7604 Kridsadaporn

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7604 Kridsadaporn
Discovered by Robert H. McNaught
Discovery site Siding Spring Observatory
Discovery date 31 August 1995
MPC designation 7604 Kridsadaporn
1995 QY2
Orbital characteristics[1]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc 11341 days (31.05 yr)
Aphelion 4.8986418 AU (732.82638 Gm)
Perihelion 1.3253310 AU (198.26670 Gm)
3.111986 AU (465.5465 Gm)
Eccentricity 0.5741206
5.49 yr (2005.2 d)
0° 10m 46.323s / day
Inclination 20.45079°
Earth MOID 0.520837 AU (77.9161 Gm)
Jupiter MOID 1.75987 AU (263.273 Gm)
Jupiter Tisserand parameter 2.859
Physical characteristics

7604 Kridsadaporn is a Mars-crossing asteroid discovered by R. H. McNaught on 31 August 1995 at Siding Spring Observatory near the town of Coonabarabran, Australia. Kridsadaporn's high orbital eccentricity of just over 0.574[1] places it within a group of objects known as Asteroids in Cometary Orbit (ACOs).[2][3] Due to its unusual orbital parameters, Kridsadaporn is listed by the IAU Minor Planets Center as an Unusual Minor Planet.[4]

Discovery and naming[edit]

Kridsadaporn was discovered using the 0.5-m Uppsala Schmidt Telescope, as part of the Siding Spring Survey (SSS), which itself is part of a broader network of Near-Earth object search programs.[5] The then-unnamed asteroid was initially assigned the provisional designation 1995 QY2.[1] In April 2005 it was renamed by its discoverer (Robert McNaught)[6] in honour of Kridsadaporn Ritsmitchai,[note 1] a then recently deceased friend and colleague[7] at the Research School of Astronomy and Astrophysics at the Australian National University, who worked and resided at Siding Spring Observatory.

Kridsadaporn (กฤษฎาพร  [krìsàdāːpʰōn], กฤษดาพร  [krìsàdāːpʰōn]) is a Thai name comprising two words: "kridsada" (กฤษฎา) of Sanskrit origin, meaning "supernatural powers, divine, celestial"; and "porn" (พร) meaning "blessing, benediction, favour".[note 2] Often Thai first names are suffixed with "porn" (พร) denoting, "a blessing from the Buddha", referring to both the gift of a child, and the favour of particular attributes, referred to within the name, manifesting within the child. In Thai tradition, a child's name is chosen using complex Buddhist name giving rituals where Thai astrology is widely used, often in consultation with a Buddhist monk.[11][12] Parents of a newly-born child named Kridsadaporn (กฤษฎาพร) may believe, or may accept, the name's meaning as, "a blessing from the Buddha; a child, gifted with divine qualities and supernatural powers".


An approximation known as the Tisserand criteria (T) is applied to cometary encounters with planets (such as Jupiter) and used to describe their orbital inter-relationship.[13] Asteroidal-appearing bodies in elliptical orbits with Jovian Tisserand parameters Tj < 3 only began to appear in search programs in the mid-1980s - Kridsadaporn's Jovian Tisserand parameter is Tj = 2.858.[1] Before this, the failure to identify these objects was used as an argument against the existence of extinct cometary nuclei. Over the past two decades, an increasing number of asteroids, based upon their orbital and physical characteristics, have been suggested as extinct or dormant comets candidates. It is now considered likely that within the asteroid population there exist a significant number of dormant or extinct comets.[14]

More recently, Kridsadaporn has received closer attention after having been included in a number of studies relating to the analysis of spectral properties of asteroids in cometary orbits (ACOs);[3][15] and, collisional activation processes, and the dynamic and physical properties of ACOs.[2][16] The investigation of ACOs is considered important in the understanding of formation processes of cometary dust mantles and the end states of comets, so as to determine the population of Jupiter family comets (JFCs), and, to also understand the dynamical processes involved in the transport mechanism of asteroids from typical asteroidal orbits to cometary-like ones.[3]

In earlier studies, ACOs have sometimes been referred to as cometary asteroids or comet-asteroid transition objects.[16]


Trajectory of 7604 Kridsadaporn

Kridsadaporn's highly elliptical orbit has similar orbital characteristics to those of the Jupiter-family comets (JFCs) which populate the Jovian Tisserand invariant range 2 ≤ Tj ≤ 3, which supports the scenario that a significant number of asteroids in cometary orbits are extinct or dormant cometary candidates.[2]

Mars-crossing orbit[edit]

Kridsadaporn is amongst another group of bodies [Mars-crossing (MC) and/or near-Earth object (NEO) populations] that may have originated from the main asteroid belt as fragments injected into a mean-motion resonance or secular resonance, developing increasingly higher orbital eccentricity over time resulting in the perihelion distance becoming smaller than the aphelion distances of the inner planets. At their birth, near-earth asteroids (NEAs) and MC orbits are in resonance, and when their orbital eccentricity becomes large enough, to the point that their orbits cross those of the inner planets, their orbits then become modified in a random-walk fashion. This results in a complex interplay between planetary encounters and resonances which may lead to a range of unexpected outcomes including cometary-type orbits; solar collisions; or, eventual ejection from the Solar System.[16][17]

