Santa Claus will not be the only visitor to our night sky on Christmas Eve.
On Christmas Eve (December 24), Mercury will shine brightly in the sky above Earth, reaching its highest altitude above the horizon at sunset on Christmas Day before disappearing from the sky as 2022 transitions into 2023.
During the two days of Christmas, the planet closest to the Sun will reach its highest point in the sky, 12 degrees above the horizon (a little more than a fist’s breadth at arm’s distance) during its current winter evening appearance, shining at a magnitude of -0.6, acc In heaven (opens in new tab).
Related: Night Sky, December 2022: What You Can See Tonight [maps]
An apparition is a period of time when an object in the solar system is visible from Earth. Mercury apparitions can occur in either the morning or evening sky, depending on whether the planet is east or west of the Sun.
When Mercury is in the east, it rises and sets after the Sun and can be seen in the early evening. On the other hand, when it is in the west, it rises and sets before the sun and can be seen just before sunrise. Flowing east of the Sun, Mercury’s ongoing evening phenomenon lasts from December 4th to January 3rd.
Despite its increase in brightness, Mercury will still not be a “Star of Bethlehem” in the evening sky. The smallest planet in the solar system will still be a challenge as this feature is not one of the most prominent.
Also, it’s best to act sooner rather than later to see the planet. This is because Mercury will fade in brightness towards the end of the December to January apparition as it passes between and the Sun and heads towards an arrangement called inferior conjunction.
In inferior conjunctions, the illuminated sides of the planets face away from Earth. This causes them to appear as thin crescents that are just about lit.
Mercury is a planet that can only be seen above Earth at twilight, meaning it can be difficult to spot during this thin crescent phase. As a result, the planet closest to the Sun is easier to spot in the run-up to Christmas Day than in the days after.
Mercury is usually difficult to see because, as the Sun’s closest planetary neighbor, it is often obscured by the star’s glare. The best time to try to see Mercury from Earth is therefore at times when it is furthest from the Sun, known as the “greatest elongation” moments.
These periods occur about every three to four months and last a few weeks each. Mercury last reached its greatest elongation and thus its furthest distance from the sun during this current phenomenon on December 21st.
Whether you’re new to observing the sky or you’ve been at it for years, don’t miss our guides to the best binoculars and the best telescopes for observing Mercury or anything else in the sky. To capture the best possible sky observing images, we have recommendations for the best cameras for astrophotography and the best lenses for astrophotography.
Editor’s note: If you take a great photo of Mercury and want to share it with Space.com readers, send your photos, comments, and your name and location to [email protected]
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