The Perseids meteor shower peaks tonight. If the storms hold off, one meteor should be visible every two minutes for five hours after midnight.  

Across the northern hemisphere we’re treated to the Perseids meteor shower every August. Many of the tips for observing the meteors are fairly self-explanatory.

For example, avoid looking at your phone so your eyes adjust to the dark night sky. 

But what is it that causes a meteor shower? And why do we see the Perseids every August? Here’s a brief guide to the science behind your stargazing.

What is a meteor?

Firstly, I should make it clear that observing a meteor shower isn’t really stargazing at all. What we see shooting across the sky is, in fact, comet dust. 

Comets orbit in highly elliptical paths. That is, if Earth’s route is almost circular, a comet moves along tracing more of a squashed circle. Because of this, their distance to the Sun constantly changes. When passing near to the Sun, the icy, rocky comet heats up and partially vaporises.

Photo by Vincentiu Solomon

Once a comet completes many orbits, it leaves a path of small debris in its wake. A meteor shower occurs when Earth passes through this path. The Perseids meteor shower takes place as we travel through the comet Swift-Tuttle’s orbit, and it doesn’t matter if the comet itself is nowhere nearby. 

Since we know when our orbit crosses the paths of comets in our solar system, it is easy to predict meteor showers. Our spectacular crossroads with Swift-Tuttle happens every August, but there are many others throughout the year. 

How big are meteors? 

Not very. In fact, most of the pieces are as small as a grain of sand. The reason we spot them is the burst of light produced when the meteor burns up in the atmosphere. 

If you’ve ever thought sand on the beach was scorching, consider this: a hot meteor can briefly exceed 5500°C. To help put that number into perspective, that also happens to be the surface temperature of the Sun.

Great balls of fire

While most meteors are minuscule, occasionally slightly larger chunks of cometary material are found in the debris. 

When these hit the Earth’s atmosphere, a fireball is created. These brighter explosions of light also last a little longer and may even be spotted by those of us who live glued to our phone screens. 

Photo by Luca Micheli on…

Weather permitting

Of course, seeing anything is dependent on the clouds staying away. If that fails, Italian astronomer Gianluca Masi is here to save the night. His Bellatrix Astronomical Observatory is hosting a live virtual telescope viewing of the Perseids meteor shower for those struck by bad weather. 

And if naturally occurring meteors aren’t exciting enough, Japanese company ALE (Astro Live Experiences) is planning to paint the sky with artificial ‘shooting star’ pellets by 2023. Over 400 years since Guy Fawkes, fireworks are finally getting an upgrade. 

Until then, we’re left with the natural wonders. Whether you observe with your eyes or virtually, understanding the science of tonight’s meteor shower will no doubt help bring it to life. 

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