Look up! You could see a green-tailed comet from the Milky Way’s origins

Written by Danielle Chiriguayo, produced by Brian Hardzinski

The comet C/2022 E3 has a green tail. Photo by Dan Bartlett/NASA.

For days, the night sky has been graced by a comet called C/2022 E3 (Z.T.F.). It last passed through our solar system 50,000 years ago. It makes the closest planetary approach on Wednesday. With the right conditions, the comet is visible to the naked eye, and if you get a good look, you’ll see a glowing green tail.  

The ideal time to catch a glimpse of it is near midnight, according to E.C. Krupp, astronomer and the director of the Griffith Observatory. He recommends getting away from city light pollution and finding clear skies.  

Krupp says the comet is circling the North Pole. It’s green due to its physical and chemical properties, which react to ultraviolet radiation from the sun.

“Comets are essentially great, big, dirty snowballs. That means they have water, ice, and carbon, and some of it [is heated] as a gas. That is what you might say boiling off of the small mountain of gas and dirt. Those molecules of carbon are hit by ultraviolet radiation, light from the sun. And that energetic light splits those molecules,” he explains. “They break apart and recombine, and they emit green light.”

Many comets never get close to Earth and often float in the outer solar system. The ones that do make it have either their trajectories gravitationally disturbed, or have extremely long orbits, like this one.

“Whenever one of these comes in, we're privileged just to see it, because when these comets appear, they're really interesting. But also, they are material left over from the very origins of the solar system. … We're looking at some material that's really part of the creation that ultimately leads to us.”



  • E.C. Krupp - astronomer, director of the Griffith Observatory