Mercury at inferior conjunction marks the disappearance of Mercury from the western sky as an evening object and its transition to the eastern sky as a morning object.
Mercury at inferior conjunction
Mercury at inferior conjunction position in its orbit when it passes between the sun and the earth.
If Mercury passes directly in front of the Sun’s disk as seen from Earth then it is called the transit of Mercury. So transit is a special case of inferior conjunction.
During the inferior conjunction, planet Mercury appears to pass closest to the sun (within two degrees) on our sky’s dome as it is located in front of the sun as seen from the earth.
It’s normally not possible to observe planet Mercury during the inferior conjunction as it lost in the Sun’s glare. You have to wait for few days to observe Mercury again and after inferior conjunction it will be visible in the eastern sky preceding sunrise.
Mercury is the fastest moving planet in our solar system, so it usually takes less than a month to reach maximum angular separation (called greatest western elongation) on our sky’s dome from the inferior conjunction position.
During the inferior conjunction, planet Mercury appears dark (0% illuminated) or in its “new” phase and biggest, as it’s located on the same side of the sun as the earth. At this position, Mercury’s apparent diameter is almost three times greater than its superior conjunction position.
Please remember that inferior conjunction is only seen for Mercury and Venus, as their orbits are located within the Earth’s orbit.
Mercury closest to the Earth
During the inferior conjunction, planet Mercury reaches its perigee, i.e., closest to the Earth.
Mercury at inferior conjunction in 2024
Planet Mercury will reach its next inferior conjunction on August 19, 2024, at 02:00 UTC (10 p.m. EDT on August 18).
| Date | Time (UTC) |
|---|---|
| April 11, 2024 | 23:00 |
| August 19, 2024 | 02:00 |
| December 06, 2024 | 02:00 |
| March 24, 2025 | 20:00 |
How often does Mercury reach inferior conjunction?
Mercury reaches its inferior solar conjunction position once every 116 days. It’s called the synodic period of Mercury. It is the interval of time Mercury takes to orbit the sun and come back to the same position with respect to the Earth. It is slightly greater than the actual orbital period of Mercury (88 days) because our Earth is also in motion in its orbit.
Mercury events in 2024
| Date | Events | Remarks |
|---|---|---|
| January 12, 2024 | Mercury at greatest western elongation | Best time to watch Mercury in the eastern sky before sunrise |
| February 28, 2024 | Mercury at superior conjunction | Transition of Mercury from a morning object to an evening object |
| March 24, 2024 | Mercury at greatest eastern elongation | Best time to watch Mercury in the western sky following sunset |
| April 11, 2024 | Mercury at inferior conjunction | Transition of Mercury from an evening object to a morning object |
| May 9, 2024 | Mercury at greatest western elongation | Best time to watch Mercury in the eastern sky before sunrise |
| June 14, 2024 | Mercury at superior conjunction | Transition of Mercury from a morning object to an evening object |
| July 22, 2024 | Mercury at greatest eastern elongation | Best time to watch Mercury in the western sky following sunset |
| August 19, 2024 | Mercury at inferior conjunction | Transition of Mercury from an evening object to a morning object |
| September 5, 2024 | Mercury at greatest western elongation | Best time to watch Mercury in the eastern sky before sunrise |
| September 30, 2024 | Mercury at superior conjunction | Transition of Mercury from a morning object to an evening object |
| November 16, 2024 | Mercury at greatest eastern elongation | Best time to watch Mercury in the western sky following sunset |
| December 06, 2024 | Mercury at inferior conjunction | Transition of Mercury from an evening object to a morning object |
| December 25, 2024 | Mercury at greatest western elongation | Best time to watch Mercury in the eastern sky before sunrise |
Read about all Mercury events: Mercury at inferior conjunction Mercury at greatest western elongation Mercury at superior conjunction Mercury at greatest eastern elongation
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