Calc requested by F to the A to the T to the E to the Albania. Feat can be found here: Let's Play Chrono Trigger (DS version) #28 : End of an Era.
The star is 2 pixels, and the screenheight is 508 pixels.
2atan(tan(70/2)*(2/508)) = 0.003730820242 Radians
0.003730820242×180°/π = 0.21376025399° Degrees
The sun has a diameter of 1,391,400,000 meters
Angsizing nets us a distance of 372,950,000,000 meters
The star becomes visible at 15:15:85 (yes, I made sure it was the exact same one) and Lavos flies past it at 15:15:97
0.97 - 0.85 = 0.12s
372,950,000,000 meters / 0.12s = 3.10791667 × 10^12 m/s
The Earth-Alpha Centauri distance is 4.367 ly
He starts flying to Earth at 15:08, and reaches Earth at 15:27
4.367 ly / 19s = 2.17442777 × 10^15
Note: This method may be prone to cinematic timing.