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Northern Perseids battle the moon

Medusa is conquered, but how will the Perseids fair with the moon? wallyg/flickr

Over in the northern hemisphere, where summer is in full swing, it’s the time of the Perseids meteor shower. Generally it’s their best shower of the year, with 100 meteors predicted each hour over August 12-13.

It’ll be fewer this year, as the meteor shower is happening just after full moon. But can we see any of the action from here in Australia?

The Perseids are linked to the constellation of Perseus. This is a northern constellation, so it’s difficult to view from the southern hemisphere. But for those in northern Australia it does appear briefly above the horizon during August. It can be seen low in the northern sky from around 2am until dawn.

From Darwin at 4am, Perseus and the radiant for the meteor shower can just be seen above the horizon. Museum Victoria/Stellarium

Fortunately, the early hours of the morning are also the best time to see meteors. This is because our part of the Earth will be oriented to face the forward direction of the Earth as it orbits the sun.

It’s a bit tricky to visualise, so imagine for a moment that the Earth is a car driving around the sun. At sunrise we are looking out of the windscreen, facing the direction the “Earth-car” is travelling. But at sunset, we are looking out of the car’s rear window and seeing where we’ve been.

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That’s what makes dawn the best time to see meteors because we are meeting them head-on.

The other thing you want is for the radiant to be high in the sky, because then you can see meteors travelling in all directions. Since Perseus is low in the north, we’ll really only see those that are travelling away from the horizon.

However, it has been known for some long-pathed Perseids to be seen from southern Australia, appearing to come from a point below the northern horizon.

A bright Perseids fireball manages to beat the light of the moon on August 11. NASA

But what will really subdue the Perseids this year is that the shower’s peak is occurring a few days after full moon (and it was a super one at that!). Some of the fainter meteors are sure to be lost as their light will be drowned out by the moon brightening up the sky. Predicted rates for the shower are expected to max out at 30 meteors per hour.

The good news is that Perseids are often fast, bright and frequently leave persistent trails. In fact, the shower often produces very bright meteors known as fireballs. NASA has been tracking fireball activity across the US since 2008 and have shown that the Perseids produce the most fireballs of all the usual meteor showers.

Rate of fireballs measured by NASA’s All Sky Fireball Network. NASA

What I find interesting is that the Geminids come a close second. This is a great meteor shower for us in the southern hemisphere as it occurs during our summer around mid-December and we can easily see the constellation of Gemini.

After all, one of the important things to remember about meteor showers is that, at best, you only see a meteor every few minutes or so. What you really want is to enjoy a summer’s night out camping under the stars and appreciating the view.

While those in the northern hemisphere can spend a summer night watching out for the Perseids, the best thing for us might be to tune into a live broadcast, such as that from Slooh, which will start at the reasonable hour of 9am (AEST) August 13. And keep an eye on to see what NASA’s All Sky Fireball Network sees as well.

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