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A LOWER INITIAL ABUNDANCE OF SHORT-LIVED Ca-41 IN THE EARLY SOLAR SYSTEM AND ITS IMPLICATIONS FOR SOLAR SYSTEM FORMATION

Liu, Ming-Chang and Chaussidon, Marc and Srinivasan, Gopalan and McKeegan, Kevin D (2012) A LOWER INITIAL ABUNDANCE OF SHORT-LIVED Ca-41 IN THE EARLY SOLAR SYSTEM AND ITS IMPLICATIONS FOR SOLAR SYSTEM FORMATION. In: ASTROPHYSICAL JOURNAL, 761 (2).

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Official URL: http://dx.doi.org/10.1088/0004-637X/761/2/137

Abstract

The short-lived radionuclide Ca-41 plays an important role in constraining the immediate astrophysical environment and the formation timescale of the nascent solar system due to its extremely short half-life (0.1 Myr). Nearly 20 years ago, the initial ratio of Ca-41/Ca-40 in the solar system was determined to be (1.41 +/- 0.14) x 10(-8), primarily based on two Ca-Al-rich Inclusions (CAIs) from the CV chondrite Efremovka. With an advanced analytical technique for isotopic measurements, we reanalyzed the potassium isotopic compositions of the two Efremovka CAIs and inferred the initial ratios of Ca-41/Ca-40 to be (2.6 +/- 0.9) x 10(-9) and (1.4 +/- 0.6) x 10(-9) (2 sigma), a factor of 7-10 lower than the previously inferred value. Considering possible thermal processing that led to lower Al-26/Al-27 ratios in the two CAIs, we propose that the true solar system initial value of Ca-41/Ca-40 should have been similar to 4.2 x 10(-9). Synchronicity could have existed between Al-26 and Ca-41, indicating a uniform distribution of the two radionuclides at the time of CAI formation. The new initial Ca-41 abundance is 4-16 times lower than the calculated value for steady-state galactic nucleosynthesis. Therefore, Ca-41 could have originated as part of molecular cloud materials with a free decay time of 0.2-0.4 Myr. Alternative possibilities, such as a last-minute input from a stellar source and early solar system irradiation, could not be definitively ruled out. This underscores the need for more data from diverse CAIs to determine the true astrophysical origin of Ca-41.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to IOP PUBLISHING LTD, ENGLAND
Keywords: meteorites, meteors, meteoroids;nuclear reactions, nucleosynthesis, abundances;protoplanetary disks
Department/Centre: Division of Mechanical Sciences > Centre for Earth Sciences
Depositing User: Francis Jayakanth
Date Deposited: 25 Jan 2013 12:40
Last Modified: 25 Jan 2013 12:40
URI: http://eprints.iisc.ac.in/id/eprint/45635

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