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.
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).
• SsODNet & the Quareo web service use "Types" of objects which are all included in EPN-TAP list:
"Asteroid","Spacecraft","Comet","Exoplanet","Spacejunk","Satellite","Planet","Dwarf Planet","Star"
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", "27:4"]
This is a composite and multi-level parameter, each object may have several values attached.
(other values are related to spacecraft and spacejunk, see here: http://vo.imcce.fr/webservices/ssodnet/?quaero#types_and_classes)
Satellites of asteroids are tagged as satellites with parent = primary, and have no "class"
No interstellar object are included in 2020.
MPC (original site & derived EPN-TAP service) uses orbit_class !!! This is a free comment string which is not always informed (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, Unclassified
=> Is there a clear IAU nomenclature with 2 sub levels?
EPN-TAP services use target_class (compulsory), dynamical_class and dynamical_type (optionals)
• Target_class related to small bodies are:
asteroid, dwarf_planet, comet
• There is a recurring issue with dwarf_planet, not always identified as such in databases / services
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 + possibly 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)?, Hot classical, Cold classical, 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
Target_class | dynamical_class | dynamical_type |
---|---|---|
comet | JFC (or Jupiter-family) Halley-type Long-period Interstellar? Main Belt Comet | |
asteroid | NEO | Athen Apollo Amor Atira |
MBA | families (Hungaria, Phocaea, Hilda, Cybele…) Mars-crosser? | |
Trojan | associate primary? | |
Centaur | ||
TNO | resonances, or Resonant Plutino (= res 2:3)? Hot classical Cold classical Scattered Disk object Detached object | |
dwarf_planet#asteroid | MBA TNO |
• TNOsarecool uses dynamical_type , including res 2:5, res 1:2, Plutino, Hot classical, Cold classical, SDO (Scattered disk object), Detached object, Inner Oort obj (not strictly KBO?)
• Basecom uses comet_type with values: dynamically new, Halley-type comet, Jupiter-family comet, long-period comet
• M4ast uses no dynamic classification
• SBNAF uses no dynamic classification (doesn't associate a type, leaves it to other services - probably MPC)
• DynAstVO
Uses dynamical_class: MBA, NEO and Null + add Centaur?
Also uses dynamical_type including Athen Apollo Amor Atira, plus other things:
CENTAUR (class NULL) - should be in dynamical_class
PHOCAEA (class NULL) - an MBA family (dynamical_class should be MBA)
I, IIA, IIB (class MBA)
• 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)
For asteroid satellites, this refers to the primary.
Table 2 - comparison of values found in existing services/contexts
SSODnet class: | target_class | dynamical_class | dynamical_type | DynClass | Orbit_class |
"MB" "Middle" "Inner" (either MB or Classical) "Outer" (either MB or Classical) "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" (type: Dwarf Planet, various classes) | Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Comet Asteroid Asteroid Asteroid Asteroid Comet Asteroid Comet Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Comet Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Asteroid Dwarf_planet | MBA MBA MBA or TNO MBA or TNO NEO ? NEO MBA Trojan NEO MBA MBA TNO TNO NEO TNO TNO Centaur TNO TNO JFC TNO TNO TNO TNO TNO TNO TNO TNO TNO TNO NEO TNO TNO TNO TNO TNO TNO TNO TNO MBA or TNO | Inner? External? APOLLO Hungaria AMOR Hilda Cybele ATEN Hot classical & Cold classical? Hot classical & Cold classical? SDO Plutino Detached object res 1:2 res 2:5 ATIRA | Trojan TNO> Resonant TNO> Cold C. & TNO> Hot C.? TNO> Cold C. & TNO> Hot C.? Centaur TNO> Scattered D.O. TNO> Plutino TNO> Detached O. | |
Not identified in SSODnet (a family; MB / Inner) No distinction between hot and cold classical objects | Comet Asteroid Asteroid | MBA MBA | Inner Oort obj Phocaea I, IIA, IIB |