There is a chance, albeit a small one – that Earth may encounter a debris stream from comet 46P/Wirtanen between 10 – 12 December, the later date coinciding with the start of the Geminids peak.
This means we could see a brand-new meteor shower in 2023:
“New research has indicated that on 12 December 2023, the Earth may travel through a trail of dust left behind by Comet 46P/Wirtanen back in 1974,” explains Dr Darren Baskill, an astrophysicist from the University of Sussex.
A mysterious hyperactive alcohol comet
46P/Wirtanen is a short-period ‘Jupiter-family’ comet, which takes just 5.4 years to orbit the Sun. This family of comets are so named after Jupiter, because their orbits are primarily determined by the gravitational influence of the gas giant. More than twice as massive as all the other planets combined, Jupiter has a significant effect on bodies within the Solar System.
Comet 46P/Wirtanen is what’s known as a ‘hyperactive’ comet. This means that it shows more activity than expected (i.e., the comet is emitting more than expected), given the small size of its nucleus. It has an estimated diameter of 1.4km (0.9 miles), and narrow-band observations taken from the 2018 apparition suggest that 40 per cent of the nucleus surface is active.
Observations from the W. M. Keck Observatory on Maunakea in Hawaiʻi found that during the most recent approach in 2018, the comet was releasing unusually high amounts of alcohol. And, also unusually, that another process – beyond radiation from the Sun – was heating up the comet. Comet Wirtanen clearly has more secrets to reveal, and maybe future apparitions (the next closest approach in May 2024) will provide some answers.
The comet was the original target for ESA’s Rosetta spacecraft, however, due to the mission being delayed the original launch window was missed. A new target, 67P/Churymov-Gerasimenko, was established instead.
A new meteor shower from Comet Wirtanen?
Back in 1974 – and then again in 1980 – 46P/Wirtanen ejected a meteoroid stream, which previously had not intersected with the path of Earth’s orbit. Modelling by the IMCCE l’Observatoire de Paris has revealed, however, that there was an encounter in 2007 and 2018. An encounter with the stream is again predicted for December this year, when the Earth will pass through a denser part of the meteoroid stream.
It’s important to emphasise that this is based on modelling only; no meteor shower has so far been confirmed.
But the modelling reveals that meteors from 46P/Wirtanen are making it to Earth.
How to differentiate simultaneous meteor showers
So, if we do see a meteor shower – how can we differentiate these meteors from those of the Geminids?
We’ll be able to differentiate this shower from the Geminids by the radiant and velocity of the meteors observed. The radiant for this new shower will be near the faint constellation of Sculptor in the southern sky, and at around 15km/s (10.3 km/s before the influence of Earth's gravity), the meteors would be much slower than the Geminid meteors. The shower (if it occurs) is yet unnamed.
Dr Baskill shares some more tips on how to tell Geminid meteors from these potential ‘new’ meteors:
“Well, the Geminid meteors originate from the asteroid 3200 Phaethon, whose dust particles are much larger than the finer cometary dust. So, if you see a brighter meteor, it’s likely to be a Geminid shooting star originating from asteroid Phaethon, rather than the fainter meteors expected from Comet Wirtanen,” he explains.
Trusty Geminids to the rescue
But don’t worry if we don’t get a bonus meteor shower this year, as the year still has the most beautiful shower up its sleeve:
“While the number of meteors caused by this dust trail is very uncertain, it will almost certainly be overshadowed by the richest meteor shower of the year – the Geminid meteor shower,” says Baskill.
Why now?
So why haven’t we seen the shower from Comet Wirtanen before?
“While the dozen-or-so primary meteor showers have all been well-studied thanks to them occurring annually like clockwork, other meteor showers are much harder to predict,” says Baskill.
“This can be due to a range of reasons, including the orbit of the comet changing slightly over time, or the wind from the Sun gently blowing and moving these dust streams around.”
About our expert, Dr Darren Baskill
Darren Baskill is an outreach officer and lecturer in the department of physics and astronomy at the University of Sussex. He previously lectured at the Royal Observatory Greenwich, where he also initiated the annual Astronomy Photographer of the Year competition.
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