A ‘little green smudge’ in our sky

Look to the skies tomorrow and you might be lucky enough to see a rare green comet that only passes earth every 50,000 years – and may never pass again.

The United States National Aeronautics and Space Administration [Nasa] said the cosmic snowball of frozen gases, rock and dust – which goes by the catchy name of comet C/2022 E3 [ZTF] – was discovered by astronomers using the wide-field survey camera at California’s Zwicky Transient Facility in early March 2022.

The comet will be visible in Wairarapa skies this week but only barely with the naked eye, according to local amateur astronomer and Wairarapa Dark Sky Association committee member Dr Tom Love – although a decent pair of binoculars will do the trick.

“It’s about the same brightness as the faintest star you can see with the naked eye,” he said.

The comet may only look like a little green smudge, but it has been around since the beginning of the solar system.

The comet came from the Oort cloud, a large collection of comets at the edge of the solar system.

“Comets from the Oort cloud come every few years, this particular comet only passes the earth every 50,000 years.”

What makes all Oort comets special is they are a bit of astronomical history, Love said, and give us a glimpse of the original, mostly unaltered material from the early solar system.

“The comet was probably formed in the very beginning of the whole solar system, somewhere between four-and-a-half and five billion years ago.”

Because the comet may hit other objects and be thrown off orbit, this could be the only time comet C/2022 E3 [ZTF] will be able to be seen from earth – and even if it’s not, you would have to live another 50,000 years to spot it again.

For the best view of the comet, Love said people should try to get away from light pollution and ensure they have good sightlines north.

The comet will be found to the right of Mars, the bright orange-red star to the north. To the right of Mars sits Matariki, otherwise known as Pleiades.

“At the moment, it is a little bit underneath Mars, and it’ll pass quite close to Mars on the night of February 11.”