Brazilian Researchers Identify the Oldest Solar Twin

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It follows an article published day (09/25) in the english website of the Agência FAPESP highlighting that Brazilian Researchers identify the oldest solar twin.

Duda Falcão

Articles

Brazilian Researchers Identify

the Oldest Solar Twin

By Karina Toledo

September 25, 2013

Published in Astrophysical Journal Letters,

the study offers clues to what our star will

be like 4 billion years from now (release)

Agência FAPESP – A group of international astronomers led by researchers at Universidade de São Paulo (USP) has identified the oldest known solar twin in the Capricorn constellation: HIP 102152.

In addition to offering clues about what our Sun will be like as it ages, the study shows a strong correlation between the degree of lithium found in this type of star and its age, helping solve an age-old mystery in astronomy.

HIP 102152 is located 250 light-years from Earth and has an estimated age of 8.2 billion years – almost double that of the Sun, which is 4.6 billion years old. To observe the star, the team, which was composed of scientists from the United States, Australia, Germany, the United Kingdom, Portugal and Brazil, utilized the Very Large Telescope (VLT) array at the European Southern Observatory (ESO), located in Northern Chile.

Part of the FAPESP-funded study occurred during the post-doctorate of TalaWanda Rose Monroe, at the Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG) at USP. The results are available in the on-line version of the Astrophysical Journal Letters.

“As human existence is too short to study the Sun’s evolution, one alternative is to observe similar stars in different phases of evolution. This star HIP 102152 gives us an opportunity to see how the Sun will be 4 billion years from now,” said Monroe in a press conference organized by IAG on August 28 to announce the discoveries.

The researcher explained that solar twins are very rare stars that have a mass, gravity, temperature and chemical composition very similar to the Sun’s. The team used a UVES spectrograph at the ESO to analyze the properties of HIP102152 and those of another younger solar twin, 18 Scorpii, whose age was estimated at 2.9 billion years.

“Spectroscopy is a powerful technique that allows one to break the starlight into the several colors that comprise it. This allows us to observe the chemical elements that are found in the stellar atmosphere, as well infer its mass, age and metallicity,” explained Monroe.

According to Jorge Luis Meléndez Moreno, who supervised Monroe’s study at IAG, the result of the analysis revealed that, like the Sun, HIP 102152 has a chemical composition that allows for the formation of rocky planets around it.

“Previous studies have shown that the Sun, when compared to similar stars, has a deficiency of chemical elements that are abundant in meteorites, asteroids and rocky planets such as the Earth, Mars and Mercury. The Sun’s missing material was probably used to form the terrestrial planets of our solar system. Because HIP 102152 has this same level of deficiency in these elements, there is a strong possibility that it also originated planets like the Earth,” explained Meléndez.

According to the researcher, studies have been conducted since 2011 at the European Astral Observatory in the quest for rocky planets orbiting HIP 102152, but none have been found.

“This is good because the easiest planets to find are gaseous giants like Jupiter. And if a planet of this type existed in the most internal regions of the star’s orbit, the so-called habitable zone, it would completely destabilize the orbit of a rocky planet,” said Meléndez.

Nevertheless, pondered the researcher, finding rocky planets with a mass as small as the Earth’s would not be possible with the equipment available today.

“We will continue looking for these planets until 2015, but we will only be able to detect super earths, or planets with masses five or ten times greater than ours. But we also intend to seek out twin earths in the future, with help of new, more precise instruments that are being developed at ESO, if Brazil’s membership in the Observatory is approved by congress,” commented Meléndez.

Mystery Solved

The study coordinated by Monroe also helped explain an age-old mystery that has intrigued astronomers for more than 60 years, namely, why some stars have higher levels of lithium than others and why the Sun’s lithium levels are lower than those of the majority of solar twins detected.

“The study of meteorites revealed that the quantity of lithium found in the Sun when the Solar System was being formed was 160 greater. No one can explain what has happened to this element. It is a mystery in the classical theory of stellar evolution,” said Melendez.

The volume of lithium found in HIP 102152, however, is even lower than that of the Sun, and that in the younger 18 Scorpii is higher. According to USP’s team, these results indicate that as a star ages, its lithium abundance declines.

“This finding is very important, not only because it allows us to use this chemical element to determine the age of the star but also because it adds new ingredients to models of how stars evolve. It can help astrophysicists understand the mechanism that allows for lithium transport from the most external regions of the star to the most internal areas, where it will be destroyed,” said Meléndez.

The first solar twin was found in 1997, and only a few stars of this type have been identified since then.

The article High precision abundances of the old solar twin HIP 102152: Insights on Li depletion from the oldest sun (doi: 10.1088/2041-8205/774/2/L32) can be read at http://iopscience.iop.org/2041-8205/774/2/L32/pdf/2041-8205_774_2_L32.pdf.

Source: English WebSite of the Agência FAPESP