Mercury farthest from the sunrise on December 25
The innermost planet Mercury orbits the sun every 88 days. And Earth is moving, too. So Mercury goes between us and the sun pretty often, about every 116 days. It did this last on December 6, 2024, reaching the point astronomers call inferior conjunction. And since then, Mercury has been speeding ahead of Earth in orbit. It re-emerged in our dawn around mid-month. Mercury reached its greatest morning elongation – its greatest apparent distance from the rising sun – on December 25, 2024.
By the way, this Mercury elongation did not favor either hemisphere.
In the meantime, the innermost planet – named for the fleet-footed messenger god of the ancient Romans – will be visible for a few more weeks.
Mercury greatest elongation, December 2024
When to watch: Officially, Mercury became visible toward the middle of December 2024 in the morning sky. Look for it about 40 minutes before sunrise. At greatest elongation – December 25, 2024 – Mercury is farthest from the sunrise on our sky’s dome. And after that, when it’ll be edging back toward the sunrise, it’ll brighten a little bit more, making Mercury easier to spot – although low – in the morning twilight.
Where to look: Look in the sunrise direction as the sky is getting lighter.
Greatest elongation is on December 25 at 3 UTC (9:00 p.m. CDT on December 24). Mercury is shining at -0.3 magnitude that morning. And it is 22 degrees from the sun.
Through a telescope on and around December 25, Mercury appears 69% illuminated, in a gibbous phase, and 6.4 arcseconds across.
Note: Once you spot it, notice that Mercury brightens quickly as December progresses, reaching a magnitude of around -0.4 (bright, but in bright morning twilight) by the end of the month. Mercury will slip away in the morning glare in January 2025.
January finder charts
For precise sun and Mercury rising times at your location:
Old Farmer’s Almanac (U.S. and Canada)
timeanddate.com (worldwide)
Stellarium (online planetarium program)
Mercury events in 2025
Note: Times are in UTC
Feb 8, 2025: Superior conjunction (passes behind sun from Earth)
Mar 8, 2025: Greatest elongation (evening)
Mar 24, 2025: Inferior conjunction (races between Earth and sun)
Apr 21, 2025: Greatest elongation (morning)
May 30, 2025: Superior conjunction (passes behind sun from Earth)
Jul 4, 2025: Greatest elongation (evening)
Aug 1, 2025: Inferior conjunction (races between Earth and sun)
Aug 19, 2025: Greatest elongation (morning)
Sep 13, 2025: Superior conjunction (passes behind sun from Earth)
Oct 29, 2025: Greatest elongation (evening)
Nov 20, 2025: Inferior conjunction (races between Earth and sun)
Dec 7, 2025: Greatest elongation (morning)
Mercury charts from Guy Ottewell
A comparison of elongations
Mercury’s greatest elongations are not equal. Indeed, some are “greater” than others. For example, the distance of Mercury from the sun on our sky’s dome varies from about 28 degrees (maximum) to 18 degrees (minimum).
Also, Mercury elongations are better or worse depending on the time of the year they occur and your location on Earth. So, for both hemispheres, spring evenings and autumn mornings are best.
As an illustration, the chart below – from a Northern Hemisphere perspective – might help you visualize these differences.
Heliocentric solar system, January 2025
Seasons make a difference
So, in the autumn for either hemisphere, the ecliptic – or path of the sun, moon and planets – makes a narrow angle to the horizon in the evening. Conversely, it makes a steep slant, nearly perpendicular, in the morning. So – in autumn from either hemisphere – morning elongations of Mercury are best. Then, Mercury appears higher above the horizon and farther from the glow of the sun. Conversely, evening elongations in autumn are harder to see.
On the other hand, in the spring for either hemisphere, the situation reverses. Then, the ecliptic and the horizon meet at a sharper angle on spring evenings and at a narrower angle on spring mornings. So, in springtime for either hemisphere, evening elongations of Mercury are best. Meanwhile, morning elongations in springtime are harder to see.
Bottom line: Mercury reached its greatest elongation – greatest distance from the sunrise – on December 25, 2024. Look east at dawn. It’ll disappear from the morning sky in January.
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