Grab the chance to see Mercury shining in the evening sky

Mercury is currently putting on its best show of the year for stargazers in northern latitudes, with Venus helping us find it. Here’s how to see Mercury.

Here is Mercury at its last favourable evening apparition in April 2017. It is the bright object below centre, just above an anvil-shaped thunder cloud, in this photo, taken on 1 April, 2017, from near Faversham, Kent, in the UK. Image credit: Paul Sutherland

The innermost planet of the Solar System, Mercury never strays far from the Sun in the sky. But in March evenings, its orbital path is tilted at a steep angle so that it appears higher in the sky than at other times.

This means that at its greatest distance from the Sun as seen from Earth on March 15th – called its greatest elongation east – it will stand more than 10° above the western horizon when it becomes visible, about half an hour after sunset.

Mercury will be zero magnitude at that time, so as bright as the brightest stars. It would stand out in a dark sky, but less so when it is in bright twilight and at a low elevation.

Thankfully, you can find it more easily due to the return to evening skies of the next planet in order from the Sun, Venus.

Our inner neighbour lies a few degrees below Mercury, but it is much brighter and so will be easy to spot, as long as you have a clear western horizon, unobstructed by hills, buildings or low cloud.

How Mercury and Venus will appear, low in the evening sky, about half an hour after sunset on March 15th, 2018. Image credit: Skymania using Stellarium

Once you have located Venus, look above and slightly to the right of it. You should then be able to see Mercury. If you have never seen the planet before – and many people go through life without ever doing so – now’s an excellent chance!

Grab the opportunity while you can because it will last only a few days before Mercury moves rapidly back towards the Sun as seen from Earth. The slim crescent Moon will be close by on the evenings of March 18th and 19th.

Binoculars will make it even easier to see, but make sure only to use them after sunset. There’s no point looking any earlier anyway, and you risk damage to the eye if you accidentally view the Sun through them while sweeping the sky.

Mercury is a rocky planet but is too tiny to show any detail in a small telescope. Its diameter is only 4,880 km, which is smaller than Ganymede and Titan, the largest moons orbiting Jupiter and Saturn.

Related: Skymania’s guide to Mercury

Related: What to see in the night sky this month


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