Viewing the planets


Because they lie closer into the Sun than the Earth, Mercury and Venus are called inferior planets.

As viewed from Earth, Mercury and Venus never get very far from the Sun.

  • The maximum elongation angle for Mercury is 28 degrees.
  • The maximum elongation angle for Venus is 45 degrees.

    Therefore Mercury and Venus are visible only either shortly after sunset or shortly before sunrise. And our view of Venus changes, showing phases much like the Moon's.

    When the Mercury or Venus is directly between the Earth and the Sun, we say it is at inferior conjunction.

    When the Mercury or Venus is directly behind the Sun as viewed from Earth, we say it is at superior conjunction.

  • The other planets lie outside the Earth's orbit and are hence called superior planets. Click here if you want to remind yourself what the planet lineup looks like.

    All of the superior planets can be visible at any time of night, sometime during their orbit.

    When a superior planet lies directly behind the Sun, we say it is at conjunction.

    When a superior planet lies directly opposite the Sun as viewed from the Earth, we say it is at opposition.

    If Jupiter were at opposition, when would it rise? when would it set? when would it be on the meridian?


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