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To convert solar radii to km: multiply by 696,340. To convert solar radii to AU: multiply by 0.00465.
1 R☉ = 6.9634 × 10⁸ m = 696,340 km ≈ 109 × Earth's radius ≈ 0.00465 AU.
For example, 1 Sun's Radius (R☉) = 7.360343e-8 Light Year (ly).
| Sun's Radius (R☉) | Light Year (ly) |
|---|---|
| 0.1 | 7.360343e-9 |
| 0.5 | 3.680172e-8 |
| 1 | 7.360343e-8 |
| 2 | 1.472069e-7 |
| 5 | 3.680172e-7 |
| 10 | 7.360343e-7 |
| 25 | 0.000001840085829 |
| 50 | 0.000003680171657 |
| 100 | 0.000007360343315 |
| 500 | 0.00003680171657 |
| 1000 | 0.00007360343315 |
The solar radius is the radius of the Sun, approximately 6.9634 × 10⁸ meters (about 696,340 km).
1 R☉ = 6.9634 × 10⁸ m = 696,340 km ≈ 109 × Earth's radius ≈ 0.00465 AU.
To convert solar radii to km: multiply by 696,340. To convert solar radii to AU: multiply by 0.00465.
Describing stellar sizes: Betelgeuse ≈ 700 R☉, Sirius ≈ 1.7 R☉, a white dwarf ≈ 0.01 R☉.
You could line up about 109 Earths across the Sun's diameter. The largest known star (UY Scuti) is about 1,700 R☉.
Confusing solar radius with solar diameter — the diameter is 2 R☉. Also, stellar catalogs list radius, not diameter.
The Sun's radius (109 × Earth) gives a sense of scale: you could fit over a million Earths inside the Sun by volume.
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.



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