The scope is this page is to compare how small bodies are grouped in existing data services, and to define a working scheme to describe these objects with EPNCore — preliminary lists are included in EPN-TAP 2.0, should be consolidated for v2.1.
The final goal is to help users identify data of interest in data services, not to actually classify all objects - therefore, several values of a parameter can be associated to a single object, reflecting possible variations in scientific interpretations (e.g., comet vs asteroid) or evolving classifications (e.g., dwarf planet vs asteroid).
In red: Updated in Feb 2024 (self-note: as per Small bodies sub-types.xlsx)
• SsODNet & the Quareo web service use "Types" of objects which are all included in EPN-TAP target_class list:
"Asteroid","Spacecraft","Comet","Exoplanet","Spacejunk","Satellite","Planet","Dwarf Planet","Star"
New in 2024 and populated : "Interstellar Object","Rogue Planet" (to be added to target_class in EPNCore v2.1) - also appear as classes
as well as “Classes“ which are sub-divisions of some types (and other classes, up to 3 levels):
• SsODNet uses "Classes" of objets. For small bodies: ["MB", "Middle", "Inner", "Outer", "NEA", "Mars-Crosser", "Apollo", "Hungaria", "Trojan", "Amor", "Hilda", "Cybele", "KBO", "Resonant", "Aten", "Short-period", "Classical", "Main", "Centaur", "SDO", "Halley-type", "3:2", "Jupiter-family", "7:4", "9:5", "5:3", "Detached", "11:6", "2:1", "Long-period", "5:2", "4:3", "7:3", "19:9", "Atira", "3:1", "11:8", "5:4", "12:5", "9:4", "8:3", "11:3", "7:2","11:2", "11:3"]
New in 2024 and populated : "Phocaea","Parabolic", "New","Encke-type","Chiron-type","External", "Hyperbolic"
• This is a composite and multi-level parameter, each object may have several values attached — in some cases this is not hierarchical though.
(other values are related to spacecraft and spacejunk, see here: http://vo.imcce.fr/webservices/ssodnet/?quaero#types_and_classes)
Queries are like, eg: (beware of case and parentheses)
Satellites of asteroids are tagged as satellites with parent = primary, and have no "class"
Some classes have sub-classes with the same name (eg, Inner/Outer for both MB and KBO/Classical), but no overlap — can't be used by themselves
No interstellar objects are included in 2020 - 2 in 2024
• To retrieve the values of a given object (case sensitive): https://api.ssodnet.imcce.fr/quaero/1/sso?q=Palermo
Dynamical class does not always correspond exactly to MPC (ex: 100085 - Amor on one side, Apollo on the other)
Apparently the most comprehensive source, and looks OK — comets TBC though (see below)
Classifications are based on:
- KBO: Gladman et al 2008 2008ssbn.book...43G (see also this notebook)
update (to be implemented early 2024) in Volk and Van Laerhoven, 2024: https://iopscience-iop-org.ezproxy.obspm.fr/article/10.3847/2515-5172/ad22d4 & https://zenodo.org/records/10558440
- Comets: Levison, 1996 1996ASPC..107..173L, slightly simplified (but coexists with the previous, largely independent, classification in short/long period which Levison says is not physical. And the expected overlaps do not fit in detail)
- NEA and Mars-crossers: as per review in Carry et al 2016 2016Icar..268..340C - see also Bottke et al 2002 and Greenstreet et al 2012
- Other asteroids (main belt and nearby families): stated as common knowledge — is there a reference or review?
EPN-TAP services use target_class (compulsory), dynamical_class and dynamical_type (optionals)
• Target_class related to small bodies are:
asteroid, dwarf_planet, comet
To be added to target_class in EPNCore v2.1: "Interstellar Object"
• There is a recurring issue with dwarf_planet, not always identified as such in databases / services
The EPN-TAP recommendation is to put "dwarf_planet#asteroid" in target_class — beware that Pluto can appear under "planet" in older databases
Current dwarf planets are: Ceres, Pluto, Eris, Haumea, Makemake + candidates: Quaoar, Sedna, Orcus, Gonggong
• Similarly, "comet#asteroid" can be used for transitional objects. Current recognized transitional objects are:
(2060) Chiron (95P/Chiron)
(7968) Elst-Pizarro (133P/Elst-Pizarro)
(60558) Echeclus (174P/Echeclus) => (avoid / correct French name)
(118401) LINEAR (176P/LINEAR) = LINEAR 52
(4015) Wilson-Harrington (107P/Wilson-Harrington) = 1979 VA
• 2 other parameters are avalaible: dynamical_class and dynamical_type (which should be a subdivision of the former, TBC). Both should provide a clear list of values, based on those of existing services.
