Binocular comet promises more for 2017

A comet is currently visible with binoculars or a small telescope in the evening sky. Known as Comet 45P/Honda–Mrkos–Pajdušáková, this is not a newcomer but has been known since 1948 when it was discovered.

Comet 45P
Comet 45P can be seen at the centre of this image, photographed on the evening of 29 December, 2016. Image credit: Paul Sutherland/Skymania

It bears the names of its discoverers – Minoru Honda, Antonín Mrkos, and Ľudmila Pajdušáková – while the 45P tag indicates that it was the 45th periodic comet, or regular visitor, to be found.

The comet takes just 5.25 years to make one circuit of the Sun, travelling close in from a point beyond Jupiter. Like that comet visited by ESA’s Rosetta space probe, Comet 67P/Churyumov-Gerasimenko, it will once have had an orbital period of hundreds or thousands of years before it was captured by our largest planet’s gravitational pull.

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Comet 45P reaches perihelion, its closest point to the Sun, on December 31, when it will be at half the distance of the Earth. Then it begins its steady retreat back into the depths of the Solar System.

It is not an easy object to spot at the moment. The comet lies at around half the altitude of Venus as soon as it gets dark, and since it is too faint to see with the unaided eye, any haze or murk will hide it. However, if you have a particularly clear horizon, free of cloud, you might be able to see its fuzzy coma, or head, with a pair of binoculars. It might be worth looking for if you’re observing Venus and the crescent Moon nearby after dusk on New Year’s Eve and New Year’s Day.

Chart showing Comet 45P's position over the New Year.
Chart showing Comet 45P’s position over the New Year, with the Moon and Venus as they will appear on December 30. Chart by Skymania using Cartes du Ciel software

Our photograph shows how unspectacular the comet is at the moment. Its coma registered on images taken with the writer’s Fuji XM-1 camera with a 135mm Olympus Zuiko lens. However the sky was not dark enough to allow for a long enough exposure or high enough film speed to reveal more than a hint of its tail. The photo here is made up of 27 individual 10-second exposures stacked together to improve contrast.

The comet should actually become easier to spot in February, following its conjunction with the Sun. That is because it passes close to Earth as it moves away from the Sun, and rapidly races across the sky through the constellations of Aquila, Hercules, Corona Borealis and Bootes in a matter of days. Though it will still be a binocular target, it will become high in the hours before dawn and visible against a dark sky.

2017 promises to be a good year for comet fans, with a number likely to become bright enough to be seen in binoculars. We will tell you more about them nearer the time.

Chart showing Comet 45P's position in the morning sky in February.
Chart showing Comet 45P’s position in the morning sky in February. Chart by Skymania using Cartes du Ciel software.
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By Paul Sutherland

Paul Sutherland has been a professional journalist for nearly 40 years. He writes regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy, plus he has authored three books on astronomy and contributed to others.

2 thoughts on “Binocular comet promises more for 2017

  • 02/09/2017 at 8:30 pm

    What compass direction will I be looking to find Comet 45P/Honda-Mrkos-Pajdušákova during early February? I’m a constelation neophyte.

  • 02/09/2017 at 11:47 pm

    Generally, you will be looking towards the east, but remember that the position of the comet among the stars will change as the Earth rotates.

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