When the Earth is closest to the sun, it is known as?

The correct option is Perihelion.

Earth's Perihelion and Aphelion:

• 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.
• Mathematicians and astronomers estimate that in the year 6430, over 4000 years from now, the timing of the Perihelion and the March Equinox will coincide. 

Perigee and Apogee:

• Like the Earth's orbit around the Sun, the Moon's path around the Earth is elliptical. 
• The point in the Moon's orbit that is closest to the Earth is called the Perigee and the point farthest from the Earth is known as the Apogee.
• The terms are also sometimes used interchangeably with the Earth's Perihelion and Aphelion.

 

Perihelion: The Earth reaches its perihelion on January 3 every year at a distance of about 147 million km from the Sun.
 
Aphelion: The Earth reaches its aphelion on July 4 every year when the Earth is at a distance of 152 million km.