Weywot
 Quaoar and Weywot (left of Quaoar) imaged by the Hubble Space Telescope in 2006 | |
| Discovery[1][2] | |
|---|---|
| Discovered by |
|
| Discovery date | 14 February 2006 |
| Designations | |
Designation | Quaoar I |
| Pronunciation | /ˈweɪwɒt/ |
| S/2006 (50000) 1[4] | |
| Orbital characteristics[5] | |
| Epoch 23 March 2008 (JD 2454549.42)[5] | |
| 13289±189 km (2023)[6] 13900±200 (2013)[5] | |
| Eccentricity | 0.056±0.093 (2023)[6] 0.137±0.006 (2013)[5] |
| 12.4311±0.0015 d (2023)[6] 12.4314±0.0002 d (2013)[5] | |
| Inclination | 15.8°±0.7° (to ecliptic) |
| 1.0°±0.7° | |
| 335°±0.7° | |
| Satellite of | 50000 Quaoar |
| Physical characteristics | |
| ≈ 170 km[7][8] | |
| Albedo | ≈ 0.03[a] |
| 24.7[10][b] | |
| ≈ 8.3[b] | |
Weywot (formal designation (50000) Quaoar I; provisional designation S/2006 (50000) 1) is a natural satellite or moon of the trans-Neptunian dwarf planet 50000 Quaoar. It was discovered by Michael Brown and Terry-Ann Suer using images acquired by the Hubble Space Telescope on 14 February 2006. Named after the Tongva sky god and son of Quaoar, Weywot is thought to be a fragment of Quaoar that was ejected into an eccentric orbit around the dwarf planet by a major impact event billions of years ago. The moon has an estimated diameter of 170 km (110 mi) and it orbits Quaoar every 12.4 days at an average distance of 13,300 km (8,300 mi). Weywot is thought to play a role in maintaining Quaoar's distant ring by gravitationally influencing it in an orbital resonance.
Discovery
Weywot was first imaged by the Hubble Space Telescope on 14 February 2006, during Michael Brown's survey for satellites around large trans-Neptunian objects (TNOs) using Hubble's high-resolution Advanced Camera for Surveys.[1][11] Consecutive images from that date showed that Weywot appeared stationary relative to Quaoar and was visibly separated by 0.35 arcseconds.[1][12]: 1547 After Brown's Hubble survey concluded in late 2006, he and his colleague Terry-Ann Suer reported their newly-discovered TNO satellites to the Central Bureau for Astronomical Telegrams, which published their discovery of Weywot alongside three other TNO satellites on 22 February 2007.[11][1]
To determine Weywot's orbit, Brown reobserved Weywot with Hubble in March 2007 and March 2008.[10] With his colleague Wesley Fraser, Brown published the first preliminary orbit of Weywot in May 2010. Fraser and Brown were unable to precover Weywot in earlier ultraviolet Hubble images of Quaoar from 2002, either because the satellite was obscured by Quaoar or it was too faint in ultraviolet light.[12]: 1548
Name
Upon discovery, Weywot was given a provisional designation, S/2006 (50000) 1.[4] Brown left the choice of a name up to the Tongva, whose creator-god Quaoar had been named after. The Tongva chose the sky god Weywot, son of Quaoar.[13] The name of Weywot was officially announced by the Minor Planet Center in a notice published on 4 October 2009.[14]
Orbit
Weywot orbits Quaoar at an average distance of 13,300 km (8,300 mi) and takes 12.4 days to complete one revolution.[10][6]: 3 Its orbit is inclined by about 16° with respect to the ecliptic plane, indicating that the Quaoar system rotates prograde with respect to the ecliptic.[5]: 359
Weywot has an unusually high orbital eccentricity of 0.14, which contradicts theoretical predictions that Quaoar's tidal forces should have circularized Weywot's orbit within a timescale of 100 million years, if the satellite had accreted in orbit around Quaoar.[5]: 361 Instead of having a synchronous rotation tidally locked to Quaoar, Weywot's high eccentricity may subject it to a spin-orbit resonance similar to the planet Mercury, where its rotation period is an integer ratio of its orbital period.[5]: 361 Several possible explanations for Weywot's high eccentricity include collisions with other bodies, an origin as a collisionally ejected fragment of Quaoar, orbital resonances, or gravitational perturbations by other massive bodies.[5]: 362 Of these scenarios, Weywot most likely formed as a fragment of Quaoar that was ejected into an eccentric orbit by a major impact event billions of years ago, but did not completely circularize to tidal forces.[15] The trans-Neptunian dwarf planet 225088 Gonggong hosts a similarly eccentric satellite named Xiangliu, which is inferred to have formed in the same way as Weywot.[15]
