Earth

Earth is the third planet from the Sun, and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago.^[24][25][26] Earth's gravityinteracts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth orbits around the Sunin 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.^{[n 5]}

Earth

The Blue Marble, the first full-view photograph of the planet, was taken by Apollo 17 astronauts en route to the Moon in 1972
Designations
Adjectives	Earthly, terrestrial
Orbital characteristics
Epoch J2000[n 1]
Aphelion	152100000 km[n 2] (94500000 mi; 1.017 AU)
Perihelion	147095000 km[n 2] (91401000 mi; 0.98327 AU)
Semi-major axis	149598023 km[1] (92955902 mi; 1.00000102 AU)
Eccentricity	0.0167086[1]
Orbital period	365.256363004 d[2] (1.00001742096 yr)
Average orbital speed	29.78 km/s[3] (107200 km/h; 66600 mph)
Mean anomaly	358.617°
Inclination	7.155° to the Sun's equator; 1.57869°[4] to invariable plane; 0.00005° to J2000 ecliptic
Longitude of ascending node	−11.26064°[3] to J2000 ecliptic
Argument of perihelion	114.20783°[3]
Satellites	1 natural satellite: the Moon 5 quasi-satellites >1 800 operational artificial satellites[5] >16 000 space debris[n 3]
Physical characteristics
Mean radius	6371.0 km (3958.8 mi)[6]
Equatorial radius	6378.1 km (3963.2 mi)[7][8]
Polar radius	6356.8 km (3949.9 mi)[9]
Flattening	0.0033528[10] 1/298.257222101(ETRS89)
Circumference	40075.017 km equatorial(24901.461 mi)[8] 40007.86 km meridional(24859.73 mi)[11][12]