Astronomers find Sun’s oldest ‘twin’, solving mystery about stellar aging

Astronomers studying a star nearly identical to our Sun — a 'solar twin' — have made some important discoveries, clearing up a mystery about the age and composition of the Sun, and possibly showing that this star has a planet system similar to our own.

Anyone looking for answers about our Sun can get a lot of help from 'solar twins'. By examining these stars, they can get an idea of whether the Sun is remarkable in some way, or if it's fairly typical. They can also see what our Sun was probably like in the past, and what it will possibly be like in the future.

One question that's been on astronomer's minds for awhile is whether or not there's a connection between a star's age and the amount of lithium they detect in it. Lithium is a fairly simply element, which was created along with hydrogen and helium during The Big Bang, and it would have been abundant in the materials that formed the Sun. However, now, the Sun has only a very small amount of lithium in it, roughly 1% the original amount. Higher amounts have been seen in younger stars, like 18 Scorpii, another solar twin in the study, but no specific connection to age could be made until now.

Recently astronomers gathered the light from a star called HIP 102152, which is located 250 light years away from us, in the constellation Capricornus. Their observations showed that this star could be called an identical twin of our Sun, except that it's much older (around 8.2 billion years old, or 3.6 billion years older than the Sun), and the amount of lithium they detected from it gives them the solid connection they were looking for.

"We have found that HIP 102152 has very low levels of lithium," said study lead author TalaWanda Monroe, of the Universidade de São Paulo, according to an ESO statement. "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."

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The fact that HIP 102152 is considered a nearly identical twin of the Sun will be some exciting news for planet hunters.

According to the study, there's a particular pattern they see in the elements and chemicals that make up HIP 102152 that they don't see in all solar twins, but they do see in our Sun. The reason this pattern shows up is because those elements and chemicals that are missing or deficient in the Sun went into making the rocky planets and asteroids in our solar system. Therefore, with HIP 102152 showing this same pattern, it's quite likely that it has the same kind of rocky planets and asteroids orbiting it as well.

Adding to that, since astronomers haven't detected any large gas giant planets orbiting close to the star, that increases the odds that any rocky planet that might be there would be orbiting inside the star's habitable zone. That makes HIP 102152 a great candidate for a followup study by anyone looking for extrasolar planets.

If you'd like to know where HP 102152 is, this video, made by the European Southern Observatory, gives a good look as it zooms in on the location of our Sun's oldest twin.

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