An international team led by Brazilian astronomers has used ESO’s Very Large Telescope toidentify and study the oldest solar twin known to date. Located 250 light years from Earth, thestar HIP 102152 is more like the Sun than any other solar “brother”, with the exception of being almost four billion years older. This primitive but practically identical twin gives us an unprecedented opportunity toappreciate what the sun will look like when it ages. Furthermore, the new observations provide, for the first time, an important and clear link between the age of a star and its lithium content, and further suggest that HIP 102152 could host rocky terrestrial planets.
Astronomers have been observing the Sun through telescopes for only 400 years, a tiny fraction of the star’s age, which is more than four billion years old. Thus, it is extremely difficult to study the history and future evolution of our star, but it is possible ifwe look for unusual stars with the same characteristics but at different stages of their lifes. The new identical but elderly twin of the Sun could help solve this difficulty.
Jorge Meléndez (University of São Paulo, Brazil), and his team studied two solar twins, one believed to be younger than the Sun (18 Scorpii) and the other expected to be older (HIP 102152). The UVES spectrograph, installed on ESO’s Very Large Telescope (VLT) at the Paranal Observatory, was used to break down the light coming from these stars and thus study their chemical composition and other properties in great detail.
Thus they discovered that HIP 102152, in the constellation Capricorn, is the oldest known solar twin so far. It is estimated that it is about 8,200 million years old, compared to the 4,600 million years of our own Sun. On the other hand, it was confirmed that the star 18 Scorpii was indeed younger than our star (with about 2,900 million years of age ).
Thestudy of the former solar twin HIP 102152It will allow scientists to predict what might happen to our Sun when it reaches that age. For now, it has already revealed an unknown about its composition: why is its lithium content so surprisingly low? Lithium, the third element in the periodic table, was created in the Big Bang along with hydrogen and helium. For years astronomers have wonderedwhy some stars seem to have less lithium than others. With the new observations of HIP 102152, a big step has been taken towards solving this mystery, by determininga strong correlation between the age of a star like the Sun and its content of this element. Currently our Sun contains only 1% of the original lithium that the material from which it was formed had. However, HIP 102152 has very low levels of lithium, clearly showing that older solar twins do indeed have less lithium than our own Sun or younger solar twins. “Now we can be sure thatstars somehow destroy the lithium that makes them up as they age“conclude the scientists.
