Weywot

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Weywot
Weywot hst.jpg
Quaoar and Weywot (left of Quaoar) imaged by the Hubble Space Telescope in 2006
Discovery [1] [2]
Discovered by
Discovery date14 February 2006
Designations
Designation
(50000) Quaoar I [4] : 134 
Pronunciation /ˈweɪwɒt/
S/2006 (50000) 1 [5]
Orbital characteristics [6] : 13 
Epoch 13 February 2006 (JD 2453780.42)
13309±231 km
Eccentricity 0.018±0.016
12.431013±0.000210 d
Inclination 38.04°±1.40° (to celestial equator)
15.4°±1.4° (to ecliptic) [a]
356.9°±1.5°
292°±25°
Satellite of 50000 Quaoar
Physical characteristics
≈ 200 km [7]
Albedo ≈ 0.04 [7]
24.7 [8] [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 Quaoar. It was discovered by Michael Brown and Terry-Ann Suer using images taken by the Hubble Space Telescope on 14 February 2006. It is named after the Tongva sky god and son of Quaoar. Weywot is about 200 km (120 mi) in diameter and 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 outer ring by gravitationally influencing it in an orbital resonance.

    Contents

    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] [9] Consecutive images from that date showed that Weywot appeared stationary relative to Quaoar and was visibly separated at an angular distance of 0.35 arcseconds. [1] [10] : 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. [9] [1]

    To determine Weywot's orbit, Brown reobserved Weywot with Hubble in March 2007 and March 2008. [11] [12] [8] Together 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. [10] : 1548 

    Name

    Upon discovery, Weywot was given a provisional designation, S/2006 (50000) 1. [5] 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. [4] : 134 

    Orbit

    Orbit diagrams of the Quaoar–Weywot system
    Quaoar-Weywot orbit diagram projected.png
    Viewed from Earth
    Quaoar-Weywot orbit diagram top.png
    Viewed top-down over Quaoar's north pole

    Weywot orbits Quaoar at an average distance of 13,300 km (8,300 mi) and takes 12.4 days to complete one revolution. [6] : 13  Its orbit is likely coplanar (orbital inclination close to zero) with respect to Quaoar's equator, [14] : 1  although it appears to be inclined relative to Quaoar's outermost ring by 4.8°±1.6°. [6] : 13  If Weywot orbits coplanar with Quaoar's equator, then its orbital inclination with respect to the ecliptic plane would be approximately the same as Quaoar's axial tilt of 15° with respect to the ecliptic. [14] : 1  Weywot's orbit is nearly circular with an eccentricity of 0.018±0.016. [6] : 13  A circular orbit implies that Weywot may have formed out of a disk of material that orbited Quaoar within 100 million years after the Solar System's formation. [15] : 362 

    Before 2019, Weywot's orbit was highly uncertain due to limited number of observations. Due to its great distance from Earth, Weywot's orbit shows little parallactic change in perspective when observed from Earth, which leads to mirror ambiguity where two possible inclinations could equally fit Weywot's orbit. [15] : 359  [10] : 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. [15] : 359  Weywot's orbit was previously thought to have a high eccentricity of 0.14, which led astronomers to speculate that its apparently eccentric orbit could have been caused by collisions with other bodies, gravitational perturbations, slow tidal circularization, or an origin as a collisionally-ejected fragment of Quaoar. [16] [15] Uncertainties in Weywot's orbit were eliminated after astronomers obtained precise measurements of Weywot's positions from stellar occultations beginning on 4 August 2019, which allowed researchers to unambiguously settle on a prograde, 12.4-day circular orbit for Weywot. [17] : 6  [6] : 13 

    Ring dynamics

    In February 2023, astronomers announced the discovery of a distant ring orbiting Quaoar at a distance of 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). [17] : 3  This near-coincidence suggests Weywot could play a role in perturbing the ring by producing irregularities in the ring's width and density. Together with Quaoar's 1:3 spin-orbit resonance that lies slightly farther from the ring, the 6:1 Weywot mean-motion resonance is thought to help prevent the ring from accreting into a solid body. [17] : 6  It is unknown which of these two resonances plays a more dominant role in maintaining the ring, as the underlying parameters necessary to calculate their effects are poorly known. [17] : 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] [8] Combined with its close proximity to Quaoar, Weywot's faintness makes observations difficult, leaving it resolvable only to the most sensitive telescopes such as the Hubble Space Telescope and the Keck Telescopes. [9] For these reasons, most of Weywot's physical properties such as its mass, color, and light curve have yet to be measured. [10] : 1547 

