April brings the Lyrid meteor shower, which peaks on Thursday April 22, although some meteors will be visible between the 16th and 26th this month. The usual peak rate of meteors from this shower is not that much – typically 10 to 15 per hour, although the meteors can be both bright and long lasting.
Lyrid meteors appear to stream from the bright star Vega in the constellation Lyra – look high to the east after midnight to see Vega. The meteors may appear anywhere in the sky, and are best seen late – try looking for them from 2 am. But the Lyrids have nothing to do with Vega. The source of the shower is Comet Thatcher – discovered by A E Thatcher from New York City in 1861. Every year in April, the Earth plows through Thatcher’s drawn-out dusty tail. Flakes of comet dust, most no bigger than grains of sand, strike Earth’s atmosphere travelling really fast and disintegrate as streaks of light–meteors!
The Lyrids are particularly interesting for a few reasons. First, observations have been identified back to at least 2600 years – back to 687 BC – which is longer than any other meteor shower. Second, the meteor shower occasionally experiences an outburst of about 100 meteors per hour. And the shower is a source of the occasional fireball – larger meteors that cast shadows for a split second and leave behind smoky debris trails that linger for minutes.
The historical references to the Lyrids are interesting: a newspaper in Richmond, Virginia on April 23rd, 1803, described the shower as follows:
“Shooting stars. This electrical phenomenon was observed on Wednesday morning last at Richmond and its vicinity, in a manner that alarmed many, and astonished every person that beheld it. From one until three in the morning, those starry meteors seemed to fall from every point in the heavens, in such numbers as to resemble a shower of sky rockets…”
It’s worth noting that the “electrical phenomenon” is the actual meteors – they were only recognised as having an origin beyond the Earth 80 or so years later.
Most recent outbursts were in 1803, 1922, and 1982. But making predictions for when the next outburst will occur has been really tough. The outbursts occur when Earth moves through an unusually dense clump of comet debris. But with the actual time period of this meteor stream unknown, and with few observations, either visually or by radar, astronomers have not been able to accurately calculate where and when the next clump of comet stuff will hit us. Some have worked out the next outburst of activity is due in 2040 – but predictions in the past have turned out to be wrong – so don’t panic if you head out in 29 years and don’t see a major outburst. Just look out this week for a few bright meteors amongst the April showers.