The older twin of the Sun

An international team led by Brazilian astronomers used the VLT (Very Large Telescope) of the ESO to identify and study the older twin of the Sun so far known.  To 250 light-years from Earth, the star HIP 102152 is closer to the Sun than any other solar twin – except that has about four billion years older.  This older twin, but almost identical, gives us an unprecedented opportunity to see how the Sun differs from the older twin Sun. The new observations also provide for the first time a clear link between the age of the star and its content of lithium, suggesting that HIP 102152 can host Rocky planets of Earth type.



Astronomers observed the Sun with a telescope for 400 years – only a very small fraction of the age of the Sun, which is now more than four billion years old.  It is difficult to study the history and the future development of our star, but we can get it looking those rare stars almost exactly equal to ours but which are in different stages of life.  Astronomers have now identified a star that is essentially an identical twin to the Sun which is about 4 billion years older than our Sun– almost like seeing a real version of the twin paradox. Jorge Melendez (Universidad de São Paulo, Brazil), Chief of staff and co-author of the new paper, explains: “For decades astronomers have searched the twin stars of the Sun to better understand the source of our energy and life.

But very few have been found: the first was only discovered in 1997.  Now we have obtained spectra of exceptional quality from VLT and we can examine the solar twins with extreme precision, to answer the question if the Sun is really a special Star “. The team studied solar twins-one that we thought was younger than the Sun (18 Scorpii) and one older (HIP 102152).  They used the UVES spectrograph on the VLT (Very Large Telescope) at ESO’s Paranal Observatory to split light into its component colors in order to study in detail the chemical composition and other properties of these stars.

They found that HIP 102152, constellation Capricornus, is the oldest solar twin so far found.  It is estimated that 8.2 billion years, compared to 4.6 of our Sun.  On the other hand has confirmed that 18 Scorpii is younger than the Sun- with an age of about 2.9 billion years. Studying old solar twin HIP 102152 enables scientists to predict what could happen in the Sun as they reach that age, and in this sense the discovery has already made significant.  “One of the points that we wanted to clarify is if the Sun has a chemical composition typical,” says Melendez, “and, more importantly, why it has a content of lithium strangely so low?” Lithium, the third element of the periodic table, was created in the Big Bang along with the hydrogen and helium.

Astronomers for years reflect on why some stars seem to have less other lithium.  With the new HIP 102152 observation it was taking a big step forward in solving this riddle, identifying a strong correlation between the age of a solar-type star and its lithium content. The Sun contains just the 1% of lithium present in the material from which it is formed.  Examinations of the younger solar twins suggest that these babies have much larger amounts of lithium, but so far they couldn’t show a clear correlation between age and lithium content. Tala Wanda Monroe (Universidad de São Paulo), the first author of the article concludes: “we found that HIP 102152 has really low lithium content.

This shows clearly for the first time that the older solar twins have clearly less lithium than their younger twins.  We can now be sure that the stars somehow destroy lithium in time and that the lithium content of the Sun is normal for his age “. The final implication of the story is that HIP 102152 has a slightly different chemical composition from most other solar twins, but it is very similar to the Sun.  Both show a shortage of elements that are abundant in meteorites and the Earth.  This is a strong indication that HIP 103252 can host Rocky planets of Earth type.

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