The July Pegasids meteor shower

Key facts

Peak

around 10–11 July

Active

early to late July

Rate at peak (ZHR)

about 3

Speed

about 63 km/s

Radiant

Pegasus (about 5° west of the star Markab, Alpha Pegasi)

Parent body

Probably comet C/1979 Y1 (Bradfield)

Dates shift slightly from year to year. This year's peak is in the events calendar, and the meteor-shower planner shows how high the radiant climbs from where you live, night by night.

The July Pegasids are a small, swift shower that opens the summer meteor season, a few weeks before the Delta Aquariids, Alpha Capricornids and Perseids build up.

The parent comet. The stream is probably linked to comet C/1979 Y1 (Bradfield), one of 18 comets discovered by William Bradfield, an amateur astronomer in South Australia who searched the sky with a small telescope for decades. The comet takes roughly three centuries to go round the Sun, so it will not return until the late 2200s. The "C/" in its name marks it as a non-periodic or long-period comet, as opposed to "P/" for a periodic one, and "1979 Y1" means it was the first comet found in the second half of December 1979.

The radiant. The meteors appear to come from Pegasus, about five degrees west of Markab, the star at the south-western corner of the Great Square of Pegasus. In July the Square rises in the east in the late evening and climbs high by dawn.

What to expect. Only about three meteors an hour under a dark sky. The meteors are very fast, entering the atmosphere at over 60 kilometres per second, because the parent's orbit carries its dust head-on into Earth. Fast meteors tend to be short, quick streaks, and many July Pegasids are faint.

Viewing from the UK. The radiant is well placed after midnight. The problem is twilight: in early to mid-July the sky over Scotland and northern England never gets fully dark, so faint meteors are lost. Southern England is a little better.

Viewing worldwide. Because the radiant lies close to the celestial equator, the shower can be seen from both hemispheres. Southern hemisphere observers have long, dark winter nights in July, and the radiant rises in the north-east after midnight.

The July Pegasids are a good shower for learning to tell meteors apart by speed and direction, since few other showers are active so early in July.

Viewing tips

1. Watch after midnight, when the Great Square of Pegasus is high in the east.
2. Find Markab, the south-western corner of the Square, and look nearby.
3. Expect quick, short streaks: these are among the faster summer meteors.
4. From northern Britain, accept that twilight limits you to the brightest meteors.
5. Use the night to practise recording time, brightness and direction for later showers.