Convert Gigayears to Sidereal Years
Convert Gigayears (Ga) to Sidereal Years (a_sid) instantly and accurately.
Conversion Formula
a_sid = Ga × 999962045.8
About Gigayears
A gigayear (1 Ga) = 10⁹ yr ≈ 3.156 × 10¹⁶ s - the timescale of stellar evolution and cosmology. Universe age: 13.787 ± 0.020 Ga (Planck CMB). Sun: 4.603 Ga old; red giant in ~5 Ga. A 0.1 M☉ red dwarf lives ~10,000 Ga. Uranium-238 half-life = 4.468 Ga (used in radiometric dating). Proton decay (GUT prediction): ~10³⁴ yr = ~10²⁵ Ga. 1 Ga = 10⁹ yr.
About Sidereal Years
The sidereal year = Earth's orbital period relative to the stars = 365.25636 days = 31,558,149.8 s - about 20 min 24 s longer than the tropical year. The gap arises from precession of the equinoxes (~50 arcsec/year westward drift), which causes the tropical year to end slightly before the sidereal orbit completes. JPL DE440 ephemerides and J2000.0 epoch are anchored to the sidereal frame. 1 a_sid = 365.25636 d.
Quick Reference Table
| Gigayears (Ga) | Sidereal Years (a_sid) |
|---|---|
| 1 Ga | 999962000 a_sid |
| 2 Ga | 2 × 109 a_sid |
| 5 Ga | 5 × 109 a_sid |
| 10 Ga | 10 × 109 a_sid |
| 25 Ga | 2.5 × 1010 a_sid |
| 50 Ga | 5 × 1010 a_sid |
| 100 Ga | 10 × 1010 a_sid |