October 19, 2016 8:00 pm
This guest blog post is by Kirk Long, StarTalk’s newest intern. Kirk is majoring in physics while minoring in mathematics and piano at Idaho State University.
Halley’s comet reaches out to touch us on October 21st
The Orionids are the second major meteor shower in October, and they will reach their peak on the morning of October 21st. Unlike the Draconids earlier this month, the Orionids are best viewed during the predawn hours in the early morning. The Orionids are one of my favorite meteor showers because of their connection to Halley’s comet – one of the most significant and widely known comets. Although Halley’s comet won’t be returning to our solar neighborhood until the middle of 2061, each year we encounter some of its leftovers when they burn up in the October sky as the Orionid meteor shower. As the comet swings through the interior of the solar system it is rapidly heated by our sun, shedding layers of gas and dust behind it. Astronomers can predict pretty accurately when and where the Earth will collide with this trail, and also predict the rate of meteors you might see during each hour of observation – this year astronomers are forecasting 10-20 meteors an hour at the peak.
The Orionids are exceptionally fast moving meteors, which means that as they burn up they create a trail of ionized gas in the atmosphere that can glow for a few seconds after the meteor itself has disappeared. The reason these meteors are called the Orionid meteor shower (and not Halley’s meteor shower) is because the radiant – the area meteors in the shower appear to originate from – is contained within the constellation of Orion, specifically within Orion’s club. Meteors from the Orionids can and will appear anywhere in the night sky, but if you spot one and aren’t sure whether it’s an Orionid or not, a pretty accurate way to make sure you’ve seen a bit of dust from Halley’s comet and not just a random meteor is to “trace” the meteor’s path back across the sky and check to see if you end up near the radiant – this chart from EarthSky’s Guide to the Orionids does an excellent job of illustrating where to look.
The most important factor in viewing any astronomical event is having clear and dark skies – if you live in a place like Idaho (I do) just drive 20 minutes in any direction away from the city lights, but if you live in a more populated area (like my colleagues at StarTalk do) getting away from the lights might require a bit more planning. Unfortunately, this year the peak of the Orionids coincides with a waning gibbous moon that will be up all night, meaning some fainter meteors may be washed out in the glare of the moonlight no matter how far away from the city lights you are.
Calling the Orionids a meteor shower might be overselling them a bit – at a rate of 10-20 meteors an hour during the peak it’s closer to a meteor “drizzle” and the moonlight certainly won’t help things. Don’t let this discourage you, however, because witnessing a falling Orionid streak across the night sky is a must for any budding astronomer to check off his or her bucket list. In my experience, with modest meteor showers like this there’s less pressure to get out there on the night that everything peaks, and you can instead work viewing into your schedule without worrying about missing some crazy, spectacular, once in a million show. I would recommend waiting until a few days after the peak (the nights I’ve tentatively selected for my own observing – conditions permitting – are the nights of October 27 and 28) when the moon will be rising later in the morning. You won’t see 10-20 an hour, but just because it’s not the peak doesn’t mean there aren’t still sightings to be had.
To check conditions before observing, I use the “astronomer’s forecast”, and I also like to check the moonrise and set times. Temper your expectations – if you observe for an hour or two expect to see at least one but probably no more than six or seven – and remember to trace the path of the meteor backwards to make sure you saw a true Orionid.
What makes the Orionids special to me are their connection to Halley’s comet – when I see a bit of dust burn up in the night sky, I know that that dust came from not only the very beginnings of our solar system but was also connected to one of astronomy’s most influential innovators, Edmund Halley. Even if I only see one Orionid meteor, I can’t help but feel for a brief, ephemeral moment, a small personal connection across time and space to Mr. Halley. Carl Sagan once said (in his reflection on the famous Pale Blue Dot) that “astronomy is a humbling and character building experience” – to me, moments where we can appreciate a perspective outside our own – especially a cosmic perspective – are experiences worth losing a little sleep over.
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