The Orionid meteors are debris from Halley’s comet. Every October they become visible for several nights when the Earth intersects Halley’s orbit. At peak, if the night is dark and cloudless, up to 70 meteors an hour can be seen.
This year, prime viewing times are likely to be the nights of October 20, 21, and 22 – Friday, Saturday, and Sunday – although they are likely to remain visible, if less frequent, as late as November 7. The best times are between 2am and 5am.
The meteors are called ‘Orionids’ because from the perspective of Earth-based observers they appear to originate within the constellation Orion. This is easy to locate in the sky: most people can pick out the line of three stars known as Orion’s Belt.
If you then look a bit to the left you’ll see a very bright star, known as Betelgeuse. The origin site of the Orionids, known as the “radiant”, is just to its north.
Knowing this, however, is pretty much irrelevant for amateur astronomers. The meteors themselves don’t really show up until they have moved roughly 30 degrees from the radiant point.
By that stage, they will be zipping all over the place, in every direction. Choosing an observation point that offers a panoramic view of the sky is a good idea.
The meteors become visible when they collide with the Earth’s atmosphere, about 100 kilometres up, at a speed of approximately 66 kilometres per second. About half of them will produce a trail of ionised gas that will linger for several seconds after impact.
If the weather is kind, a very early morning (or very late night) spent lying on a blanket and staring at the stars could deliver the best free entertainment of the year.
Andrew Masterson is a former editor of Cosmos.
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