When I was going to my tuition in south Kolkata(India) I suddenly noticed a green light high in the SW direction it diameter was about 6-13 meters,when I saw this I understood that it was something like a UFO as I had saw something like that before but this time this different as this was spherical than triangle like I had saw before it emit green light then suddenly it flashed like a explosion and suddenly went away from me but it looked like it was falling at a slow speed it left a trail of green light.I don't know what was that but it looked like a UFO.I want to know what was that....so please help me by solving this report