I was smoking a cigarette on a 2nd floor window of my house. my head was outside the window, as i was triyng to avoid the smoke to get inside the house. suddenly at my left side i saw a very brilliant sphere with a pure-constant and deep white light (absolutely not blinking in any way) travelling at a very fast speed of around 300-400km/h in a rectilineal trajectory and producing no sound. the object disappeared behind some trees, located 300-400 m from where i was. the maximum altitud of the object was 150-200 m. the whole sighten took place in between 2-3 seconds, but i could straight and clearly see it for almost two seconds. inmediately after the object dissapeared a lot of dogs started to bark (a lot, since it was in a rural-urbanised area). i wasnt afraid at all and never startled, it was all very natural. it took me some seconds after the disappearing of the object that i realised it was a ufo. i realised it was a ufo, because the speed of the object was very high, and no sound was made (no plane of any kind, nor a drone, even less an helicopter). it wasn't a comet or some spatial rubish, because of the altitud, the trajectory and the speed. it just didnt matched with any kind of known object to me, in that place, time, area and other dettails. sorry for the ortographic faults.