{"id":43504,"date":"2023-03-27T12:59:49","date_gmt":"2023-03-27T12:59:49","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=117427"},"modified":"2023-03-27T13:32:35","modified_gmt":"2023-03-27T13:32:35","slug":"how-to-see-planet-mercury-at-its-best-this-apriland-beyond","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/how-to-see-planet-mercury-at-its-best-this-apriland-beyond\/","title":{"rendered":"How to see planet Mercury at its best this April\u2026and beyond"},"content":{"rendered":"

Mercury returns favourably to our twilight skies in April 2023. Find out how to locate it and what you can see through a telescope. <\/p>

By Charlotte Daniels\n \t\t<\/p>

Published: Monday, 27 March 2023 at 12:00 am<\/p>

\n\n

As an inner planet, Mercury presents new and exciting challenges to planetary astronomers. As it happens, Mercury is going to be a great planet to view in April 2023, and in this guide we\u2019ll reveal how to make the most of it.<\/p>\n

Due to its proximity to the Sun, extra care must be taken to observe Mercury safely, which adds to the challenge.<\/p>\n

There are particular times that are best to view this elusive, mysterious planet, and this April we can seize the opportunity. Get ready to enjoy one of the Solar System\u2019s unsung heroes.<\/p>\n

For regular stargazing advice delivered to your inbox, sign up to receive the BBC Sky at Night Magazine e-newsletter<\/a> and listen to our weekly Star Diary podcast<\/a>.<\/strong><\/em><\/p>\n

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Image of Mercury taken by the MESSENGER spacecraft. Credit: NASA\/JPL-Caltech<\/span><\/figcaption> NASA\/JHUAPL<\/i><\/span><\/div>\n

Mercury\u2019s orbit explained<\/b><\/h2>\n

The fastest planet in the Solar System, Mercury<\/a> is named after the messenger of the Greek gods, renowned for speed. And time is certainly of the essence with this planet.<\/p>\n

To catch Mercury, we need to understand how its position relative to the Sun affects its visibility.<\/p>\n

Mercury is 0.4 astronomical units (AU) away from the Sun and orbits at speeds of up to 47km per second, compared to Earth\u2019s relaxed pace of 30km per second.<\/p>\n

When it reaches its closest point to the Sun, Mercury is at its fastest and it then slows down slightly the further away it gets. As the innermost planet, it also has the shortest year, taking 88 Earth days to circle the Sun.<\/p>\n

The gravitational influence of the Sun affects Mercury\u2019s orbit in other ways too.<\/p>\n

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The rays of Mena crater on Mercury. Credit: NASA\/JPL<\/span><\/figcaption><\/div>\n

Mercury\u2019s journey around the Sun is highly \u2018eccentric\u2019, or egg-shaped: this means the distance between the two can vary from 46,000,000km to 69,000,000km.<\/p>\n

Moreover, just because Mercury\u2019s years are short, it doesn\u2019t mean its days are. In fact, it rotates so slowly on its axis that it completes one full rotation roughly every 59 Earth days.<\/p>\n

When we consider the speed that Mercury travels versus its slovenly rotational rate, we realise it doesn\u2019t experience conventional sunrises and sunsets to mark day and night times \u2013 one \u2018solar day\u2019 (a full day\u2013night cycle) on Mercury is 176 Earth days!<\/p>\n

Another thing that makes Mercury unique is its lack of moons. Anything likely to be bound to the planet is instead attracted by the strong pull of its host star.<\/p>\n

Mercury elongations and conjunctions<\/b><\/h2>\n
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The best time to catch the planet is at eastern or western elongation, when its orbit brings it far enough from the Sun\u2019s glare<\/span><\/figcaption><\/div>\n

Because Mercury is the planet closest to the Sun, it always appears close by and is often swallowed by our home star\u2019s glare.<\/p>\n

Mercury\u2019s appearances are therefore closely linked with our sunrise and sunsets, making it a morning or evening object, rather than something we can look for during later hours.<\/p>\n

The best time to view Mercury is during greatest elongation, which next occurs on 11 April 2023<\/strong>.<\/p>\n

This is when Mercury is farthest from the Sun, so it is placed far either to the east or west side of it (known as eastern and western elongations, respectively).<\/p>\n

What we\u2019ll have on 11 April<\/strong> is a greatest eastern elongation event. This places it a little further from the Sun\u2019s glare and at its highest altitude, helping us to view it.<\/p>\n

The angular separation due to elongation can vary from roughly 20\u00b0 to 28\u00b0, the equivalent of one handspan to three clenched fists next to each other, held at arm\u2019s length.<\/p>\n

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Mercury in the morning sky. Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

When positioned at the eastern side of the Sun, Mercury appears in our evening skies; when at the western side it appears in early morning skies.<\/p>\n

When it makes its evening appearances, the planet is seen above the western horizon shortly after sunset in twilight<\/a> (as it will be around 2\u201315 April<\/strong>), and as a morning planet it appears in the east shortly before sunrise (as it will be around 27\u201331 May<\/strong>).<\/p>\n

A very clear eastern horizon will be needed.<\/p>\n

These elongation events mark Mercury\u2019s best and safest observing periods. Because Mercury is closest to the Sun, elongations are regular and happen every 3\u20134 months.<\/p>\n

It\u2019s at this point that the planet will appear highest above the horizon, placing it at the best position to observe as it will be clear of light pollution and least affected by atmospheric seeing<\/a>.<\/p>\n

Mercury reaches this point on 11 April, making this a great time to start looking for it. Even so, it never strays far from the Sun, with this elongation only reaching a maximum angular separation of 19.5\u00b0.<\/p>\n

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27 March, view to the west through 7\u00d750 binoculars 45 minutes after sunset. Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

Mercury inferior and superior conjunctions<\/strong><\/h2>\n

Inferior and superior conjunctions are specific to the inner planets, and mark times when we can\u2019t view Mercury.<\/p>\n