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2016-11-18 The Neptune Trojans and the Vertical Moving Trans-Neptunian Objects

Time Coordinate: 3:30 pm 18th Nov. 2016 (Friday)

Space Coordinate: NTHU General Building II, R521

Speaker: Dr. Hsing-Wen Lin (National Central University)

The Neptune Trojans and the Vertical Moving Trans-Neptunian Objects

Many primitive bodies exist in the vast regions of the solar system beyond Jupiter, of which the largest population is the trans-Neptunian objects (TNOs). The details of the orbital distribution of the TNOs preserve information about the evolution of the solar system. In this talk, I will introduce our two recent works, which are related to TNO studies: 1. The Neptune Trojans: dynamically very hot or not that hot? and 2. The vertical moving TNOs: is there a perpendicular Kuiper Belt?

Currently 17 Neptune Trojans (NTs), the asteroids in co-orbital 1:1 mean motion resonance with Neptune, have been found. The very high and wide orbital inclination distribution of NTs implies an unusual formation mechanism of NTs; the NT have to be captured from a pre-excited planetesimal disk. Recently, we used Pan-STARRS 1 (PS1) survey data to study the orbital distribution of NTs and found that the inclination distribution is rather low compare with the results of previous studies. The new result may suggest that NTs can be captured from a planetesimal disk without pre-excited.

In the PS1 survey data, we also identified an unusual TNOs, 2011 KT13 (nicknamed Niku). This object has an 110 degree orbital inclination; it has a retrograde and almost vertical moving orbit. Together with other five high-inclination TNOs, the six vertical moving objects appear to occupy a common orbital plane. We found that this alignment is statistical significant; the probability occurring by chance is only 0.016%. Our simple simulations including the hypothetical Planet Nine fail to maintain the common orbital plane, therefore, an unknown mechanism is required to explain the observed clustering.

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