April brings the Lyrid meteor shower, which peaks on the night of April 21/22, although some meteors will be visible between 16 – 26 April. The usual peak rate of meteors from this shower is not much more than the background rate – 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. Try to have Vega at the edge of your field of view – dress warmly and plan to head outside for at least 30 minutes. This will allow your eyes to adjust to the darkness. Optical instruments are not needed to go meteor hunting – the flashes of ‘falling stars’ are so quick that you wouldn’t be able to get a telescope or set of binoculars turned in time.
The source of the shower is Comet Thatcher – discovered by A.E. Thatcher 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 49 km/s (that’s over 170 km/h) and disintegrate as streaks of light–meteors!
The Lyrids are particularly interesting for a couple of reasons. First, observations have been identified back to 687 BC – which is longer than any other meteor shower. Second, the meteor shower occasionally experiences an outburst to around 100 meteors per hour. The shower is also a source of the occasional fireball – larger meteors that can cast brief shadows and leave a trail in the sky.
There were outbursts in 1803, 1922, and 1982. A newspaper in Richmond, Virginia on April 23, 1803, described the outburst 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 recognized as having an origin beyond the Earth 80 or so years later.
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 22 years and don’t see a major outburst. Just look out this weekend for a few bright meteors amongst the April showers.
This article has been updated and adapted from a “What is the Stars” episode, first broadcast on Lyric FM in April 2011. Featured image is of the Perseid Meteors.