A light-year is the distance that light travels in a vacuum in one Julian year (365.25 days). It is approximately 9.46 trillion kilometers.

2 light-years is equal to 18,922,000,000,000 kilometers.

Astronomers use light-years because the distances to stars and galaxies are so vast that using kilometers would result in extremely large and unwieldy numbers. Light-years provide a more manageable scale.

According to our current understanding of physics, nothing with mass can travel at the speed of light. Objects approach the speed of light, their mass increases infinitely, requiring infinite energy to accelerate further.