The Orionids come but once a year, and it has come around again! Here's how, when, and why to watch the meteor shower today, along with one other strange phenomenon that you may be able to catch alongside it.
Top image: Slooh Observatory composite of the Orionids shower
What are the Orionids?
The Orionids are made up from debris burning up in the atmosphere from Halley's Comet. The number of meteors you'll see during this shower varies quite a bit from year-to-year — and this year, quite frankly, may be a slightly thin shower. Slooh Observatory is predicting a peak of 30 meteors an hour (a respectable showing), while NASA estimates that we're going to peak at just a dozen meteors per hour this year. Compare that to the average of one hundred meteors per hour we glimpsed this past summer during the fast-falling Perseids.
Image: Halley's comet nucleus, shedding the debris that we'll see today as the Orionids / ESA
Still, even if the number of meteors isn't much to get jazzed about, what this year's Orionids lack in number, they make up for in a few other ways.
Smoke on the sky
Part of what makes this shower so enjoyable is the sky around it — with a radiant (the point where the shower appears to originate from our vantage point here on Earth) nestled in between two of the most easily recognisable constellations, Orion and Gemini.
But even more stunning is its speed. Orionid meteors are unusually quick, streaking across the sky at almost 150,000 mph, making them the second fastest meteor shower of the year (edged out just narrowly by the Leonids). Those short, quick trails of light are in themselves pretty cool, but they also mean that conditions are unusually good for catching an odd phenomenon: meteor smoke.
Sometimes, as it streaks across the sky, a meteor or fireball will actually explode. Sounds pretty dramatic — and it is, not because you can see the explosion though, but because it leaves behind a thick trail of ionized air in its wake (not actually smoke). This trail lingers in the air, actually being shifted around by atmospheric wind into wavy shapes that can last much longer than the original streak of the meteor, sometimes even minutes.
This can happen in a variety of different showers (like you see in the example from this summer's Perseids above). But meteor smoke is particularly likely to be observed when the meteors are moving at a very high speed — making today's meteor shower one of the best chances you'll get to catch sight of it, like in this stunning example from the 2012 Orionids:
So, How do I watch?
So how can you catch the Orionids, and all those spooky meteor smoke trails they may leave in their wake? It's pretty easy. There's just a couple things to keep in mind.
What time is the shower? You can catch the Orionids starting early Thursday morning (AU time) and continues throughout the day. NASA is predicting the heaviest fall during the middle of the day.
Wait, won't that be in Australia's daylight? Darkness is always, always the number one rule for good meteor shower visibility — but, because we live in Australia, we're out of luck here. So, if you're usually a backyard astronomer, this may be a good time to head over to the Slooh site at 11am AEDT, you'll see it!
Image: Orionid meteors in a curved lens view/ Brocken Inaglory