Perseids
The Perseids is a prominent annual meteor shower that occurs each summer, peaking around mid-August. It is renowned for producing bright streaks of light in the night sky, referred to as meteors or "shooting stars." The meteor shower derives its name from the constellation Perseus, from which the meteors appear to radiate, though they do not originate from that location in space. The Perseids result from Earth passing through debris left by the comet 109P/Swift-Tuttle, which completes an orbit around the sun approximately every 133 years. This shower typically begins in mid-July and extends into late August, with the most meteors visible during the nights of August 11 to 13, when observers can see up to 100 meteors per hour under optimal conditions. The Perseids are especially popular among sky watchers due to the warm summer nights and the colorful fireballs produced by its larger particles. As part of a broader phenomenon, meteor showers occur when Earth intersects the trails of debris from comets or asteroids, making the Perseids one of the most significant and well-observed meteor showers of the year.
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Perseids
The Perseids is an annual meteor shower that lasts for several weeks each summer and reaches its peak during mid-August. Meteors, colloquially known as “shooting stars,” appear in the night sky as brief streaks of light. A meteor shower occurs when a larger than normal amount of meteors seem to radiate from a point in the sky. The Perseids gets its name because the streaks of light seem to be emanating from the constellation of Perseus. The shower is the result of Earth passing through the debris field left over from a large comet. Because of the number of meteors per hour and the vivid streaks of light they leave behind, the Perseids is considered the most popular meteor shower of the year among many sky watchers.
Background
Our solar system was formed about 4.5 billion years ago from a giant interstellar cloud of gas and dust. As the cloud began spinning, more than 99 percent of its matter coalesced at the center, forming the sun. Much of the remaining gas and dust clumped together to form the planets, moons, asteroids, and comets. The smallest pieces of debris left over from the formation of the solar system are called meteoroids. These range from small fragments of asteroids or comets to tiny specks no larger than a grain of sand. Most meteoroids are smaller than a pebble. A meteoroid that impacts Earth’s atmosphere and burns up before reaching the ground is called a meteor. Larger meteoroids that survive to reach the surface are called meteorites.
Meteoroids are constantly colliding with Earth, although few ever reach the ground. The vast majority burn up as meteors when they hit the planet’s atmosphere. As they do, they appear as fast-moving streaks of light. This flash of light is caused by the energy given off as the meteors slam into Earth’s atmosphere at speeds of up to 160,000 miles per hour (257,500 kilometers per hour). At these speeds, the meteor strips electrons from the atoms in the atmosphere, creating a brilliant streak of light. Most meteors burn up in a region of the atmosphere about 50 to 75 miles (81 to 121 kilometers) above the surface. However, some slower moving meteors can penetrate through to lower levels of the atmosphere.
Most meteoroids are fragments left over by the passage of comets, celestial bodies made of ice, frozen gases, rock, and dust that travel though the solar system as they orbit the sun. As a result, most meteoroids are composed of less-dense, “fluffy” material rather than the more rocky fragments left over by asteroids. On occasion, a larger or rockier meteor can leave behind a brighter, more colorful, and longer lasting streak known as a fireball.
Overview
Sky watchers can observe at least a few meteors every night of the year under the right conditions. A meteor shower occurs when Earth’s orbit takes it through the debris field left behind by a passing comet, or in rare cases, an asteroid. Meteor showers occur several times a year. Most last for a few weeks at a time, with peak viewing coming over the span of a few hours or days when the number of meteors is at its maximum. Smaller meteor showers have a maximum rate of about 10 to 15 per hour. The largest showers can produce a maximum of about 120 meteors per hour during their peak. In very rare cases, such as when a “parent” comet has recently passed by, meteor showers can become meteor storms. For example, the Leonid meteor storm in November 1833 produced an estimated 72,000 meteors per hour at its peak.
