Modest but reliable, the annual Leonid meteor shower returns this week. Take an hour or two to relax and enjoy the show.
As the country buckles down yet again due to new COVID-19 restrictions we need face-time with the stars more than ever. The Leonid meteor shower presents an opportunity to relax and forget the stress while watching fragments of Comet 55P/Tempel-Tuttle flash overhead.
The annual meteor shower peaks on Tuesday morning, November 17th, under a moonless sky. While the Leonids are known for great storms of meteors that occur approximately every 33 years, most years — this one included — produce 10–15 per hour. Though modest, the Leonids are ever-reliable. The best time to watch will be between 2 a.m. and dawn when Leo climbs up into the eastern sky. Meteors will stream from a point called the radiant located inside the Sickle of Leo, a familiar asterism that resembles the farming tool used for hand-cutting grain.
The Leonids originate from Comet 55P/Tempel-Tuttle, a small comet that measures 3.6 kilometers across and orbits the Sun every 33 years. It last reached perihelion (its closest approach to the Sun) in 1998 and will do so again in 2031, when meteor counts are expected to bump up to around 100 per hour. Every mid-November the Earth plows through the trail of dusty debris left behind by the comet. Dust particles strike the atmosphere at high speed, where they're heated to more than 3,000°F and briefly incandesce. Simultaneously, the object's rapid passage ionizes the air along its path, causing it to luminesce. Together they create the familiar flash of a meteor.
No Equipment Needed
One of the joys of meteor-watching is that no equipment is required unless you count a comfortable reclining chair. That's why I encourage families to include their children in the activity. And while the hour is early, we're all stuck at home anyway due to the pandemic. You can try to catch a little shut-eye later in the day. Rise early and spend an hour with the shower, dressed warmly of course! I always wear gloves and lined boots and then cover myself in a thick blanket. Cozy is high on my list when it comes to meteor showers.
You can face any direction you like to see the Leonids, but I prefer to look 45° to one side of the radiant, either northeast or southeast. From this viewpoint you'll see a mix of short-trailed meteors near the radiant itself and long "streakers" peeling off to either side. To maximize your shower enjoyment watch from the least light-polluted place you can find. If you can't leave home and your neighbor's yard light is a problem, this would be an excellent opportunity to walk over and politely ask if they might turn it off for just one night.
While you're out under the stars waiting for the next meteor, you're bound to notice other things the same way hunters do when they spend a day in a deer stand. For example, you might see the slow movement of the constellations from east to west, a simple fact that confounded generations of humanity until Copernicus set things straight in the 16th century. Incredibly, I'm writing this while whirling to the east at 1,142 kilometers per hour. To find out how fast you're spinning, use this calculator.
Float Away with the Stars
In the wee hours, the slow westward drift of the stars begins to retire wintertime constellations like Orion and Taurus and introduce spring groups like Virgo, Corvus, and Boötes in the eastern sky. Both Venus and Mercury join the vernal scene at the start of morning twilight. Look closer, and you'll see that Venus is in conjunction with Virgo's brightest star Spica on November 17th.
Two fists to the upper right of the radiant in the faint constellation Cancer, you might notice a puff of light or hazy spot. That's the Beehive Cluster, or M44, one of the brightest star clusters in the sky but a little too far away (about 577 light-years) to discern any of its approximately 1,000 stars with the naked eye. In binoculars it's a completely different story! Three fists below the Beehive you'll see the solitary bright star Alphard, the heart of Hydra, the Water Snake. Alphard is an orange giant star about 50 times larger than the Sun. Can you detect its color? The Sun will appear nearly the same color when it evolves into a giant star in about 5 billion years.
How quickly our perception of time and space changes when we spend an hour watching a meteor shower. Maybe that's the reason seeing a speeding scratch of light is so exciting — while you've been mellowing to slower celestial cycles something so sudden jars the senses. And Leonids certainly can catch you by surprise. They're among the fastest of all meteors with speeds around 71 kilometers per second (160,000 miles per hour), twice the velocity of December's Geminids.
Cometary particles enter the atmosphere and burn up in the mesosphere, between 80 and 120 kilometers above the ground. Most visible Leonids range in size from 1 millimeter to 1 centimeter. The vast majority of meteors are only the size of sand grains. Larger ones produce the brilliant fireballs for which this shower is famous.
Because of their great altitude, meteors don't normally produce audible sounds, but there are anecdotal reports of hisses, pops, and rustling noises. Very Low Frequency (VLF) radio waves may resonate with objects in the environment like dried leaves and grasses to produce the sounds. A more recent theory proposes radiative heating from especially brilliant fireballs as the mechanism.
Hear Meteors Here
Either way, if it's cloudy Tuesday morning, there's another way to "observe" the Leonids. Listen to them! The trails of ionized air make ideal if brief reflective surfaces for radio waves in the 50MHz band used by ham radio operators. Go to LiveMeteors.com, turn up your audio, and click the play arrow on the screen to hear the low whistle of incoming meteors in real time. If you listen during the peak of the shower, return during an off-time to compare the results. I stopped there several days ago and heard a variety of fascinating whistles, some brief and others more nuanced.
Approximately every 33 years Earth passes through denser filaments of Tempel-Tuttle dust that were emplaced during previous visits of the comet — the sky literally rains with meteors. During the 1966 storm, meteor counts briefly reached 10–20 meteors PER SECOND over Western North America. The 2001 Leonid storm with its numerous fireballs remains the top meteor shower of my life. Studies have shown that no Leonid storms will occur in either 2033 or 2066 (darn!). The next potential storm isn't due until 2099. Seize this meteoric moment.