If you live in the northern and southern hemispheres and feel so inclined to engage in a little astronomy, this is a great weekend to do so. Between Saturday evening, October 20th, and just before sunrise Sunday morning, October 21st, the annual Orionid meteor shower – the offspring of Halley’s Comet are about to put on quite a show.
The best time to look is before sunrise Sunday, when Earth encounters the most dense part of Halley’s debris stream. Observing is easy: Wake up a few hours before dawn, go outside and look to the eastern sky. No telescope is needed. Here in Arizona, that will be before 6 a.m.
Locally, the meteorologists are suggesting that star gazers look to the south. They also predict clear conditions, so the viewing and the dancing is expected to be off the charts!
According to SpaceDex [Ref 1], the Orionids meteor shower has been observed for nearly 200 years, with the earliest sighting credited to E.C. Herrick of Connecticut, who in 1839, was the first individual to state that there is meteor activity annually around the 8th and 15th of October. Orionids is one of the top meteor showers to observe during the 4th quarter of the year, producing up to 20 green and yellow meteors per hour during its peak. Orionids appear every autumn, with about 20 or so meteors per hour. [NASA said the past few years have been more active, with about 60 per hour.] Orionids meteors are also known to be speedy, with meteors soaring through the night sky at approximately 66 km/s (147,638 miles per hour)—ninja reflexes are required to capture the magic on camera.
Most meteor showers are the product of earth passing into the dust particles of a comet. Many thousands of years ago, Halley’s Comet left a trail of dust behind as it traveled through space. The Orionids meteor shower takes place when earth travels right through that trail of dust and debris every year. What appear to be shooting stars are actually tiny grains of dust burning up in Earth’s atmosphere.
As a reminder, the definition of comet, meteoroid, meteor, and meteorite were covered in an earlier post, Mining for Asteroids (published May 2, 2012):
- comet is a relatively small, at times active, object whose ices can vaporize in sunlight forming an atmosphere (coma) of dust and gas, and sometimes, a tail of dust and/or gas.
- meteroid a small particle from a comet or asteroid orbiting the sun.
- meteor is the light phenomena which results when a meteoroid enters the earth’s atmosphere and vaporizes. A meteor is also referred to as a shooting star.
- meteorite is a meteoroid that survives its passage through the earth’s atmosphere and lands upon the earth’s surface, i.e. what’s left over after the meteor strikes the earth.
“In addition to Orionids, you can expect to see brilliant Venus, red Mars, the dog star Sirius and bright winter constellations such as Orion, Gemini and Taurus. Even if you don’t spy a meteor, the rest of the sky is dynamite,” according to a NASA press release.
1. Orionids Meteor Shower, http://www.spacedex.com/orionids/