plan­ets on dis­play

The swiftest planet in the So­lar Sys­tem re­turns to the dawn skies this month – make sure you’re in the right place to see it

All About Space - - Contents -

Your chance to catch a good glimpse of Mer­cury be­fore the Sun ob­scures it again

It seems like an age since Mer­cury watch­ers had any­thing to smile about. The clos­est planet to the

Sun has been hard or im­pos­si­ble to see in the sky for months, ei­ther too close to the Sun to be seen or even hid­den be­hind it. But fi­nally this enig­matic, Sun-baked world is on view again, vis­i­ble in the morn­ing sky as a cop­per-hued star that is bright enough to be seen eas­ily with the naked eye.

At the start of our ob­serv­ing pe­riod Mer­cury will be ris­ing in the south­east at around 6:30am, an hour-and-a-half be­fore the Sun. Ob­servers with the low­est, flat­test and least ob­structed hori­zons in that di­rec­tion will en­joy the best views, be­cause Mer­cury’s close phys­i­cal prox­im­ity to the Sun means it never strays far from it in the sky, so it never climbs very far up above the hori­zon. If you have trees, tall build­ings or hills to the south­east of your usual view­ing lo­ca­tion you might like to con­sider a trip to some­where with a more favourable view if you are set on see­ing lit­tle Mer­cury.

The best time to see Mer­cury will be around mid­De­cem­ber. Mer­cury will be 21 de­grees from the Sun – about as far as it ever gets – and should be easy to see with the naked eye. If you don’t spot it straight away, don’t worry; many peo­ple, even those who con­sider them­selves to be ex­pe­ri­enced ob­servers, of­ten need a lit­tle time to find it. Once you have found it – and don’t worry if you need to sweep the sky with a pair of binoc­u­lars to track it down – you’ll find you can go back to it eas­ily again and again.

Mer­cury isn’t alone in the sky this month – it has some very fa­mous and re­gal com­pany. Jupiter, con­sid­ered by many to be the king of the plan­ets, lies down to Mer­cury’s lower left, very close to the hori­zon, while Venus, the bright­est planet by far, will be blaz­ing brightly to the up­per right of Mer­cury.

On the morn­ings of 22 and 23 De­cem­ber

Mer­cury and Jupiter will have a close en­counter of the ce­les­tial kind where they will shine very close to­gether in the sky. In fact, they’ll be so close – just a de­gree, or a Moon’s width, apart – that they will both fit in the same binoc­u­lar field of view, and even in a tele­scope’s low-power eye­piece’s field of view too. How­ever, the pair­ing will be very low in the sky, so don’t be too dis­ap­pointed if you don’t man­age to see this con­junc­tion; you’ll have other chances.

Few probes have vis­ited Mer­cury, but one is en-route right now. ESA’s BepiColombo probe blasted off in Oc­to­ber. It will ar­rive at and be­gin to study Mer­cury in 2025, after fly­ing past Earth and Venus along the way.

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