In 2013 and prior, orbit determinations for Weywot were complicated by the issue of mirror ambiguity, where two possible inclinations could equally fit Weywot's orbit due to the lack of parallactic change in its projected orbital plane.[5]: 359 [12]: 1548–1549 That is, it could not be recognized whether Weywot orbited prograde or retrograde with respect to the ecliptic. The discontinuity of known observations of Weywot at the time also resulted in a 0.39-day alias in its orbital period, which allowed for even more possible orbit solutions with different orbital periods.[5]: 359 These issues were eventually resolved when Weywot was observed occulting a star on 4 August 2019, which provided a precise measurement of its position that allowed researchers to unambiguously settle on a prograde 12.4-day orbit for Weywot.[6]: 6
Ring dynamics
In February 2023, astronomers announced the discovery of a distant ring orbiting Quaoar at a distance 4,148 km (2,577 mi), which nearly coincides with the 6:1 mean-motion orbital resonance with Weywot that lies slightly interior to the ring at 4,021 km (2,499 mi).[6]: 3 This near-coincidence implies Weywot plays a role in perturbing the rings and producing irregularities in the ring's width and density. Together with Quaoar's 1:3 spin-orbit resonance which also nearly coincides with the ring, the 6:1 Weywot mean-motion resonance is thought to help confine the ring to a narrow radial width and prevent it from accreting into a larger body. It is unknown which of these two resonances play a more dominant role in maintaining the ring, as the underlying parameters necessary to calculate their effects are poorly known.[6]: 6 The ring is likely coplanar to Weywot's orbit, with an inclination difference of 6°±8°.[6]: 6
Physical characteristics
Weywot is extremely dim, with an apparent magnitude of 24.7—that is, 5.6±0.2 magnitudes fainter than Quaoar in visible light.[1][10] Combined with its close proximity to Quaoar, Weywot's faintness makes observations difficult, leaving it resolvable only to the most sensitive telescopes such as Hubble and the Keck Telescopes.[11] For these reasons, Weywot's light curve and color have yet to be measured.[12]: 1547
As of 2019[update], Weywot is thought to be about 170 km (110 mi) in diameter (1⁄6 to 1⁄7 of Quaoar), based on a single observation of a stellar occultation by Weywot on 4 August 2019.[7]: 26 Given Weywot's magnitude difference from Quaoar, this occultation-derived diameter suggests Weywot has a geometric albedo of about 0.03,[9] which is considerably darker than Quaoar's albedo of 0.1.[7]: 26 Weywot was previously thought to have a diameter of 81 ± 11 km (50 ± 7 mi), about half that of the occultation measurement, because researchers based this estimate only on Weywot's relative brightness and assumed it had a similar albedo as Quaoar.[16]: 15 [12]: 1547
Notes
- ^ Geometric albedo calculated given absolute magnitude H = 8.3 and diameter D = 170 km.[9]
- ^ a b Weywot is 5.6±0.2 magnitudes fainter than Quaoar in visible wavelengths.[1][2] The apparent magnitude of Weywot by itself is the sum of this magnitude difference and Quaoar's apparent magnitude of 19.0. Likewise, the absolute magnitude of Weywot is the sum of this magnitude difference and Quaoar's absolute magnitude of 2.74.[10]
References
- ^ a b c d e f Green, Daniel W. E. (22 February 2007). "Satellites of 2003 AZ_84, (50000), (55637), and (90482)". IAU Circular (8812). Central Bureau for Astronomical Telegrams: 1. Bibcode:2007IAUC.8812....1B. Archived from the original on 19 July 2011. Retrieved 5 July 2011.
