Have you ever seen the planet Mercury with your own eyes? It’s notoriously difficult to catch being situated so close to the Sun and often hard to pinpoint. You’ll only ever see it as a tiny disc in binoculars, very close to sunrise or sunset.
Over the next couple of days, centred on the Dec 21st solstice, there’s a unique opportunity to see Mercury as it forms a conjunction with bright Jupiter low in the south east in morning skies.
You’ll need a good unobstructed horizon to the SE to catch it. Use Venus as a guide to first find Jupiter, then look through your binoculars and you should see Mercury sitting above.
The window is pretty narrow, from around 7.30pm to 8.30pm. The longer you wait the higher Mercury will rise but the brighter the sky, as the Sun rises.
Good luck and clear skies.
Mercury through a 10 inch telescope
Mercury is only 40% larger than the moon but very difficult to spot
The planet Mercury can be very tricky to observe. It’s close proximity to the sun means we generally only have brief opportunities to observe it low on the horizon either before or after sunset.
Right now Mercury is approaching maximum eastern elongation (on March 15th to be precise) meaning the planet is up for longer after the sun sets. The window is still pretty brief with only about 45 mins of useful time to work with after sunset.
Your best chance is to pick a clear evening and head out somewhere with a good unobstructed view to the West. You don’t need dark skies as the Sun will still be producing a lot of light between 6 and 8pm.
At the moment, and at Highland latitudes, the action starts about 6.30pm just after the Sun sets. Wait a while then scan the western horizon and you should see Venus first, which will appear brighter. Use this as a guide for finding Mercury which will sit slightly above it over the next few days.
6.20pm 14th March 2018, 57 degrees north
The longer you wait after the sunset the easier Mercury will be to see due to darkening skies but also harder due to it moving lower and lower towards the horizon, adding more atmospheric distortion to your views.
If you do see it take a note of its crescent phase. We almost always see Mercury as a crescent because it would be too close to the sun to see it in a full or new aspect. One exception to this is during a solar transit when Mercury crosses directly across the disc of the sun. The next opportunity to witness this will be 11th November 2019, which gives you plenty of time to prepare a solar filter for safe observing of the solar disc. Happy planet hunting meanwhile.
Transits reveal the true scale of the Sun
Heavily cratered Mercury
If you have flat and unobstructed views towards the south west there’s a chance of observing one of the most elusive planets this evening – Mercury.
Mercury is hard to see because it orbits so close to the sun, meaning it’s usually lost in the glare of our parent star.
However the planet is currently at its maximum eastern elongation from the Sun, so there’s a small window of opportunity to spot Mercury just after sunset low in the south west. Grab a pair of binoculars and see if you get lucky.
For us high northern latitude observers it’s a tough ask due to the currently flat orientation of the ecliptic, but even if you don’t see Mercury you should catch Saturn sitting just a little higher on the horizon.
Mercury goes through several peak elongations from east to west during a year, providing alternating opportunities to see the planet in pre-dawn or evening skies
Maximum eastern elongation
Despite being closest to the sun, Mercury isn’t the planet with the highest temperatures – that prize goes to Venus with its thick carbon dioxide cloud base. This is because Mercury has no atmosphere to trap or distribute heat. If you were able to stand on Mercury, your daytime temperatures would be a blistering 427C. However, if you hid in the shadow of a large crater or travelled into the dark half of Mercury, temperatures would plummet to a freezing -173C! Again, due to a lack of atmosphere to smooth out the temperature extremes.