Unlike last year when a nearly-full Moon scuppered proceedings, tonight's Geminid meteor shower in 2023 is set to be spectacular. The Geminids peak on a new Moon, so conditions are good, and we may even start to reap the benefits of these crisp, cold nights; clear skies.
Make the most of it this year – because next year, in 2024, the Geminids peak on a full Moon – so it won’t be nearly as good. The Geminids are an excellent shower to get young astronomers involved in as the shower starts relatively early – around 9pm to 10pm – and they’re multicoloured!
So how do you spot a Geminid? How can you tell it apart from a sporadic or Andromedid? What causes the different colour meteors? Where in the sky do you look?
If want to plan ahead for upcoming meteor showers in the UK, be sure to read up on all the details with our comprehensive meteor shower guide, or if you’re looking for more stargazing tips, check out our astronomy for beginners guide.
When is the Geminid meteor shower 2023?
The Geminid meteor shower will peak tonight, Wednesday 13 December. The shower will remain visible until 20 December 2023, when it overlaps with the Ursid meteor shower.
The Geminids are a decent length, and one of the best and most reliable showers of the whole year. It’s also one of the most active, and has a peak that spreads over several nights between 12 – 15 December – helpful when trying to contend with ever-changing weather.
When is the best time to see the Geminid meteor shower?
Unlike other meteor showers, when there’s a short window for the definitive ‘best time’ to watch – the Geminids have a broad maximum. This means we’ve got more chances to spot some shooting stars:
“The Geminid meteor shower is arguably the best of the year. Its activity peak in mid-December is high, and also broad in terms of how long it lasts,” says veteran astronomer Pete Lawrence.
“During 2023, the Moon is new on 12 December, meaning it won’t interfere at all. Peak nights are 12/13, 13/14 and 14/15 December and given clear skies, there’s the potential for up to 12 hours of darkness each night,” explains Lawrence.
According to NASA, the Geminid meteor shower will begin around 9pm to 10pm on the nights that it’s visible, with the Royal Observatory Greenwich noting that it’s the one major shower that shows good activity before midnight.
How many Geminid meteors will you be able to see?
Under perfect conditions, the zenithal hourly rate, or ZHR of the Geminds will be 150. This means we could see a maximum of 120 to 150 meteors per hour at the peak. However, even with this year’s excellent conditions, the reality is likely to be less. Nevertheless, we can expect to see around 60 meteors per hour, or around one or two meteors a minute, from around 10pm-ish until dawn.
“At its peak, the Geminid’s zenithal hourly rate – the number of meteors you’d expect to see under perfect conditions – would be around 120 meteors per hour. In practice, the actual number will be lower than this, but still high enough to be impressive,” Lawrence says.
In relation to other meteor showers, the Geminids have a relatively moderate speed of 126,000km per hour (78,000 miles per hour), or 35 km per second (22 miles per second).
(The fastest meteors come from the Leonids in November, which are around twice as fast as the Geminids.)
When the Geminids were first observed in the mid-1800s, the showers were not nearly as impressive as they are today, yielding only around 10–20 meteors per hour. Since then, the shower has grown to around 120 meteors per hour, and is thought to still be intensifying every year.
Multicoloured meteors
The Geminids are bright, and can appear white, yellow, or green in colour, and occasionally even red, orange, or blue. This is down to the presence of metals that make up the debris, in much the same way we engineer fireworks to appear colourful when they explode.
The air a meteor is passing through also plays a role in the colour we see, but in general it’s the different chemical elements that produce different colours of meteors. As the meteor enters Earth’s atmosphere, these different chemicals ionise and emit light.
Most Geminid meteors will appear to be yellow or white in colour, which is indicative of a high iron/magnesium ratio, but we may also be able to spot some purple meteors from calcium-rich debris, or beautiful blue-green colours from magnesium.
Geminid meteor colours and what they mean
Yellow: Iron, magnesium
Green/blue: Nickel, magnesium
Purple: Calcium-rich
Blue: Magnesium-rich with ionised calcium
Red and orange: Sodium, potassium, nitrogen, oxygen
Where to look in the sky to see the Geminids
Meteor showers are generally named after the constellation in which their radiant is located.
The radiant for a meteor shower refers to the point in the sky from which the meteors appear to originate.
For the Geminids, they appear to originate from the constellation Gemini, however this not the actual ‘source’, it’s just how we perceive it from Earth:
“A perspective effect makes Geminid meteors emanate from a location close to the star Castor in the constellation of Gemini during peak activity,” says Lawrence.
