A unique green comet passing by for the first time since the Stone Age is making its closest approach to Earth this week, even visible to the naked eye for some viewers. And those curious to see it should grab the chance, because it won’t return in our lifetime — or perhaps ever, Bay Area astronomers say.
Known as C/2022 E3 (ZTF), the comet was discovered last March by the Zwicky Transient Facility in Southern California, according to Geoff Mathews, an astronomy instructor at Foothill College in Los Altos Hills.
Data has confirmed that the comet originated in the Oort Cloud, “a collection of icy bodies orbiting the Sun at the outer fringe of the solar system” — a common source for the cosmic ice balls, said Gerald McKeegan, an adjunct astronomer at the Chabot Space & Science Center in Oakland.
“It is therefore likely that this comet is in a closed orbit and previously passed through the inner solar system about 52,000 years ago,” he said.
While a comet on such a closed elliptical orbit could be expected to return again tens of thousands of years in the future, its path could be interrupted by gravitational pull from other heavenly bodies, and by its own evaporation. The comet could then change or extend its orbit by millions of years, or even end up in a hyperbolic orbit - meaning it gains enough speed to escape the sun’s gravity entirely and exit the solar system.