The Perseids is one of the most prolific meteor showers of the year, with a maximum rate of about 100 per hour. The shower begins about mid-July and continues into the last week of August; however, the peak viewing of the event usually occurs about August 11 to 13. Because the particles that create the shower are larger than most cometary debris, it is known for producing brighter than normal streaks of light and more abundant fireballs. The number and brightness of the meteors, coupled with the fact that mid-August nights are typically warm, make the Perseids the most viewed meteor shower of the year by both astronomy buffs and the public.
The names of meteor showers are derived from the constellations from which they appear to emanate. The Perseids meteors seem to radiate from the constellation Perseus, the legendary hero of Greek mythology. However, the meteors do not actually come from that part of space. Because they travel along parallel paths, they seem to originate from a single point to an observer on the ground. This is a trick of perspective, similar to how railroad tracks seem to start at a single, distant point to a person standing down the tracks. The Perseid meteors are moving at about 130,000 mph (210,000 km/h) when they strike Earth’s atmosphere. The best time for viewing the meteor shower is after midnight closer to the early morning hours, although they can usually be seen in the Northern Hemisphere starting about 10 p.m.
The comet responsible for producing the Perseids is called 109P/Swift-Tuttle, a 16-mile (25.7 kilometer) wide object that circles the sun once every 133 years. The comet was discovered in 1862 by astronomers Lewis Swift and Horace Parnell Tuttle, who made their observations independently of each other. In 1865, Italian astronomer Giovanni Schiaparelli discovered that Swift-Tuttle was responsible for creating the Perseid meteor shower. The comet has a very elongated and steep orbit when compared to the orbits of Earth and the other planets. For that reason, it travels at a very high speed, meaning its debris field is also moving very fast when it impacts Earth. Swift-Tuttle is the largest celestial object to repeatedly cross Earth’s orbit, although it is not expected to collide with the planet for at least the next few thousand years. The comet made its last approach to the sun in 1992 and is not expected to return until July 2126.
Bibliography
Christoforou, Peter. “The Great Leonids Meteor Storm of 1833.” Astronomy Trek, 16 Apr. 2018, www.astronomytrek.com/the-great-leonids-meteor-storm-of-1833/. Accessed 7 Jan. 2020.
Lewin, Sarah. “Comet Swift-Tuttle: The Icy Parent of the Perseid Meteor Shower.” Space.com, 9 Aug. 2016, www.space.com/33677-comet-swift-tuttle-perseid-meteor-shower-source.html. Accessed 5 Jan. 2020.
McClure, Bruce, and Deborah Byrd. “Perseid Meteors 2019: All You Need to Know.” EarthSky, 8 Aug. 2019, earthsky.org/astronomy-essentials/everything-you-need-to-know-perseid-meteor-shower. Accessed 7 Jan. 2020.
“Meteor Shower Calendar 2020–2021.” American Meteor Society, 2020, www.amsmeteors.org/meteor-showers/meteor-shower-calendar/. Accessed 7 Jan. 2020.
Miller, Katrina. "The Perseids Meteor Shower Is Peaking. Here's How to Watch It." The New York Times, 11 Aug. 2024, www.nytimes.com/2024/08/09/science/perseids-meteor-shower-how-to-watch.html. Accessed 7 Nov. 2024.
“Perseids.” NASA Science, 19 Dec. 2019, solarsystem.nasa.gov/asteroids-comets-and-meteors/meteors-and-meteorites/perseids/in-depth/. Accessed 7 Jan. 2020.
Richardson, James. “Meteor FAQS.” American Meteor Society, 2020, www.amsmeteors.org/meteor-showers/meteor-faq/. Accessed 7 Jan. 2020.
Ryabova, Galina O., David J. Asher, and Margaret D. Campbell-Brown, editors. Meteoroids: Sources of Meteors on Earth and Beyond. Cambridge UP, 2019.
“2020 Meteor Showers.” University of Texas McDonald Observatory, 2020, stardate.org/nightsky/meteors. Accessed 7 Jan. 2020.