2015 GT50

Lore & Background

2015 GT50 was first observed by the Outer Solar System Origins Survey using the Canada–France–Hawaii Telescope at Mauna Kea on 13 April 2015. It belongs to a small group of detached objects whose perihelion distances are 30 AU or more and semi-major axes are 250 AU or more. Such orbits cannot be achieved without some perturbing object, which has led to the Planet Nine hypothesis, positing a massive trans-Neptunian planet as the perturber.

Unlike other similar trans-Neptunian objects whose orbital longitudes of perihelion either cluster in anti-alignment or alignment with the modeled orbit of Planet Nine, 2015 GT50's major axis is almost at a right angle to that of the putative planet. Konstantin Batygin of Caltech suggests this is only a cosmetic disagreement with his and Mike Brown's predictions, noting that without changing the putative orbit of Planet Nine, 2015 GT50 falls into one of the predicted resonant orbits—though he adds this may be a coincidence. This conclusion is not unanimous; others have suggested that a population of objects with orbital characteristics similar to those of 2015 GT50 may be at odds with the Planet Nine hypothesis.

Reader's Guide

2015 GT50 holds significance as an outlier among the detached trans-Neptunian objects that constitute one line of evidence for the Planet Nine hypothesis. While most such objects have orbital longitudes of perihelion that cluster either in alignment or anti-alignment with the modeled orbit of Planet Nine, 2015 GT50's major axis is nearly perpendicular to that of the putative planet. This discrepancy has been addressed by Konstantin Batygin of Caltech, who argues it is only a cosmetic disagreement and that 2015 GT50 falls into one of the predicted resonant orbits without requiring changes to the putative orbit of Planet Nine, though he notes this may be coincidental. However, the article states that this conclusion is not unanimous, and others have suggested that the existence of a population of objects with orbital characteristics similar to those of 2015 GT50 may be at odds with the Planet Nine hypothesis. Thus, 2015 GT50's legacy is as a contested data point in the ongoing debate over the existence of Planet Nine, illustrating both the predictive power and the unresolved tensions within the hypothesis.

Did You Know?

• It is one of a small number of detached objects with perihelion distances of 30 AU or more and semi-major axes of 250 AU or more.
• Unlike other similar objects, 2015 GT50's major axis is almost at a right angle to the modeled orbit of the putative Planet Nine.
• Konstantin Batygin of Caltech suggests that 2015 GT50 falls into one of the predicted resonant orbits of Planet Nine, though he notes this may be a coincidence.