User login


Earth - Rotating Model
Credit: Almond/NASA

Earth is the third planet from the Sun. It is the largest of four terrestrial planets and the only known place in the universe where life has evolved.

The Earth's atmosphere is composed mainly of Nitrogen (78%) and oxygen (21%), with traces of water vapor, carbon dioxide and other gases. About 70% of Earth's surface is covered with liquid water, the rest of surface consists of continents and islands with the polar regions being mostly covered with ice.

Cutaway showing Earth's internal layers
Credit: Wikimedia

Earth's interior is divided into layers, it has a solid iron inner core, a liquid outer core, a mantle and a crust (see the diagram on the left).

As the Earth orbits the Sun it turns on its axis, taking 24 hours (1 day) to rotate right around. It takes 365.25 days to complete one orbit around the Sun.

The Earth has seasons because its axis is tilted by about 23°. When the northern half of the Earth (northern hemisphere) is pointing towards the Sun it has Summer. At this time the southern hemisphere is pointing away from the Sun and has winter.

Earth has one large natural rocky satellite, called the Moon, which orbits once every 27.3 days. The Moon is the fifth largest natural satellite (or moon) in the Solar System.

Planet Data Sheet show »« hide
Facts and FiguresMercuryVenus EarthMarsJupiter SaturnUranusNeptune
Orbital Distance (AU)10.380.72 1.01.525.2 9.4519.230.06
Radius (KM)2,4406,052 6,3783,39771,492 60,26825,55924,746
Mass (Earth Masses)20.0550.82 1.00.11318 95.214.517.1
Year Length
(Earth Days)
88225 365.2568711.9
Day Length
(Earth Days)
176117 0.430.750.67
Surface Gravity (g)30.380.91 1.00.382.34 0.930.921.12
Surface Temperature-200 to
400 °C
460 °C -80 to
50 °C
-150 to
20 °C
-110 °C -140 °C-190 °C-200 °C
Number of moons00 1263 602713
Notes: 1 1 AU (or Astronomical Unit) = 149,600,000 KM and is the mean distance from the Earth to the Sun
2 1 Earth Mass = 5,980,000,000,000,000,000,000,000 KG : 3 1 g = 9.8 m/s2


Please note that over the weekend of the 26-28th May 2017 we will be switching over to our brand new website - during this time there may be periods where the site is difficult to access, and users will be unable to request observations from the telescope. Please bear with us during this time. All should be back up and running by the 29th May 2017.