SAN DIEGO – Starting Wednesday night, San Diegans might be able to spot an unusual comet discovered at Palomar Observatory in the night sky.

The comet, known as C/2022 E3 (ZTF) or “green comet,” was discovered by astronomers with Caltech last year at Palomar Observatory.

Wednesday night will be the first time in nearly 50,000 years, according to scientists, that the comet will be close enough for stargazers to see with an unaided eye in dark skies.

“Tonight is when it makes its closest passage to the Earth, so it becomes the brightest that we will encounter,” Dr. Cameron Hummels, the director of public education at Caltech, said to 

According to Hummels, researchers at the facility were conducting a survey of the sky using a custom-built mosaic camera installed on Palomar’s 48-inch Samuel Oschin Telescope that is able to capture a series of images to track any changes that happen from one image to the next.

The camera has discovered thousands of galactic objects since 2018, including rare cosmic tidal disruption events, supernovae and atypical asteroids.

While the green comet is only one of these findings, it’ll be one of the first celestial items people can catch a glimpse of since the comet C/2020 F3, or “comet NEOWISE” graced the night sky back in 2020.

“There are lots of objects that travel from the outer solar system, but not all of them put on a visual display bright enough that you can see with the unaided eye,” Hummels said to “This is the first one that’s been bright enough in the last three years or so.”

The green comet, nicknamed for its fluorest color, was first discovered by researchers early last March by researchers at the Zwicky Transient Facility located in Palomar Observatory, just outside of San Diego.

“Comets are generally what we refer to as ‘dirty snowballs,’ because they have a lot of water, ice and carbon dioxide, as well as other volatiles that are present accompanied by dust and dirt,” Hummels said. 

“When they get close to a hot object, like a star, they start to heat up and melt, (evaporating) those ices which kind of puffs up and turns into this big, diffuse ball of gas,” he continued. “That gas reflects light from the sun, so you can see it in the sky.”

That’s where he says the comet’s green color comes from: as some of the more complex molecules in a comet get hit by the sun’s rays, they fluoresce with the green color.

“Lots of comets end up being green,” Hummels said. “It’s not unique to this type of comet.”

While it’ll take a few weeks for the green comet to completely pass by Earth, any stargazers looking to catch a glimpse of it while it’s at its brightest should grab a telescope or binoculars and try to go to a dark sky location, away from city lights.