Astronomers using ESO’s Very Large Telescope have identified the oldest solar twin known to date.
This image shows the Sun-like star HIP 102152. Credit: ESO/ Digitized Sky Survey 2. Acknowledgement: Davide De Martin.
The star, labeled HIP 102152, is located 250 light-years from Earth in the constellation of Capricornus. It is more like the Sun than any other solar twin – except that it is about 4 billion years older.
HIP 102152 gives scientists an unprecedented chance to see how the Sun will look when it ages.
The new observations also provide an important first clear link between a star’s age and its lithium content, and in addition suggest that HIP 102152 may be host to rocky terrestrial planets.
“For decades, astronomers have been searching for solar twins in order to know our own life-giving Sun better. 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 scrutinize solar twins with extreme precision, to answer the question of whether the Sun is special,” Dr Jorge Melendez from the Universidade de São Paulo, Brazil, who is a second author of a paper published in the Astrophysical Journal Letters (full paper in .pdf).
Dr Melendez and his colleagues studied two solar twins – one that was thought to be younger than the Sun – 18 Scorpii, and one that was expected to be older – HIP 102152.
They used the UVES spectrograph on the Very Large Telescope (VLT) to split up the light into its component colors so that the chemical composition and other properties of these stars could be studied in great detail.
They found that HIP 102152 is the oldest Sun’s twin known to date. It is estimated to be 8.2 billion years old, compared to 4.6 billion years for our own Sun. On the other hand 18 Scorpii was confirmed to be younger than the Sun – about 2.9 billion years old.
This image tracks the life of a Sun-like star, from its birth on the left side of the frame to its evolution into a red giant star on the right. Credit: ESO / M. Kornmesser.
Studying the ancient solar twin HIP 102152 allows scientists to predict what may happen to our own Sun when it reaches that age, and they have already made one significant discovery.
“One issue we wanted to address is whether or not the Sun is typical in composition. Most importantly, why does it have such a strangely low lithium content?” Dr Melendez said.
Lithium, the third element in the periodic table, was created in the Big Bang along with hydrogen and helium.
Astronomers have pondered for years over why some stars appear to have less lithium than others.
With the new observations of HIP 102152, they have taken a big step towards solving this mystery by pinning down a strong correlation between a Sun-like star’s age and its lithium content.
Our own Sun now has just 1 per cent of the lithium content that was present in the material from which it formed. Examinations of younger solar twins have hinted that these younger siblings contain significantly larger amounts of lithium, but up to now scientists could not prove a clear correlation between age and lithium content.
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Bibliographic information: TalaWanda R. Monroe et al. 2013. High Precision Abundances of the Old Solar Twin HIP 102152: Insights on Li Depletion from the Oldest Sun. ApJ 774, L32; doi: 10.1088/2041-8205/774/2/L32
