Small bodies sub-types

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

• 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