471325 Taowu
Taowu imaged by the Canada–France–Hawaii Telescope on 22 May 2014 | |
| Discovery[1] | |
|---|---|
| Discovered by | Mount Lemmon Survey |
| Discovery site | Mount Lemmon Obs. |
| Discovery date | 31 May 2011 |
| Designations | |
| (471325) Taowu | |
| Pronunciation | /ˌtaʊˈwuː/ |
Named after | Taowu |
| |
| TNO[2] · centaur[3][4] distant[1] | |
| Orbital characteristics | |
| Epoch 17 October 2024 (JD 2460600.5) | |
| Uncertainty parameter 2 | |
| Observation arc | 14.05 yr (5,131 d) |
| Earliest precovery date | 10 May 2010 |
| Aphelion | 47.588 AU |
| Perihelion | 23.839 AU |
| 35.713 AU | |
| Eccentricity | 0.3325 |
| 213.43 yr (77,955 d) | |
| 42.884° | |
| 0° 0m 16.625s / day | |
| Inclination | 110.311° |
| 243.903° | |
| ≈ 15 May 1999 ±0.13 days[2] | |
| 322.913° | |
| Physical characteristics | |
| 177 km (assumed albedo 0.058)[4] | |
| 22[1] | |
| 7.45[2][1] | |
471325 Taowu (provisional designation 2011 KT19, formerly nicknamed Niku (/ˈniːkuː/)) is a trans-Neptunian object whose orbit is tilted 110° with respect to the ecliptic. Thus, it has a nearly polar retrograde orbit around the Sun from the reference point of Earth's orbital plane.[5]
Discovery
Taowu was discovered on 31 May 2011 by the Mount Lemmon Survey in Arizona. It was announced by the Minor Planet Center on 2 June 2011, after other telescopes confirmed the object with additional observations.[6] The object was given the minor planet provisional designation 2011 KT19, which reflects its discovery date.[6] Initial calculations of Taowu's orbit using these few observations suggested it was a centaur on a prograde elliptical orbit (semi-major axis 28 AU, eccentricity 0.41, inclination 38°).[6][5]: 2 However, Taowu was only observed for up to 8 days before being lost, due to large uncertainties in its orbit.[5]: 2
In 2016, a team of astronomers led by Ying-Tung Chen performed a search for outer Solar System objects in observations by the Pan-STARRS 1 survey.[7][8][5]: 1 They rediscovered Taowu in Pan-STARRS observations from 2013–2016 and recognized it had an unusual retrograde polar orbit. Chen's team made follow-up observations at Lulin Observatory in Taiwan and found additional observations of the object in archival images from the Dark Energy Survey and Canada–France–Hawaii Telescope.[8][5]: 2 After Chen's team submitted their observations of Taowu to the Minor Planet Center, it was recognized that Taowu had been previously observed by the Mount Lemmon Survey in 2011.[5]: 2 Taowu received its permanent minor planet catalog number 471325 on 18 August 2016 and the Minor Planet Center declared Mount Lemmon Survey as the object's official discoverer.[9]: 512
Name
The object is named after Taowu (檮杌; Táowù), one of the Four Perils in Chinese mythology. The name follows the International Astronomical Union's naming conventions for centaurs on Neptune-crossing orbits (perihelion <30 AU), which are named after mythological chimeras.[10]: 8 The name was announced by the International Astronomical Union on 3 February 2025.[11]
The object had previously been nicknamed Niku (逆骨; nìgǔ) by Ying-Tung Chen, who was involved with rediscovering the object and studying its orbit in 2016. The nickname is a Mandarin adjective meaning "rebellious", in reference to the object's unusual retrograde orbit.[8][7]
Orbit
Taowu is in a 7:9 resonance with Neptune. Currently it is the only object with a nearly polar orbit that is in resonance with a planet.[12] Notably, it is part of a group of objects that orbit the Sun in a highly inclined orbit; the reasons for this unusual orbit are unknown as of August 2016.[5] Taowu's orbital characteristics have been compared to those of 2008 KV42 (nicknamed "Drac"). The orbits of Taowu, 2008 KV42, 2002 XU93, 2010 WG9, 2007 BP102, and 2011 MM4 appear to occupy a common plane, with three in prograde and three in retrograde orbits. The probability of this alignment occurring by chance is 0.016%. These orbits should leave a common plane in a few million years because the precession of prograde and retrograde orbits are in opposite directions. Simulations including the hypothetical Planet Nine did not maintain a common orbital plane and the plane does not coincide with the plane of the predicted high-inclination large semi-major axis objects of that model. Other simulations with a few Earth-mass dwarf planet on a high-inclination orbit also failed to reproduce the alignment.[5]
| The orbit of Taowu (white) in relation to Pluto and the planets of the Solar System |
| The orbit of Taowu (purple), is shown with another steep retrograde TNO, 2008 KV42 (yellow), and the other planets. Pluto's orbit is in red. |
Physical characteristics
The diameter of Taowu has not been measured, but it can be estimated from its brightness (absolute magnitude) using a range of plausible values for its surface reflectivity (geometric albedo). If Taowu reflects between 5% and 25% of visible light, then its diameter is between 100 and 200 km (62 and 124 mi).[13] A 2023 study has attempted to check if Taowu exhibits brightness variability due to its rotation, but results have not yet been published.[14]
References
- ^ a b c d "(471325) Taowu = 2011 KT19". Minor Planet Center. Retrieved 3 February 2025.
