Orionids

Lore & Background

Meteor showers were connected to comets in the 1800s. E.C. Herrick made an observation in 1839 and 1840 about the activity present in the October night skies. Alexander Herschel produced the first documented record that gave accurate forecasts for the next meteor shower. The Orionids meteor shower is produced by Halley's Comet, which was named after astronomer Edmund Halley and last passed through the inner Solar System in 1986 on its 75–76 year orbit. When the comet passes through the Solar System, the Sun sublimates some of the ice, allowing rock particles to break away from the comet. These particles continue on the comet's trajectory and appear as meteors when they enter Earth's upper atmosphere.

The meteor shower radiant is located in Orion about 10 degrees northeast of Betelgeuse. The Orionids normally peak around October 21–22 and are fast meteors that make atmospheric entry at about 66 km/s (150,000 mph). Halley's comet is also responsible for creating the Eta Aquariids, which occur each May as a result of Earth passing close to the descending node of Halley's comet. An outburst with a zenithal hourly rate of over 100 occurred on 21 October 2006 as a result of Earth passing through the 1266 BCE, 1198 BCE, and 911 BCE meteoroid streams. In 2015, the meteor shower peaked on October 26. Some Orionid showers have had double peaks, as well as plateaus of activity lasting several days.

Reader's Guide

The Orionids are notable as one of two meteor showers produced by Halley's Comet, the other being the Eta Aquariids. Historical outbursts occurred in 585, 930, 1436, 1439, 1465, and 1623. The Orionids occur at the ascending node of Halley's comet, which reached its closest distance to Earth around 800 BCE. Currently Earth approaches Halley's orbit at a distance of 0.154 AU (23.0 million km; 14.3 million mi; 60 LD) during the Orionids. The next outburst might be in 2070 as a result of particles trapped in a 2:13 mean-motion resonance with Jupiter. The shower's connection to Halley's Comet was established after meteor showers were linked to comets in the 1800s, with early observations by E.C. Herrick in 1839 and 1840 and the first documented accurate forecast by Alexander Herschel. The Orionids remain a reliably observed annual event, with occasional enhanced activity providing opportunities for study and public interest.