what is its objective?
Its main objective is to promote and safeguard the science of astronomy in all its aspects through international cooperation.
International Astronomical Union
Its main objective is to promote and safeguard the science of astronomy in all its aspects through international cooperation
give any three differences between planets and stars Planet -  it is round or has planetary geology; "moves" like a planet. Star - an astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. when did the need for a definition arise? In January 2005, with the discovery of the trans-Neptunian object Eris. what can you tell me about the last object you just mentioned? UNANSWERABLE is there any establishment that is responsible for defining/ naming the planets? Yes, the International Astronomical Union (IAU). when was it founded? 28 July 1919
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International Astronomical Union [SEP] Introduction
The International Astronomical Union (IAU; , UAI) is an international association of professional astronomers, at the PhD level and beyond, active in professional research and education in astronomy. Among other activities, it acts as the recognized authority for assigning designations and names to celestial bodies (stars, planets, asteroids, etc.) and any surface features on them. The IAU is a member of the International Science Council (ISC). Its main objective is to promote and safeguard the science of astronomy in all its aspects through international cooperation. The IAU maintains friendly relations with organizations that include amateur astronomers in their membership. The IAU has its head office on the second floor of the "Institut d'Astrophysique de Paris" in the 14th arrondissement of Paris.