Astronomers in the Northern Hemisphere should get a glimpse of it as soon as possible – this week or early next week – because then it will take another 400 years for this wandering ice ball to return.
The one-kilometer-wide comet will safely pass Earth on September 12, less than 125 million kilometers from us.
Early risers should look towards the northeastern horizon about an hour and a half before sunrise – more specifically, less than ten degrees above the horizon, near the constellation Leo. The comet gets brighter as it gets closer to the sun, but sinks lower into the sky, making it harder to spot.
Although the comet is visible to the naked eye, it is extremely faint.
“So you need good binoculars to see it, and you need to know where to look,” warned Paul Chodas, director of NASA’s Center for Near-Earth Object Exploration.
The comet will make its closest approach to the sun around September 17 – closer than Mercury – before leaving the solar system. This assumes it won’t decay when it hits the sun, but Chodas says it’s likely it will survive its passage.
Italian astronomer Gianluca Masi, the founder of the Virtual Telescope project, reminded in an email that next week is “the last viable chance” to see the comet from the Northern Hemisphere before it is lost in the bright sunlight.
“The comet is beautiful right now, with a long, very textured tail, it’s a joy to photograph with a telescope,” he said.
If it survives its encounter with the sun, the comet should be visible in the Southern Hemisphere by the end of September, Mr. Masi said, low on the horizon at dusk.
Astronomers have been tracking the rare green comet since it was discovered by a Japanese amateur astronomer in mid-August. Comet Nishimura now bears his name.
It’s rare for an amateur to discover a comet these days, given all the professional surveys of the sky by powerful ground-based telescopes, Mr Chodas said, adding: “This is his third discovery, so good for him.”
The comet’s last visit was about 430 years ago, Chodas said. This was about a decade or two before Galileo invented the telescope.