of short-lived radionuclides and early solar system chronology
- Two big questions in Solar System formation
concern the timescales of high temperature processing (e.g.,
formations of solids, temperature fluctuations in the disk .
. . etc) in the early evolutionary stages, and the
astrophysical environment in which the solar protoplanetary
disk resided. Although how and where the Solar System formed
4.5 Gyr ago is largely unknown, astronomical observations of
young stellar objects provide some constraints on the
lifetimes of their different evolutionary stages and the
environments in which they formed. However, one major
deficiency is that astronomical estimates usually have too
low a temporal resolution for high temperature processing in
the solar nebula. In order to understand the finer scale
chronologies of solid formation, I use a laboratory approach
— analyses of daughter isotopes from now-extinct,
short-lived radionuclides in meteorites.
- Radioactivities with half-lives > 100
Myrs are considered short-lived. Such half-lives are short
compared to the age of the Solar System, but are long enough
to survive over a sufficient amount of time in the solar
nebula to be incorporated into the oldest rocks, namely
Ca-Al-rich Inclusions (CAIs). The short lifetimes of these
radioactivities make them suitable for fine-scaled
chronologies in the early Solar System. Among all
short-lived radionuclides, I am particularly interested in
four isotope systems: 7Be–7Li (t1/2
= 53 days), 10Be–10B (t1/2
= 1.5 Myr), 26Al–26Mg (t1/2
= 0.7 Myr) and 41Ca–41K (t1/2
= 0.1 Myr). The refractory nature, very short half-lives,
and diverse nucleosynthetic origins of the parent isotopes
mean that they can potentially provide important constraints
on the timescales of the formation of the earliest solids
and the astrophysical processes that occurred at the
very beginning of the Solar System (within the first
several million years).
- References: Liu,
M.-C., McKeegan, K. D., Goswami, J. N., Marhas, K.
K., Sahijpal, S., Ireland, T. R., and Davis, A. M. 2009, Isotopic
Records in CM Hibonites: Implications for Timescales of
Reservoir Mixing in the Solar Nebula. Geochimica
et Cosmochimica Acta, 73,
M.-C., Nittler, L. R., Alexander, C. M. O'D
and Lee, T. 2010, Lithium-Beryllium-Boron
Compositions in Meteoritic Hibonite: Implications for
Origin of 10Be and Early Solar System
Astrophysical Journal Letters, 719,
Liu, M.-C., Chaussidon, M., Gopel, C., and
Lee, T. 2012, A
Heterogeneous Solar Nebula as Sampled by CM Hibonite.
Science Letters, 327, 75–83.
Chaussidon, M., Srinivasanl, G., and McKeegan, K. D. 2012, A
Lower Initial Abundance of Short-lived 41Ca in the Early
Solar System and Its Implications for Solar System
Formation. The Astrophysical Journal, 761,
Liu, M.-C., 2014, On
the Injection of Short-lived Radionuclides from a Supernova into the Solar Nebula: Constraints from the Oxygen Isotopes. The Astrophysical Journal Letters, 781, L28.