Aliens on the planet Xargon spot a distant dying star, 5 light years far. If we see the star dying today then after how much time will the star's explosion be heard by the Xargonians? (Assume Xargonians to be an immortal peace loving race) speed of sound 3×102 m/s
Never ever
First of all, light year is the unit of distance and second name of Buzz from Toy Story ("To infinity, and beyond!!”). Now, sound can't travel in vacuum of space because it needs a medium to propagate. So one will never "hear” the explosion!