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Discovery
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| Discovered by | E. P. Rubenstein, L.-G. Strolger |
| Discovery date | October 1, 1999 |
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Designations
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| MPC designation | (47171) 1999 TC36 |
| Alternate name(s) | none |
| Minor planet category |
Trans-Neptunian object Plutino[1][2] |
| Epoch June 14, 2006 (JD 2453900.5) | |
| Aphelion | 47.952 AU (7173.592 Gm) |
| Perihelion | 30.560 AU (4571.710 Gm) |
| Semi-major axis | 39.256 AU (5872.651 Gm) |
| Eccentricity | 0.222 |
| Orbital period | 245.96 a (89838.309 d) |
| Average orbital speed | 4.69 km/s |
| Mean anomaly | 346.981° |
| Inclination | 8.416° |
| Longitude of ascending node | 97.059° |
| Argument of perihelion | 295.003° |
| Satellites | S/2001 (47171) 1: 139+22 −18 km,[3] 0.746 ± 0.06×1018 kg[3] |
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Physical characteristics
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| Dimensions | Assuming albedo=0.07:[3] A1=286 +45 414±38 km[4] (effective system diameter) |
| Mass | 12.75 ± 0.06×1018 kg (A1+A2+B)[3] 14.20 ± 0.05×1018 kg (A1+A2)[3] |
| Mean density | 0.542 +0.317 −0.211 g/cm3[3] |
| Equatorial surface gravity | 0.039–0.020 m/s2 |
| Escape velocity | 0.117–0.096 km/s |
| Sidereal rotation period |
synchronos |
| Albedo | 0.07 ± 0.01[4] |
| Temperature | ~45–44 K |
| Spectral type | (red) B-V=0.99; V-R=0.65[5] |
| Apparent magnitude | 19.8[6] |
| Absolute magnitude (H) | 5.37[5] |
(47171) 1999 TC36 (also written: (47171) 1999 TC36) is a system comprising three trans-Neptunian objects (TNOs). 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,[1] and, currently only being 30.7 AU from the Sun,[6] is among the brighter TNOs.
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The combined observations by the infrared Spitzer Space Telescope[4] and the Hubble Telescope allow an estimation of the diameters of the components and consequently provide the range of possible values for the objects’ bulk density.[3] The very low estimate of 0.3–0.8 g/cm3 obtained in 2006 when the system was thought to be a binary would require an unusually high porosity of 50–75%, assuming an equal mixture of rock and ice.[7] The direct measurement of sizes of all three components of the system in 2009 has resulted in an improved average density of 0.532+0.317
−211 g/cm3 confirming the earlier conclusion that the object is probably a rubble pile.[3]
(47171) 1999 TC36 has a very red spectral slope in visible light[5] and a flat spectrum in near infrared. There is also a weak absorption feature near the wavelength of 2 μm, probably caused by water-ice. The best model reproducing the near infrared spectrum includes tholins, crystalline water ice, and serpentine as surface materials. These results are for the integrated spectrum of all three components of the system.[8]
(47171) 1999 TC36 is a triple system consisting of a central primary, which is a binary itself, and a small moon (component B). The moon, discovered from 8 December 2001 observations by C. A. Trujillo and M. E. Brown using the Hubble Space Telescope and announced on 10 January 2002,[9] has an estimated diameter of 139 +22
−18 km and a semi-major axis of 7411 ± 12 km, orbiting its primary in 50.302 ± 0.001 days.[3] The moon is estimated to only have a mass of about 0.75×1018 kg.[3]
In 2009, analysis of Hubble images revealed that the primary is itself composed of two similar-sized components.[3] This central pair has a semi-major axis of around 867 km and a period of about 1.9 days. Assuming equal albedos of about 0.07, the primary components are approximately A1=286+45
−38 km and A2=265 +41
−35 km in diameter.[3] The component B orbits the barycenter of the A1+A2 system. The system mass estimated from the motion of the component B is 12.75 ± 0.06×1018 kg.[3] The orbital motion of the A1 and A2 components gives somewhat a higher mass estimate of 14.20 ± 0.05×1018 kg. The discrepancy is probably related to unaccounted gravitational interactions of the components in a complex triple system.[3]
There exist two main hypotheses on how the triple system of 1999 TC36 appeared. The first one is a giant collision and subsequent reaccretion in the disc. The second one is gravitational capture of third object by a preexisting binary. The similar sizes of A1 and A2 components favor the latter hypothesis.[3]
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