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After waiting for most of the day, he eventually saw the transit when clouds obscuring the Sun cleared at about 15:15, half an hour before sunset. His observations allowed him to make a well-informed guess for the diameter of Venus and an estimate of the mean distance between the Earth and the Sun (59.4 million mi (95.6 million km; 0.639 AU)).
Moving far backwards in time, more than 200,000 years ago Venus sometimes passed by at a distance from Earth of barely less than 38 million km, and will next do that after more than 400,000 years. Venus and Earth come the closest, but they come less often closer than Venus and Mercury . [ 10 ]
The obelisks for the four inner planets are all contained within the commons area stretching north towards Seneca Street. Mercury is situated to scale about 12.7 yards (11.6 meters) away from the Sun, Venus another 10 yards (9.1 meters) away, Earth another 9.3 yards (8.5 meters) away, and Mars another 17.1 yards (15.6 meters) away.
Careful observations of the 1769 transit of Venus allowed astronomers to calculate the average Earth–Sun distance as 93,726,900 miles (150,838,800 km), only 0.8% greater than the modern value. [293] Uranus, having occasionally been observed since 1690 and possibly from antiquity, was recognized to be a planet orbiting beyond Saturn by 1783. [294]
When Venus lies between Earth and the Sun in inferior conjunction, it makes the closest approach to Earth of any planet at an average distance of 41 million km (25 million mi). [4] [note 3] [172] Because of the decreasing eccentricity of Earth's orbit, the minimum distances will become greater over tens of thousands of years.
A light-year is the distance light travels in one Julian year, around 9461 billion kilometres, 5879 billion miles, or 0.3066 parsecs. In round figures, a light year is nearly 10 trillion kilometres or nearly 6 trillion miles. Proxima Centauri, the closest star to Earth after the Sun, is around 4.2 light-years away. [89]
This diagram shows various possible elongations (ε), each of which is the angular distance between a planet and the Sun from Earth's perspective. In astronomy, a planet's elongation is the angular separation between the Sun and the planet, with Earth as the reference point. [1] The greatest elongation is the maximum angular separation.
Solar System – gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets (including Earth), with the remainder being significantly smaller objects, such as dwarf planets and small Solar System bodies.