Second alignment plane of solar system discovered

Date:
September 29, 2020
Source:
National Institutes of Natural Sciences
Summary:
A study of comet motions indicates that the Solar System has a
second alignment plane. Analytical investigation of the orbits of
long-period comets shows that the aphelia of the comets, the point
where they are farthest from the Sun, tend to fall close to either
the well-known ecliptic plane where the planets reside or a newly
discovered 'empty ecliptic.' This has important implications for
models of how comets originally formed in the Solar System.



FULL STORY ==========================================================================
A study of comet motions indicates that the Solar System has a second
alignment plane. Analytical investigation of the orbits of long-period
comets shows that the aphelia of the comets, the point where they are
farthest from the Sun, tend to fall close to either the well-known
ecliptic plane where the planets reside or a newly discovered "empty
ecliptic." This has important implications for models of how comets
originally formed in the Solar System.


==========================================================================
In the Solar System, the planets and most other bodies move in roughly
the same orbital plane, known as the ecliptic, but there are exceptions
such as comets.

Comets, especially long-period comets taking tens-of-thousands of years
to complete each orbit, are not confined to the area near the ecliptic;
they are seen coming and going in various directions.

Models of Solar System formation suggest that even long-period comets originally formed near the ecliptic and were later scattered into the
orbits observed today through gravitational interactions, most notably
with the gas giant planets. But even with planetary scattering, the
comet's aphelion, the point where it is farthest from the Sun, should
remain near the ecliptic.

Other, external forces are needed to explain the observed
distribution. The Solar System does not exist in isolation; the
gravitational field of the Milky Way Galaxy in which the Solar System
resides also exerts a small but non- negligible influence. Arika
Higuchi, an assistant professor at the University of Occupational and Environmental Health in Japan and previously a member of the NAOJ RISE
Project, studied the effects of the Galactic gravity on long- period
comets through analytical investigation of the equations governing orbital motion. She showed that when the Galactic gravity is taken into account,
the aphelia of long-period comets tend to collect around two planes.

First the well-known ecliptic, but also a second "empty ecliptic." The
ecliptic is inclined with respect to the disk of the Milky Way by about
60 degrees. The empty ecliptic is also inclined by 60 degrees, but in
the opposite direction.

Higuchi calls this the "empty ecliptic" based on mathematical nomenclature
and because initially it contains no objects, only later being populated
with scattered comets.

Higuchi confirmed her predictions by cross-checking with numerical
computations carried out in part on the PC Cluster at the Center
for Computational Astrophysics of NAOJ. Comparing the analytical and computational results to the data for long-period comets listed in NASA's
JPL Small Body Database showed that the distribution has two peaks,
near the ecliptic and empty ecliptic as predicted. This is a strong
indication that the formation models are correct and long-period comets
formed on the ecliptic. However, Higuchi cautions, "The sharp peaks are
not exactly at the ecliptic or empty ecliptic planes, but near them. An investigation of the distribution of observed small bodies has to include
many factors. Detailed examination of the distribution of long-period
comets will be our future work. The all-sky survey project known as the
Legacy Survey of Space and Time (LSST) will provide valuable information
for this study."

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========================================================================== Journal Reference:
1. Arika Higuchi. Anisotropy of Long-period Comets Explained by Their
Formation Process. The Astronomical Journal, 2020; 160 (3): 134
DOI: 10.3847/1538-3881/aba94d ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200929123458.htm

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