They return year after year, and for many of us, they spell holidays and warm summer nights. But who — or what — are they? The Perseid meteors, of course!
Each year around mid-August, Earth passes close to the orbit of periodic comet 109P/Swift-Tuttle, whose wake is peppered with billions of dust particles that give rise to the famous Perseid meteor shower. However, the quality of the celestial show varies dramatically from year to year, mainly as a function of Earth’s distance from the densest parts of the particle stream, but also as a function of the Moon’s presence.
The Perseids in 2024
The Perseids will take place under very good astronomical circumstances in 2024. The “classic” maximum of this shower is expected between 9 a.m. and noon (Eastern time) on August 12, which means daytime in North America. However, observations from the last few years show there is some variability in the moment Earth comes closest to the dust stream from comet Swift-Tuttle, which swings through the inner Solar System every 133 years.
Considering the time of expected maximum, the most favourable night for observers in Eastern Canada will be August 11 to 12, with the previous and next nights being very good alternatives if the weather doesn’t cooperate. This year the first quarter Moon occurs on August 12; because it sets around 11 p.m., it will be out of the way during the most favourable hours of the night, when the radiant is highest in the sky during the second half of the night until dawn. Under clear, reasonably dark skies with good transparency, away from light pollution, one could expect to count up to 50 Perseids per hour on the morning of August 12. Let’s hope for great weather for the occasion!
Note that secondary maxima have also been detected in recent years, among which a brief but intense burst of Perseids that sometimes appears one and a half days after Earth crosses the nominal centre of the meteor stream: Watch for this possible enhanced meteor activity after midnight on August 13 to 14. In 2024, Earth is also expected to cross several very ancient dust filaments between midnight and 7 a.m. on August 12, but the intensity and duration of the resulting spikes of activity is extremely difficult to predict—so keep your eyes open! Observations spanning several days are needed to study this complex meteor stream, which is still full of surprises.
The Perseids are active from the end of July through the third week of August, though at much lower rates. The radiant of this meteor shower emerges above the northeast horizon during the evening and climbs higher in the sky during the night. This explains why the number of meteors steadily increases on a given night, until daybreak puts an end to your observing session. Don’t forget your wish list!
The outlook for 2025 is a bit dire: intense light from the waning gibbous Moon will interfere with the meteors after it rises around 10 p.m.
