spaceSpace and Physics

A Green Comet Just Exploded In Brightness – And It Could Be Visible To The Naked Eye Soon


Jonathan O'Callaghan

Senior Staff Writer

Okay, not quite this. But kinda close. ChaiwatUD/Shutterstock

A comet appears to have exceptionally brightened in the night sky, as it moves closer to the Sun – and it may even become visible to the naked eye.

Called PanSTARRS (C/2017 S3), it was seen with a bright green coma – a cloud of dust and gas surrounding the comet – around July 2. Just two days earlier, it had been 16 times dimmer, suggesting it is being heated by the Sun.


“Comet PanSTARRS (C/2017 S3), which had been chillin' at magnitude 12.5, experienced an outburst some time on June 30th, rocketing to magnitude [about] 9.5 overnight,” Sky and Telescope noted. They added that the brightness and size of the coma continued to increase, a “sure sign of a gas blast from the outburst”.

The comet will reach its closet point to the Sun on August 16, within the orbit of Mercury, so there is a chance it could become even brighter in the night sky. The best views are expected around August 4 and 5, after which its proximity to the Sun and daylight will hamper views.

On, astronomer Michael Jäger‎ of Austria said the coma of the comet was about 4 arcminutes wide. That equates to about 260,000 kilometers (160,000 miles), which is about twice the size of Jupiter. Yep, that’s pretty big.


PanSTARRS (C/2017 S3) was first spotted last year, hence the “2017” designation within its name. It now appears to have a tail behind the nucleus, or core, of the comet. From the northern hemisphere, you should be able to spot it with a telescope.


The comet is on a very elongated orbit around the Sun, with some suggestions this may be the first time it has entered the inner Solar System. It likely originated in the Oort cloud, the vast cloud of comets that surrounds our Solar System.

No one is quite sure what will happen when it approaches the Sun. It may reach a magnitude of 4, which would be bright enough to see with naked eye from a dark sky site. But if bursts like this again, it could become even more visible.

If it survives, it’ll then make its way out of the Solar System. Who knows when, or if, we’ll ever see it again.


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