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The astronomical unit (symbol: au, or AU) is a unit of length defined to be exactly equal to 149,597,870,700 m. Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its modern redefinition in 2012.
Earth radius (denoted as Rđ¨ or ) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid, the radius ranges from a maximum of nearly 6,378 km (3,963 mi) ( equatorial radius, denoted a) to a minimum of nearly 6,357 km (3,950 mi) ( polar radius, denoted b ).
The solar radius is usually defined as the radius to the layer in the Sun 's photosphere where the optical depth equals 2/3: [1] 695,700 kilometres (432,300 miles) is approximately 10 times the average radius of Jupiter, 109 times the radius of the Earth, and 1/215th of an astronomical unit, the approximate distance between Earth and the Sun.
A light-year, alternatively spelled light year ( ly ), is a unit of length used to express astronomical distances and is equal to exactly 9,460,730,472,580.8 km (Scientific notation: 94,607.304725808 x 10 8 km) , which is approximately 5.88 trillion mi. As defined by the International Astronomical Union (IAU), a light-year is the distance that ...
The average diameter of the orbit of the Earth relative to the Sun. Encompasses the Sun, Mercury and Venus. Inner Solar System ~6.54 AU 9.78Ă10 8: 8.99: Encompasses the Sun, the inner planets (Mercury, Venus, Earth, Mars) and the asteroid belt. Cited distance is the 2:1 resonance with Jupiter, which marks the outer limit of the asteroid belt.
From the value of the diurnal parallax, one can determine the distance to the Sun from the geometry of Earth. The first known estimate of the solar mass was by Isaac Newton. In his work Principia (1687), he estimated that the ratio of the mass of Earth to the Sun was about 1 â 28 700. Later he determined that his value was based upon a faulty ...
Earth's circumference is the distance around Earth. Measured around the equator, it is 40,075.017 km (24,901.461 mi). Measured passing through the poles, the circumference is 40,007.863 km (24,859.734 mi). Measurement of Earth's circumference has been important to navigation since ancient times.
Earth orbit (yellow) compared to a circle (gray) Earth orbits the Sun at an average distance of 149.60 million km (8.317 light minutes, 92.96 million mi) [1] in a counterclockwise direction as viewed from above the Northern Hemisphere. One complete orbit takes 365.256 days (1 sidereal year ), during which time Earth has traveled 940 million km ...