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How Fast Do Planets Rotate Around Their Orbits?

While one planet may take years to complete an orbit around a star, another may zoom around a star in days. To measure the orbits of other planets, scientists use Earth's one-year orbit as the standard.

Solar System Planets
- In our solar system, Mercury has the shortest orbit of 88 Earth days. Venus takes 225 Earth days to revolve around the sun, Mars 687 days, Jupiter 12 years, Saturn 29.5 years, Uranus 84 years and Neptune 165 years, according to World Book at NASA.
Background to Exoplanets
- An exoplanet is a planet outside our solar system. Astronomers determine the orbital periods of exoplanets by noting how often the host star dims, which implies that the planet is passing in front of it.
Fast Orbits
- Some exoplanets outside our solar system have shorter orbital periods than Mercury's. For instance, the European Southern Observatory states that one planet orbiting around a solar-type star designated OGLE-TR-3 moves around its star in 28 hours and 33 minutes.

Astronomy