- ^ a b Johnston, Wm. Robert (21 September 2014). "(50000) Quaoar and Weywot". Asteroids with Satellites Database. Johnston's Archive. Retrieved 26 May 2009.
- ^ Suer, Terry-Ann. "Publications". sites.google.com. Retrieved 11 February 2023.
- ^ a b "JPL Small-Body Database Browser: 50000 Quaoar (2002 LM60)". Jet Propulsion Laboratory. Retrieved 11 February 2023.
- ^ a b c d e f g h i j k Fraser, Wesley C.; Konstantin, Batygin; Brown, Michael E.; Bouchez, Antonin (January 2013). "The mass, orbit, and tidal evolution of the Quaoar-Weywot system" (PDF). Icarus. 222 (1): 357−363. arXiv:1211.1016. Bibcode:2013Icar..222..357F. doi:10.1016/j.icarus.2012.11.004. S2CID 17196395.
- ^ a b c d e f g h B. E. Morgado; B. Sicardy; F. Braga-Ribas; J. L. Ortiz; H. Salo; F. Vachier; et al. (8 February 2023). "A dense ring of the trans-Neptunian object Quaoar outside its Roche limit". Nature. 614 (7947): 239–243. Bibcode:2023Natur.614..239M. doi:10.1038/S41586-022-05629-6. ISSN 1476-4687. Wikidata Q116754015.
- ^ a b c Kretlow, Mike (January 2020). "Beyond Jupiter – (50000) Quaoar" (PDF). Journal for Occultation Astronomy. 10 (1). International Occultation Timing Association: 24–31. Bibcode:2020JOA....10a..24K.
- ^ "2022 Asteroidal Occultation Preliminary Results – 50000(1) Weywot 2022 Jun 11". www.asteroidoccultation.com. International Occultation Timing Association. 11 June 2022. Archived from the original on 12 February 2023.
- ^ a b Bruton, Dan. "Conversion of Absolute Magnitude to Diameter for Minor Planets". Department of Physics, Engineering and Astronomy. Stephen F. Austin State University. Retrieved 12 February 2023.
- ^ a b c d e Grundy, Will (21 March 2022). "Quaoar and Weywot (50000 2002 LM60)". www2.lowell.edu. Lowell Observatory. Retrieved 11 February 2023.
- ^ a b c Brown, Michael (July 2005). "Icy planetoids of the outer solar system". Mikulski Archive for Space Telescopes. Space Telescope Science Institute. Bibcode:2005hst..prop10545B. #10545, Cycle 14. Retrieved 11 February 2023.
- ^ a b c d e Fraser, Wesley C.; Brown, Michael E. (May 2010). "Quaoar: A Rock in the Kuiper Belt" (PDF). The Astrophysical Journal. 714 (2): 1547–1550. arXiv:1003.5911. Bibcode:2010ApJ...714.1547F. doi:10.1088/0004-637X/714/2/1547. S2CID 17386407.
- ^ Street, Nick (August 2008). "Heavenly Bodies and the People of the Earth". Search Magazine. Heldref Publications. Archived from the original on 18 May 2009. Retrieved 8 January 2020.
- ^ "M. P. C. 67220" (PDF). Minor Planet Circulars (67220). Minor Planet Center: 134. 4 October 2009. Retrieved 12 February 2023.
- ^ a b Arakawa, Sota; Hyodo, Ryuki; Shoji, Daigo; Genda, Hidenori (December 2021). "Tidal Evolution of the Eccentric Moon around Dwarf Planet (225088) Gonggong". The Astronomical Journal. 162 (6): 29. arXiv:2108.08553. Bibcode:2021AJ....162..226A. doi:10.3847/1538-3881/ac1f91. S2CID 237213381. 226.
- ^ Fornasier, S.; Lellouch, E.; Müller, T.; Santos-Sanz, P.; Panuzzo, P.; Kiss, C.; et al. (July 2013). "TNOs are Cool: A survey of the trans-Neptunian region. VIII. Combined Herschel PACS and SPIRE observations of nine bright targets at 70-500 µm". Astronomy and Astrophysics. 555: 22. arXiv:1305.0449v2. Bibcode:2013A&A...555A..15F. doi:10.1051/0004-6361/201321329.
