The First Meteor Storm In 20 Years May Be Coming, Or Not
The 2013 Leonid meteor shower was not a patch on the storm exactly 12 years before, but still produced photos like this. This month could see arguably the most spectacular astronomical event in two decades, a complete no-show, or something in between. On a clear night under a dark sky, you'll probably get to see a few meteors on any given night. Meteor showers are measured by the Zenith Hourly Rate (ZHR), the number one might see without clouds or light pollution if the point of origin was directly overhead. Meteors occur when bits of dust or gravel hit the Earth's atmosphere, burning up in the process.
When comets or asteroids break up, bits of rock are left scattered across a patch of the Solar System. After a comet's dissolution, these patches start small and concentrated. The Tau Herculids (named after a star in the direction from which they initially appeared to come) are among the youngest meteor showers, left behind as Comet 73P/Schwassmann–Wachmann 3 broke up in 1995. The components of Comet 73P/Schwassmann-Wachmann 3 photographed by the Hubble telescope in 2006. Calculating the exact location of such patches is tricky, although it has improved a lot in recent years.
South Americans will see fewer meteors, since the radiant point will be low in the north, but can be more confident the Sun will have set when the storm occurs. Meteor showers or storms lose much of their dazzle in moonlight, but so soon after a new moon that won't be a problem for this event. The 2001 Leonid storm lasted several hours, but the Tau Herculids are expected to be much shorter – perhaps only 15 minutes – if there's a storm at all.
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