what can you tell me about the last object you just mentioned?
UNANSWERABLE
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.
wiki:304984
Definition of planet [SEP] Introduction
The definition of "planet", since the word was coined by the ancient Greeks, has included within its scope a wide range of celestial bodies. Greek astronomers employed the term "asteres planetai" (ἀστέρες πλανῆται), "wandering stars", for star-like objects which apparently moved over the sky. Over the millennia, the term has included a variety of different objects, from the Sun and the Moon to satellites and asteroids. In modern astronomy, there are two primary conceptions of a 'planet'. Disregarding the often inconsistent technical details, they are whether an astronomical body "moves" like a planet (that is, whether its orbit and relationship to other bodies are similar to those of the classical planets) or whether it "looks" like a planet (that is, whether it is round or has planetary geology).