Astronomer Mark Thompson is getting ready to observe a meteor shower this weekend, and so should you.
- The Lyrids are notoriously unreliable, but the shower will peak in the early hours of Sunday morning.
- As the comet C/1861 G1 Thatcher orbits the sun, it leaves a dusty trail in its wake, producing the Lyrids.
It's been observed annually for over 2,500 years, with some years more spectacular than others. Each year, the April sky brightens around 21/22nd of the month with light from the Lyrid meteor shower and, of all the showers, this one is perhaps one of the most unreliable.
This year, the shower peaks around 3 a.m. (GMT) on April 22 and as a bonus, the moon is well out of the way so the sky will be nice and dark, granting us ideal meteor spotting conditions.
Nearly every meteor shower, and there are about 20 good ones each year, is the result of the Earth moving through the orbit of a comet. In the case of the Lyrid shower, it's the orbit of comet C/1861 G1 Thatcher and, as it continues on the 415 year orbit around the sun, it sheds material.
At the core of the comet is a solid nucleus that is made up of ices and rocks and for most of its life it's lurking in the cold depths of the Solar System reaching the outermost point at 110 times the distance between the Earth and sun -- around three-times the distance that Pluto orbits the sun.
When it returns to the warmth of the inner solar system, the heat of the sun warms the cometary ices, turning them from a solid straight into gas -- a process known as sublimation. The escaping gas helps to dislodge some of the dust and rock in the nucleus leading to a trail of debris along its orbit.
When the Earth moves through the comet's orbit it sweeps up the debris and as the particles impact our atmosphere we see them as meteors or "shooting stars." It's this process that means the best time to observe meteor showers is during the early hours of your location almost regardless of the exact time of the peak. This is because you will be on the forward-facing side of the Earth as it enters the cloud, almost like the front of your car getting covered by flies as you drive through a swarm.
The peak activity is determined by the density of the cloud of debris and it's at this point that the most particles will hit the Earth. To see the best display of any particular shower you need your 'early morning' to coincide with hitting the densest part of the debris. However, unfortunately, it's very hard to determine the exact point where peak activity occurs. For this year's Lyrids, peak is expected between 3am and 9am (GMT) on the 22nd, so if this coincides with your morning, you should be in a good place for a reasonably good show.
The real beauty of meteor showers is that they require no equipment to enjoy; just wrap-up warm and gaze up at the sky.
The meteors will all seem to come from the constellation of Lyra, hence their name, but the best way to see them is look up at the sky, in a direction that isn't toward Lyra and wait. Good luck!