Did You Know: Space – What is a light-year?
A light-year is the distance light is able to travel in a year. In space, things are very far apart, so astronomers use light-years to measure how far away things are from each other. In one year, light can travel nearly 6.2 trillion miles (10 trillion km).
Closest neighbor
The closest star to our sun is more than four light-years away. This means light from that star takes more than four years to reach the Earth.
Speed of light
In one second, light can travel 186,500 miles (300,000 km) through space. This means light from the sun takes more than eight minutes to reach the Earth.
How fast can we travel in space?
A fast orbit
The International Space Station orbits the Earth at a speed of around 17,400 mph (28,000 kph).
At this speed it travels around the Earth once every 90 minutes.
Speedy spacecraft
The NASA spacecraft Juno reached a top speed of about 165,000 mph (265,000 kph) as it traveled to the planet Jupiter in 2016.
The Milky Way
The Milky Way galaxy has hundreds of billions of stars. Light from these stars takes many years to reach us on the Earth.