Deciphering satellite formation in the trans-Neptunian region: the case of Weywot
Session 13.01 Spectroscopy
Friday 06-28 | 12:00 - 12:20

In the last five years, several stellar occultations by Weywot, the only known satellite of the TNO (50000) Quaoar, have been detected with one chord from Namibia, two chords from the US, one chord from New Zealand, and five chords from the US. While constraints are provided by all of the events mentioned above, it is the last event that provides the best understanding of Weywot's size and shape. Preliminary analyses from these events result in an equivalent diameter of around 170 km, much larger than that estimated from Herschel data, which indicated a diameter of ~80 km. Because no rotational information is known about Weywot, we are limited in the accuracy that we can provide for the diameter of the body. Our new, larger estimate of Weywot's diameter requires a visual geometric albedo of ~4%, considering that it is 5 mag fainter than Quaoar. Quaoar's albedo, on the other hand, is about three times larger (12.4 ± 0.6%). Additionally, Weywot's orbital eccentricity, e, is somewhere between 0 and 0.1 (Vachier communication). The large difference in the albedo between Weywot and Quaoar supports the possibility of Weywot being a captured satellite. However, an effective diameter of almost 200 km places its size in a similar range to those of other dwarf planet satellites, which are believed to have formed from very different scenarios.

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