THE FUTURE OF THE SUN: AN EVOLVED SOLAR TWIN REVEALED BY COROT
ACCEPTED TO APJL., ASTRO-PH:1305.3652 PREPRINT
A team of Japanese and Brazillian astronomers led by Jose Dias do Nascimento (Department of Theoretical and Experimental Physics, Universidade Federal do Rio Grande do Norte [DFTE, UFRN], Brazil) has found the farthest known solar twin in the Milky Way Galaxy-- CoRoT Sol 1, which has about the same mass and chemical composition as the Sun.
Spectra from the High Dispersion Spectrograph (HDS) on the Subaru Telescope showed that CoRoT Sol 1 is about 6.7 billion years old while space-based data from the CoRoT (Convection, Rotation and planetary Transits) satellite indicated a rotation period of 29 +/- 5 days. This newly discovered, evolved solar twin allows astronomers to uncover the near future of our solar system's central star--the Sun.
Spectra from the High Dispersion Spectrograph (HDS) on the Subaru Telescope showed that CoRoT Sol 1 is about 6.7 billion years old while space-based data from the CoRoT (Convection, Rotation and planetary Transits) satellite indicated a rotation period of 29 +/- 5 days. This newly discovered, evolved solar twin allows astronomers to uncover the near future of our solar system's central star--the Sun.
Being the closest star from Earth, the Sun has been extensively studied by different techniques. Despite the effort of many astronomers, we do not know yet how peculiar is the Sun among stars. In particular, the true rotation of stars similar to the Sun are unknown, except for the youngest Suns, but there is alack of studies in mature stars like the Sun or in more evolved ones. The main characteristics that determine the evolution of a star are mass (its amount of matter) and the chemical composition. Thus, studying stars with the same mass and composition as the Sun, the so-called solar twins, we can know more about our own Sun, as solar twins of different ages cover different snapshots during the evolution of the Sun (Figure).
he satellite CoRoT has provided precise space-based data from which it is possible to determine the rotation periods of stars. Our Team has selected the best solar twin candidates spanning a range of rotation periods, so that the evolution of the rotation period of the Sun can be studied in detail. In our initial attempt three of our solar twin candidates were observed at the Subaru telescope. A large telescope is needed as the CoRoT solar twins are faint and we need to spread out the stellar light, i.e., to obtain a stellar spectrum, to study in detail the characteristics of the stars. After a detailed analysis we found that one of our solar twin candidates is indeed a star with a mass and chemical composition similar to solar, but in a light more evolved stage, being thus precious to study the future of the Sun.
How old is CoRoT Sol 1 ?
Is just about the one of most difficult questions you can ask about a star. High quality spectra, could shed a new light in the question of stellar ages. The discovered solar twin, which we call CoRoT Sol 1, is about 2 billion years older than the Sun, and its rotation period is as the Sun's.
Also, from the Subaru spectra of the CoRoT Sol 1 we found that it has a Li abundance lower than solar (Figure above), this element decrease with age. Although the overall chemical composition of CoRoT Sol 1 is similar to the Sun, its detailed abundance pattern show some differences, as is also shown by most nearby solar twins which are relatively brighter.
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