Sidereal Orbital Period of Mercury
| Value | 7,600,521.6 s |
| Status | Conventional / typical value |
| Source | NASA NSSDC Planetary Fact Sheet, Mercury (sidereal orbit period) |
| Categories | Astronomicalsolar-systemplanets |
| Planck time | 1.4097892e+50 tP |
| attosecond | 7.6005216e+24 as |
| femtosecond | 7.6005216e+21 fs |
| picosecond | 7.6005216e+18 ps |
| nanosecond | 7.6005216e+15 ns |
| shake | 760,052,160,000,000 shake |
| microsecond | 7,600,521,600,000 μs |
| millisecond | 7,600,521,600 ms |
| second | 7,600,521.6 s |
| minute | 126,675.36 min |
| hour | 2,111.256 h |
| sidereal day | 88.209851 sd |
| day | 87.969 d |
| week | 12.567 wk |
| fortnight | 6.2835 fn |
| month | 2.8902113 mo |
| year | 0.240846 yr |
| decade | 0.0240846 dec |
| century | 0.00240846 cent |
| millennium | 0.000240846 mil |
| megayear | 2.4084600e-07 Myr |
| eon | 2.4084600e-10 eon |
Learning zone
Mercury circles the Sun in under 88 days at an average 47.4 km/s, half again Earth's orbital speed, and Kepler's second law makes the pace uneven: near perihelion it reaches 59 km/s, near aphelion it slows to 39. The ancients could not see any of that, but they could see the planet dart from one side of the Sun to the other in weeks — hence the messenger god, and the modern adjective mercurial.
The period pairs with the 58.646-day rotation in a locked 3:2 ratio, with the strange consequence that a solar day on Mercury — noon to noon — lasts 176 Earth days, exactly two Mercury years. An observer at the right longitude would watch the Sun rise, halt, loop briefly backwards as orbital motion outpaces the spin near perihelion, and then resume its crawl westward.