{"id":62656,"date":"2024-08-19T08:25:32","date_gmt":"2024-08-19T08:25:32","guid":{"rendered":"http:\/\/b08ed08c-5af4-499d-9c53-254c6bd233f0"},"modified":"2024-08-19T08:39:42","modified_gmt":"2024-08-19T08:39:42","slug":"how-to-observe-mercury-with-naked-eye-and-telescope","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/how-to-observe-mercury-with-naked-eye-and-telescope\/","title":{"rendered":"How to observe Mercury with naked eye and telescope"},"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 <\/p>

Published: Monday, 19 August 2024 at 08:25 AM<\/p>

\n\n

As an inner planet, Mercury presents new and exciting challenges to planetary astronomers.<\/p>

Mercury will be a morning object in December 2024 and will be a great planet to observe this winter.<\/p>

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

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

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>

Find out more about observing the planets in autumn and winter 2024<\/a><\/em><\/strong><\/p>

Image of Mercury taken by the MESSENGER spacecraft. Credit: NASA\/JPL-Caltech – NASA\/JHUAPL<\/figcaption><\/figure>
**Mercury’s orbit explained<\/b><\/h2>**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>
To catch Mercury, we need to understand how its position relative to the Sun affects its visibility.<\/p>
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>
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.<\/p>
As the innermost planet, it also has the shortest year, taking 88 Earth days to circle the Sun.<\/p>
The gravitational influence of the Sun affects Mercury\u2019s orbit in other ways too.<\/p>
$\"The$
The rays of Mena crater on Mercury. Credit: NASA\/JPL<\/figcaption><\/figure>
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>
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>
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>
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>
**Mercury elongations and conjunctions<\/b><\/h2>** $\"The$
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<\/figcaption><\/figure>
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>
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>
The best time to view Mercury is during greatest elongation, which next occurs on **5 September 2024<\/strong>.<\/p>**
**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>**
What we\u2019ll have on **5 September<\/strong> is a greatest western elongation event. This places it a little further from the Sun\u2019s glare and at its highest altitude, helping us to view it.<\/p>**
**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>**
**$\"Mercury$** Mercury in the morning sky. Credit: Pete Lawrence<\/figcaption><\/figure>
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>
When it makes its evening appearances, the planet is seen above the western horizon shortly after sunset in twilight<\/a>, and as a morning planet it appears in the east shortly before sunrise.<\/p>
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>
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>
$\"We\u2019ll$
We\u2019ll get long mornings with bright Mercury come December 2024. Credit: Pete Lawrence<\/figcaption><\/figure>
Mercury inferior and superior conjunctions<\/strong><\/h2>
Inferior and superior conjunctions are specific to the inner planets, and mark times when we can\u2019t view Mercury.<\/p>
Inferior conjunctions<\/strong> refer to times when Mercury or Venus pass directly between Earth and the Sun, positioning them in front of the Sun at sunrise and sunset, so they are lost in its glare.<\/li>
**Superior conjunctions<\/strong> refer to times when these two planets are positioned on the opposite side of the Sun to Earth, again making them unviewable.<\/li><\/ul>**What to see when observing Mercury<\/strong><\/h2>
So what can we observe when the time is right for Mercury? Despite its challenges, the planet can be appreciated with and without a telescope.<\/p>
Naked eye<\/strong><\/h3>
If viewed with the naked eye, it tends to appear as a bright point object, similar in appearance to a star, with its magnitude varying from as bright as mag. \u20132.8 to a dim mag. +7, when it is only visible through binoculars or a telescope.<\/p>
If close to the horizon, atmospheric turbulence might make it appear to \u2018twinkle\u2019 like a star<\/a>.<\/p>
However, if you take some time to study it unaided you will detect a subtle, rosy, golden tinge that singles it out from the starry background.<\/p>
Mercury\u2019s apparent diameter, depending on its distance from Earth, can range from 4.5 arcseconds at apogee to 12.9 arcseconds at perigee.<\/p>
$\"To$
To the naked eye, Mercury appears as a distinct dot in the sky. Credit: Pete Lawrence<\/figcaption><\/figure>
Telescope<\/strong><\/h3>
A pair of low-powered binoculars will help you locate the planet, particularly at times when it is dimmer.<\/p>
Because Mercury is often viewed against brighter skies, a telescope will help you locate it.<\/p>
Again, you\u2019ll want clear western or eastern horizons (depending on when you\u2019re viewing).<\/p>
With a 3-inch scope you\u2019ll start to appreciate Mercury\u2019s phases.<\/p>
Although the planet is unobservable at its full phase during superior conjunction and at its new phase at inferior conjunction, even in the short windows of opportunity in between you will notice changes in its phases.<\/p>
While we won\u2019t see craters, on nights of exceptional seeing and minimal turbulence, we may discern some surface details with larger-aperture telescopes.<\/p>
With all planetary astronomy, seeing conditions will greatly affect observations. Therefore, providing it\u2019s safe to do so, try to catch the planet at its highest possible altitude, at a minimum of one hour outside of sunrise or sunset times.<\/p>
$\"Mercury$
Mercury and Venus at sunset. Credit: Pete Lawrence<\/figcaption><\/figure>
A word on safety<\/strong><\/h2>
Because it is so closely bound to our Sun, it is imperative when viewing Mercury to avoid the risk of viewing the Sun directly.<\/p>
Never try to find Mercury in broad daylight or during conjunctions; aim instead for elongation events.<\/p>
Ascertain the sunrise or sunset time on the day of observation and use a sky guide to establish the angular separation of Mercury from the Sun. Ensure that the full disc of the Sun is behind the horizon at the time of viewing.<\/p>
This article originally appeared in the April 2023 issue of <\/strong><\/em>BBC Sky at Night Magazine<\/strong>**.<\/strong><\/em><\/p> <\/body><\/html>\n**
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