Halley's Comet meteor shower peaks Monday and Tuesday

Monday, October 20, 2014, 8:45 PM - After all the excitement this weekend about Comet Siding Spring's close flyby of Mars, why not get out and enjoy an amazing cometary show of our own, right here from Earth, as the Orionid meteor shower peaks over the next two nights.

Halley's Comet, perhaps the most famous comet of all, hasn't been seen since since the mid-1980s, and it won't be seen again until at least the year 2060. However, if you look up in the sky tonight and tomorrow night, you may be able to witness a little reminder of the comet's passing.

As this (or any) comet passes through the inner solar system, the heat from the Sun causes it to throw off gas, ice and dust into a large coma and a long debris tail. Even after the comet is long gone, though, that debris remains along the comet's orbit, like a stream running through space. If the debris stream happens to be close to Earth's orbit - close enough that the Earth plunges into it - those tiny bits of ice and dust enter the upper atmosphere travelling at tens of thousands of kilometres per hour, and they flash through the night sky as bright meteors.

Courtesy: Stellarium

Right now, Earth is passing through the debris left behind as Halley's Comet passed by Earth's orbit on its way towards perihelion (the point in its orbit where it's closest to the Sun). As the debris particles streak through the upper atmosphere, the meteors appear to originate from a point near the constellation Orion (the Hunter), and thus astronomers named this the Orionid meteor shower (or, if you prefer, just 'the Orionids'). There's also another meteor shower produced by Comet Halley - the Eta Aquariids in May - which is when Earth passes through the comet's trail from after perihelion, but that one doesn't put on as good of a show as the Orionids.

We actually entered the stream a few weeks ago, and we'll pass out of it sometime in early November. Over the next two nights, though, we are passing through the densest part of the debris, which produces the 'peak' of the meteor shower. During the peak, the Orionids produce about 20-30 meteors per hour, but some years (like 2007) we can encounter denser regions of the stream than usual, producing outbursts of up to 70 meteors per hour.

The video above, by Science@NASA, references the 2012 Orionids, but most of the information in it is still valid (except for the positions of the planets).

No matter what time zone you're in, the meteor shower this year will be going on from around 10 pm local time until dawn (when Orion is visible above the horizon until when the Sun washes out the sky).

The phase of the Moon, a thin crescent as it wanes towards New Moon (and a solar eclipse!) on Thursday/Friday, will make viewing easier, since it means nice dark skies until very early morning.

However, the amount of cloud overhead will certainly affect how much you'll see. It seems as though southern Ontario and Quebec, and southwestern British Columbia won't be so lucky for this show, as they'll mostly be overcast both nights. The rest of the country looks clear enough to potentially see something, though (check your local forecast before heading out, though). Another factor is the amount of light pollution inundating your region, as the constant glow from city lights causes the faintest meteors get 'washed out' and missed. Dark Sky Finder (click here) is an excellent resource for seeing exactly how much light pollution is affecting your area and where to go to escape it.