Across the Northern Hemisphere, now is the time to catch a new comet before it disappears for 400 years

A newly discovered comet is swinging through our cosmic neighborhood for the first time in more than 400 years.

Stargazers in the northern hemisphere should catch a glimpse as soon as possible — either this week or early next week — because it will be another 400 years before the wandering snowball returns.

The 1-kilometer (half-mile) comet will pass safely near Earth on September 12, passing at a distance of 78 million miles (125 million km).

Early risers should look toward the northeast horizon about an hour and a half before dawn—to be precise, less than 10 degrees or so above the horizon near the constellation Leo. The comet’s brightness will increase as it approaches the sun, but it will decrease in the sky, making it difficult to spot.

Although visible to the naked eye, the comet is very faint.

“So you really need a good binocular to catch it and you also need to know where to look,” said Paul Chodas, director of NASA’s Center for Near-Earth Object Studies.

The comet will approach the sun – closer than Mercury – around September 17 before leaving the solar system. That’s assuming it doesn’t disintegrate when it gets through sunlight, although Chodas said it “is more likely to survive through it”.

Italian astronomer Gianluca Massi, founder of the Virtual Telescope Project, said in an email that next week represented the “last possible chance” to see the comet from the northern hemisphere before it gets lost in the sun’s glare.

He said: “The comet looks amazing now, with a very long and organized tail, which is fun when photographed with a telescope.”

If it survives its close approach to the sun, Massey said, the comet should be visible in the southern hemisphere by the end of September, and will be low on the horizon at evening twilight.

Stargazers have been tracking the rare green comet since its discovery by an amateur Japanese astronomer in mid-August. Comet Nishimura now bears his name.

Chodas said it’s very unusual for an amateur to spot a comet these days, given all the professional sky surveys with powerful ground-based telescopes. “This is his third discovery, and it’s very good for him,” Chodas said.

Chodas said the comet last visited about 430 years ago. It was about a decade or two before Galileo invented the telescope.