A pair of once-in-a-lifetime comets are rocketing through our skies right now, and it's a rare treat because they won't be back for hundreds of years. The comets, C/2025 A6 (Lemmon) and C/2025 R2 (SWAN) , look similar.

You can spot these green gaseous globes and their streaming tails right now, with SWAN shining the brightest on Monday, Oct. 20, NBC News reports. Just a day later, on Tuesday, Oct. 21, Lemmon will make its peak showing in the dark sky.

You'll be able to see Lemmon without any equipment, but SWAN will be pretty faint, says Jason Steffen , assistant professor of physics and astronomy at UNLV.

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"Current models are showing the [Lemmon] comet will lik

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