The Earth is passing through the stream of particles left by Comet Tempel-Tuttle. Here’s how you can maximise your chances of spotting a Leonid this November.
The Leonids are underway and can be seen streaking across the night sky, clouds permitting. The Moon is waning, so interfering light from the Moon is becoming less as we approach the meteor shower's peak.
So, what’s the best way to maximise your chances of spotting a Leonid? What causes the Leonid meteor shower? And, when exactly should you look up to see it?
If you’re keen to make the most of the longer (if somewhat, colder) evenings, make sure you check out our astronomy for beginners' guide and our full Moon calendar. For a full roundup of this year's meteor showers, we’ve got all the essentials listed in our meteor shower calendar.
The Leonid meteor shower began on the 6 November and will continue through to the 30 November. The shower peaks on 17-18 November, when we can expect to see around 10 to 15 meteors per hour.
The Leonids have a relatively short period of activity of around three weeks, just under half that of the Orionid meteor shower that’s just come to a finish.
The best time to look up and maximise your chances of spotting a Leonid is between midnight and the hours before dawn, when Earth is facing the incoming meteoroids.
The radiant (the direction from which the meteors appear to originate) is in the large constellation Leo. Leo is located between the constellations Cancer and Virgo, and it’s easy to spot thanks to the distinctive backwards question mark comprising the face of the lion.
The Leonid meteor shower is best seen from the northern hemisphere, although they are also visible from the southern hemisphere. However, as Ian Todd, content editor for BBC Sky at Night magazine explains, you don’t actually need to locate Leo in order to spot a Leonid:
"I always thought that to see the Leonid meteor shower, you should find the radiant and then slowly look away from it. Then, any meteor you see that appears to be moving away from Leo is a Leonid.
"But, if you just look two-thirds of the way up in the sky in any direction, and if you see something, follow the trail back. If the trail went into Leo, then you've seen a Leonid meteor."
So don’t worry if your view of Leo is obstructed; the meteors will be visible across the night sky, cloud cover permitting. Looking away from the radiant will allow you to potentially see ‘longer’ meteors, as opposed to the shorter meteors you might spot nearer the radiant. This is due to an effect called ‘foreshortening’ – an optical illusion that causes a meteor’s train to look shorter because it is angled towards us.
The Leonids are a result of the Comet 55P/Tempel-Tuttle as it makes its journey around the Sun. As the Earth moves through the trail of dust and debris left behind by this comet, these particles interact with our atmosphere, producing a trail of excited atoms. This, in turn, produces the light we see as meteors or ‘shooting stars’.
In astronomical terms, Comet Tempel-Tuttle is a relatively small comet, with a nucleus of ‘just’ 3.6km. It has an orbital period of 33.22 years, so because it’s less than 200 years – that makes it a periodic comet. It last reached perihelion (the comet’s closest approach to the Sun) in 1998, and will return again in 2031.
In 2022, we are expecting to see around 10 to 15 meteors per hour, however light from a waning Moon (last quarter) may make viewing conditions difficult, though not impossible.
A rather exciting event happens approximately every 33 years. This is when debris from Comet Tempel-Tuttle produces a ‘meteor storm’, and hundreds (or thousands) of meteors can be seen streaking across the sky. The Leonids have been responsible for exceptional displays on previous occasions, the most recent being during the 1999-2001 meteor storm when viewers observed up to 3,000 meteors per hour! Sadly, in 2022 we are not due a meteor storm.
Numbers have fallen since the Millennium, and realistically in 2022, we’re more likely to see around 10 to 15 per hour. The strongest-ever meteor storm on record was in 1833 when stargazers were treated to a whopping 100,000 meteors per hour!
The Leonids are the fastest meteors ever recorded (around 70km per second), and often leave lingering trails. This year, the Leonids reach maximum activity on a waning Moon, in the last quarter of the lunar cycle. The Moon has around 43 per cent illumination on the 17 November, which drops to 33 per cent on the 18 November, so conditions are not ideal – but at least it’s not a full Moon.
If you can, find an area away from light pollution. Night temperatures on the 17-18 November are expected to be cool, around 7 to 10°C with a light cloud and gentle breeze in London – but remember to check your local weather forecast. Even so, be sure to wrap up warm, as you’re probably not going to be moving around much.
If the rain holds off, lie back in a reclining chair, hammock, or on a blanket, and let your eyes adjust to the darkness for around 10 to 20 minutes.
After a while, your eyes will become more accustomed to seeing meteor trails as they streak across the sky. Try not to look at other bright sources of light – such as your phone – during this time. If you do need to check something on your phone, use a red filter. This is because the rod cells in our eyes are not sensitive to red light, and therefore it doesn’t interrupt the accumulated night vision. Many astronomers use red light torches and filters for this reason.
Iain is the content editor for BBC Sky at Night magazine, writing regularly about meteor showers and stargazing events.