What is ~ clear (but names are TBC):
dynamical_class: MBA, NEO, TNO, Trojan, Centaur, JFC (or Jupiter-family), Halley-type, Long-period… + Main Belt Comet (= active asteroids)?
dynamical_type: families, resonances… + Plutino (=res 2:3)?, Classical (with several subdivisions possible: Hot vs Cold, or Inner/Outer/Middle), Scattered Disk object, Detached object…
• Similarly, a given object can be described by several values, especially when the classificiation is unclear or changing with time.
Table 1 - Provisional values for EPNCore parameters - to be revised
Target_class | dynamical_class | dynamical_type |
---|---|---|
comet | JFC (or Jupiter-family) Halley-type Long-period Main Belt Comet (all this TBC) Parabolic Hyperbolic | |
asteroid | NEO | Aten Apollo Amor Atira |
MBA | Inner Middle Outer Cybele Hilda dynamical families? - more likely another parameter | |
Hungaria | ||
Phocaea | ||
Mars-crosser | ||
Trojan | associate primary? May be through the primary_body parameter | |
Centaur | ||
TNO | Resonant Plutino (= res 2:3)? Classical Hot classical / Cold classical? or Main/Inner/Outer? Scattered Disk object Detached object | |
dwarf_planet#asteroid | MBA TNO | |
interstellar_object |
• MPCorb updated 2024 (original site & derived EPN-TAP service) uses orbit_class. This is a free comment string which is not always informed and may contain extra info (can’t be used easily for searches…)
Values include 4 NEO types + Objects with perihelion distance < 1.665 AU, Hungaria, MBA, Phocaea, Hilda, Jupiter Trojan, Distant object (comprising both TNO and Centaurs), None (new in 2024, but > 80,000 of them - some are MBA)
In 2020 there were also: Unclassified, MBA - deprecated
Some look inconsistent, eg: 3 objects have orbit_class saying both Distant Object & NEO (2016 XK24, 2017 UR52, 2019 EJ3, all Amor) — check if this is from the original site or a gremlin in the ENP_TAP service
Not always matching the SSODNet values, see above
Queries / object are like:
https://www.minorplanetcenter.net/db_search/show_object?utf8=%E2%9C%93&object_id=K16X24K
• TNOsarecool updated 2024: uses dynamical_type , including res 2:5, res 1:2, res 4:7, Plutino, Cubewano (= Classical), Hot classical, Cold classical, SDO (Scattered disk object), Detached object, Inner Oort obj (not strictly KBO?), Centaur
Note: this includes several granules for Sycorax, a Uranus moon with target_class = asteroid, to be corrected
• Basecom uses comet_type with values: dynamically new, Halley-type comet, Jupiter-family comet, long-period comet
This is pretty close to the pre-Levison 1996 classification (with dynamically new comets highlighted among long-period ones), but that doesn't match SSODNet (which seems to implement both schemes) — therefore comet types are TBC
• M4ast uses no dynamic classification
• SBNAF uses no dynamic classification (doesn't associate a type, leaves it to other services - probably MPC)
• DynAstVO updated 2024:
As of March 2024, the service is intended to include only NEAs - however, other classes appear in the service (only ~15 at the time of review).
After discussion with the developers: the dynamic class is identified by an internal procedure, based on orbital parameters. This may provide incorrect results e.g. when they are affected by a large uncertainty. But the split between class and type looks inconsistent.
Uses dynamical_class, with values : MBA, NEO and (a few) NULL
Also uses dynamical_type including Aten Apollo Amor Atira (for NEA), plus other things:
CENTAUR (class NULL) - should be in dynamical_class
TROJAN (class NULL)
PHOCAEA (class NULL) - a MB-periphery dynamic family, traditionally not in MB — should thus be in dynamical_class
I, IIA, IIB (class MBA) - stand for I: Inner belt & II: Medium belt (2 groups depending on semi-major axis)
• LuckyStar table (web site in Brasil):
Contains asteroids and satellites data.
