ann17045 — Announcement

1I/2017 U1 (ʻOumuamua)
14 November 2017
The IAU approves new type of designation for interstellar objects
After astronomers recently discovered a new type of interstellar object, the IAU Executive Committee approved a new designation to use for these objects. From now on the letter “I” is used to indicate “interstellar”.

On 19 October 2017, Dr. Robert Weryk, a postdoctoral fellow at the Institute for Astronomy, of the University Hawaii-manoa, discovered a moving object using the Pan-STARRS telescope. At the time of discovery, the object was 0.2 AU (30 000 000 km) from Earth. The object was initially classified as a comet (C/2017 U1) and later as an asteroid (A/2017 U1). However, further observations indicated that because of its hyperbolic orbit and record-breakingly high eccentricity, the object was never gravitationally bound to the Solar System: a prototype of a new class of objects, an “interstellar asteroid”, had been discovered!

As the new object did not fit into any of the existing IAU designation schemes, it was necessary for a new one to be defined. The IAU Minor Planet Center, based at the Harvard-Smithsonian Center for Astrophysics, is responsible for identifying, designating and computing the orbit for minor planets, comets and outer irregular natural satellites of the major planets. The MPC proposed to the IAU Executive Committee that they adopt a designation scheme similar to the one used for comets and asteroids (characterised by the letters “C” and “A” respectively), using the letter “I” standing for “interstellar”. The IAU Executive Committee approved the proposal in less than 24 hours and the new object is now officially known as 1I/2017 U1.

In addition to the technical designation, the MPC also exceptionally assigned the name 'Oumuamua to the new object, as proposed by the Pan-STARRS team. In Hawaiian 'Oumuamua means “a messenger from afar arriving first” that quite appropriately reflects the nature of the object and its discovery.

Considering the growing interest in the observation and orbit determination of asteroids (see for example the International Asteroid Warning Network (IAWN) initiative, it is expected that the discovery of 1I/2017 U1 ('Oumuamua) will soon be joined by discoveries of more of such interlopers entering the inner Solar System from interstellar space. The scheme for their designation is ready, while the procedure for assigning them a name, similar to the one in use for minor planets, will soon be decided.



Piero Benvenuti
General Secretary, International Astronomical Union
Paris, France
Tel: +33 1 43 25 83 58

Lars Lindberg Christensen
IAU Press Officer
Garching bei München, Germany
Tel: +49 89 320 06 761
Cell: +49 173 38 72 621

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1I/2017 U1 (ʻOumuamua)