Light Year to Astronomical Unit Converter
Unit Converter
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32 units available
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How to Convert Light Year to Astronomical Unit
To convert ly to km: multiply by 9.461 × 10¹². To convert ly to parsecs: multiply by 0.3066.
1 ly = 9.4607 × 10¹⁵ m = 63,241 AU = 0.3066 pc ≈ 9.461 trillion km.
For example, 1 Light Year (ly) = 63240.87339 Astronomical Unit (AU).
Light Year to Astronomical Unit — Common Values
| Light Year (ly) | Astronomical Unit (AU) |
|---|---|
| 0.1 | 6324.087339 |
| 0.5 | 31620.43669 |
| 1 | 63240.87339 |
| 2 | 126481.7468 |
| 5 | 316204.3669 |
| 10 | 632408.7339 |
| 25 | 1581021.835 |
| 50 | 3162043.669 |
| 100 | 6324087.339 |
| 500 | 31620436.69 |
| 1000 | 63240873.39 |
About Light Year (ly)
Definition
The light-year is the distance that light travels in one Julian year (365.25 days) in a vacuum, approximately 9.461 × 10¹⁵ meters.
Mathematical Relationship
1 ly = 9.4607 × 10¹⁵ m = 63,241 AU = 0.3066 pc ≈ 9.461 trillion km.
Conversion Formula
To convert ly to km: multiply by 9.461 × 10¹². To convert ly to parsecs: multiply by 0.3066.
Practical Applications
Expressing distances to stars: Proxima Centauri ≈ 4.24 ly, Sirius ≈ 8.6 ly, Vega ≈ 25 ly.
Interesting Facts
When you see a star 100 light-years away, you're seeing it as it was 100 years ago — you're literally looking into the past.
Common Mistakes
Thinking a light-year is a unit of time — it's a unit of distance! It's how far light travels in one year.
Educational Tips
Light speed = ~300,000 km/s. In one year, light covers ~9.46 trillion km. That distance is one light-year.
About Astronomical Unit (AU)
Definition
The astronomical unit is a unit of length approximating the mean Earth-Sun distance, defined as exactly 149,597,870,700 meters.
Mathematical Relationship
1 AU = 149,597,870,700 m ≈ 149.598 Gm ≈ 499 light-seconds ≈ 8.317 light-minutes.
Conversion Formula
To convert AU to km: multiply by 149,597,870.7. To convert AU to light-years: divide by 63,241.
Practical Applications
Spacecraft mission planning, expressing planetary orbit sizes, and solar system scale models.
Interesting Facts
Light takes about 8 minutes and 20 seconds to travel 1 AU. Mars is about 1.52 AU from the Sun, Jupiter about 5.2 AU.
Common Mistakes
Thinking the AU is the exact Earth-Sun distance — Earth's actual distance varies from ~147 to ~152 Gm over the year due to orbital eccentricity.
Educational Tips
AU makes the solar system manageable: Mercury ≈ 0.39 AU, Venus ≈ 0.72, Earth = 1, Mars ≈ 1.52, Jupiter ≈ 5.2, Saturn ≈ 9.5.