Orbital evolution[edit]

Detailed investigations into Kridsadaporn’s dynamic evolution have been carried out by creating 15 "clone" orbits, integrated forward over a period of 1.2 × 106 years, by changing the last digit of its orbital parameters. Nine (9) clones demonstrated moderate chaotic behaviour jumping between the Jovian mean-motion resonances of 15:7, 9:4, and 11:5 with some orbits becoming Earth-crossers within the integration period. The remaining six (6) clones grew in orbital eccentricity until becoming Jupiter-crossers, and then, behaving as Jupiter-family comets, they were ejected from the Solar System over periods in the order of 105 years.[16]

The most prominent Kirkwood gaps, corresponding to locations at orbital resonance with Jupiter

The histogram of asteroid semi-major axis has several prominent dips in the distribution. These gaps are more sparingly populated with objects of higher orbital eccentricity. Known as Kirkwood gaps, these dips in distribution density correspond to the location of orbital resonances with Jupiter. Objects with eccentric orbits continue to increase in orbital eccentricity over longer time-scales to eventually break out of resonance due to close encounters with a major planet.[18] Kridsadaporn, with a semi-major axis of e = 3.110626,[1] corresponds to a very narrow gap associated with the 11:7 resonance[16] within a series of weaker and less sculpted gaps.

Physical characteristics[edit]

Kridsadaporn is of a C-type taxonomic classification[3] typified as dark carbonaceous objects.[19]

A number of studies[3][15] included Kridsadaporn within a sample of asteroids in cometary orbits in order to understand the relationships in spectral characteristics between ACOs, the Jupiter-family comets, and the outer main belt asteroids. The only finding was that comets present neutral or red feature-less spectra.[3] Earlier studies[20] suggested that comets in all stages of evolution - active; dormant; and, dead - were very dark, often reddish, objects with spectra similar to D-type, P-type and C-type asteroids of the outer Solar System with probably carbonaceous dust containing reddish organic compounds controlling their colour and albedo characteristics.[3]

Origins of ACO objects[edit]

Studies analysing the albedo distribution of a sample of asteroids in cometary orbits,[21] found in general that they exhibit lower albedos than objects with Tj > 3 and further concluded that all ACOs in that sample with Tj < 2.6 had albedos pV < 0.075 - similar to those measured for cometary nuclei - suggesting cometary origins.[3]

A sample of objects, which included Kridsadaporn, was used in a study[3] of the relationship between the Jovian Tisserand invariant and spectral properties of asteroids in cometary orbits, which determined that all observed ACOs within the sample with Tj < 2.9 were feature-less. Kridsadaporn, with its Jovian Tisserand invariant of 2.858,[1] falls within the feature-less (without bands) comet-like spectral group. These studies also concluded that ACOs with featured spectra (with bands) typical of the main belt had Tj ≥ 2.9 while those with Tj < 2.9 demonstrated comet-like spectra, suggesting that the subsample of ACOs with 2.9 ≤ Tj ≤ 3.0 could be populated by a large fraction of interlopers from the inner part of the belt.[2]

Kridsadaporn has a perihelion distance q = 1.3224 AU.[1] A study of the relationship between the size distribution profile and perihelion distances of ACOs[22] concluded that a sub-sample of ACOs with a perihelion distance q > 1.3 AU had a size distribution profile similar to that of the Jupiter family comets, suggesting that sub-sample to be composed of a significant fraction of dormant comets, while a large fraction of ACOs with q < 1.3 AU could more likely be scattered objects from the outer main belt.[2]

Objects with a Jovian Tisserand invariant Tj ≤ 3 and taxonomic properties consistent with a low albedo, however, are not enough to imply that they are dormant or extinct comets. The fraction of low albedo, Tj ≤ 3, objects actually being dormant or extinct comets is estimated to be 65% ± 10%.[15]


  1. ^ "Kridsadaporn (San) Ritsmitchai (1964-2004) was born in Songkhla, Thailand. She and her husband Martin Callaway both lived and worked at Siding Spring Observatory. San is remembered in Coonabarabran for her caring nature and community work. She died tragically in a car accident".[1]
  2. ^ Kridsada is sometimes Romanized as gritsada, kritsada and often kruetsada. However, Thai script rules[8] for Sanskrit borrow-words vowels transcribe it as "krisada", (กฤษดา) while retaining the original meaning associated with "kridsada". Many Thai first names are suffixed with "porn" (พร) pronounced as "phaawn", transliterated using the Royal Thai General System as "phon"[9] however, variations in translation methods sometimes result in it being Romanized as "pon"[10] - in which case an "r" is often added for a truer phonetic approximation.


