Stargazers will have a prime opportunity this week to witness remnants of Halley’s Comet as the annual Orionid meteor shower reaches its overnight peak on Oct. 21 and Oct. 22.
Every October, Earth plows through a cloud of cosmic dust shed by the famous comet during its journeys around the sun. When these sand-grain-sized fragments collide with the upper atmosphere, friction and rapid compression heat the surrounding air, generating narrow streaks of luminous plasma known as shooting stars.
How and when to watch
Under pristine conditions, skywatchers can expect to see between 10 and 20 meteors per hour during the peak. However, catching the display will require careful timing because of moonlight.
A bright waxing gibbous moon will illuminate the sky for most of Wednesday night, washing out many of the fainter meteors. Outlets reported varying estimates of the moon’s brightness, with Space.com citing a 74 percent illuminated lunar disc and Sky & Telescope reporting an 82 percent gibbous moon in Aquarius. Stargazers will get their best views after the moon sets, which occurs around 3 a.m. local time, leaving a dark window of nearly three hours before twilight begins.
Astronomers recommend finding a safe, open viewing area far from city streetlights. Telescope or binoculars are unnecessary, as meteors move too quickly to track through lenses. Observers should give their eyes 20 to 30 minutes to adapt to darkness and recline on a lounge chair with warm clothing and blankets.
Origin and ancient history
Halley’s Comet travels in a retrograde orbit, moving around the sun in the opposite direction of the planets. Because its scattered particles also move in retrograde, Earth meets the debris nearly head-on at roughly 18 1/2 miles per second. The dust grains slam into the atmosphere at about 148,000 miles per hour, or 66 kilometers per second, making the Orionids among the fastest meteor showers of the year.
While meteors can streak across any part of the sky, their paths trace backward to a radiant point near the club of the constellation Orion, just above the bright red supergiant star Betelgeuse. Experts suggest looking 40 to 90 degrees away from Orion, where meteors leave longer, more vivid glowing trains.
The Orionid stream is ancient. According to Sky & Telescope, researchers traced the current stream to an encounter between Halley’s Comet and Jupiter roughly 23,000 years ago. Historical records show observers in China and Japan recorded strong Orionid activity as early as 585 A.D., while Western astronomers including American researcher Edward C. Herrick formally documented the shower during the 1830s.
Other sights in the predawn sky
The shower remains active each year from Oct. 2 through Nov. 7, providing alternate viewing opportunities on neighboring mornings if clouds interfere with the peak. Early risers watching the sky this week can also spot Mars and Jupiter climbing above the eastern horizon.
Astronomers note that observers should also glance at Betelgeuse itself. Sky & Telescope reported that European researchers recently observed the red supergiant fading to magnitude 1.0, raising questions about whether the star is entering another significant dimming phase similar to its historic drop in brightness between 2019 and 2020.
