The green comet coming our way
THE frosty green glow of a comet has suddenly flared as it plummets towards our Sun, raising hopes it could become visible in daytime skies.
PanSTARRS C/2017 S3 is a newcomer.
It was only discovered last year.
Skywatchers dubbed it something of a 'wildcard'. And it's starting to live up to expectations.
It suddenly flared some 16-times brighter than it had been on July 2. This is because it has been warmed to the tipping-point necessary for an eruption of previously frozen gas.
It's a moment that was caught on camera by Austrian amateur astronomer Michael Jager.
The comet's nucleus is now casting out an eerie green tail, some 260,000km in diameter.
At this size, it's already easy to spot with simple telescopes in the northern hemisphere.
But it's going to get much closer yet.
NASA's Jet Propulsion Laboratory HORIZONS Solar System Dynamics system predicts the comet will brighten rapidly between mid-July and the first days of August.
But this is not certain.
C/2017 S3 hasn't been seen before. And its orbit - coming from high above the plane of the Solar System - suggests this may be its first dive into the inner solar system.
So we don't know what it's made of. It may burn off its gas quickly. Or it may flare further.
It's not even known if it will survive its plunge towards the sun.
C/2017 S3 could explode from the pressure of gas boiling deep in its icy heart.
If all goes well and its tail continues to flare, the northern hemisphere may get to see it from late July before it becomes obscured by the Sun's glare.
It should hopefully become visible to the naked eye in Australia shortly before sunrise around August 15. This is after it swings past the Sun, 11 degrees away, and heads back out to the Oort cloud.
If so, it won't likely be seen again for another 200 years.
But C/2017 S3 isn't likely to be the best comet viewing this year. 46P Wirtanen swings past on its 5.4 year orbit in December. It will pass high through southern skies, and will probably become visible to the naked eye on November 23.