Observations of dwarf planet (136199) Eris and other large TNOs on Lulin Observatory

To provide comprehensive observations and in-depth standy of the physical property of the trans-neptunian objects (TNOs), the Lulin Observatory in Taiwan has started a program to study the time variabilities of lightcurves of large TNOs and dwarf planets. Our initial results show that (50000) Quaoar has a significant brightness variation of Δm ∼ 0.3 with a rotation period of about 18.84 h while (136199) Eris (formerly 2003 UB313) has very little brightness variation (Δm ∼ 0.05). The rotation period of Eris is hence highly uncertain even though a periodicity of 3.55 h is suggested by our measurements.