‘Opposition’ of Mars

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Due to an event referred to as “opposition”, which takes place every two years and two months, Mars has outshined Jupiter, becoming the third brightest object (moon and Venus are first and second, respectively) in the night sky during the month of October (2020).

While Mars’ closest approach to Earth was on October 6, the opposition will happen on October 13, which will give the planet its “biggest, apparent size of the 2020s”.


What is ‘opposition’?

  • Opposition is the event when the sun, Earth and an outer planet (Mars in this case) are lined up, with the Earth in the middle.
  • The time of opposition is the point when the outer planet is typically also at its closest distance to the Earth for a given year, and because it is close, the planet appears brighter in the sky.
  • An opposition can occur anywhere along Mars’ orbit, but when it happens when the planet is also closest to the sun, it is also particularly close to the Earth.


When does ‘opposition’ happen?

  • Earth and Mars orbit the sun at different distances (Mars is farther apart from the Sun than Earth and therefore takes longer to complete one lap around the sun).
  • In fact, opposition can happen only for planets that are farther away from the Sun than the Earth. In case of Mars, roughly every two years, the Earth passes between Sun and Mars, this is when the three are arranged in a straight line.
  • Further, as the Earth and Mars orbit the sun, there comes a point when they are on the opposite sides of it, and hence very far apart. At its farthest, Mars is about 400 million km from the Earth.
  • In case of opposition, however, Mars and Sun are on directly opposite sides of the Earth. In other words, the Earth, Sun and Mars all lie in a straight line, with the Earth in the middle.


Why is it called ‘opposition’?

  • Because from the perspective on Earth, the Sun and Mars appear to be on the opposite sides of the sky, Mars is said to be in “opposition”. Essentially, the opposition is a reference to “opposing the sun” in the sky.
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