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How fast is our Earth orbiting the Sun? We all know that the Earth takes one year to orbit the Sun, but do we know what speed this corresponds to? This is an easy value to calculate and is in some ways similar to the rotation speed calculation.

Two values are required to determine this value. The first is the Earth's average distance from the Sun:

aEarth = 149.598261 x 106 km

The second value is the Earth's orbit period, which we know is one year. What exactly is one year in days, hours, etc.?

The "sidereal year" is determined by the time required by the Earth to return to the same position in its orbit. This value can easily be looked up:

Torbit = 365.256363004 days = 8766.1526 hours

The circumference of the Earth's orbit can now be calculated using the following equation:

CEarth = 2πa

CEarth = 9.4 x 108 km

The velocity that the Earth has while in orbit can now be calculated using the circumference of the Earth's orbit and the time required to travel this distance:

vorbit = CEarth Torbit

vorbit = 107,225 km/h = 29.78 km/s = 87 times the speed of sound

Wow! This speed is approximately 91 times faster than Earth's equatorial rotation speed! Although this sounds really fast, this speed is only 1/10000th the speed of light.

This value is actually the average orbit speed that the Earth moves in its orbit. The Earth's orbit is not perfectly circular, so its speed varies slightly over the year. It is at its fastest around January 3 and at its slowest around July 3.

Below is a table of the average orbit speeds of the major Solar System bodies: The Sun is not included here because it is the parent body and therefore does not orbit in this ideal case.



BODY aorbit (km) Corbit (km) Torbit (hrs) vorbit (km/hr)
 
MERCURY 5.79091 x 107 3.639 x 108 2,111.2584 172,362
VENUS 1.0820893 x 108 6.79896 x 108 5,392.8166 126,074
EARTH 1.49598261 x 108 9.4 x 108 8,766.1526 107,225
OUR MOON 384,399 2.415250x 106 655.718 3,683
MARS 2.279391 x 108 1.43218x 109 16,487 86,866
CERES 4.13832587 x 108 2.6 x 109 40,332 64,465
JUPITER 7.785472 x 108 4.89175 x 109 103,958 47,055
SATURN 1.43344937 x 109 9.0066 x 109 258,221 34,879
URANUS 2.876679082 x 109 1.80747 x 1010 739,178 24,452
NEPTUNE 4.503443661 x 109 2.82959 x 1010 1.44456 x 106 19,588
PLUTO 5.906376272 x 109 3.71108 x 1010 2.1747193 x 106 17,065
ERIS 10.12 x 109 6.35858 x 1010 4.8864 x 106 13,013



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Rotation Speed was Last Updated on December 08, 2010