Article

# Astronomy. The cradle of the solar system.

• ##### L. A. Leshin
Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504, USA.
Science (Impact Factor: 31.2). 06/2004; 304(5674):1116-7. DOI: 10.1126/science.1096808
Source: PubMed

ABSTRACT The recent discovery of decay products of 60Fe in meteorites challenges
conventional wisdom about the environment in which the Sun and planets
formed. Rather than a region like the well-studied Taurus-Auriga
molecular cloud, the solar system must have formed instead in a region
more like the Eagle nebula--a region that contained one or more massive
stars that went supernova, injecting newly synthesized radionuclides
into the nascent solar system. In their Perspective, Hester et al.
discuss a scenario by which the solar system--and other low-mass stars
like the Sun--could have formed. Radiant energy from massive, luminous
stars first compresses surrounding interstellar gas, triggering the
formation of Sun-like stars, then quickly disperses this material,
exposing newborn stars and their protoplanetary disks to harsh radiation
from the massive stars. When the massive stars go supernova, they pelt
surrounding protoplanetary disks with ejecta laden with the products of
stellar nucleosynthesis that are required to explain the isotopic
composition we see today.

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ABSTRACT: Abstract Every Galactic environment is characterized by a stellar density and a velocity dispersion. With this information from literature, we simulated flyby encounters for several Galactic regions, numerically calculating stellar trajectories as well as orbits for particles in disks; our aim was to understand the effect of typical stellar flybys on planetary (debris) disks in the Milky Way Galaxy. For the solar neighborhood, we examined nearby stars with known distance, proper motions, and radial velocities. We found occurrence of a disturbing impact to the solar planetary disk within the next 8 Myr to be highly unlikely; perturbations to the Oort cloud seem unlikely as well. Current knowledge of the full phase space of stars in the solar neighborhood, however, is rather poor; thus we cannot rule out the existence of a star that is more likely to approach than those for which we have complete kinematic information. We studied the effect of stellar encounters on planetary orbits within the habitable zones of stars in more crowded stellar environments, such as stellar clusters. We found that in open clusters habitable zones are not readily disrupted; this is true if they evaporate in less than 10(8) yr. For older clusters the results may not be the same. We specifically studied the case of Messier 67, one of the oldest open clusters known, and show the effect of this environment on debris disks. We also considered the conditions in globular clusters, the Galactic nucleus, and the Galactic bulge-bar. We calculated the probability of whether Oort clouds exist in these Galactic environments. Key Words: Stellar interactions-Galactic habitable zone-Oort cloud. Astrobiology 13, 491-509.
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##### Article: [Fe II] 1.64 um Features of Jets and Outflows from Young Stellar Objects in the Carina Nebula
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