Astronomy:55565 Aya

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55565 Aya
Hubble Space Telescope image of Aya taken in December 2005
Discovery[1][2]
Discovered byPalomar Obs.[lower-alpha 1]
Discovery sitePalomar Obs.
Discovery date10 January 2002
Designations
(55565) Aya
Pronunciation/ˈaɪə/
Named afterAya
2002 AW197
Minor planet categoryTNO[3] · classical (hot)[4]: 56 
distant[1] · Scat-Ext[5]
Orbital characteristics[7][3]
Epoch 25 February 2023 (JD 2460000.5)
Uncertainty parameter 2[1]
Observation arc27.15 yr (9,915 d)
Earliest precovery date29 December 1997
|{{{apsis}}}|helion}}53.280 AU
|{{{apsis}}}|helion}}41.112 AU
47.196 AU
Eccentricity0.1289
Orbital period324.02 yr (118,349 d)
Mean anomaly299.003°
Mean motion0° 0m 10.951s / day
Inclination24.382°
Longitude of ascending node297.481°
|{{{apsis}}}|helion}}≈ 5 May 2078[6]
±0.4 days[3]
295.928°
Known satellites0
Physical characteristics
Mean diameter768±39 km[8]
Rotation period8.86±0.01 h[9]: 6 [10]: 1132–1133 
8.78 h[11]: 6 
Geometric albedo0.112+0.012
−0.011[8]
IR[12][13] · (moderately red)
B–V = 0.920±0.020[14]
V–R = 0.560±0.020[14]
V–I = 1.170±0.010[13]
Apparent magnitude20.0[15][1]
Absolute magnitude (H)3.568±0.046[16]
3.44[3]


55565 Aya (provisional designation 2002 AW197) is a large trans-Neptunian object in the classical Kuiper belt. It was discovered on 10 January 2002 by astronomers at Palomar Observatory.

Aya is a large object, most likely at least 700 km in diameter. It has a rotation period of 8.8 hours and has a moderately red color.[12] The object's brightness does not significantly vary as it rotates, which indicates it is likely spheroidal.

History

Discovery

Aya was discovered on 10 January 2002, by astronomers at Palomar Observatory in San Diego County, California, United States.[1] Astronomers involved in the discovery were Michael Brown, Chad Trujillo, Eleanor Helin, Michael Hicks, Kenneth Lawrence and Steven Pravdo.[2] The object was discovered during Brown and Trujillo's Caltech Wide Area Sky Survey, which used Palomar Observatory's 1.22-meter (48 in) Samuel Oschin telescope to search for bright Kuiper belt objects.[17]: 100, 103  This survey, which was operated jointly with the nightly Near Earth Asteroid Tracking (NEAT) program at Palomar,[17]: 100  would later discover several other large objects beyond Neptune, including the dwarf planets Eris, Sedna, and Quaoar.[18]: 214 

Aya was found through manual vetting of potential moving objects identified by Brown and Trujillo's automatic image-searching software.[17]: 101  In terms of absolute magnitude, Aya was the second-brightest Kuiper belt object known at the time.[19] It was detected at a red-filter apparent magnitude of 19.7.[2] Aya was further observed by Trujillo and Brown using telescopes at Palomar and Mauna Kea Observatory during February to April 2002.[2] The discovery was announced by the Minor Planet Center on 20 July 2002 and the object was given the minor planet provisional designation of 2002 AW197.[2]

The 1.2-meter Samuel Oschin telescope that was used to discover Aya at Palomar Observatory
Discovery images of Aya from 10 January 2002

Further observations

Within a month after Aya's discovery, Trujillo and Brown collaborated with Jean-Luc Margot and Frank Bertoldi to measure the object's diameter and thermal emission using the IRAM 30m radio telescope at Sierra Nevada, Spain.[20][19] Astronomers also found additional observations of Aya from the time before and during its discovery, which allowed for further refinement of orbit calculations.[21] The earliest pre-discovery observation of Aya comes from an image taken on 29 December 1997 by the NEAT/GEODSS program at Haleakalā Observatory, Hawaii.[1][21] As of 2025, Aya has been observed for over 27 years, or about 8% of its orbital period.[3][1]

