The spring months can be a quiet time for meteor spotters, but we do have one worthwhile shower in April and that is The Lyrids. The Lyrids shower is active from 14th - 30th April. As with almost all of the regular meteor showers, this one is caused by the debris stream left behind by a comet (the exceptions being the Quadrantids and Geminids which are caused by asteroid debris). As tiny particles of comet debris burn up in our atmosphere, it causes a meteor or “shooting star”.
The comet responsible for the April Lyrids is C/1861 G1 (Thatcher) which is a long period comet. As the name suggests, long period comets take a long time to revisit the inner solar system, usually between 200 – 10,000 years; Comet Thatcher has a period of 415 years. Although the rates aren’t high for this shower, it is the strongest annual meteor shower from a long period comet. The Lyrids shower has been observed for 2,705 years; the exact origin of it was traced back to observations made by Chinese astronomers and were dated 16th March 687 BC.
The peak of the Lyrids this year is expected at 7pm BST on 22nd April, and there will a 36 hour period where rates are highest. This means your best observing times are on the nights of 21st / 22nd April and 22nd / 23rd April. The Moon is around First Quarter during the peak, so the best time for observing will be after midnight once the Moon has set. By this time the radiant will be 60 degrees above the horizon so the rates will be higher.
The zenith hourly rate for the Lyrids is consistently around 20 meteors per hour, but every 60 years it can get an outburst of activity. In 1922 and 1982 there were rates of 90 meteors per hour reported and in 1803 there as many as 700 per hour reported! Sadly, this year it is not forecast to produce an outburst. Remember that a “Zenith Hourly Rate” (ZHR) assumes that the observer is in a dark sky location, that the radiant is at the zenith (the point the directly above your head), and that the observer can see in all directions. Obviously even under ideal circumstances we cannot see the entire sky at once, so a ZHR of 20 will translate to seeing at most around 10 meteors per hour.
Observing meteor showers is always better from a dark sky site, but this is really essential with the Lyrids because many of them are quite faint, around mag +2. But that said, about a quarter of them leave a persistent trail so they are fun to observe. And there is always a chance of a larger piece of debris causing a Lyrid fireball, as seen in this amazing photo by Brian Emfinger taken on 22nd April 2012.
The name given to a regular meteor shower depends on where the radiant lies. Meteors that belong to a particular meteor shower all seem to originate from the same point in the sky if you trace the path back. The radiant for this shower lies close to the bright star Vega in the small constellation of Lyra. But when observing a meteor shower, looking directly towards the radiant is not necessary; meteors may occur anywhere in the sky. At least 45 degrees away from the radiant and about 45 degrees above the horizon is the best position to observe and is also a good place to point your camera if you want to try and capture photos of Lyrid meteors.
There is another minor shower which slightly overlaps with the Lyrids, and that is the Eta Aquarids. Although predominantly a southern hemisphere shower, Eta Aquarid meteors, which are caused by debris from Comet 1P/Halley, can be seen from the northern hemisphere, so if you do see a meteor during the peak of the Lyrids, don’t just assume that it is a Lyrid that you’ve seen; check it’s path back across the sky to see where it originated. It may surprise you to learn that there is a second Lyrids meteor shower. The June Lyrids was only discovered in 1966 by Stan Dvorack and is a minor shower which is active between 10th – 21st June. It is a minor shower with a ZHR of 8 – 10 meteors per hour. These meteors are caused by debris from comet C/1915 C1 Mellish.
On 24th April in 1874, during the Lyrids peak, Professor Scharfarik from Prague, Czechoslovakia made a really interesting observation. At the time he was observing the daytime First Quarter Moon through his 4” refractor telescope when he saw an “apparition on the disc of the Moon of a dazzling white star” which was described as “quite sharp and without a perceptible diameter”. This could have been a head-on meteor spotted during the daytime through the telescope, or it may have been a TLO (transient lunar object) in the form of larger Lyrid meteorite impacting the lunar surface. Although the rates aren’t that high, the Lyrids are still well worth going out and observing because one the most predictable things about meteor showers is how unpredictable they can be. You may just be lucky and see something as unusual as Professor Scharfarik did!
Astronomy Now Magazine – April 2018 issue
Sky at Night Magazine – April 2018 issue