The Big Green Comet

Dr Phil Spark, UNE Discovery

It is always interesting looking at the night sky, seeing the Moon and some of the planets. Just after sunset it is currently possible to see Venus, Jupiter and Mars. There are a number of other interesting celestial objects in the sky right now as well. They are comets. The most notable in the news recently is “The Green Comet” which is in the direction of Mars. The name of this green comet is Comet ZTF.

Caption: Comet ZTF and Mars (13 Feb 2023). Image Credit & Copyright: Donato Lioce. * See image explanation below.

The comet is not visible with the naked eye as its brightness keeps on fading as it returns to the outer Solar System. If you look a little bit below Mars with a telescope or a pair of binoculars you may see a fuzzy looking green object. This is the Green Comet. Its white dust tail you may also see in one direction and in the opposite direction its light blue ion tail. Each of these tails are composed of different materials and interact with the Sun differently.


Why has Comet ZTF been in the news?

The ABC News reported “its debut in the night sky was discovered by astronomers in early 2022, using a wide-field survey camera at an observatory in California. But on February 2, it caught the attention of astrophotographers and space enthusiasts alike.

Because that was when the comet was closest to Earth – about 41.8 million kilometres away – in a very long time. Although it’s not uncommon for comets to make rare appearances in the sky due to the size of their orbits, the green comet was last seen roughly 50,000 years ago.

The sheer distance means the comet, despite measuring one-kilometre wide, might only be slightly visible to the naked eye. Light pollution also affects visibility so its natural green glow can only be picked up by astrophotography.

That’s why star-searchers joined the chase to capture the phenomenon – jumping on the opportunity to put their cool gadgets to use and flex their sky imaging skills.”

So, in early February, ZTF was in its closest approach to Earth in 50,000 years! Now that is a very, very long time.  Did you spot the green comet and manage to take a photo?  We’d love to see it.

* Image Explanation: Nicknamed the Green Comet for its bright green coma, C/2022 E3 (ZTF) passed almost in front of Mars, the much-more distant planet earlier in February, very near in time to when this photo was taken. The two sky icons were captured here behind a famous Earth icon — the Matterhorn, a mountain in the Alps between Switzerland and Italy with a picturesque peak. Both the foreground and background images were taken on the same evening by the same camera and from the same location. The comet’s white dust tail is visible to the right of the green coma, while the light blue ion tail trails towards the top of the image. Orange Mars is well in front of the numerous background stars as well as the dark nebula Barnard 22 to its lower right. Although Mars remains visible in the evening sky for the next few months, Comet ZTF has already begun to fade as it returns to the outer Solar System.