The Daytime Arietids meteor shower

Key facts

Peak

around 7 June

Active

mid-May to late June

Rate at peak (ZHR)

about 30 (radio rates higher); few seen by eye

Speed

38 km/s

Radiant

Aries (close to the Sun in the sky)

Parent body

Probably part of the Machholz complex (linked to comet 96P/Machholz and families of sungrazing comets)

Dates shift slightly from year to year. This year's peak is in the events calendar.

The Daytime Arietids are among the strongest meteor showers of the whole year, yet almost nobody sees them. Their radiant lies only about 30 degrees from the Sun, so it is above the horizon mainly during daylight, when the meteors are invisible to the eye.

Discovery by radar. The shower was discovered in 1947 at Jodrell Bank in Cheshire, where Bernard Lovell's team was using radar left over from the Second World War to study meteors. Radar detects the trail of electrically charged gas, or ionisation, that a meteor leaves in the upper atmosphere, and it works by day as well as by night and through cloud. The discovery of strong daytime showers in June 1947 showed that a large part of the meteor population had simply been missed by visual observers.

The parent. The Arietids share orbits with a family of objects called the Machholz complex. Its best-known member is comet 96P/Machholz, which passes very close to the Sun every five years or so. The complex also includes two groups of sungrazing comets, the Marsden and Kracht families, small comets seen by solar observatory spacecraft as they skim the Sun. The Southern Delta Aquariids belong to the same complex. Which body is the main parent is not settled.

What to expect by eye. Just before dawn, the radiant rises in the east about an hour ahead of the Sun. A few Arietids may then be seen as earthgrazers: meteors that skim the upper atmosphere almost horizontally, leaving long, slow-looking trails. Rates are low, perhaps one or two in a session.

Radio observing. Radio is the best way to follow this shower. Amateur observers tune a receiver to a distant transmitter just below the horizon and listen for brief reflections from meteor trails. The Arietids blend with the Daytime Zeta Perseids in early June, producing strong radio activity for several days. The shower peaks around 7 June, sometimes a day or so later.

Viewing. In the UK, short June nights mean twilight is already bright when the radiant rises, so visual sightings are rare. Tropical observers have a slightly better chance.

Viewing tips

1. Use a radio receiver to detect this shower by day or night.
2. Look low in the east in the hour before dawn for long earthgrazing meteors.
3. Never look towards the rising Sun, and stop observing well before sunrise.
4. Compare radio counts on 6–9 June with a quiet week to see the shower clearly.
5. Remember these meteors share the sky with the Daytime Zeta Perseids at the same time.

Read about the parent: Comet Machholz, and the other comets behind meteor showers.