Watch for shooting stars this weekend if you're vacationing away from the city lights — you may be able to catch some fireballs from the Perseid meteor shower before they get washed out by the brightest supermoon of the year. And you may also spot meteors from another shower that's underway, the Delta Aquariids.
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The Perseid meteor shower takes place each August as the Earth passes through debris left by the Comet Swift-Tuttle. It peaks each year from Aug. 11 to 13 - conveniently when many people are camping or cottaging away from city lights, and summertime temperatures make it a pleasure to lie outside beneath the starry sky. At the peak of the Perseids, skywatchers can usually expect to see around 120 meteors per hour, including many fireballs brighter than the planet Venus… But maybe not this year.
The meteors are best seen when the sky is dark – fainter meteors tend to be washed out by light, whether from city street lamps or natural sources such as the full moon.
Unfortunately, this year's Perseid peak almost exactly coincides with a full moon, and not just any full moon. It's a supermoon – a full moon that can be up to 14 per cent bigger and 30 per cent brighter than a regular full moon.
The Aug. 10 supermoon isn't just any supermoon, either – it's the second and the brightest of three in a row.
Because the moon's orbit around the Earth is elliptical and lopsided, it's 50,000 kilometres closer to the Earth on one side of its orbit than the other. Full moons that take place when it's at or close to the perigee, the point in the moon's orbit when it's closest point to Earth, look bigger.
While moons are considered supermoons if they take place on the same day as the perigee, the Aug. 10 one will take place during the same hour, "arguably making it an extra-super moon," according to NASA Science News.
The supermoon and Perseid peak at the same time have prompted some astronomers to recommend you start looking for the Perseids early this year.
"Late July and early August may be your best bets for meteor-watching in 2014, likely better than the moon-drenched mornings of the Perseids’ peak on Aug. 11, 12 and 13," wrote Bruce McClure and Deborah Byrd in the 2014 meteor shower guide for the astronomy news website EarthSky this week.
The good news is there's evidence the Perseid meteor shower is already ramping up. Seven Perseid fireballs — meteors brighter than the planet Venus — were detected on Wednesday alone by NASA's all-sky fireball network, a group of 12 cameras designed to detect and count fireballs.
The Perseids have a relatively broad peak compared to other meteor showers, with enhanced activity "often covering a week or more," wrote amateur astronomer David Dickinson on the astronomy website Universe Today.
Also, another summer meteor shower, the Delta Aquariids is well underway and just past its official peak of July 29 to 30. While that meteor shower is best seen in the southern hemisphere and its meteors tend to be fainter, five of its fireballs were captured by the all-sky fireball Wednesday along with the seven Perseid fireballs.
According to McClure and Byrd, the Delta Aquarids lack a definite peak, but "amble along fairly steadily throughout late July and early August."
This weekend's meteor viewing should also be enhanced by the fact that the moon will set around midnight on Friday and Saturday.
Generally, the best time to view meteor showers is in the two hours before dawn. The Perseids should appear to come from close to the constellation Perseus in the north-northeast sky, while the Aquariids will originate in the southern sky.