where are they headquartered?
Brussels, Belgium
International Astronomical Union
The IAU was founded on 28 July 1919, at the Constitutive Assembly of the International Research Council (now the International Science Council) held in Brussels, Belgium.
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 what is its objective? Its main objective is to promote and safeguard the science of astronomy in all its aspects through international cooperation.
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International Astronomical Union [SEP] History
The IAU was founded on 28 July 1919, at the Constitutive Assembly of the International Research Council (now the International Science Council) held in Brussels, Belgium. Two subsidiaries of the IAU were also created at this assembly: the "International Time Commission" seated at the International Time Bureau in Paris, France, and the "International Central Bureau of Astronomical Telegrams" initially seated in Copenhagen, Denmark. The 7 initial member states were Belgium, Canada, France, Great Britain, Greece, Japan, and the United States, soon to be followed by Italy and Mexico. The first executive committee consisted of Benjamin Baillaud (President, France), Alfred Fowler (General Secretary, UK), and four vice presidents: William Campbell (USA), Frank Dyson (UK), Georges Lecointe (Belgium), and Annibale Riccò (Italy).