Tonight – the night of April 20-21, 2016 – the Lyrid meteor shower is picking up steam, yet under the light of an almost-full waxing gibbous moon. On a dark, moonless night, this shower may offer 10 to 15 meteors per hour at its peak. The maximum number of Lyrid meteors may well rain down during the predawn hours on April 22, though the full moon will probably wash out the show. The shower’s radiant point is just to the right of the beautiful blue-white star Vega, which is the brightest light in the constellation Lyra the Harp. Vega should be bright enough to overcome the glare of the bright moon.
What is a radiant point? If you trace the paths of these Lyrid meteors backward on the sky’s dome, you’ll find that they appear to originate from near Vega, which is the heavens’ 5th brightest star. It’s from Vega’s constellation Lyra that the Lyrid meteor shower takes its name.
You don’t need to identify Vega in order to watch the Lyrid meteor shower. The idea that you must recognize a meteor shower’s radiant point in order to see any meteors is completely false. Any meteors visible the sky often appear unexpectedly, in any and all parts of the sky.
However, knowing the rising time of the radiant point helps you know when the shower is best in your sky. Assuming you’re in the Northern Hemisphere, Vega rises above your local horizon – in the northeast – around 9 to 10 p.m. local time. It climbs upward through the night.
The higher Vega climbs into the sky, the more meteors that you are likely to see. By midnight, Vega is high enough in the sky that meteors radiating from her direction streak across your sky. Just before dawn, Vega and the radiant point shine high overhead. That’s one reason the meteors will be more numerous before dawn – at least on a night when the moon isn’t washing out meteors.
Note for Southern Hemisphere observers: Because this shower’s radiant point is so far north on the sky’s dome, fewer Lyrid meteors are visible from southerly latitudes. Bu if you’re game, try watching between midnight and dawn on April 22.
So why near Vega? Why do the meteors radiate from this part of the sky? The radiant point of a meteor shower marks the direction in space – as viewed from Earth – where Earth’s orbit intersects the orbit of a comet. In the case of the Lyrids, the comet is Comet Thatcher. This comet is considered the “parent” of the Lyrid meteors. Like all comets, it is a fragile icy body that litters its orbit with debris. When the bits of debris enter Earth’s atmosphere, they spread out a bit before they grow hot enough (due to friction with the air) to be seen. So meteors in annual showers are typically seen over a wide area centered on the radiant, but not precisely at the radiant.
In a good year, you might see as amany 20 meteors per hour in a dark, moonless sky. That’s in contrast to the year’s best showers – the Perseids of August and Geminids of December – both of which typically produce about 60-120 meteors per hour.
Still, the April Lyrids can surprise you. They’re known to have outburts of several times the usual number – perhaps up to 60 an hour or so – on rare occasions. Meteor outburts are not predictable. So – like a fisherman – you must take your lawn chair, a thermos of something to drink, whatever other gear you feel you need – and wait. You’ll be reclining outside in a dark location, breathing in the night air and gazing up at the starry heavens. Not a bad gig.
Bottom line: On any clear night around April 20-23, 2016, the Lyrid meteor shower will kick off at late evening, though under the glare of the bright moon. That’s true no matter where you are on Earth, but – since the radiant point of the shower is so far north – meteor numbers will be reduced for Southern Hemisphere observers. The dark hour before dawn will be best for all observers. In 2016, the peak of the Lyrid shower is predicted to come at the same hour as the full moon.