  1. ^ a b c d e f g h "JPL Small-body browser - 7604 Kridsadaporn". Jet Propulsion Laboratory. Retrieved 13 April 2016. 
  2. ^ a b c d e Díaz, C. G.; Gil-Hutton, R. (2008). "Collisional activation of asteroids in cometary orbits". Astronomy and Astrophysics. 487: 363–367. Bibcode:2008A&A...487..363D. doi:10.1051/0004-6361:20079236. Retrieved 2011-03-29. 
  3. ^ a b c d e f g h i Licandro, J.; et al. (2008). "Spectral properties of asteroids in cometary orbits" (PDF). Astronomy and Astrophysics. 481: 861–877. Bibcode:2008A&A...481..861L. doi:10.1051/0004-6361:20078340. Retrieved 2011-03-29. 
  4. ^ "List of Unusual Minor Planets". IAU Minor Planets Center. 
  5. ^ Stokes, Grant H.; Evans, Jenifer B.; Larson, Stephen M. (2002). "Near-Earth Asteroid Search Programs". Asteroids III. Tucson: University of Arizona Press: 45–54. Bibcode:2002aste.conf...45S. Retrieved 2011-04-20. 
  6. ^ "Naming Astronomical Objects". International Astronomy Union. Archived from the original on 5 May 2011. Retrieved 2011-04-01. 
  7. ^ "Annual Report, staff list" (PDF). Research School of Astronomy and Astrophysics, Australian National University. 2003. p. 21. Retrieved 2011-04-01. 
  8. ^ "Extended Definition: Thai alphabet". Webster's Online Dictionary. Archived from the original on January 22, 2005. Retrieved 2011-04-02. 
  9. ^ "Internet resource for the Thai language". Thai-language.com. Retrieved 2010-04-02. 
  10. ^ "Thai<>English Dictionary". thai2english.com. Retrieved 2011-04-02. 
  11. ^ Snae, Chakkrit. "Constructing a Rule Based Naming System for Thai Names Using the Concept of Ontologies" (PDF). Naresuan University Phitsanulok, Thailand. Retrieved 2010-04-02. 
  12. ^ de Young, John E. (1958), Village life in modern Thailand, University of California Press, p. 53 
  13. ^ Brant, John C.; Chapman, Robert D. (2004), Introduction to asteroids, Cambridge University Press, p. 69, ISBN 0-521-00466-7 
  14. ^ Weissmen, Paul R.; et al. (1998). Evolution of comets into asteroids. Asteroids II; Proceedings of the Conference, Tucson, AZ, Mar. 8-11, 1988 (A90-27001 10-91). University of Arizona Press. pp. 880–920. Bibcode:1989aste.conf..880W. Retrieved 2011-04-12. 
  15. ^ a b c Binzel, Richard P.; et al. (2004). "Observed spectral properties on near-Earth objects:results for population distribution, source regions, and space weathering processes" (PDF). Icarus. 170: 259–294. Bibcode:2004Icar..170..259B. doi:10.1016/j.icarus.2004.04.004. 
  16. ^ a b c d e di Martino, M.; et al. (1998). "Dynamic and physical properties of comet-asteroid transition objects". Astronomy and Astrophysics. The Smithsonian/NASA Astrophysics Data System. 329: 1145–1151. Bibcode:1998A&A...329.1145D. Retrieved 2011-04-12. 
  17. ^ Froeschlé, Claude; et al. (1995), "Secular resonances and the Dynamics of Mars-crossing and near-Earth asteroids", Icarus, ScienceDirect, 117 (1): 45–61, Bibcode:1995Icar..117...45F, doi:10.1006/icar.1995.1141, retrieved 2011-04-12 
  18. ^ Tsiganis, Kleomenis; et al. (March 29, 2002). "Stable Chaos versus Kirkwood Gaps in the Asteroid Belt: A Comparative Study of Mean Motion Resonances" (PDF). 159. Icarus: 284–299. Bibcode:2002Icar..159..284T. doi:10.1006/icar.2002.6927. Retrieved April 20, 2011. 
  19. ^ Chodas, Paul. "Introduction to Comets and Asteroids" (PDF). JPL/Caltec. Retrieved 2011-04-12. 
  20. ^ Hartmann, William K.; et al. (June 19, 1986). "The relationship of active comets, "extinct" comets, and dark asteroids". 69 (1). Icarus: 33–50. Bibcode:1987Icar...69...33H. doi:10.1016/0019-1035(87)90005-4. Retrieved 2011-04-12. 
  21. ^ Fernández, Yanga R.; et al. (2005). "Albedos of asteroids in comet-like orbits". The Astronomical Journal. 130: 308. Bibcode:2005AJ....130..308F. doi:10.1086/430802. Retrieved 2011-04-12. 
  22. ^ Alvarez-Candel, A.; Licandro, J. (2006). "The size distribution of asteroids in cometary orbits and related populations". Astronomy and Astrophysics. 458 (3): 1007–1011. Bibcode:2006A&A...458.1007A. doi:10.1051/0004-6361:20064971. Retrieved 2011-04-12. 

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