Accorrding to space.com
If the sun appears a bit more intense than normal to you this week, you're not seeing things. The Earth has just made its closest approach to our nearest star for the year.
The orbital milestone is known as "perihelion," and it marks the time when the distance between the Earth and the sun is at its smallest. The event occurs every year in early January, and in 2012 it took place Wednesday, Jan. 4 at 8 p.m. EST (or Jan. 5 at 0100 GMT, depending on your time zone).
On average, the Earth orbits the sun at a distance of about 93 million miles (150 million kilometers). This distance is known as 1 astronomical unit (AU), and it serves as a yardstick for distances to other planets in our solar system. Mars, for example, is about 1.5 AU from the sun, while Jupiter is about 5.2 AU from the star.
But like the other planets in our solar system, the Earth's orbit is not a perfect circle. Instead, it is slightly elliptical — or oval-shaped — meaning it has a closest point to the sun (perihelion) and a farthest point (which is known as aphelion).