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◼ Mercury lies in the evening sky. Mars is still bright and visible from dusk. The first meteor shower of the year, the Quadrantids, is spoiled by bright moonlight. Here’s more about the stars and planets you can see in the night sky in January 2021.
January’s star chart
Click on the image above, or the following text for an interactive map of constellations visible in the sky. It can be adjusted for any time and date.
We also have a map of the night sky set up for mid-latitudes in the southern hemisphere.
The planets in January 2021
Mercury lies in the evening sky in January, having rounded the far side of the Sun on 20 December. It will become visible low in the southwest from the second week of January, though you will need a clear horizon, free of hills, buildings, and clouds to see it. Binoculars will greatly help if you look in the fading twilight after sunset. During the second week of January, Mercury also passes close to Jupiter and Saturn, but this attractive clustering of planets, so near the horizon, will be difficult to spot without exceptionally good skies. A thin crescent Moon will lie close by on the 14th. During the rest of January, Mercury will become easier to spot as it moves further from the Sun. It reaches its greatest elongation east on the 24th, when it will be at magnitude -0.6. Read more about Mercury.
Venus is still closing back in on the Sun and so the window to see our inner neighbour becomes shorter as January progresses. At the start of the month, Venus rises around an hour and a half before the Sun from mid-northern latitudes, shining at magnitude -3.9. But by the end of January, Venus rises just half an hour or so before the Sun, and so will be difficult to see low down in the brightening dawn. Venus is now on the far side of its orbit, so shows a small gibbous phase through a telescope. Read more about planet Venus, and also see our guide to observing Venus.
Mars is the best placed planet in the sky this month, though it is steadily receding from the Earth and fading in brightness following opposition in October. You can see it to the south as soon as the sky darkens (or to the north if you are in the southern hemisphere). At the start of January, Mars is at magnitude -0.2, with an apparent diameter of around 10 seconds of arc, in the constellation of Pisces, but it crosses into the constellation of Aries on the 5th. By the end of January, its diameter has shrunk to around 8 seconds of arc and its brightness faded to +0.4 so that it resembles a bright star. The waxing Moon passes close by on 20 and 21 January. Mars also closes in on the much fainter, distant planet Uranus. They will be just 1.7 degrees apart on the 21st. Here is a link to our special article on how to observe this conjunction between Mars and Uranus. You can also read our guide to Mars.
Jupiter reaches the end of its current apparition this month. If you have a clear, unobstructed southwestern horizon, you may be able to spot the king of the planets in the first days of the month, shining at magnitude -2, but it soon is lost in the glare of twilight and rounds the back of the Sun on 28 January, an event known as conjunction. With exceptional skies, and binoculars, you may be able to see innermost planet Mercury enter the same region of the sky, along with the fainter Saturn, during the second week of January. Read more about planet Jupiter.
Saturn is also reaching the end of its current apparition, gradually diverging from Jupiter again following last month’s Great Conjunction. It reaches conjunction with the Sun, when it passes on its far side, on 24 January. With clear skies and an unobstructed horizon, you may be able to see Saturn a little over a degree away from Jupiter at the very beginning of January. Binoculars will help due to its very low elevation and twilight. Its magnitude of +0.6 will eb greatly dimmed by the depth of atmosphere its light must pass through when so low in the sky – an effect called extinction. Read more about Saturn.
Uranus lies in the constellation of Aries, and is visible as soon as it gets dark, and into the early morning hours. In a dark sky, this planet is theoretically visible with the unaided eye, shining at a dim magnitude 5.7. However, you are unlikely to see it without binoculars, while a telescope will help to reveal its greenish disk. Mars will lie close by, as detailed in the notes for that planet, above. Here is our special guide to this conjunction. Read more about Uranus.
The outer ice giant Neptune is visible from nightfall, to the southwest if you’re in the northern hemisphere, and can be seen during the early evening as it sinks lower in the sky. It lies in the constellation of Aquarius. Neptune is a couple of magnitudes fainter than its twin, Uranus, and shines at magnitude 7.9 this month. You will be able to glimpse it with binoculars, or a small telescope, which will show its bluish tint. Read more about Neptune.
The stars in January 2021
In late evening in early January, the winter constellations dominate the night sky. Due south you will see the very recognisable figure of Orion, the Hunter, with three stars marking his belt, and his arms raised, as if holding a club and shield. Look at a string of fainter stars running down from the belt, with a pair of binoculars, to see an obvious misty patch. This is the famous Orion Nebula, Messier 42, and it is a fine object to study with a small telescope.
To Orion’s upper right, you will find Taurus, the Bull, poised to challenge Orion. The constellation of Taurus is home to two easy-to-see clusters of stars. One is the Hyades, a V-shape which marks the head of the Bull, and where you will find the brightest star, Aldebaran, though it is actually between us and the cluster, and unrelated to it. Nearby, spot the Pleiades, or Seven Sisters, which is a compact grouping of young stars. A telescope or binoculars will reveal many more than seven in this cluster, which is also labelled Messier 45.
Overhead, you will find Auriga, the Charioteer, and on either side, Gemini, the Twins, and Perseus. Return to Orion’s belt and follow it down to its lower left to find Sirius, the apparent brightest star in the night sky, in the constellation of Canis Major, the Big Dog. Ursa Major, the Great Bear, is rising high in the northeast, and if you follow the curve of its tail, you will find another bright star low in the east. This is Arcturus, in the constellation of Bootes, the Herdsman.
Poor year for the Quadrantid meteor shower
The first meteor shower of 2021, the Quadrantids, reaches its sharp peak over the nights of 2/3 and 3/4 January, but a bright gibbous Moon, above the horizon for most of the night, will drown out all but the brightest meteors, making the shower very difficult to observe in 2021. This is a shame as the peak rate, or ZHR, for the Quadrantids can be very high at around 120 an hour under ideal conditions. The shower is named after an obsolete constellation, and its radiant lies to the north of Bootes, so this is strictly a northern hemisphere shower even in the best years!
Last Quarter: Jan 6
New Moon: Jan 13
First Quarter: Jan 20
Full Moon: Jan 28
The Moon always makes a great target for a small telescope, which come into view as its phases change. We’ve a guide to where to find 50 of the best lunar features, plus a checklist to download so you can tick them off as you spot them! Don’t have a telescope? Here’s our guide to choosing one.
Fifty fantastic features – our amazing Moon
Here’s our guide to observing some of the finest sights on the Moon with small telescopes. Our pages of charts will help you find interesting features to seek out yourself, including craters, lava flows, mountain ranges and deep chasms!
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