Aphelion: It is the point in the Earth’s orbit when it is farthest from the sun (152.5 million km). Aphelion occurs on the 3rd or 4th of July. It is the point in the orbit of a planet, asteroid, or comet at which it is furthest from the sun.
On July 4, 2008, our planet is at the distant end–a point astronomers call “aphelion.” This puts us farther from the Sun than we are at any other time of year. It is when the planet is furthest from its parent star, and perihelion is when the planet is closest to its parent star. For example, when the Earth is at perihelion, it is 147.1 million km from the Sun, in early January, and at aphelion, the Earth is 152.1 million km from the Sun in early July.
The Earth is closest to the Sun, or at the perihelion, about 2 weeks after the December Solstice, when it is winter in the Northern Hemisphere. Conversely, the Earth is farthest away from the Sun, at the aphelion point, 2 weeks after the June Solstice, when the Northern Hemisphere is enjoying warm summer months.