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JAMES D. Gilmour 《Space Science Reviews》2000,92(1-2):123-132
The tendency of iodine to be mobilised during secondary processing is reflected both in the presence of 129XeXS in secondary minerals and in the bulk 129XeXS/I ratios in meteorites. Comparison of absolute ages derived through calibration of chronometers based on 129Xe, 53Mn and 26Al against the Pb-Pb system yields a plausible timescale for the early solar system. In this system, the earliest chondrule
ages are most readily interpreted as representing formation after the beginning of parent body processing.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Robert H. Nichols Jr. 《Space Science Reviews》2000,92(1-2):113-122
Variations in the abundances of short-lived radionuclides such as 26Al (τ1/2 ≈ 0.74 Ma) and 53Mn (τ1/2 ≈ 3.7 Ma) in meteoritic solids may be used to infer relative formation intervals of these solids in the nebula at precisions
of less than 1 Ma. In a strict chronometric interpretation of the isotopic variations, whereby criteria such as spatial and
temporal isotopic homogeneity and closed system isotopic evolution are met, solid formation occurred in the nebula for at
least several million years. This is longer than some theoretical and astronomical estimates for the duration of the active
nebula. The evidence for live 41Ca (τ1/2 ≈ 0.10 Ma) in meteoritic inclusions further indicates that the onset of solid formation occurred quite early, perhaps within
a few hundred thousand years after the onset of the collapse of the sun's parent molecular cloud. Failure of the chronometric
interpretation may arise for a variety of reasons, including but not limited to, the late, inhomogeneous injection of material
from a nearby stellar source or the local production of short-lived radionuclides by an energetic particle irradiation, e. g., from T Tauri (X-wind) or galactic cosmic ray sources. Although some isotopic evidence exists that the criteria required
for a strict chronometric interpretation are not met by each of the short-lived chronometers, there is no compelling reason
to shorten the interval of solid formation in the nebula to less than 1 Ma.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
3.
Hsien Shang Frank H. Shu Typhoon Lee Alfred E. Glassgold 《Space Science Reviews》2000,92(1-2):153-176
We discuss the interaction between the magnetosphere of a young star and its surrounding accretion disk. We consider how an
X-wind can be driven magnetocentrifugally from the inner edge of the disk where accreting gas is diverted onto stellar field
lines either to flow onto the Sun or to be flung outwards with the wind. The X-wind satisfies many observational tests concerning
optical jets, Herbig-Haro objects, and molecular outflows. Connections may exist between primitive solar system materials
and X-winds. Chondrules and calcium-aluminum-rich inclusions (CAIs) experienced short melting events uncharacteristic of the
asteroid belt where meteorites originate. The inner edge of the solar nebula has the shortest orbital timescale available
to the system, a few days. Protosolar flares introduce another timescale, tens of minutes to hours. CAIs may form when solids
are lifted from shaded portions of the disk close to the Sun and are exposed to its intense light for a day or so before they
are flung by the X-wind to much larger distances. Chondrules were melted, perhaps many times, by flares at larger distances
from the Sun before being launched and annealed, but not remelted, in the X-wind. Aerodynamic sorting explains the narrow
range of sizes with which CAIs and chondrules are found in chondritic meteorites. Flare-generated cosmic-rays may induce spallation
reactions that produce some of the short-lived radioactivities associated with primitive solar system rocks.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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