Numbering and naming

The object received its permanent minor planet catalog number of 55565 from the Minor Planet Center on 16 February 2003.[22]: 324  On 30 June 2025, it was given the name Aya, after the goddess of dawn and the wife of the sun god Shamash in Akkadian mythology.[23]: 15 

Orbit and classification

Aya's orbit is outside that of Pluto's, with a higher inclination and different orientation
Diagram showing top and tilted views of the orbits of Aya (pink), Pluto (purple) and the outer planets

Aya is a trans-Neptunian object (TNO) orbiting the Sun at a semi-major axis or average distance of 47.2 astronomical units (AU).[7][lower-alpha 2] It follows an elliptical orbit with an eccentricity of 0.13.[7] During its 324-year orbital period, Aya comes within 41.1 AU from the Sun at perihelion and up to 53.3 AU at aphelion.[7] It has an orbital inclination of 24.4° with respect to the ecliptic.[7] Aya last passed perihelion in July 1753 and will make its next perihelion passage in May 2078.[25][6]

Aya is located in the classical region of the Kuiper belt 39–48 AU from the Sun,[4]: 53  and is thus classified as a classical Kuiper belt object (or sometimes a "cubewano").[4]: 55  Aya's high orbital inclination qualifies it as a dynamically "hot" member of the classical Kuiper belt, which implies that it was gravitationally scattered out to its present location by Neptune's outward planetary migration in the Solar System's early history.[26]: 230  Hence, Aya is sometimes classified as a "scattered" object.[5][27]: 165 

Physical characteristics

History of diameter estimates for Aya
Year of
Publication		 Diameter
(km)		 Method Refs
2002 886+115
−131 		thermal
(IRAM) 		[19][28]: 187 
2005 700±50 thermal
(Spitzer) 		[29][30]
2008 734.6+116.4
−108.3 		thermal
(Spitzer) 		[27]: 172 
2009 742+98
−104 		thermal
(Spitzer, remodeled) 		[31]: 291 
2014 768±39 thermal
(Herschel + Spitzer) 		[8]


Size, shape, and rotation

Pair of far-infrared images of Aya by the Spitzer Space Telescope

Measurements of Aya's infrared thermal emission by the Herschel and Spitzer space telescopes give a diameter of 768+39
−38 km (477+24
−24 mi).[8] This makes Aya slightly smaller than the dwarf planet Ceres.[19] Aya is large enough that some astronomers consider it a dwarf planet candidate.[32][33]: 178  Aya's brightness fluctuates very little as it rotates, which could indicate it has a spheroidal shape.[34]: 856–857 [33]: 177 

Aya likely has a rotation period of around 8.8 hours, according to telescopic observations of its brightness changes over time. Aya's subtle brightness variations can make it difficult to determine its light curve and true rotation period.[11]: 6  The first measurements of Aya's rotation period made during 2002–2003 obtained a likely period of 8.86±0.01 hours.[9]: 6 [10]: 1132–1133  Although other alias periods of 13.94, 6.49, and 15.82 hours are possible, the 8.86 hour period stands out as the most likely.[10]: 1135  Observations from 2003–2004 obtained a period of 8.78 hours,[11]: 6  whereas another set of observations from 2003 could not determine a period.[35]: 790, 795 

Surface

Aya has a dark, reddish surface with a geometric albedo of about 11%.[8] The visible and near-infrared spectrum of Aya lacks obvious absorption features, which suggests that tholins mostly cover its surface.[36]

