Santa Claus won’t be the only visitor to our night sky this Christmas Eve.
On Christmas Eve (December 24), Mercury will shine brightly in the skies above Earth, reaching its peak altitude above the horizon at sunset on Christmas Day before fading from the skies as 2022 progresses into 2023.
Over the two days of Christmas, the planet closest to the sun will peak in the sky on its current winter evening apparition, 12 degrees above the horizon (just over a fist at arm’s length), while glowing with a magnitude of -0.6, according to In the sky (opens in a new tab).
Related: Night sky, December 2022: what you can see tonight [maps]
An apparition is a period of time during which an object in the solar system is visible from Earth. Apparitions of Mercury can occur in 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. When it is in the west, on the other hand, it rises and sets before the sun and is seen shortly before sunrise. Running east of the sun, Mercury’s continuous nocturnal appearance lasts from December 4 to January 3.
Despite its increase in brightness, Mercury will still not be the “Star of Bethlehem” in the evening sky. The smallest planet solar system will always be a challenge to spot as this appearance is not one of the most important.
Moreover, acting as soon as possible is the best bet to see the planet. This is because Mercury’s brightness will fade towards the end of the December to January apparition as it transitions between and the sun moving towards an arrangement called inferior conjunction.
During inferior conjunctions, the planets have their illuminated sides turned away from Earth. This makes them appear as thin, dimly lit crescents.
Mercury is a planet that can only be seen above Earth at dusk, which means it’s hard to spot during this thin crescent phase. As a result, the planet closest to the sun will be easier to spot before Christmas Day than in the days after.
Mercury is generally a difficult planet to see because, as the closest planetary neighbor to the sun, it is often obscured by the glare of starlight. The best time to attempt to see Mercury from Earth is therefore during the times when it is farthest from the sun, the so-called times of “greatest elongation”.
These periods occur approximately every three to four months and last for a few weeks at a time. Mercury last reached its greatest elongation and thus greatest separation from the sun during this current apparition on December 21.
Whether you’re new to stargazing or have been doing it for years, make sure you don’t miss our guides to the best binoculars and the best telescopes to see Mercury or anything else in the sky. To capture the best skywatching images you can, we’ve got recommendations for the best. cameras for astrophotography and best lenses for astrophotography.
Editor’s note: If you take a great photo of Mercury and would like to share it with Space.com readers, send your photo(s), comments, and name and location to spacephotos@space.com.
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