Image made by Cheryl Kahla using Midjourney
The rare green comet – named C/2022 E3 (ZTF) – will be visible to people in the southern hemisphere next week, but you don’t want to miss this rare sighting.
The National Aeronautics and Space Administration (Nasa) said the passing of the comet will be an “awesome opportunity to make a personal connection with an icy visitor from the distant outer solar system”. [1]
This article was originally published on Monday, 30 January but a website gremlin ate it during the recent RSA outage. It was republished on 7 February.
The comet has an orbit dating back thousands of years and will come within 42 million kilometres of Earth during February.
Those in the northern hemisphere were the first to see it, and now it’s our turn – the comet will be visible to South Africans between 10 and 12 February.
It’s unlikely we’ll ever see it again in our lifetime (or during our current stage of evolution, ie, Homo Sapiens).
In fact, scientists say the last time C/2022 E3 (ZTF) was in our region of space, was when Neanderthals still walked the Earth (and they went extinct some 40 000 years ago). [2]
The possibility also exists that the “eccentric” green comet would never pass by Earth again, as it could potentially be out of its original path.
Jessica Lee, an astronomer at Royal Observatory Greenwich, explained:
“We don’t have an estimate for the furthest it will get from the Earth yet — estimates vary — but if it does return it won’t be for at least 50,000 years. Some predictions suggest the orbit is so eccentric it’s no longer in an orbit, so it’s not going to return at all and will just keep going.”
According to the South African Astronomical Observatory (SAAO), the comet “will be near Mars on [Saturday] 11 February”.
SAAO said it could be observed by looking towards the Taurus constellation in the evening sky. If weather conditions allow for it, you might need binoculars to see it.
Speaking of binoculars, Nasa said: “The comet will be easy to spot with binoculars, and it’s just possible it could become visible to the unaided eye under dark skies.”
Keep in mind that a variety of factors will determine visibility, such as the weather, light pollution, etc.
The first naked-eye observation of the comet was made on 16 January 2023, when it had an estimated magnitude of 5.4, according to the Comet Observation Database. [3]
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The green hue is likely due to the presence of diatomic carbon (dicarbon) around the comet’s head, and the way the molecule (C2) is blown apart when the comet nears the sun. [4]
Dicarbon is a green, gaseous inorganic chemical, and forms when two carbon atoms bond together.
The C2 molecule undergoes photodissociation after it evaporates from the nucleus, and it is this process that gives a comet a green glow.
It was only in 2022 that scientists solved the 90-year-old mystery of why comets’ heads are green, but never the tails. The discovery was made by a graduate student at MIT. [5]
The green comet was discovered as it was passing through Jupiter’s orbit on 2 March 2022.
Astronomers at the Zwicky Transient Facility – staff scientist Frank Masci and former postdoctoral scholar Bryce Bolin – spotted the comet while using a wide-field survey camera.
Professor Thomas Prince at Caltech’s Division of Physics, Mathematics and Astronomy said C/2022 E3 (ZTF) “was spotted because of its motion in a sequence of images taken” by Masci and Bolin.
The comet was initially classified as a meteor. Professor Prince said:
“At the time it was discovered, it was not known to be a comet. That came later after follow-up observations by many telescopes worldwide.” [6]
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[1] NASA JPL
[2] Neanderthal Extinction by Competitive Exclusion. PLOS ONE
[3] Comet Observation Database (COBS) [link temporarily unavailable due to global ransomware attack]
[4] Photodissociation of dicarbon: How nature breaks unusual multiple bonds
[5] MIT NEWS: Why are comet heads green — but not their tails?
[6] Caltech-Discovered Comet Makes an Earth Flyby
