SPACE EDUCATION
Light-Year Converter
A light-year is the distance light travels in one Earth year — about 9.461 trillion kilometers (5.879 trillion miles). It's a unit of distance, not time. This calculator converts any number of light-years into the four units astronomers use most often.
Enter a value above to convert
Famous Cosmic Distances in Light-Years
| Object | Distance | Note |
|---|---|---|
| The Sun | 0.0000158 ly (8.3 light-minutes) | How long sunlight takes to reach Earth |
| Voyager 1 | 0.00251 ly (22 light-hours) | Most distant human-made object |
| Proxima Centauri | 4.246 ly | Nearest star to the Sun |
| Sirius | 8.6 ly | Brightest star in our night sky |
| Vega | 25 ly | Reference star for stellar magnitudes |
| Trappist-1 | 40 ly | Star with seven Earth-sized planets |
| Center of Milky Way | ~26,000 ly | Sagittarius A* black hole |
| Andromeda Galaxy | 2.5 million ly | Nearest large galaxy |
| Edge of observable universe | 46.5 billion ly | Cosmic horizon (co-moving distance) |
Frequently Asked Questions
Is a light-year a measure of time?
No. A light-year measures distance — specifically, the distance light travels in one Earth year (about 9.461 trillion km). The 'year' in the name refers to time, but the unit itself is a distance.
How long is one light-year in kilometers?
About 9.461 trillion kilometers, or 9.461 × 10^12 km. In miles, that's about 5.879 trillion miles.
What is the difference between a light-year and a parsec?
Both are distance units used in astronomy. One parsec equals 3.2616 light-years. Parsecs are based on stellar parallax measurements and are favored by professional astronomers; light-years are more common in popular science.
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