★ Lyrid Meteor Shower

The Lyrids are the first good meteor shower after the quiet weeks of late winter, and one of the oldest on record. They are not a rich shower: on a typical peak night you can expect a meteor every few minutes from a dark site. But they are reliable, April nights are kinder than January ones, and now and then the Lyrids surprise observers with a short burst of much higher rates.

Where the meteors come from

The Lyrids are dust from Comet C/1861 G1 (Thatcher), which A. E. Thatcher discovered on April 5, 1861. It is a long-period comet that takes about 415 years to go around the Sun, so it has been seen on only one visit and will not be back for centuries. Earth runs through its trail of grains every April, and they hit the atmosphere at about 49 km/s.

When to watch

The Lyrids are active from April 14 to 30, but rates are low except within a day or so of the peak around April 22. The table above gives the expected peak time and the Moon. The maximum shifts by a few hours from year to year and the best rates last only a few hours, so watch on the nights of April 21–22 and 22–23.

From mid-northern latitudes the radiant rises in the northeast in the late evening, and watching becomes worthwhile from about 10:30 p.m. It climbs to nearly overhead by the last hour or two before dawn, when rates are best. From the Southern Hemisphere it rises later and stays lower, so watch well after midnight.

How to find the radiant

Despite the name, the radiant at the peak is not in Lyra. It lies just inside Hercules, about 2 degrees from the Lyra border and about 8 degrees southwest of Vega, a little less than a fist's width at arm's length. Vega is the easiest guide: it is the brightest star low in the northeast in the late evening, and very high before dawn. From Vega, look toward the Keystone, the lopsided square of four stars that marks the body of Hercules. The radiant is about a third of the way from Vega to the Keystone.

What to expect

IMO gives a peak ZHR of about 18. With the radiant high before dawn, 10 to 15 meteors an hour is a good count from a dark rural site, and about 5 from the suburbs. IMO's analyses suggest that peaks arriving near the usual time tend to be stronger, around 23, while early or late peaks are weaker, down to about 14.

At 49 km/s the Lyrids are medium-speed meteors. Their population index (r = 2.1) means a good share of bright ones, with occasional fireballs, though they do not usually leave long, glowing trains. Outbursts have briefly reached 90 to 100 an hour, but they have not been predictable.

Viewing tips

• Make your main watch the last two or three hours before dawn, when Vega and the radiant are high.
• April nights can turn cold after midnight, so bring a warm jacket and a blanket to lie on.
• Look at a dark patch of sky some way from Vega, where Lyrids show longer paths.
• A wide-angle camera on a tripod, taking a long series of exposures, has a fair chance of catching a bright Lyrid.

History and notable displays

NASA traces the Lyrids back about 2,700 years, to a Chinese record from 687 BC, although one catalogue of historical Asian records assigns that sighting to the Eta Aquariids instead. NASA lists bursts of up to 100 meteors an hour seen in Virginia in 1803, Greece in 1922, Japan in 1945 and the United States in 1982, when IMO observers recorded a short-lived ZHR of 90.

IMO data show that the length of the peak varies as well as its timing: the period with more than half the peak rate has lasted anywhere from about 15 to 62 hours, averaging about 32.