(47171) 1999 TC36 is a trans-Neptunian object (TNO). It was discovered in 1999 by Eric P. Rubenstein and Louis-Gregory Strolger during an observing run at Kitt Peak National Observatory (KPNO). Dr. Rubenstein was searching images taken by Dr. Strolger as part of the Low-Z Supernova Search program. It is classified as a plutino with a 2:3 mean motion resonance with Neptune, and currently only being 30.7 AU from the Sun, is among the brighter trans-Neptunian objects. Read more
In 2009, analysis of Hubble images confirmed that 1999 TC36 is a triple system. The primary is composed of two similar-sized components. The central pair have a semi-major axis of ~867 km with a period of ~1.9 days.
Title: Asteroid (47171) 1999 TC36, A Transneptunian Triple Authors: S. D. Benecchi, K. S. Noll, W. M. Grundy, H. F. Levison
We present new analysis of HST images of (47171) 1999 TC36 that confirm it as a triple system. Fits to the point-spread function consistently show that the apparent primary is itself composed of two similar-sized components. The two central components, A1 and A2, can be consistently identified in each of nine epochs spread over seven years of time. In each instance the component separation, ranging from 0.023±0.002 to 0.031±0.003 arcsec, is roughly one half of the Hubble Space Telescope's diffraction limit at 606 nm. The orbit of the central pair has a semi-major axis of a~867 km with a period of P~1.9 days. These orbital parameters yield a system mass that is consistent with Msys = 12.75±0.06 10^18 kg derived from the orbit of the more distant secondary, component B. The diameters of the three components are dA1= 286(+45,-38) km, dA2= 265(+41,-35 km and dB= 139(+22,-18) km. The relative sizes of these components are more similar than in any other known multiple in the solar system. Taken together, the diameters and system mass yield a bulk density of p=542(+317,-211) kg m^-3. HST Photometry shows that component B is variable with an amplitude of >=0.17±0.05 magnitudes. Components A1 and A2 do not show variability larger than 0.08±0.03 magnitudes approximately consistent with the orientation of the mutual orbit plane and tidally-distorted equilibrium shapes. The system has high specific angular momentum of J/J'=0.93, comparable to most of the known Transneptunian binaries.