The Planet Quiz Show  


Mercury has the shortest year (88 Earth days), and Neptune has the longest year (165 Earth years). The farther away a planet is from the sun, the slower its orbital motion becomes. This results from a much smaller gravitational pull by the sun for the planet and a longer orbital path that the planet must follow. Because of these factors, the farther away a planet is from the sun or another star, the longer it must take to complete one orbit. The following table gives the orbital periods of the eight planets.


Orbital Periods of the Eight Planets

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune
88 days 225d 365.24d 687d 11.9 years 29.5y 84y 165y

[MESSENGER views Mercury]
Cratered Mercury zips around the sun in only 88 Earth days. How many years old would you be if you lived on Mercury? Hint: Multiply your age by the number four. Mercury makes about four trips around the sun for every trip the Earth takes. MESSENGER image EW0108820027G, NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington...

[Voyager 2 picture of Neptune]
Neptune is the slowpoke of the eight planets in our solar system. It requires 165 Earth years to complete one orbit around the sun. On its approach to this blue world in August 1989, Voyager 2 captured this image of the fourth and outermost of the giant liquid planets. This image easily shows two of the four oval cloud features tracked by the cameras. The large dark oval near the left edge circled Neptune every 18 hours. The second dark spot, at the lower right edge of the picture, circled Neptune every 16 hours. These spots are no longer in existence, but other spots in Neptune's clouds have formed and disappeared according to observations made by the Hubble Space Telescope. NASA Voyager 2 image PIA00046...

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