The alignment plane of the solar system is the plane where planets orbit the sun. Researchers have recently completed a study of comet motions that indicates the solar system has a second alignment plane. The plane is illustrated in the image, with the yellow marks being the alignment plane for planets and the blue being the new alignment plane for comets.
The grid in the background of the image indicates the alignment plane of the Galactic disk. Researchers were conducting an analytical investigation of the orbits of long-period comets. They discovered that the comets’ aphelia, which is the point where they are the farthest from the sun, tend to fall either on the ecliptic plane where planets reside or the newly discovered “empty ecliptic.”
The discovery has implications for models of how comets initially formed in the solar system, within our solar system planets, and most of the bodies moving roughly the same orbital plane, which is known as the ecliptic. There are exceptions, particularly with long-period comets that can take tens of thousands of years to complete an orbit. Those comments aren’t confined to an area near the ecliptic but are viewed coming and going in various directions.
Solar system models suggest that the comets initially formed near the ecliptic and were later scattered in the other orbits through gravitational interactions, particularly interactions with gas giant planets. However, even with planetary scattering, the comet’s aphelion, which is the point where it’s the farthest from the sun, should remain near the ecliptic. Scientists went looking for other forces to explain the observed distribution of comets.
What was discovered is that when Galactic gravity is taken into account, the aphelia of long-period comets tend to collect around two planes, with the first being the known ecliptic of the planets. The second being the “empty ecliptic.” The planetary ecliptic is inclined by 60 degrees to the disk of the Milky Way, and the empty ecliptic is inclined by 60 degrees in the opposite direction. The empty ecliptic gets its name because it contains no objects and is only populated with scattered comets.