How to see the green comet making its way past Earth

Last month,NASA watched closely as an asteroid the size of a delivery truck whipped past our planet in one of the closest such encounters ever recorded.

The creator of NASA’s impact hazard assessment system,Davide Farnocchia,called our near-miss with the asteroid – formallyknown as 2023 BU – as “extraordinarily close”. The rock measured 3.5 metres by 8.5 metres.

Now,in yet another exciting extraterrestrial event for 2023,stargazers are trying to get a glimpse of the latest shiny new thing – Comet C/2022 E3 (ZTF).

Comet C/2022 E3 (ZTF) hasn’t been near earth in about 50,000 years.

Comet C/2022 E3 (ZTF) hasn’t been near earth in about 50,000 years.Jose Francisco Hernandez

The comet was discovered by astronomers in March last year at a facility in Southern California,and it hasn’t come this close to Earth since the last ice age.

C/2022 E3 (ZTF) is unique because it produces a bright-green light as it zips past Earth.

Astrophotographers in the northern hemisphere have already captured the stunning event and now the comet is coming within view of Australia.

Given it won’t be back for another 48,000 years,it’s one you won’t want to miss.

So,what is this mysterious green rock?

Australian National University astrophysicist Brad Tucker describes the comet as “a dirty snowball”.

Basically,it’s the combination of leftover bits and dregs from the edge of the solar system,such as frozen methane,carbon,nitrogen and water.

Right now,this grubby little ice ball is heading towards the sun.

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As it slowly warms up,these frozen gases start to melt,which is what gives it a green tinge.

When will I be able to see it?

The further north you live in Australia,the more time you will have to see the comet.

Those in the Northern Hemisphere spotted C/2022 E3 (ZTF) from February 1,with the comet zooming past the Earth as its closest point on February 2 –just 42 million kilometres away.

Tucker estimates those living in northern cities such as Darwin and Townsville will get the first glimpse of glorious green on Tuesday,February 7,whereas Sydneysiders,Melburnians and those in Perth will best see the comet around Saturday.

“It’s on track to come south but,as it does,it will move higher and further away from Earth ... it won’t be as bright for those in the Southern Hemisphere.”

As for the time of day,Tucker said the best viewing hour is about 9pm AEDT,when the sun is gone but the moonlight is not yet at its peak.

Will I need a telescope to see it?

Whether you’ll be able to see the comet with the naked eye is still up for debate among astronomers.

According to Tucker,this is because “comets are a lot like cats,you never know what they’re going to do next”.

There’s a chance the comet could burn bright and steady enough to see it without needing binoculars or a telescope – but it could burn quickly and turn into a bit of fizzer.

“The brightness comes from how much of the ice melts and turns into the gas,and you can’t really predict that,” he said.

“Comets are notoriously hard to predict.”

Tucker recommends heading away from the city and taking binoculars with you.

“You just want a clear view – the darker,the better,” he said.

If you aren’t able to get out of the city – even just getting away from street lights will help,such as sitting in the middle of an oval.

When are we likely to see our little green friend again?

The last time C/2022 E3 (ZTF) was viewable from Earth was about 50,000 years ago,and is predicted to re-appear in about 48,000 years.

“So yes,unless you’re going to be around in 48,000 years and,hey I don’t like to judge,this will be your last chance to see it,” Tucker said.

The good news is comets are being discovered all the time as technology improves,with more and more people also becoming space searchers.

“There are a lot more comets to come,” Tucker said.

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Sarah Keoghan is a journalist for The Sydney Morning Herald.

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