    As of 2023, Weywot is thought to be about 200 km (120 mi) in diameter, based on multiple observations of a stellar occultation by Weywot on 22 June 2023. [7] Occultations by Weywot have been observed previously on 4 August 2019, 11 June 2022, 26 May 2023, and 22 June 2023, which all gave similar diameter estimates of about 170 km (110 mi). [6] Given Weywot's magnitude difference from Quaoar, this occultation-derived diameter suggests Weywot has low geometric albedo of about 0.04, considerably darker than Quaoar's albedo of 0.12. [7] 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. [18] : 15  [10] : 1547  [7]

    Notes

    1. ↑ Given Weywot's orbit pole ecliptic latitude of 74.6°±1.4°, [6] : 13  subtracting this angle from the ecliptic north pole of +90° gives the inclination with respect to the ecliptic: i = +90° – (74.6°) = +15.4°.
    2. 1 2 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. [8]

    References

    1. 1 2 3 4 5 6 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.
    2. 1 2 Johnston, Wm. Robert (21 September 2014). "(50000) Quaoar and Weywot". Asteroids with Satellites Database. Johnston's Archive. Retrieved 26 May 2009.
    3. ↑ Suer, Terry-Ann. "Publications". sites.google.com. Retrieved 11 February 2023.
    4. 1 2 "M. P. C. 67220" (PDF). Minor Planet Circulars (67220). Minor Planet Center: 134. 4 October 2009. Retrieved 12 February 2023.
    5. 1 2 "JPL Small-Body Database Browser: 50000 Quaoar (2002 LM60)". Jet Propulsion Laboratory . Retrieved 11 February 2023.
    6. 1 2 3 4 5 6 7 Braga-Ribas, F.; Vachier, F.; Desmars, J.; Margoti, G.; Sicardy, B. (February 2025). "Investigating the formation of small Solar System objects using stellar occultations by satellites: present, future and its use to update satellite orbits". Philosophical Transactions of the Royal Society A. 383 (2291): 22. arXiv: 2503.00874 . doi:10.1098/rsta.2024.0200. S2CID   276645375.
    7. 1 2 3 4 5 Fernandez-Valenzuela, E.; Holler, B.; Ortiz, J. L.; Vachier, F.; Braga-Ribas, F.; Rommel, F.; et al. (October 2023). Weywot: the darkest known satellite in the trans-Neptunian region. 55th Annual DPS Meeting Joint with EPSC. Vol. 55. San Antonio, Texas. Bibcode:2023DPS....5520204F. 202.04.
    8. 1 2 3 4 Grundy, Will (21 March 2022). "Quaoar and Weywot (50000 2002 LM60)". www2.lowell.edu. Lowell Observatory. Retrieved 11 February 2023.
    9. 1 2 3 Brown, Michael (July 2005). "Icy planetoids of the outer solar system". Mikulski Archive for Space Telescopes. Space Telescope Science Institute: 10545. Bibcode:2005hst..prop10545B. Cycle 14. Retrieved 11 February 2023.
    10. 1 2 3 4 5 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.
    11. ↑ Brown, Michael (July 2006). "The largest Kuiper belt objects". Mikulski Archive for Space Telescopes. Space Telescope Science Institute: 10860. Bibcode:2006hst..prop10860B. Cycle 15. Retrieved 27 April 2023.
    12. ↑ Brown, Michael (July 2007). "Collisions in the Kuiper belt". Mikulski Archive for Space Telescopes. Space Telescope Science Institute: 11169. Bibcode:2007hst..prop11169B. Cycle 16. Retrieved 27 April 2023.
    13. ↑ 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.
    14. 1 2 C. L. Pereira; B. Sicardy; B. E. Morgado; F. Braga-Ribas; E. Fernández-Valenzuela; D. Souami; et al. (2023). "The two rings of (50000) Quaoar". Astronomy & Astrophysics . arXiv: 2304.09237 . Bibcode:2023A&A...673L...4P. doi:10.1051/0004-6361/202346365. ISSN   0004-6361. Wikidata   Q117802048.
    15. 1 2 3 4 Fraser, Wesley C.; Batygin, Konstantin; Brown, Michael E.; Bouchez, Antonin (January 2013). "The mass, orbit, and tidal evolution of the Quaoar-Weywot system". Icarus. 222 (1): 357−363. arXiv: 1211.1016 . Bibcode:2013Icar..222..357F. doi:10.1016/j.icarus.2012.11.004. S2CID   17196395.
    16. ↑ 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.
    17. 1 2 3 4 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.
    18. ↑ 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 .
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