MPEC 2017-V17 : NEW DESIGNATION SCHEME FOR INTERSTELLAR OBJECTS

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M.P.E.C. 2017-V17 Issued 2017 Nov. 6, 21:00 UT The Minor Planet Electronic Circulars contain information on unusual minor planets and routine data on comets. They are published on behalf of Division F of the International Astronomical Union by the Minor Planet Center, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Prepared using the Tamkin Foundation Computer Network MPC@CFA.HARVARD.EDU URL https://www.minorplanetcenter.net/ ISSN 1523-6714 NEW DESIGNATION SCHEME FOR INTERSTELLAR OBJECTS The discovery of A/2017 U1 has presented a slight nomenclature problem. Since both the original and future barycentric orbits for this object are significantly hyperbolic, this object is not bound to our solar system and the current apparition is likely to be the only time that the object is observable. Due to the unique nature of this object, there is pressure to assign a name. The minor-planet designation scheme does not allow a name to be assigned to this object based on the brief arc of observation. Recent e-mail exchanges between the IAU General Secretary, the IAU Division F President, the co-chairs of the IAU Working Group on Small Body Nomenclature and the Minor Planet Center have discussed this nomenclature issue. A solution has been proposed that solves the problem. A new series of small-body designations for interstellar objects will be introduced: the I numbers. This new sequence will be similar in form to the comet numbering system and assignment of the numbers will be handled by the Minor Planet Center. Provisional designations for interstellar objects will be handled using the C/ or A/ prefix (as appropriate), with the designation using the comet system. Accordingly, the object A/2017 U1 receives the permanent designation 1I and the name ʻOumuamua. The name, which was chosen by the Pan-STARRS team, is of Hawaiian origin and reflects the way this object is like a scout or messenger sent from the distant past to reach out to us (ʻou means reach out for, and mua, with the second mua placing emphasis, means first, in advance of). Correct forms for referring to this object are therefore: 1I; 1I/2017 U1; 1I/ʻOumuamua; and 1I/2017 U1 (ʻOumuamua). This first interstellar object is being handled as a special case. A small committee of the WGSBN will be created to codify the circumstances under which an object will qualify for an I-number and the rules that will apply to the names, bearing in mind the precedent set by this case. A formal report will follow their deliberations. Gareth V. Williams (C) Copyright 2017 MPC M.P.E.C. 2017-V17

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