spaceSpace and Physics

A Newly Discovered Comet Will Make Its Closest Approach To Earth In Millennia This Month - Here's How To See It


Robin Andrews

Science & Policy Writer

The new comet (in green), seen here alongside the Northern Trifid nebula on October 2, 2017. @peachastro via Twitter

Rejoice, stargazers, for we have a double serving of good news for you! Firstly, it seems that a comet that’s long been slinking its way through the cosmos incognito has recently been detected; secondly, if you’ve got a pair of binoculars, you should be able to see it without the aid of any of those massive, high-tech telescopes.

Designated as C/2017 O1 ASAS-SN, it was first spotted back in July by the Chile-based All Sky Automated Survey for Supernovae (ASAS-SN) system, hence the name. As you may have guessed, this observational system is supposed to be looking for the spectacular deaths of high-mass stars, but as it turns out, a comet is too spectacular not to pay attention to.


According to, the comet was spotted moving from the constellation of Cetus (the Whale) to the west of Eridanus (the River) back in early August. It’s since shifted into Taurus (the Bull), and has been dancing through the Hyades and Pleiades star clusters in September.

Right now, it’s between Auriga and Perseus, the Charioteer and the Hero, and it’s heading towards Camelopardalis (the Giraffe). Throughout this astronomical journey, its beautiful tail could be observed streaking off into the shadows.


On October 14, it will reach its perihelion – the closest point in its eccentric orbit to the Sun – at a not inconsiderable distance of 224 million kilometers (139 million miles) from our local star. This means that it’ll be within the orbit of Mars, close enough for anyone with a pair of binoculars to see if light pollution levels are low, and the Moon isn’t out.

The best time to see it will be on October 18, though. It is at this point that, due to its orbital path, the comet will be closest to Earth despite having already started to move away from the Sun.


The brightness of the comet has peaked and waned rather erratically ever since it was discovered earlier this year. Right now, it’s a fairly bright magnitude 8 object, one that appears as a fuzzy streak of light in the night sky.


If you’re lucky, you may see a flash or two of green in the comet’s tail or its gaseous envelope, the coma. This is due to the sublimation (transformation of a solid straight into a gas) of diatomic carbon within the comet’s nucleus as it approaches the Sun.

If you can see it, we’d certainly recommend it; its stretched orbit means that it will next visit the Sun several thousand years from now.



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