Astro Cat Explains… Meteor Showers
There are two well-known meteor showers visible in the sky from late July until mid-August. But what makes these tiny rocks light up our night skies every year? The Prof is on hand to explain all, and it starts with asteroids and comets…
Asteroids can be found anywhere in the solar system, but you’ll find most of them in the asteroid belt between Mars and Jupiter. Asteroids are simply rocks, which have been around since the beginning of the solar system but weren’t used up to form the planets. Many rocks in the early solar system were pulled by the Sun’s gravity into spinning spheres like Earth and Mars, but these rocks got left out. An asteroid may range in size from just 1 metre across to the dwarf planet Ceres, which is 975km across!
Unlike asteroids, comets are icy bodies. They mostly exist in the Kuiper Belt and Oort Cloud, much closer to the edges of the solar system than the asteroid belt. That’s why they’re so icy – the Sun’s light and heat simply cannot reach them! However, some comets may be nudged or pulled by the gravity of another large object (like a planet), and begin a journey towards the inner solar system. These comets develop their own orbits, that may take hundreds of years to complete each time. And whenever a comet gets too close to the Sun, it begins to melt, leaving a huge icy tail behind it. Sometimes, you can even see them in the night sky.
So how do meteors reach us?
Some people are afraid that the Earth is constantly in danger of being hit by an asteroid, or an icy comet. However, large space rocks are very rare – and the Earth is bombarded by tiny ones all the time! Most do not even hit the surface of the Earth itself: they burn up in the atmosphere. This is what you are seeing when you watch a meteor shower. For example, when Halley’s Comet passes through the inner solar system every 75 years or so, the Sun melts and breaks off some of its matter. These tiny particles are scattered around the solar system, and when Earth comes into contact with them, they burn up brightly in our atmosphere. This gives us the Orionid shower in October, as well as the Eta Aquarids in May.
When are the next meteor showers?
Although moonlight can sometimes make meteors appear dimmer and less obvious in the skies, we should have some good opportunities in the second half of 2017. On the 27-30th July, the Delta Aquarids will be shooting across the sky. You’ll have the best chance of seeing them south of the equator, but they will be visible every in the early hours of each morning. But these meteors aren’t alone: The Perseids start in late July too, and peak in mid August!
You can learn more about asteroid and comets, and the solar system as a whole, in the book Professor Astro Cat’s Frontiers of Space (where this post’s awesome artwork comes from!), and in our app Professor Astro Cat’s Solar System. Happy stargazing!