One of the best fall meteor showers peaks this week, when pieces of the famous Halley's Comet streak across Earth's atmosphere as fast-moving "shooting stars."

The Orionid meteor shower will peak overnight Wednesday (Oct. 21) through Thursday (Oct. 22), potentially producing around 20 meteors per hour under a dark sky, according to Time and Date. The Orionids are caused when Earth passes through the debris left by Halley's Comet, which last passed through the inner solar system in 1986 and will return in 2061.

Halley's Comet is presently beyond the orbit of Neptune, according to The Planets Today, but it doesn't need to be close to Earth to cause "shooting stars." Every time the comet travels through the inner solar system, heat from the sun causes it to shed dust and rocky particles along its orbital path. Earth's own orbit takes the comet through streams of that ancient debris several times a year, with the particles vaporizing as they slam into our planet's atmosphere.

The Orionids are particularly fast meteors, striking Earth's atmosphere at around 41 miles per second (66 kilometers per second). They can produce bright streaks, occasional fireballs (extremely bright, sometimes colorful meteors) and "persistent trains" — glowing trails that remain visible briefly after a meteor has disappeared. The best way to view them is with the naked eye, although a nice pair of stargazing binoculars or a small backyard telescope will help you enjoy more sights during peak skywatching season this fall.

Halley's Comet produces not one but two annual meteor showers. Its orbit comes close to Earth's at two different points, so our planet encounters the comet's debris twice each year — once during the Orionids in late October, and again during the Eta Aquariid meteor shower in early May.

There's a slight complication with the Orionids this year. A 71%-illuminated waxing gibbous moon will brighten much of the night, making it harder to spot meteors. However, the moon will set early Thursday morning, creating a valuable window of darkness before dawn. That's also when the constellation Orion will be high in the sky, making the predawn hours the best time to watch.

You can trace the paths of Orionid meteors back to their radiant: the famous red supergiant star system Betelgeuse in the constellation Orion. (That's why the shower is called the Orionids.) However, there's no need to look directly at Orion. Meteors seen farther from the radiant can produce longer streaks across the sky; each one comes from a tiny piece of Halley's Comet completing a journey that began many centuries ago.

A mysterious "guest star" recorded by medieval astronomers nearly 850 years ago has revealed new secrets after scientists obtained the clearest images yet of its explosive aftermath.

New observations of Pa 30, thought to be the leftovers of a historic supernova called SN 1181, show that its spectacular firework-like filaments are not smooth streams of material. Instead, they consist of chains of tiny gas knots.

SN 1181 is so called because astronomers in China and Japan recorded its brief appearance in the year 1181, when they saw it as a naked-eye object in the constellation Cassiopeia. Eight surviving texts date its appearance to between Aug. 4 and 6 of that year. The mysterious object remained visible for 185 days.

"It's rare to get this level of detail on a supernova we can date to a specific week in history," Timothy Cunningham, an assistant professor of astronomy and astrophysics at the University of Warwick who led an international team of researchers to study the object, said in a statement.

SN 1181 is one of only five supernovas in the Milky Way galaxy known to have been witnessed from Earth before the invention of the telescope. (Those optical instruments first appeared in the Netherlands in 1608.) Now, advanced ground-based telescopes can produce wonderfully detailed images of those historic remnants. This latest image is from the Gemini North telescope on Mauna Kea in Hawaii and reveals about 10 times more filamentary structures in Pa 30 than have been seen before. This extraordinary detail gives astronomers fresh clues about the unusual explosion and the environment surrounding the star.

"These images give us the clearest picture yet of Pa 30's structure, and it's not what we expected," said Cunningham, whose team published their findings in The Astrophysical Journal. "The filaments are made of chains of tiny knots rather than smooth streaks, providing new constraints on the nature of the space around the star before it exploded and the physical processes that have shaped the expanding ejecta."

The knot-like structures may have resulted from variations in temperature or density in material surrounding the star as debris from the explosion expanded.

Pa 30 contains another unusual feature: a surviving star that sits almost exactly at the center of the remnant. That's highly unusual, because a supernova explosion typically sends stars away from their original positions. It suggests that the original explosion was highly symmetrical, the researchers said.

Furthermore, Pa 30 is thought to be a Type Iax supernova. Unlike standard Type Ia supernovas, which destroy their stars, a Type Iax event is a lower-energy, incomplete explosion of a white dwarf star that can leave behind a remnant known as a "zombie star." It's the only Type Iax supernova ever found.