Astronomy

Signs of the Sun's Passage

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Science  16 Sep 2011:
Vol. 333, Issue 6049, pp. 1553
DOI: 10.1126/science.333.6049.1553-c

Recent models of the evolution of our galaxy suggest that the Sun's radial position in the Milky Way has changed during its history; in particular, the Sun may have formed closer to the galactic center, where stellar densities were higher, and then migrated outward to its current position. Through numerical simulations, Kaib et al. analyzed how the migration of the Sun through more crowded galactic environments would have affected the architecture of the Oort Cloud, the vast reservoir of icy bodies that surrounds the solar system from whence long-period comets are believed to come. Because of its location at the very edge of the solar system, the Oort Cloud's dynamics are highly sensitive to stellar and galactic gravitational perturbations. These would have been much stronger if the Sun were once deeper in the galaxy and would have affected the location of the inner edge of the Oort Cloud. A closer inner edge in the past may explain the unusual orbit of the trans-Neptunian dwarf planet Sedna, which is well beyond those of the giant planets and the Kuiper Belt (the other reservoir of comets, just beyond the orbit of Neptune) but inside the current inner edge of the Oort Cloud.

Icarus 10.1016/j.icarus.2011.07.037 (2011).

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