252 research outputs found
Binaries in the Kuiper Belt
Binaries have played a crucial role many times in the history of modern
astronomy and are doing so again in the rapidly evolving exploration of the
Kuiper Belt. The large fraction of transneptunian objects that are binary or
multiple, 48 such systems are now known, has been an unanticipated windfall.
Separations and relative magnitudes measured in discovery images give important
information on the statistical properties of the binary population that can be
related to competing models of binary formation. Orbits, derived for 13
systems, provide a determination of the system mass. Masses can be used to
derive densities and albedos when an independent size measurement is available.
Angular momenta and relative sizes of the majority of binaries are consistent
with formation by dynamical capture. The small satellites of the largest
transneptunian objects, in contrast, are more likely formed from collisions.
Correlations of the fraction of binaries with different dynamical populations
or with other physical variables have the potential to constrain models of the
origin and evolution of the transneptunian population as a whole. Other means
of studying binaries have only begun to be exploited, including lightcurve,
color, and spectral data. Because of the several channels for obtaining unique
physical information, it is already clear that binaries will emerge as one of
the most useful tools for unraveling the many complexities of transneptunian
space.Comment: Accepted for inclusion in "The Kuiper Belt", University of Arizona
Press, Space Science Series Corrected references in Table
Moons Are Planets: Scientific Usefulness Versus Cultural Teleology in the Taxonomy of Planetary Science
We argue that taxonomical concept development is vital for planetary science
as in all branches of science, but its importance has been obscured by unique
historical developments. The literature shows that the concept of planet
developed by scientists during the Copernican Revolution was theory-laden and
pragmatic for science. It included both primaries and satellites as planets due
to their common intrinsic, geological characteristics. About two centuries
later the non-scientific public had just adopted heliocentrism and was
motivated to preserve elements of geocentrism including teleology and the
assumptions of astrology. This motivated development of a folk concept of
planet that contradicted the scientific view. The folk taxonomy was based on
what an object orbits, making satellites out to be non-planets and ignoring
most asteroids. Astronomers continued to keep primaries and moons classed
together as planets and continued teaching that taxonomy until the 1920s. The
astronomical community lost interest in planets ca. 1910 to 1955 and during
that period complacently accepted the folk concept. Enough time has now elapsed
so that modern astronomers forgot this history and rewrote it to claim that the
folk taxonomy is the one that was created by the Copernican scientists.
Starting ca. 1960 when spacecraft missions were developed to send back detailed
new data, there was an explosion of publishing about planets including the
satellites, leading to revival of the Copernican planet concept. We present
evidence that taxonomical alignment with geological complexity is the most
useful scientific taxonomy for planets. It is this complexity of both primary
and secondary planets that is a key part of the chain of origins for life in
the cosmos.Comment: 68 pages, 16 figures. For supplemental data files, see
https://www.philipmetzger.com/moons_are_planets
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