The Eta Aquariids meteor shower
Key facts
- Peak
- around 5–6 May
- Active
- about 19 April to 28 May
- Rate at peak (ZHR)
- about 50 (varies from year to year)
- Speed
- 66 km/s
- Radiant
- Aquarius (near the star Eta Aquarii)
- Parent body
- Comet 1P/Halley
Dates shift slightly from year to year. This year's peak is in the events calendar.
The Eta Aquariids are pieces of the most famous comet of all. Comet Halley, officially 1P/Halley, returns to the inner Solar System about every 76 years, and each visit leaves a fresh scattering of dust along its orbit. The Earth passes close to that orbit twice a year. In May we meet the Eta Aquariids, and in October we meet the Orionids, so these two showers are made of the same comet's crumbs.
The shower is named after Eta Aquarii, a star in the constellation of Aquarius, the Water Carrier, close to where the radiant sits at the peak. It was recognised as a distinct shower in the late nineteenth century, and its connection to Halley's orbit was worked out not long after. The last time Halley itself passed the Sun was in 1986, and it will next return in 2061, but the dust it has left over thousands of years continues to reach us every spring.
Fast and graceful. Eta Aquariids hit the atmosphere at about 66 km/s, among the fastest of any annual shower. Fast meteors are often bright and frequently leave trains, glowing streaks that can hang in the sky for a second or more after the meteor has gone. Because the radiant rises only shortly before dawn at many latitudes, many of the meteors you see skim in at a low angle, producing long, slow-looking paths across the sky. These are called earthgrazers, and they are some of the most beautiful sights a meteor watcher can enjoy.
What to expect. The shower has a broad maximum spread over several days around 5 to 6 May, so you do not need to catch an exact hour. Its strength varies from year to year, and some years bring noticeably higher rates; studies of Halley's dust suggest that the Earth sometimes encounters denser parts of the stream. Under good conditions in the southern hemisphere, observers might see 30 or more an hour in the last hours before dawn.
Viewing from the UK. This is the hardest major shower to see from Britain. Aquarius rises in the east only a short time before dawn, and in May the sky starts to brighten very early, especially in Scotland. The window between radiant-rise and twilight is narrow, so expect to see only a handful of meteors, mostly long earthgrazers. The best chance is in the south of England, looking east and south-east in the hour or so before dawn, with a clear, low horizon.
Viewing worldwide. The Eta Aquariids are one of the best showers of the year for the southern hemisphere and the tropics. From Australia, New Zealand, southern Africa and South America, Aquarius climbs high before dawn and the nights are long and dark in May. It is one of the strongest showers of the year there. In the northern hemisphere, places further south such as the southern United States, the Mediterranean and India do better than northern Europe.
Peak dates shift slightly each year, and the shower's broad maximum means several mornings around the peak can be worth trying.
Viewing tips
- Watch in the last two hours before dawn, when the radiant in Aquarius has risen highest before the sky brightens.
- From the UK, choose a site with a clear, low eastern horizon and expect only a few meteors.
- Look out for long, slow earthgrazers skimming low across the sky.
- Try several mornings around the peak, because the maximum is broad.
- In the southern hemisphere, treat this as one of the year's best showers.
Read about the parent: Halley's Comet, and the other comets behind meteor showers.