The bright planet Mars is making a close approach in the sky to a more distant planet, Uranus. Over the next few days, you can watch as they move to within 1.7° of each other before the distance between them widens again.
The phenomenon will be easy to spot if you have binoculars or a small telescope. Mars itself is easy to see because it currently resembles the brightest stars, shining at magnitude 0.2. But Uranus is at the limit of naked-eye visibility in pristine, dark skies, shining at magnitude 5.8, so you will certainly need optical aid to see it.
Mars is bright because it is much closer, and Earth’s outer neighbour, at a distance currently of around 164 million km.
Uranus is an ice giant, but considerably fainter because it lies much further away in the Solar System, far beyond Jupiter and Saturn, at a distance of 2.94 billion km. Both planets shine by reflected sunlight.
Mars was a lot brighter in October than it is now because it was passing through opposition and at its closest to Earth. However, it is still prominent in the evening sky, with no other planet as bright. You will find it shining due south as soon as the sky gets dark, if you are in the northern hemisphere. Southern hemisphere observers will see it roughly due north when the sky darkens.
Both planets, Mars and Uranus, are currently in the constellation of Aries, whose main three stars form an easily identified asterism.
Our chart shows the position of Mars at five-day intervals between 15 and 25 January. Mars’ motion is quite obvious in this time. Uranus, on the other hand, is hardly seen to move at all.
They will be at their closest on 21 January, at a distance of 1.7°. Remember that this event, termed a conjunction, is purely a line-of-sight effect. In reality, the two planets are widely separated in space.
The Moon will pass close by on 20 and 21 January as it approaches its First Quarter phase.
If you have a camera, you can try to photograph the two planets. A series of exposures over a few nights will record their changing alignment. A camera with manual controls is best, though some pocket cameras have night-sky settings which might be enough.
You will need to focus your lens on infinity, choose a fairly high “film” speed, or ISO, and leave the shutter open for a few seconds. A tripod, or some other way to keep the camera steady, is essential.
If you don’t have a cable release to avoid camera shake, then set a shutter delay to allow the camera to settle after you have pressed the button – it’s the facility that usually allows you time to get yourself in a family photo!
When the Moon is in the same field of view, its bright light will quickly wash out the image, restricting the length of time you can expose for. Nevertheless, Uranus is bright enough to show in your picture in just a couple of seconds.
Related: How to find Uranus in the night sky