To find Gemini, look for Orion the Hunter (check out our beginner’s guide to astronomy if you need a refresher), which is easily distinguishable by the three bright stars (Mintaka, Alnilam and Alnitak) that make up Orion’s Belt.
From Orion, look up and to the left – and you’ll see the two bright stars Castor and Pollux, high in the sky. These two stars represent each of the twins in Gemini. The Geminid radiant is just above Castor, which is the slightly fainter star of the two (Pollox is brighter and more yellow in colour).
Pro tip: Take in as much of the sky as possible
But to get the best chance at seeing the most meteors, try to take in as much of the sky as possible. Even though the meteors will appear to originate from Gemini, they will appear over the whole sky. Meteors further away from the radiant may appear to leave a longer trail, whereas meteors closer to the radiant can look shorter.
This is because, at the radiant, the meteors are angled towards us; known as ‘foreshortening’. So, for a chance to see meteors with longer tails (the result of travelling further distances away from the source), it’s best to look slightly away from the constellation.
How to increase your chances of spotting Geminid meteors
To make the most of this spectacular shower, if you can, find a dark location away from streetlights to minimise light pollution. Try to find somewhere you can take in as much of the sky in your field of vision as possible. Patience is key, as it may take some time for eyes to adjust to the darkness. A comfortable reclining position and warm clothing are advisable if you plan on spending any length of time in the cold night air.
And you don’t need any special equipment to observe the Geminids, as Lawrence explains:
“Activity occurs between 4-17 December. All you need to observe the shower is your eyes. Give them 20 minutes in darkness before starting a watch. Wrap up warm and use a sun-lounger or equivalent to lay back, looking up at an altitude of around 60 degrees (two-thirds up the sky), in any direction, south having some great stars and planets on view.”
If you have one to hand, a tally counter is a useful way to keep track of the number of meteors you see, especially when there’s likely to be as many as with the Geminids.
Why are the Geminids so good this year?
The Geminid meteor shower in 2023 promises to be the best of the year, due to the high number of meteors expected and favourable conditions. A moonless night coincides with the peak, providing optimal viewing conditions.
The only thing we’ll need to contend with is the weather:
“Some years are good for meteor showers, some not so good. The visibility and potential spectacle of such events is determined by sky quality, a function of the degree of light pollution, the Moon’s presence, and local weather,” says Lawrence.
“You can do something about light pollution and potentially the weather, by planning ahead and moving location if yours isn’t good. The Moon is less easy to deal with, and when big and bright in the sky will drown out all by the brightest meteor trails,” he adds.
So it’s very handy the Moon won’t be bothering us this year.
Where do the Geminids come from?
The Geminid meteor shower occurs when the Earth passes through a stream of dust and debris left behind by a comet or asteroid as it orbits the Sun.
But, unlike other meteor showers which favour debris from comets, the Geminids are a bit different:
“Geminid meteors have an odd source, being associated with asteroid 3200 Phaethon. Described as a ‘rock-comet’, this object has typically sand-grain sized particles strewn around its orbit which, when they encounter Earth’s atmosphere, vaporise to produce a meteor trail,” explains Lawrence.
When the Geminid meteor shower reaches its peak between 12 – 15 December, that’s when we’re passing through the densest part of the stream.
3200 Phaethon is unique, not only because most meteor showers are caused by debris from comets, rather than asteroids, but there’s another reason. Its orbit brings it closer to the Sun than any other asteroid.
A mystery to be solved
Technically, 3200 Phaethon is a near-Earth asteroid, but as it exhibits properties from both asteroids and comets, many refer to it as a ‘rock-comet’ or sometimes even a ‘dead comet’. It takes just 1.4 years to orbit the Sun.
A recent study published in The Planetary Science Journal suggests that it has a tail made of sodium gas, rather than dust as previously thought. (For comparison, most asteroids do not form a tail as they approach the Sun because they are mainly comprised of rock.)
So if Phaethon has a sodium tail, how does it create the Geminids? Is it possible that some time in the past, Phaethon ejected dust and other material that makes up the dust stream that causes the Geminids?
DESTINY+, a mission currently planned for 2025 aims to find out.
The spacecraft is currently being developed by the Japanese space agency JAXA, and will perform a flyby of Phaethon, as well as collecting samples of the dust stream. The mission will also demonstrate technologies that will enable future low-cost and high-frequency deep space exploration.
About our expert, Pete Lawrence
Pete Lawrence is an experienced astronomer, astrophotographer, and presenter on BBC's The Sky at Night. Watch him on BBC Four or catch up on demand with BBC iPlayer.
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