Mercury at its greatest western elongation on May 9, 2024, marks the best time to observe Mercury in the eastern sky before sunrise.
Mercury at greatest western elongation
The orbit of the planet Mercury is very close to the sun. That’s why it’s always seen near the sun in the sky and swings back (west) and forth (east) around the sun.
Now greatest elongation of Mercury means its maximum angular separation from the sun as seen from the earth.
When Mercury is as far west of the sun as possible, it is seen on the eastern horizon before sunrise, as it rises before sunrise and sets before sunset. It is called the greatest western elongation of Mercury.
The maximum angular distance of mercury from the sun during the greatest elongation is about 28°. So you can’t see Mercury at zenith (overhead point) in the night sky.
So the greatest western elongation of Mercury refers to the best time to observe planet Mercury in the eastern sky just before sunrise, as it’s farthest from the sun’s glare.
Please remember that Mercury reaches its greatest western elongation within one month of its inferior conjunction position.
Next greatest western elongation of Mercury in 2024
Planet Mercury will reach its next greatest western elongation on May 9, 2024 at 21:00 UTC (or 5 p.m. EDT).
When to watch: Watch planet Mercury around 30 minutes before sunrise on May 9, 2024.
Where to look: Look near the horizon in the east (along the sunrise direction).
Brightness: On the morning of May 9, 2024, planet Mercury will shine with +0.6 magnitude.
Phase: On the morning of May 9, 2024, planet Mercury will be 40% illuminated (crescent phase). However, you need a telescope to see the phases of Mercury.
Upcoming dates of the greatest western elongation of Mercury
| Date | Time (UTC) |
|---|---|
| May 9, 2024 | 21:00 |
| September 5, 2024 | 02:00 |
| December 25, 2024 | 02:00 |
| April 21, 2025 | 19:00 |
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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