Extreme trans-Neptunian object

Trujillo and Sheppard discoveries

Extreme trans-Neptunian objects discovered by astronomers Chad Trujillo and Scott S. Sheppard include:

• 2013 FT28, Longitude of perihelion aligned with Planet Nine, but well within the proposed orbit of Planet Nine, where computer modeling suggests it would be safe from gravitational kicks.^[8]
• 2014 SR349, appears to be anti-aligned with Planet Nine.^[8]
• 2014 FE72, an object with an orbit so extreme that it reaches about 4000 AU from the Sun in a massively-elongated ellipse – at this distance its orbit is influenced by the galactic tide and other stars.^{[9][10][11][12]}

Outer Solar System Origins Survey

The Outer Solar System Origins Survey has discovered more extreme trans-Neptunian objects, including:^[13]

• 2013 SY99, which has a lower inclination than many of the objects, and which was discussed by Michele Bannister at a March 2016 lecture hosted by the SETI Institute and later at an October 2016 AAS conference.^[14][15]
• 2015 KG163, which has an orientation similar to 2013 FT₂₈ but has a larger semi-major axis that may result in its orbit crossing Planet Nine's.
• 2015 RX245, which fits with the other anti-aligned objects.
• 2015 GT50, which is in neither the anti-aligned nor the aligned groups; instead, its orbit's orientation is at a right angle to that of the proposed Planet Nine. Its argument of perihelion is also outside the cluster of arguments of perihelion.

Since early 2016, ten more extreme trans-Neptunian objects have been discovered with orbits that have a perihelion greater than 30 AU and a semi-major axis greater than 250 AU bringing the total to sixteen (see table below for a complete list). Most TNOs have perihelia significantly beyond Neptune, which orbits 30 AU from the Sun.^[16][17] Generally, TNOs with perihelia smaller than 36 AU experience strong encounters with Neptune.^[18][19] Most of the ETNOs are relatively small, but currently relatively bright because they are near their closest distance to the Sun in their elliptical orbits. These are also included in the orbital diagrams and tables below.

TESS data search

Malena Rice and Gregory Laughlin applied a targeted shift-stacking search algorithm to analyze data from TESS sectors 18 and 19 looking for candidate outer Solar System objects.^[20] Their search recovered known ETNOs like Sedna and produced 17 new outer Solar System body candidates located at geocentric distances in the range 80–200 AU, that need follow-up observations with ground-based telescope resources for confirmation. Early results from a survey with WHT aimed at recovering these distant TNO candidates have failed to confirm two of them.^[21][22]