Monday, November 16th 2020, 12:50 pm - A rarely-captured phenomenon sometimes accompanies bright Leonid meteors
If your skies are clear tonight, take an hour off to head outside, find a nice place to stargaze from, and sit back to watch the peak of the Leonid meteor shower.
Each year, throughout much of November, Earth passes through a stream of icy debris left behind by a comet known as 55P/Tempel-Tuttle. As the atmosphere sweeps up bits of dust and ice from the comet trail, these meteoroids flash through the air as bright meteors.
On or around the 17th of November, we pass through the highest debris concentration in the stream. This results in perhaps a dozen or so of these bright meteors streaking through the night sky every hour. This is the peak of the Leonid meteor shower.
The debris stream of Comet 55P/Tempel-Tuttle, orbiting the Sun in relation to the planets of the inner solar system. Earth and Earth's orbit are shown in light blue. Credit: Meteorshowers.org
The Leonids aren't usually a very strong meteor shower. The best of the year — the January Quadrantids, the August Perseids, and the December Geminids — all produce around 100 meteors per hour. In contrast, if you find a dark sky site, far from any light pollution, and you have a clear, moonless night, you may see around 15 Leonid meteors each hour.
Some years, dozens and sometimes hundreds of Leonids can streak across the sky. This is especially true right after Comet Tempel-Tuttle has made its most recent pass around the Sun. The last time this happened was right after the comet's 1998 perihelion (its closest point to the Sun in its orbit). In the years that followed, several outbursts were recorded by astronomers, including nearly 100 meteors during the peak of 2008.
Back in 1833, the Leonids even produced a famous meteor storm. One report from the time estimated that over 240,000 meteors were spotted throughout the night. At the same time, another said that the rate was over 100,000 meteors per hour for the 9-hour storm.
This wood engraving, from Adolf Vollmy's Bible Readings for the Home Circle, depicts the 1833 Leonids meteor storm.
We haven't seen anything like this storm in recent times. Also, more outbursts aren't expected from this shower until at least 2031. Still, this is a shower worthy of our attention, though.
One remarkable thing about Leonid meteors, though — they're exceptionally fast. Travelling at over 70 kilometres per second through the sky, they flash very brightly and, at times, show up multi-coloured! They are also known to produce a lingering phenomenon known as persistent trains.
A persistent train forms when a meteoroid travels so fast that it strips away electrons from the air molecules in its path. These ionized air molecules linger along the meteoroid's path, and each one emits a brief burst of light when it picks up a replacement electron to neutralize that ionization. This shows up as a wispy, dimly-glowing ribbon in the sky. Trains are known to persist for some time after the meteor has gone out — from minutes to hours!
Watch below: Rare persistent train meteor captured by Gemini Observatory over Mauna Kea
(Hat-tip to astronomer Daniel Moser for the video.)
Of the Fall meteor showers, the Leonids are the most well-known for producing persistent trains.
TIPS FOR STARGAZING & METEOR WATCHING
First, some honest truth: Many people who want to watch a meteor shower end up missing out on the experience, unnecessarily.
Since the Moon and most planets are so bright in the night sky, it's easy to fall into the expectation that watching a meteor shower will be just as easy. It takes a bit of travel and effort to get the most out of a meteor shower, but it is well worth it!
First off, there's no need to have a telescope or binoculars to watch a meteor shower. They'll actually make it harder to see the event because they restrict your field of view.
Here are the three 'best practices' for watching meteor showers:
- Check the weather,
- Get away from light pollution, and
- Be patient.
Clear skies are very important for meteor-spotting. Even a few hours of cloudy skies can ruin an attempt to see a meteor shower. So, be sure to check The Weather Network on TV, on our website, or from our app, and look for my articles on our Space News page, just to be sure that you have the most up-to-date sky forecast.
Next, you need to get away from city light pollution. If you look up into the sky, are the only bright lights you see street lights or signs, the Moon, maybe a planet or two, and passing airliners? If so, your sky is just not dark enough for you to see any meteors. You might catch a bright fireball, but there's no guarantee, and those are typically few and far between. So, get out of the city, and the farther away you can get, the better!
Watch: What light pollution is doing to city views of the Milky Way
For most regions of Canada, getting out from under light pollution is simply a matter of driving outside of your city, town or village until a multitude of stars is visible above your head. In some areas, such as in southwestern and central Ontario and along the St. Lawrence River, the concentration of light pollution is too high. Unfortunately, getting far enough outside of one city to escape its light pollution tends to put you under the light pollution dome of the next city over.
In these areas of concentrated light pollution, there are dark sky preserves. However, a skywatcher's best bet for dark skies is usually to drive north and seek out the various Ontario provincial parks or Quebec provincial parks. Even if you're confined to the parking lot after hours, these are usually excellent locations from which to watch (and you don't run the risk of trespassing on someone's property).
Sometimes, based on the timing, the Moon is also a source of light pollution, and it can wash out all but the brightest meteors. We can't get away from the Moon, so we can just make do as best we can in these situations.
Once you've verified you have clear skies and you've gotten away from light pollution, this is where having patience comes in.
For best viewing, you must give your eyes time to adapt to the dark. Give yourself at least 20 minutes, but the longer, the better. A fair warning: if you skip this step, you will likely miss out on a lot of the action.
During this adjustment time, avoid all bright light sources — overhead lights, car headlights and interior lights, and cellphone and tablet screens. Any exposure to bright light during this period will cancel out some or all the progress you've made, forcing you to start over. Shield your eyes from light sources. If you need to use your cellphone during this time, set the display to reduce the amount of blue light it gives off and reduce the screen's brightness as much as possible. It may also be worth finding an app that puts your phone into 'night mode', which will shift the screen colours into the red end of the light spectrum, which has less of an impact on your night vision.
You can certainly look up into the starry sky while you are letting your eyes adjust. You may even see a few brighter meteors as your eyes become accustomed to the dark. If the Moon is shining brightly, turn so that it is out of your personal field of view.
Once you're all set, just look straight up!