- ^ a b c "JPL Small-Body Database Lookup: 471325 Taowu (2011 KT19)" (2024-05-27 last obs.). Jet Propulsion Laboratory. Retrieved 3 February 2025.
- ^ Buie, Marc W. "Orbit Fit and Astrometric record for 471325". Southwest Research Institute. Retrieved 3 February 2025.
- ^ a b Johnston, Wm. Robert (18 August 2020). "List of Known Trans-Neptunian Objects". Johnston's Archive. Retrieved 18 July 2021.
- ^ a b c d e f g h Chen, Ying-Tung; Lin, Hsing Wen; Holman, Matthew J.; Payne, Matthew J.; Fraser, Wesley C.; Lacerda, Pedro; et al. (August 2016). "Discovery of A New Retrograde Trans-Neptunian Object: Hint of A Common Orbital Plane for Low Semi-Major Axis, High Inclination TNOs and Centaurs". The Astrophysical Journal. 827 (2): 5. arXiv:1608.01808. Bibcode:2016ApJ...827L..24C. doi:10.3847/2041-8205/827/2/L24. S2CID 4975180. L24.
- ^ a b c "MPEC 2011-L09 : 2011 KT19". Minor Planet Electronic Circular. Minor Planet Center. 2 June 2011. Retrieved 18 February 2017.
- ^ a b Choi, Charles Q. (24 October 2016). "What's Up with 'Niku'? Object's Weird Orbit Puzzles Scientists". Space.com. Retrieved 21 December 2021.
- ^ a b c Dickinson, David (23 August 2016). "Retrograde Rock "Niku" Defies Orbital Trend". Sky & Telescope. Retrieved 4 February 2025.
- ^ "M.P.C. 101122" (PDF). Minor Planet Circulars (101122). Minor Planet Center: 512. 18 August 2016. Retrieved 4 February 2025.
- ^ "Rules and Guidelines for Naming Non-Cometary Small Solar-System Bodies" (PDF). IAU Working Group for Small Bodies Nomenclature. 20 December 2021. p. 10. Retrieved 4 February 2025.
- ^ "WGSBN Bulletin 5, #2" (PDF). WGSBN Bulletin. 5 (2). International Astronomical Union: 30. 3 February 2025. Retrieved 3 February 2025.
- ^ Morais, M. H. M.; Nomouni, F. (November 2017). "First trans-Neptunian object in polar resonance with Neptune". Monthly Notices of the Royal Astronomical Society: Letters. 472 (1): L1–L4. arXiv:1708.00346. Bibcode:2017MNRAS.472L...1M. doi:10.1093/mnrasl/slx125.
- ^ "Asteroid Size Estimator". Jet Propulsion Laboratory. Retrieved March 18, 2025.
- ^ Balseca Cisneros, Jose D.; Campo Bagatin, Adriano; Benavidez, Paula G. (July 2023). Rotational Variability of Tnos. Seventh edition of the Spanish Meeting of Planetary Sciences and Exploration of the Solar System. Valladolid, Spain. Bibcode:2023pses.conf80507B.