How to See Mercury in January 2021
On January 23, Mercury will reach its greatest eastern elongation and shine bright in the evening sky. In today’s article, we’ll tell you more about this event and give you tips on how to spot the planet with your own eyes.
Why is Mercury difficult for us to see?
Mercury is often called the “elusive planet”. Even people, who are not interested in astronomy, can accidentally spot Venus, Mars, or Jupiter shining in the sky, but never Mercury. Although Mercury is small, it’s quite bright to be observed with the naked eye, so why can’t we see it?
The answer is simple: Mercury is the closest planet to the Sun and, most of the time, it is obscured by the Sun’s glare. That’s why many people have never seen Mercury. However, at certain periods of time, the elusive planet becomes visible for us.
How often is Mercury visible?
The most favorable time for observation of Mercury is when the planet reaches its greatest separation from the Sun, as seen from the Earth. Astronomers call this event “the greatest elongation”. Elongations occur every 40-70 days and are a delight for any astronomy lover.
There are two types of elongations – eastern and western. When Mercury is positioned to the east of the Sun, it’s an eastern elongation, and when it’s to the Sun’s western side, it’s a western elongation. The maximum elongation angle for Mercury is between 18° and 28° east or west of the Sun. The number varies because Mercury’s orbit is slightly tilted and is not perfectly circular.
Mercury’s eastern elongation is also called the evening one because the planet is best observed during the evening hours. In contrast, the western elongation is called the morning one.
Where can you find Mercury in the sky?
On January 23, at 20:59 EST (or January 24, 01:59 GMT), Mercury will reach its greatest eastern (evening) elongation. You can start looking for the planet in the western sky around sunset. Don’t wait too long, though, as Mercury will be hanging quite low above the horizon and will sink below it an hour or two after sunset in some locations. The planet will look like a bright “evening star”, shining with a magnitude of -0.7 in the constellation Capricornus. You can observe Mercury with the naked eye or through binoculars. With a telescope, you might be able to capture Mercury’s phases that are similar to the Moon’s.
The easiest way to locate the elusive planet is to use the Star Walk 2 app. Tap the magnifier icon, type “Mercury” in the search field, and tap on the search result. Then, simply point your device at the sky and follow the white arrow to find Mercury.
Try not to miss the opportunity to see Mercury this month! If you do miss it, though, you’ll have a chance to catch the planet during the greatest western elongation in March. Happy observations!