A light-year, alternatively spelled light year (ly or lyr[3]), is a unit of length used to express astronomical distances and is equal to exactly 9 460 730 472 580.8 km, which is …

Apr 22, 2024 · Light-year is the distance light travels in one year. Light zips through interstellar space at 186,000 miles (300,000 kilometers) per second and 5.88 trillion miles (9.46 trillion …

May 28, 2020 · Get the definition of a light year in astronomy. See examples of distances in light years and how the unit compares with parsecs and AU.

Dec 13, 2025 · Light-year, in astronomy, the distance traveled by light moving in a vacuum in the course of one year, at its accepted velocity of 299,792,458 metres per second (186,282 miles …

Aug 28, 2023 · To measure really long distances and how fast light travels, astronomers and other scientists use a unit called a light-year. To reach the previously mentioned Proxima …

Feb 17, 2024 · Put simply, a lightyear is the distance light travels in space in a year, 9.46 trillion km (5.88 trillion miles) or 63,241 AU, 0.30 parsecs. Nothing travels faster than light.

Jun 9, 2023 · A light-year is the distance light travels in a year. Specifically, the International Astronomical Union defines a light-year as the distance light travels through interstellar space …

Dec 15, 2024 · A light-year is the distance light travels in one year. Light moves incredibly fast — about 186,000 miles (300,000 kilometers) per second, covering 5.88 trillion miles (9.46 trillion …

Nov 11, 2025 · The light year tells us both the distance and how long the light has been traveling, but it is fundamentally a spatial measurement. Just as a kilometer measures the distance a car …

Sep 25, 2025 · A light-year is the distance light travels in one Earth year. Learn about how we use light-years to measure the distance of objects in space.