identical to the Sun — though four billion years older — scientist have uncovered what lies ahead for our life-giving star.

Tuesday, September 17, 2013  
The lifecycle of a sun-like star. Photo by ESO The lifecycle of a sun-like star. Photo by ESO

 

Stars vary drastically in makeup and behavior, and for years scientists have been unable to answer exactly what the future holds for the Sun — until now. Using the Very Large Telescope (VLT) in Northern Chile, astronomers have discovered and studied what is essentially a replica of our Sun, though at 8.2 billion years it is almost double its age.

“For decades, astronomers have been searching for solar twins in order to know our own life-giving Sun better,” Jorge Melendez of the University of São Paulo and co-author of the study, said. “But very few have been found since the first one was discovered in 1997. We have now obtained superb-quality spectra from the VLT and can scrutinise solar twins with extreme precision, to answer the question of whether the Sun is special.”

The old star, HIP 102152, lies 250 million light years from Earth. Through studying it, scientists are able to predict what our own Sun will be like 4 billion years from now — and they have already made one important discovery.

“One issue we wanted to address is whether or not the Sun is typical in composition,” Melendez said. “Most importantly, why does it have such a strangely low lithium content?”

A light element, lithium — along with hydrogen and helium — was created early on in the universe before the first stars formed. When the Sun first came into being, it would have had a high lithium content, though now lithium has almost vanished from the Sun — scientists predict that lithium levels in the Sun are at 1 percent what they were in the Sun’s early life.

“We have found that HIP 102152 has very low levels of lithium,” TalaWanda Monroe of the University of São Paulo and lead author of the study, said. “This demonstrates clearly for the first time that older solar twins do indeed have less lithium than our own Sun or younger solar twins. We can now be certain that stars somehow destroy their lithium as they age, and that the Sun's lithium content appears to be normal for its age.”

As well as low lithium levels, HIP 102152 is similar to the sun in its deficiency of many elements abundant on Earth and in meteorites — this could be evidence that the solar twin has its own stellar system of rocky terrestrial planets.

Due to its almost non-existent humidity and clear skies, the Atacama is the world’s premier location for astronomy. Chile is home to almost half the world’s telescope infrastructure, and this is set to increase to over two thirds in the next decade.

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