See also

Notes

  1. ↑ The Minor Planet Center lists "Palomar" as the discoverer without listing specific people.[1]
  2. ↑ These orbital elements are expressed in terms of the Solar System Barycenter (SSB) as the frame of reference.[7] Due to planetary perturbations, the Sun revolves around the SSB at non-negligible distances, so heliocentric-frame orbital elements and distances can vary in short timescales as shown in JPL-Horizons.[24]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 "(55565) Aya = 2002 AW197". Minor Planet Center. https://www.minorplanetcenter.net/db_search/show_object?object_id=55565. Retrieved 2025-03-09. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Brown, M. E.; Trujillo, C. A.; Helin, E. F.; Pravdo, S.; Lawrence, K.; Hicks, M.; Marsden, B. G. (2002-07-20). "MPEC 2002-O30 : 2002 AW197". Minor Planet Electronic Circular (Minor Planet Center) 2002-O30. Bibcode: 2002MPEC....O...30B. https://minorplanetcenter.net/mpec/K02/K02O30.html. Retrieved 2025-06-19. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 "JPL Small-Body Database Lookup: 55565 Aya (2002 AW197)". Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=20055565. Retrieved 2025-06-19. 
  4. ↑ 4.0 4.1 4.2 Gladman, Brett; Marsden, Brian G.; VanLaerhoven, Christa (2008). "Nomenclature in the Outer Solar System". The Solar System Beyond Neptune. University of Arizona Press. pp. 43–57. ISBN 9780816527557. Bibcode: 2008ssbn.book...43G. https://www.lpi.usra.edu/books/ssbn2008/7002.pdf. 
  5. ↑ 5.0 5.1 Buie, Marc W.. "Orbit Fit and Astrometric record for 55565". Southwest Research Institute. http://www.boulder.swri.edu/~buie/kbo/astrom/55565.html. Retrieved 2025-06-19. 
  6. ↑ 6.0 6.1 "JPL Horizons On-Line Ephemeris for 55565 Aya (2002 AW197) from 2078-Apr-01 to 2078-Jun-01". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/api/horizons.api?format=text&COMMAND=%2755565%27&OBJ_DATA=%27YES%27&MAKE_EPHEM=%27YES%27&EPHEM_TYPE=%27OBSERVER%27&CENTER=%27@sun%27&START_TIME=%272078-04-01%27&STOP_TIME=%272078-06-01%27&STEP_SIZE=%271d%27&QUANTITIES=%2720%27. Retrieved 2025-06-19.  (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 1-sigma from JPL Small-Body Database.)
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 "JPL Horizons On-Line Ephemeris for 55565 Aya (2002 AW197) at epoch JD 2460000.5". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND='55565'&TABLE_TYPE='ELEMENTS'&START_TIME='JD2460000.5'&STOP_TIME='JD2460200.5'&STEP_SIZE='1y'&CENTER='@0'&OUT_UNITS='AU-D'. Retrieved 2025-06-19.  Solution using the Solar System Barycenter. Ephemeris Type: Elements and Center: @0)
  8. ↑ 8.0 8.1 8.2 8.3 8.4 Vilenius, E.; Kiss, C.; Müller, T.; Mommert, M.; Santos-Sanz, P.; Pál, A. et al. (April 2014). ""TNOs are Cool": A survey of the trans-Neptunian region. X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations". Astronomy and Astrophysics 564: 18. doi:10.1051/0004-6361/201322416. Bibcode: 2014A&A...564A..35V. 
  9. ↑ 9.0 9.1 Lellouch, E.Expression error: Unrecognized word "etal". (September 2013). ""TNOs are Cool": A survey of the trans-Neptunian region. IX. Thermal properties of Kuiper belt objects and Centaurs from combined Herschel and Spitzer observations". Astronomy & Astrophysics 557 (A60): 19. doi:10.1051/0004-6361/201322416. Bibcode: 2013A&A...557A..60L. 
  10. ↑ 10.0 10.1 10.2 Ortiz, J. L.; Gutiérrez, P. J.; Santos-Sanz, P.; Casanova, V.; Sota, A. (March 2006). "Short-term rotational variability of eight KBOs from Sierra Nevada Observatory". Astronomy and Astrophysics 447 (3): 1131–1144. doi:10.1051/0004-6361:20053572. Bibcode: 2006A&A...447.1131O. 
