2012 peak of the Orionid meteor shower

The Orionid meteors are debris left behind in the orbit of Comet Halley.

Very conveniently, the Orionid meteor shower in 2012 will be at its best during a weekend, on the mornings of Saturday, October 20 and Sunday, October 21.

The annual Orionid meteor shower is coming. This shower is expected to rain down its greatest number of meteors before dawn on Sunday, October 21, but the day before (Saturday, October 20) may be nearly as good. Remember, it’s difficult to predict meteor showers with absolute precision. Best yet, the waxing crescent moon will set at relatively early evening, leaving a dark sky for this year Orionid meteors!

Watch for the Orionids between midnight and dawn

As usual, the best time to watch the Orionid meteor shower will be between the hours of midnight and dawn. Keep in mind that the moon is waxing crescent, so it sets during the evening hours. But the Orionids don’t really begin to streak the nighttime sky until late evening, and they tend to increase in number in the wee hours after midnight and before dawn.

You might see some meteors on either side of the peak mornings, too, or during this week leading up to the peak.

Although we hear lots of reports from people who see meteor showers from yards, decks, streets and especially highways in and around cities, the best place to watch a meteor shower is always in the country.

Just go far enough from town that glittering stars, the same stars drowned by city lights, begin to pop into view. City, state and national parks are often great places to watch meteor showers. Try googling the name of your state or city with “city park” or “state park” as a search term. Just be sure to go early in the day and find a wide open area with a good view of the sky in all directions.

Meteors in annual showers are named for the point in our sky from which they appear to radiate. The radiant point for the Orionids is in the direction of the constellation Orion the Hunter. Hence the name Orionids.

If you trace the paths of these Orionid meteors backward, they do seem to stream from the constellation Orion. But you don’t need to know this constellation to see the meteors. The meteors often don’t become visible until they are 30 degrees or so from their radiant point – and remember, they are streaking out from the radiant in all directions. So the meteors will appear in all parts of the sky.

That’s why it’s best to find a wide-open viewing area than to look in any particular direction. Sometimes friends like to watch together, facing different directions. When somebody sees one, they can call out “Meteor!”

How many Orionid meteors will I see?

The word shower might give you the idea of a rain shower. But few meteor showers resemble showers of rain.

Meteor showers are nearly always more subtle than that, and the Orionid shower isn’t as rich a meteor shower as, for example, the Perseids in August or the Geminids in December. On years when the moon is out of the sky during the shower’s peak, you can expect to see about 15 to 20 meteors per hour at the peak. In 2012, the moonless sky will bring the fainter Orionids into view and increase the number of meteors you see.

Orionid meteors are known to be fast and usually on the faint side. But the Orionids can sometimes surprise you with an exceptionally bright meteor – one that would be visible, even in a light-polluted city – that might break up into fragments.

For me … even one meteor can be a thrill. But you might want to observe for an hour or more, and in that case the trick is to find a place to observe in the country. Bring along a blanket or lawn chair and lie back comfortably while gazing upward.

What are meteors?

Meteors are fancifully called shooting stars. They aren’t really stars. They’re space debris burning up in the Earth’s atmosphere.

The Orionid meteors are debris left behind by Comet Halley. The object at left isn’t a meteor. It’s that most famous of all comets – Comet Halley – which last visited Earth in 1986. This comet leaves debris in its wake that strikes Earth’s atmosphere most fully around October 20-22, while Earth intersects the comet’s orbit, as it does every year at this time.

Particles shed by the comet slam into our upper atmosphere, where they vaporize at some 100 kilometers – 60 miles – above the Earth’s surface.

The Orionids are extremely fast meteors, plummeting into the Earth’s atmosphere at about 66 kilometers – 41 miles – per second. Maybe half of the Orionid meteors leave persistent trains – ionized gas trails that last for a few seconds after the meteor itself has gone.

Bottom line: In 2012, the Orionid meteor shower is expected to rain down its greatest number of meteors before dawn on Saturday, October 20, or Sunday, October 21. A waxing crescent moon will set at early evening so – if you watch between midnight and dawn on those mornings – you should see some meteors!

- EarthSky