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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) = 9.4607 Petameter (Pm).
| Light Year (ly) | Petameter (Pm) |
|---|---|
| 0.1 | 0.94607 |
| 0.5 | 4.73035 |
| 1 | 9.4607 |
| 2 | 18.9214 |
| 5 | 47.3035 |
| 10 | 94.607 |
| 25 | 236.5175 |
| 50 | 473.035 |
| 100 | 946.07 |
| 500 | 4730.35 |
| 1000 | 9460.7 |
The light-year is the distance that light travels in one Julian year (365.25 days) in a vacuum, approximately 9.461 × 10¹⁵ meters.
1 ly = 9.4607 × 10¹⁵ m = 63,241 AU = 0.3066 pc ≈ 9.461 trillion km.
To convert ly to km: multiply by 9.461 × 10¹². To convert ly to parsecs: multiply by 0.3066.
Expressing distances to stars: Proxima Centauri ≈ 4.24 ly, Sirius ≈ 8.6 ly, Vega ≈ 25 ly.
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.
Thinking a light-year is a unit of time — it's a unit of distance! It's how far light travels in one year.
Light speed = ~300,000 km/s. In one year, light covers ~9.46 trillion km. That distance is one light-year.
The petameter is a unit of length equal to 10¹⁵ meters, or about 0.1 light-years.
1 Pm = 10¹⁵ m ≈ 0.1057 light-years ≈ 0.0324 parsecs.
To convert Pm to light-years: divide by 9.461. To convert Pm to parsecs: divide by 30.857.
No practical everyday applications. Would describe distances to nearby stars in metric.
1 light-year ≈ 9.46 Pm. The Oort Cloud extends to roughly 15,000 Pm from the Sun.
Case sensitivity is critical: Pm (petameter) vs. pm (picometer) differ by a factor of 10²⁷!
Remember: 1 light-year ≈ 9.46 Pm, so a few Pm is a fraction of the distance to the nearest star.



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