  11. ↑ 11.0 11.1 11.2 Thirouin, A.; Ortiz, J. L.; Duffard, R.; Santos-Sanz, P.; Aceituno, F. J.; Morales, N. (November 2010). "Short-term variability of a sample of 29 trans-Neptunian objects and Centaurs". Astronomy and Astrophysics 522: 43. doi:10.1051/0004-6361/200912340. Bibcode: 2010A&A...522A..93T. 
  12. ↑ 12.0 12.1 "LCDB Data for (55565)". Asteroid Lightcurve Database (LCDB). http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=55565%7C. 
  13. ↑ 13.0 13.1 Belskaya, Irina N.; Barucci, Maria A.; Fulchignoni, Marcello; Dovgopol, Anatolij N. (April 2015). "Updated taxonomy of trans-neptunian objects and centaurs: Influence of albedo". Icarus 250: 482–491. doi:10.1016/j.icarus.2014.12.004. Bibcode: 2015Icar..250..482B. 
  14. ↑ 14.0 14.1 Tegler, S. C.; Romanishin, W.; Consolmagno, G. J.; J., S. (December 2016). "Two Color Populations of Kuiper Belt and Centaur Objects and the Smaller Orbital Inclinations of Red Centaur Objects". The Astronomical Journal 152 (6): 13. doi:10.3847/0004-6256/152/6/210. Bibcode: 2016AJ....152..210T. 
  15. ↑ "AstDys (55565) 2002AW197 Ephemerides". Department of Mathematics, University of Pisa, Italy. https://newton.spacedys.com/astdys/index.php?pc=1.1.3.0&n=2002AW197. 
  16. ↑ Vilenius, E.Expression error: Unrecognized word "etal". (April 2014). ""TNOs are Cool": A survey of the trans-Neptunian region X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations". Astronomy & Astrophysics 564 (A35): 18. doi:10.1051/0004-6361/201322047. Bibcode: 2014A&A...564A..35V. 
  17. ↑ 17.0 17.1 17.2 Trujillo, C. A.; Brown, M. E. (June 2003). "The Caltech Wide Area Sky Survey". Earth, Moon, and Planets 92 (1): 99–112. doi:10.1023/B:MOON.0000031929.19729.a1. Bibcode: 2003EM&P...92...99T. https://link.springer.com/epdf/10.1023/B:MOON.0000031929.19729.a1?shared_access_token=bgfhf2Sq3-c-eiG985Pm_IspNOxuUNtyllpwxVxrbfBIblUlrGXFME5iw69vhaP59U4JrsXxO8WTPBcb5EFv6YjWxKeZY1EFUa0pkdSTgZUYMe-nisnFfSg2SbNiSisJlpxPbzc-gf9XwWJI4575ZT01hsDTR9qcJsr8V59z7ebAb1q1nkOl76HLGatSVny2. 
  18. ↑ Schilling, Govert (2008). The Hunt For Planet X. Springer. p. 214. ISBN 978-0-387-77804-4. 
  19. ↑ 19.0 19.1 19.2 19.3 Margot, J.-L.; Trujillo, C.; Brown, M. E.; Bertoldi, F. (September 2002). "The size and albedo of KBO 2002 AW197". American Astronomical Society, DPS Meeting #34. 34. 17.03. Bibcode: 2002DPS....34.1703M. 
  20. ↑ Trujillo, C.; Brown, M. E.; Margot, J.-L.; Bertoldi, F. (September 2002). "A Search for the Brightest Kuiper Belt Objects". American Astronomical Society, DPS Meeting #34. 34. p. 849. 09.04. Bibcode: 2002DPS....34.0904T. 
  21. ↑ 21.0 21.1 Sarneczky, K.Expression error: Unrecognized word "etal". (2002-09-05). "MPEC 2002-R12 : 2002 AW197". Minor Planet Electronic Circular (Minor Planet Center) 2002-R12. Bibcode: 2002MPEC....R...12S. https://minorplanetcenter.net/mpec/K02/K02R12.html. Retrieved 2025-06-19. 
  22. ↑ "M.P.C. 47762". Minor Planet Circulars (Minor Planet Center) (47762): 324. 16 February 2003. https://minorplanetcenter.net/iau/ECS/MPCArchive/2003/MPC_20030216.pdf#page=324. Retrieved 19 June 2025. 
  23. ↑ "WGSBN Bulletin 5, #15". WGSBN Bulletin (International Astronomical Union) 5 (15): 15. 30 June 2025. https://wgsbn-iau.org/files/Bulletins/V005/WGSBNBull_V005_015.pdf#page=15. Retrieved 30 June 2025. 
  24. ↑ "JPL Horizons On-Line Ephemeris for 55565 Aya (2002 AW197) at epochs JD 2450000.5–2460000.5". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND='55565'&TABLE_TYPE='ELEMENTS'&START_TIME='JD2450000.5'&STOP_TIME='JD2470000.5'&STEP_SIZE='200d'&CENTER='500@10'&OUT_UNITS='AU-D'. Retrieved 2025-06-19.  Solution using the Sun. Ephemeris Type: Elements and Center: @sun)