Uses a composite DynClass parameter with values: Centaur, (Planet Satellite), TNO> Cold C., TNO> Detached O., TNO> Hot C., TNO> Plutino, TNO> Resonant, TNO> Scattered D.O., Trojan (~ in line with TNOsarecool)
If target = an asteroid satellite, this refers to the primary.
• MP3C_best: the best value table does not provide classification - apparently relies on MPCOrb. Secondary TAP tables neither apparently.
Table 2 - comparison of values found in existing services/contexts (updated 2024)
SSODnet class: | target_class | dynamical_class | dynamical_type | DynClass | Orbit_class |
---|---|---|---|---|---|
"KBO" | Asteroid | TNO | Distant Object | ||
"Classical" | Asteroid | TNO | Cubewano (but coexists with Hot and Cold Cl.) | TNO> Cold C. & TNO> Hot C.? | |
"Main" | Asteroid | TNO | Hot classical & Cold classical? | TNO> Cold C. & TNO> Hot C.? | |
"Inner" | Asteroid | TNO | |||
"Outer" | Asteroid | TNO | |||
"Detached" | Asteroid | TNO | Detached object | TNO> Detached O. | |
"SDO" | Asteroid | TNO | SDO | TNO> Scattered D.O. | |
"Resonant" | Asteroid | TNO | TNO> Resonant | ||
"3:2" | Asteroid | TNO | Plutino | TNO> Plutino | |
"7:4" | Asteroid | TNO | res 4:7 | ||
"9:5" | Asteroid | TNO | |||
"5:3" | Asteroid | TNO | |||
"11:6" | Asteroid | TNO | |||
"2:1" | Asteroid | TNO | res 1:2 | ||
"5:2" | Asteroid | TNO | res 2:5 | ||
"4:3" | Asteroid | TNO | |||
"7:3" | Asteroid | TNO | |||
"19:9" | Asteroid | TNO | |||
"3:1" | Asteroid | TNO | |||
"11:8" | Asteroid | TNO | |||
"5:4" | Asteroid | TNO | |||
"12:5" | Asteroid | TNO | |||
"9:4" | Asteroid | TNO | |||
"8:3" | Asteroid | TNO | |||
"11:3" | Asteroid | TNO | |||
"7:2" | Asteroid | TNO | |||
"11:2" | Asteroid | TNO | |||
"Short-period" | Comet | (comets TBC) | |||
"Jupiter-family" | Comet | JFC | |||
"Halley-type" — therefore not a sub-type? | Comet | ||||
"Chiron-type" | Comet | ||||
"Encke-type" | Comet | ||||
"External" — not a sub-type? | Comet | ||||
"New" | Comet | ||||
(none= probably not yet known) | Comet | ||||
"Long-period" | Comet | ||||
"Halley-type" — therefore not a sub-type? | Comet | ||||
"External" — not a sub-type? | Comet | ||||
"Parabolic" | Comet | ||||
"Hyperbolic" | Comet | ||||
(none= unknown?) | Comet | ||||
"NEA" | Asteroid | NEO | |||
"Apollo" | Asteroid | NEO | Apollo | Apollo | |
"Amor" | Asteroid | NEO | Amor | Amor | |
"Aten" | Asteroid | NEO | Aten | Aten | |
"Atira" | Asteroid | NEO | Atira | Atira | |
"Mars-Crosser" | Asteroid | _ | Objects with perihelion distance < 1.665 AU | ||
"Hungaria" | Asteroid | _ | Hungaria | Hungaria | |
"Phocaea" | Asteroid | (null) | Phocaea | Phocaea | |
"MB" | Asteroid | MBA | MBA (value deprecated) | ||
"Inner" | Asteroid | MBA | I | ||
"Middle" | Asteroid | MBA | IIa and IIb | ||
"Outer" | Asteroid | MBA | (potentially) IIIa and IIIb | ||
"Cybele" | Asteroid | MBA | Cybele | _ | |
"Hilda" | Asteroid | MBA | Hilda | Hilda | |
"Trojan" | Asteroid | (null) | Trojan | Jupiter Trojan (are included) | |
"Centaur" | Asteroid | (null) | Centaur | Centaur | Distant Object |
(type: Dwarf Planet, | Dwarf_planet | MBA or TNO | (not tagged) | ||
(type: Interstellar object, | _ | _ | |||
Not identified in SSODnet No distinction between hot and cold classical objects | Comet | Inner Oort obj |
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