meteor shower

Comet Swift-Tuttle by Nathalie Ouellette

False colour image of Comet Swift-Tuttle taken with the Spacewatch Telescope. Credit: Jim Scotti, University of Arizona

False colour image of Comet Swift-Tuttle taken with the Spacewatch Telescope. Credit: Jim Scotti, University of Arizona

As you may know, we are right in the heart of the Perseid meteor shower. You can all thank Comet Swift-Tuttle for this beautiful annual spectacle! This comet, that is 26 km in diameter, has been observed for many thousands of years by ancient as well as modern astronomers, and has a fairly stable and well understood orbit. It was rediscovered in 1992, when it last made its closest approach to the Sun, at which point many thought it might be an impact risk to the Earth during its next approach on August 14th 2126. Its orbit has since been recalculated, and chances of an impact occurring are thought to be extremely low.

However, it is the largest Solar System object that makes repeated close passes of Earth. With its size and velocity, a collision with Swift-Tuttle would have approximately 27 times the energy of the K-T event impactor, most commonly known as the cause of the extinction of the dinosaurs. It is for this reason that many astronomers consider Comet Swift-Tuttle to be the single most dangerous object known to humanity. Marvel at the awesome power of the Universe! For more factoids on Swift-Tuttle and the Perseids, visit Space Magazine.

Meteor Showers! by Nathalie Ouellette

The 2012 Geminids over South Dakota. Image credit:  David Kingham .

The 2012 Geminids over South Dakota. Image credit: David Kingham.

Meteor showers are some of the most beautiful sights one can see with their naked eye, and they have the marked advantage of appearing at almost the same time every year! Very young, we’ve learned to call these luminous streaks across our sky shooting stars, but they are not stars at all, but rather flaming space debrsi! Every year, around 15,000 tonnes of these debris, from sand grain sized to boulder sized, enter the Earth’s atmosphere. As they burn up, they leave behind brightly visible paths. While few meteors survive their journey and fall to the ground as meteorites, most are completely destroyed before impact. 

A few times a year, these shooting stars happen in swarms, sometimes inundating our skies at a rate of up to thousands of meteors per hour! In such impressive cases, they are called meteor storms rather than simple showers. But why do we witness sudden surges of shooting stars at the same time every single year? The answer is comets! We all know about comets: icy bodies orbiting around our Sun, periodically appearing in our skies as bright tailed objects. The trajectory of some of these comets crosses the trajectory of Earth’s orbit. Obviously, the comets and Earth do not cross this point at the same time or that would mean bad news for us! However, comets do leave behind long-lasting trails of debris into which Earth passes once a year, like clockwork. Some of these particles crash through our atmosphere and delight us in the form of a meteor shower. The intensity of each meteor shower depends on the density of the particle cloud leftover by the comet, the position of other planets in our Solar System, the intensity of the Sun’s activity and many more complex variables. Luckily, there are over 50 meteor showers every year, many of which are visible to the naked eye so there’s always a chance to spot a shooting star. The two most prominent showers are the Perseids in mid-August and the upcoming Leonids in mid-November!