Meteor showers to watch out for during July

July marks the start of meteor season with an increase in the number of active showers, including the return of the Perseids.

A montage showing two bright Perseid meteors captured in 2018. Image credit: Paul Sutherland

The Perseid meteor shower builds to a peak on August 12-13 which unfortunately, in 2019, will be severely hampered by a near-full Moon.

Two other meteor showers have much lower peak rates than the Perseids, but reach maximum activity at more favourable times when moonlight will not interfere.

They are the α Capricornids, which officially became active on July 3 and can be seen until August 15. The shower has a prolonged peak centred on the night of July 29-30, 2019.

At its peak, the number of meteors reaches a low rate (ZHR) of only 5 per hour under ideal conditions, but a feature of the α Capricornids is that it produces many bright fireballs. You probably won’t want to sit out waiting to see one, but be prepared to spot one while out and about, or maybe set up a camera to try to catch one.

The radiant of the α Capricornids lies only 10° south of the celestial equator, in the constellation of Capricornus, which means the meteors may appear and be seen from any parts of the world while the radiant is above the local horizon.

The meteors are produced by a small, faint comet called 169P/NEAT which orbits the Sun once every 4.2 years. They appear slow-moving across the sky as they enter the atmosphere at a velocity of around 24km per second (15 miles per second).

The second of our meteor showers is the Southern Delta (δ) Aquariids. These have higher rates (ZHR) under ideal conditions of 16 meteors an hour on the might of maximum, which is again July 29-30, 2019.

The Xs mark the positions of the radiant of the α Capricornids and the Southern δ Aquariids on July 30. The radiants actually move position across the sky during the weeks either side of the peak date. Chart by Skymania, using Cartes du Ciel,

The radiant, in the constellation of Aquarius, lies further south in the sky. Thus the shower is best seen for those at more southerly latitudes, though meteors may be seen from any part of the world where the radiant lies above the horizon.

Meteors from the δ Aquariids are medium-fast, entering the atmosphere at around 41km per second (26 miles per second). The comet that supplies the dust particles producing these meteors is believed to be periodic comet 96P/Machholz.

The third meteor shower to become active in July is one of the best known because of its high rates around maximum. We’re talking about the Perseids, which are produced by the dust left by Comet 109P/Swift-Tuttle.

Though maximum does not occur until towards the end of the second week in August, the first Perseids may be seen as early as July 17, according to the International Meteor Organization. (In fact, recent research shows that Perseids have been caught on camera in early July).

A diagram illustrating the radiant effect of the Perseids. Credit: Skymania.com

You can’t expect to see anything like as many in July as the 80-100 an hour (the ZHR) at an ideal maximum. However, this year the Perseid maximum is very badly affected by a near-full Moon whose brightness will drown out all but the brightest meteors.

So, all things considered, you may well be better off watching for Perseids in the latter part of July or August when skies will be darker.

What with the α Capricornids and Southern δ Aquariids both at their peak in moonlight-free late July, and the Perseids also building in activity at that time, it could be the ideal time to do a meteor watch in 2019!

Related: A simple guide to observing meteors

Related: How to photograph a meteor shower


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