29 agosto 2012

Solar system genealogy revealed by extinct short-lived radionuclides in meteorites. Astronomy & Astrophysics, Volume 545, September 2012.

The stellar environment of the Solar System at its birth is not yet fully known, as it has accomplished 20 revolutions around the galactic centre since its formation 4.5 billion years ago. 
Matthieu Gounelle (Laboratoire de Minéralogie et Cosmochimie du Muséum National d'Histoire naturelle/CNRS) and Georges Meynet (Observatoire de Genève) established the Solar System genealogy thanx to a radioactive element, 26Al, which was present in the nascent Solar System. 
Their results are published this week in the journal Astronomy & Astrophysics.
The authors of this paper show that the parent massive star (name proposed: Coatlicue, from the Sun's mother in the Aztec cosmogony) and which is roughly 30 times more massive than our Sun, they was born with roughly 2000 stars. The star Coatlicue died in a supernova explosion.

The authors show that the parent massive star, which they propose to call Coatlicue (the Sun's mother in the Aztec cosmogony), and which is roughly 30 times more massive than our Sun, was born together with roughly 2000 stars. Coatlicue died since then in a supernova explosion. The Sun was born together with a few hundred twin stars whose chemical composition was identical to ours. These stars had a mass comparable to that of the Sun, but did not influence its development nor that of its planets. These twin stars are now dispersed in the Galaxy and cannot be identified.

Read more at: http://phys.org/news/2012-08-solar-genealogy-revealed-meteorites.html#jCp
Solar system genealogy revealed by extinct short-lived radionuclides in meteorites
M. Gounelle1 and G. Meynet2
1 Laboratoire de Minéralogie et de Cosmochimie du Muséum, UMR 7202, Muséum National d’Histoire Naturelle & CNRS, 75005 Paris, France.
2 Geneva Observatory, University of Geneva, Maillettes 51, 1290 Sauverny, Switzerland.
Astronomy & Astrophysics. Volume 545, September 2012.
Received: 14 February 2012. Accepted: 6 June 2012. Published online: 27 August 2012.


Abstract
Context. Little is known about the stellar environment and the genealogy of our solar system. Short-lived radionuclides (SLRs, mean lifetime τ shorter than 100 Myr) that were present in the solar protoplanetary disk 4.56 Gyr ago could potentially provide insight into that key aspect of our history, were their origin understood.
Aims. Previous models failed to provide a reasonable explanation of the abundance of two key SLRs, 26Al (τ26 = 1.1 Myr) and 60Fe (τ60 = 3.7 Myr), at the birth of the solar system by requiring unlikely astrophysical conditions. Our aim is to propose a coherent and generic solution based on the most recent understanding of star-forming mechanisms.
Methods. Iron-60 in the nascent solar system is shown to have been produced by a diversity of supernovae belonging to a first generation of stars in a giant molecular cloud. Aluminum-26 is delivered into a dense collected shell by a single massive star wind belonging to a second star generation. The Sun formed in the collected shell as part of a third stellar generation. Aluminum-26 yields used in our calculation are based on new rotating stellar models in which 26Al is present in stellar winds during the star main sequence rather than during the Wolf-Rayet phase alone. Our scenario eventually constrains the time sequence of the formation of the two stellar generations that just preceded the solar system formation, along with the number of stars born in these two generations.
Results. We propose a generic explanation for the past presence of SLRs in the nascent solar system, based on a collect-injection-and-collapse mechanism, occurring on a diversity of spatial/temporal scales. In that model, the presence of SLRs with a diversity of mean lifetimes in the solar protoplanetary disk is simply the fossilized record of sequential star formation within a hierarchical interstellar medium. We identify the genealogy of our solar system’s three star generations earlier. In particular, we show that our Sun was born together with a few hundred stars in a dense collected shell situated at a distance of 5−10 pc from a parent massive star having a mass greater than about 30 solar masses and belonging to a cluster containing  ~1200 stars.

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