Stargazing during the Perseids
With the collaboration of Philippe Robert-Staehler, astronomy facilitator/guide at Parc national du Mont-Mégantic.
The starry sky offers a magnificent show. Humanity’s fascination with shooting stars is so ancient that we cannot precisely say how old it actually is. So fleeting and elusive, these fine beams of light lead us to eagerly scrutinize the sky as few other celestial objects do. To better admire them, here’s some information and a few tips.
What are shooting stars?
Shooting stars are fine trails of light that suddenly appear in the night sky only to disappear just as quickly. To be precise, these luminous trails are called meteors. In fact, they have nothing in common with true fixed stars, which are huge and very distant indeed.
This meteoric phenomenon is caused by the entrance into the earth's atmosphere of fine particles of dust which are adrift in space. As the Earth travels through the solar system at the breakneck speed of 108,000 km/h, these specks of dust are struck by our planet like snowflakes by a car. At such speeds, the pressure of the shock between the speck of dust and the atmosphere is so high that the air itself is heated to the point of emitting light. It's this illumination of the air that’s poetically called a “shooting star.”
What are the Perseids?
Sometimes shooting stars don't travel alone; dozens and even hundreds make their appearance during the same evening instead. We call this a meteor shower, the most famous being the Perseids of August. They’re so well known that the label “Perseid” is sometimes wrongly attributed to all shooting stars.
These events stem from the fact that there are denser dust clouds in certain places in the solar system and they are intersected by the Earth, causing a multitude of related shooting stars. Since our planet returns to the same place on its orbit around the sun every year, meteor showers return on an annual basis as well.
The name of this particular meteor shower comes from the fact that all trajectories of these meteors in the sky seem to originate at a specific point called the radiant. In August, this point of origin is located in the Perseus constellation, which is perceived as representing a Greek mythological hero.
When can we see the Perseids?
The Perseids can be seen from around July 20 to August 25, or thereabouts. However, at the beginning and end of this period, they are rare and must be differentiated by their trajectory from different families of shooting stars. There are Perseids a-plenty from August 10 to 15, with a peak in activity during the nights of August 12 and 13.
The number of shooting stars per hour can then reach 100. If you can't Perseid-gaze on the night that the showers reach their climax, don’t despair: the nights before and after are no less interesting!
The ideal time for Perseid-gazing is after midnight and just before the first light of dawn, because we are then on the side of the Earth facing the direction of its movement in the cloud of dust. Shooting stars can be observed late into the night… or into the early morning, depending on your point of view!
The moments of early evening also have their advantages. That's when we can see Earth- grazing shooting stars, those meteors that skim the atmosphere like pebbles that we bounce over the water and which have the particularity of creating very long trails.
How can we best observe the Perseids?
To observe the Perseids comfortably, safely, and productively, make sure that you’re properly prepared!
In practical terms, you need to be comfortably dressed and properly equipped for late-night stargazing so as to ensure a pleasant experience. You don't need astronomical equipment to observe a meteor shower; it’s actually detrimental because telescopes have a narrow field of vision which may cause you to miss meteors elsewhere in the sky.
The presence of a full moon will significantly reduce the number of visible shooting stars, while clouds will put an end to your shooting-star gazing for as long as they last. In both these cases, all we can do is adapt to the circumstances of the sky.
On the ground, choose an optimal and safe observation site. Here are some important criteria:
- Get away from urban centres, street lights, signs, home lights, and other sources of interference that will hide the sky.
- Stay clear of buildings, trees, and all other landscape elements that might block your view of the sky.
- As much as possible, find a place where the sky is free of clouds.
- If you spend several hours gazing, it would be worthwhile to prepare an observation post that won’t cause you to have regrets the next day.
You should also check out as wide a swath of the sky as possible in a single glance. Don't restrict yourself to an overly narrow segment. And don't stare at the spot where a shooting star has just been seen; the next one will probably not be in the same place.
The moral of the story
All this knowledge should not make you forget that the most important aspect of observing shooting stars is your own sense of wonder before this fabulous celestial show. Let yourself be blown away by meteors in all their flamboyance!