# Light-years to Astronomical Units (ly to au)

Source: https://www.unitconvertercalculator.com/length/light-years-to-astronomical-units/

**1 ly = 63241.077084266 au**

One light-year equals approximately 63,241 astronomical units. This is one of the most important astronomical conversions, connecting solar system scale (AU) with interstellar scale (light-years). The nearest star Proxima Centauri is 4.24 light-years or about 268,000 AU away.

## Formula

Convert Light-years to Astronomical Units

## Conversion Table

| Light-years (ly) | Astronomical Units (au) |
|---|---|
| 0.001 ly | 63.241077084266 au |
| 0.01 ly | 632.41077084266 au |
| 0.1 ly | 6324.1077084266 au |
| 0.5 ly | 31620.538542133 au |
| 1 ly | 63241.077084266 au |
| 2 ly | 126482.15416853 au |
| 4.24 ly | 268142.16683729 au |
| 5 ly | 316205.38542133 au |
| 10 ly | 632410.77084266 au |
| 50 ly | 3162053.8542133 au |
| 100 ly | 6324107.7084266 au |
| 1000 ly | 63241077.084266 au |
| 100000 ly | 6324107708.4266 au |

## Units

### Light-year (ly)

The distance light travels in one Julian year (365.25 days) in vacuum. Exactly 9,460,730,472,580,800 meters. Used for interstellar distances.

### Astronomical Unit (au)

Exactly 149,597,870,700 meters by IAU 2012 definition. Roughly the average distance from the Earth to the Sun. Used for distances within our solar system.

## Background

A light-year is 63,241 AU. The Sun's gravitational influence extends to about 100,000 AU (the Oort Cloud), roughly 1.58 light-years. So the solar system in its broadest definition spans about 3.16 light-years across. The nearest star system (Alpha Centauri) begins at 4.24 light-years.

## Good to Know

The AU-to-light-year conversion reveals the cosmic loneliness of stars. Our solar system spans about 3 light-years including the Oort Cloud, but the nearest neighbor is 4.24 light-years away. Stars are islands separated by vast oceans of nothing.

## FAQ

### How many AU are in 1 light-year?

One light-year contains approximately 63,241 AU. This means light from the Sun takes about 8 minutes to travel 1 AU but about 1 year to travel 63,241 AU.

### How far is the nearest star in AU?

Proxima Centauri is about 268,370 AU (4.244 light-years) from the Sun.

### When do astronomers use AU vs light-years?

AU for solar system distances (planets, asteroids, spacecraft). Light-years for stellar and galactic distances. The crossover is roughly at the Oort Cloud boundary.

## Non-Frequently Asked Questions

### If the Sun were a basketball, how far would the nearest star be?

The Sun's diameter is about 0.00929 AU. A basketball is 24 cm. At this scale, 1 AU = 25.8 m. The nearest star (268,370 AU) would be 6,924 km away - roughly New York to London. A basketball in New York and one in London. That is how empty space is.

### How long would it take to drive 1 light-year?

At 100 km/h, driving 1 light-year (9.461 x 1012 km) would take about 10.8 million years. That is longer than the entire Cenozoic era. Your car would fossilize several times before arriving.

### Is the Oort Cloud 1 light-year away?

The Oort Cloud extends from roughly 2,000 to 100,000 AU (about 0.03 to 1.58 light-years). So the outermost edge is about 1.58 light-years from the Sun. That means comets from the Oort Cloud start their journey about 1/3 of the way to the nearest star. Space is almost entirely nothing.

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## See Also

- [Astronomical Units to Light-years](https://www.unitconvertercalculator.com/length/astronomical-units-to-light-years/)