Simply input the eccentricities to see the true orbital shapes. Earth is .02 (rounded), Mercury is .21, Pluto is .25, Halley's Comet is .97 (off the scale).
Because Earth's orbit is not a perfect circle, the Earth is actually about 3 million miles closer to the Sun around January 2 than it is on July 4. Keep in mind that 3 million miles is not that much, considering the average distance between the Earth and Sun is about 93 million miles.
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