  25. ↑ "JPL Horizons On-Line Ephemeris for 55565 Aya (2002 AW197) from 1753-Jun-20 to 1754-Jul-20". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/api/horizons.api?format=text&COMMAND=%2755565%27&OBJ_DATA=%27YES%27&MAKE_EPHEM=%27YES%27&EPHEM_TYPE=%27OBSERVER%27&CENTER=%27@sun%27&START_TIME=%271753-06-20%27&STOP_TIME=%271753-07-20%27&STEP_SIZE=%271d%27&QUANTITIES=%2720%27. Retrieved 2025-06-19.  (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 1-sigma from JPL Small-Body Database.)
  26. ↑ Lykawka, Patryk Sofia; Tadashi, Mukai (July 2007). "Dynamical classification of trans-neptunian objects: Probing their origin, evolution, and interrelation". Icarus 189 (1): 213–232. doi:10.1016/j.icarus.2007.01.001. Bibcode: 2007Icar..189..213L. 
  27. ↑ 27.0 27.1 Stansberry, John; Grundy, Will; Brown, Mike; Cruikshank, Dale; Spencer, John; Trilling, David; Margot, Jean-Luc (2008). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from the Spitzer Space Telescope". The Solar System Beyond Neptune. University of Arizona Press. pp. 161–179. ISBN 9780816527557. Bibcode: 2008ssbn.book..161S. https://web.gps.caltech.edu/~mbrown/out/kbbook/Chapters/Stansberry_Spitzer.pdf. 
  28. ↑ Grundy, W. M.; Noll, K. S.; Stephens, D. C. (July 2005). "Diverse albedos of small trans-neptunian objects". Icarus 176 (1): 184–191. doi:10.1016/j.icarus.2005.01.007. Bibcode: 2005Icar..176..184G. 
  29. ↑ Cruikshank, Dale P.; Stansberry, John A.; Emery, Joshua P.; Fernández, Yanga R.; Werner, Michael W.; Trilling, David E. et al. (May 2005). "The High-Albedo Kuiper Belt Object (55565) 2002 AW197". The Astrophysical Journal 624 (1): L53–L56. doi:10.1086/430420. Bibcode: 2005ApJ...624L..53C. 
  30. ↑ Stansberry, J. A.; Cruikshank, D. P.; Grundy, W. G.; Margot, J. L.; Emery, J. P.; Fernandez, Y. R. et al. (August 2005). "Albedos, Diameters (and a Density) of Kuiper Belt and Centaur Objects". American Astronomical Society 37: 737. Bibcode: 2005DPS....37.5205S. 
  31. ↑ Brucker, M. J.; Grundy, W. M.; Stansberry, J. A.; Spencer, J. R.; Sheppard, S. S.; Chiang, E. I.; Buie, M. W. (May 2009). "High albedos of low inclination Classical Kuiper belt objects". Icarus 201 (1): 284–294. doi:10.1016/j.icarus.2008.12.040. Bibcode: 2009Icar..201..284B. 
  32. ↑ Brown, Michael E.. "How many dwarf planets are there in the outer solar system?". California Institute of Technology. http://web.gps.caltech.edu/~mbrown/dps.html. 
  33. ↑ 33.0 33.1 Tancredi, Gonzalo (6 April 2010). "Physical and dynamical characteristics of icy "dwarf planets" (plutoids)". Proceedings of the International Astronomical Union 5 (S263): 173–185. doi:10.1017/S1743921310001717. Bibcode: 2010IAUS..263..173T. 
  34. ↑ Tancredi, Gonzalo; Favre, Sofía (June 2008). "Which are the dwarfs in the solar system?". Icarus 195 (2): 851–862. doi:10.1016/j.icarus.2007.12.020. Bibcode: 2008Icar..195..851T. 
  35. ↑ Sheppard, Scott S. (August 2007). "Light Curves of Dwarf Plutonian Planets and other Large Kuiper Belt Objects: Their Rotations, Phase Functions, and Absolute Magnitudes". The Astronomical Journal 134 (2): 787–798. doi:10.1086/519072. Bibcode: 2007AJ....134..787S. 
  36. ↑ D. Ragozzine; M. E. Brown (2007). "Candidate Members and Age Estimate of the Family of Kuiper Belt Object 2003 EL61". The Astronomical Journal 134 (6): 2160–2167. doi:10.1086/522334. Bibcode: 2007AJ....134.2160R. 



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