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A comet called Nishimura discovered just a month ago could be visible to the naked eye this weekend, giving stargazers a once-in-437-year chance to observe the celestial visitor.

The ball of rock and ice, whose exact size remains unknown, is named after Japanese amateur astronomer Hideo Nishimura who first spotted it on August 11.

It is rare for comets to reach their moment of maximum visibility so soon after their discovery, explains Nicolas Biver, an astrophysicist at the Paris Observatory. “Most are discovered months or even years before passing close to the sun,” he told AFP.

The comet passes close to the sun only once every 437 years, he explained, a long orbital period that causes it to spend much of its time in the frigid outer solar system.

As comets approach the sun from the vastness of space, heat turns their icy cores into dust and gas, which form a long tail. Sunlight reflects off this tail, allowing us to observe comets from Earth.

Nishimura, which has the scientific name C/2023 P1, will pass closest to the sun on September 17. It will be 33 million kilometers (20 million miles) from the sun, less than a quarter of the distance between Earth and the sun, Biver said.

The comet will then pass harmlessly close to the Earth at a distance of 125 m km.

For astronomers, the comet will be the easiest to observe this Saturday and Sunday, especially in the northern hemisphere. “The best thing to do is look at the sky before sunrise, looking northeast to the left of Venus, in clear, pollution-free skies,” Biver said.

People with small binoculars can easily enjoy the show. But if conditions allow, the comet could also be visible to the naked eye.

The comet’s tail is greenish because it contains more gas than dust, Biver explained.