Mercury at inferior conjunction 2024: All you need to know

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 solar conjunction
Mercury at inferior solar conjunction. (Image credit: NASA)

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.

Phases of the inner planets (Mercury and Venus)
Phases of the inner planets (Mercury and Venus). (Image credit: ESO)

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).

DateTime (UTC)
April 11, 202423:00
August 19, 202402:00
December 06, 202402:00
March 24, 202520:00

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

DateEvents Remarks
January 12, 2024Mercury at greatest western elongationBest time to watch Mercury in the eastern sky before sunrise
February 28, 2024Mercury at superior conjunctionTransition of Mercury from a morning object to an evening object
March 24, 2024Mercury at greatest eastern elongationBest time to watch Mercury in the western sky following sunset
April 11, 2024Mercury at inferior conjunctionTransition of Mercury from an evening object to a morning object
May 9, 2024Mercury at greatest western elongationBest time to watch Mercury in the eastern sky before sunrise
June 14, 2024Mercury at superior conjunctionTransition of Mercury from a morning object to an evening object
July 22, 2024Mercury at greatest eastern elongationBest time to watch Mercury in the western sky following sunset
August 19, 2024Mercury at inferior conjunctionTransition of Mercury from an evening object to a morning object
September 5, 2024Mercury at greatest western elongationBest time to watch Mercury in the eastern sky before sunrise
September 30, 2024Mercury at superior conjunctionTransition of Mercury from a morning object to an evening object
November 16, 2024Mercury at greatest eastern elongationBest time to watch Mercury in the western sky following sunset
December 06, 2024Mercury at inferior conjunctionTransition of Mercury from an evening object to a morning object
December 25, 2024Mercury at greatest western elongationBest 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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About the Author

Ashim

Ashim Chandra Sarkar founded Space & Telescope in 2022. He holds a M.Sc. in physics and has five years of research experience in optical astronomy. His passion for astronomy inspired him to open this website. He is responsible for the editorial vision of spaceandtelescope.com.

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