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Green comet discovered by Palomar Observatory flies closest to Earth Wednesday

On Wednesday night San Diegans will get their best look at a comet that hasn’t passed this close to earth in 50,000 years. The comet, which appears green, was discovered by San Diego County’s Palomar Observatory in March 2022.

Cameron Hummels is a research scientist at Caltech, which operates the Palomar Observatory in the mountains east of San Diego. He said the discovery of the comet, officially called C/2022 E3 (ZTF), was done with a device called the Zwicky Transient Facility. The device is mounted inside of a telescope, scans the night sky and then takes a lot of pictures in one place.

“They take (images) every 30 seconds or so at any segment of the sky to see if something is moving," Hummels said. “And occasionally you’ll see something moving over the course of those five images, and in this case that was the initial discovery of this comet.


Comets are dirty balls of ice that orbit the solar system. As they approach the sun they begin to melt and evaporate into a gas. And that gas makes them visible in the sky.

“Because the comet itself, the icy part of the comet itself, is less than a mile in diameter, it’s a really small guy. But the cloud of gas that surrounds that little snowball ends up being, like, thousands of miles across. And the tail that drags behind it is millions of miles in length,” Hummels said.

The comet appears green due to its molecular makeup and the way that it is illuminated by the sun.

If you want to try and see it, Hummels said it’s best to be in the desert, away from light pollution, with a telescope or binoculars and someone who is good at scanning the stars.

“Just after dusk it’ll be in the northern part of the sky, near the North Star,” he said.


Skies are supposed to be clear on Wednesday, another reason it’s the best time to see C/2022 E3 (ZTF).