Bolide
A bolide is a type of celestial object that enters Earth's atmosphere, typically originating from one of three sources: comets, asteroids, or meteoroids. These objects can range from solid rocks to icy masses, and when they travel at high speeds, they heat up upon atmospheric entry. If they emit light during this process, they are classified as meteors; if they shine brighter than Venus, they are termed fireballs. A bolide specifically refers to a meteor that explodes in the atmosphere before reaching the ground, with particularly luminous examples known as superbolides.
The explosive nature of bolides is attributed to the immense pressure and friction they encounter as they slow down in the atmosphere. While many bolides disintegrate harmlessly, some can cause significant damage. A notable instance occurred on February 15, 2013, in Chelyabinsk, Russia, where a bolide exploded with a force comparable to 500 kilotons of TNT, injuring approximately 1,000 people and damaging hundreds of buildings. Historical events, such as the Tunguska explosion in 1908, highlight the potential impact of larger bolides, which can create massive destruction and atmospheric effects. Understanding bolides is crucial for assessing their risks and impacts on Earth.
Subject Terms
Bolide
FIELDS OF STUDY: Astrometry; Astrophysics; Astronomy
ABSTRACT: A bolide is a meteor originating in outer space that explodes as it falls to Earth. Astronomers use the term to describe especially brightly burning objects or fireballs. Bolides are sometimes dangerous, but they usually land away from people.
Types of Bolides
Bolides start as one of three types of objects found in space: a comet, an asteroid, or a meteoroid. Comets are balls of ice and dust, asteroids are minor bodies that are too small to be classified as planets, and meteoroids are small chunks of rock or metal. When these objects enter Earth’s atmosphere, they heat up. If the object becomes hot enough to emit light, it is called a meteor. If it becomes brighter than the planet Venus in the night sky, it is called a fireball. If that fireball gets so hot that it explodes before reaching Earth’s surface, the object is called a bolide. Especially bright bolides may be known as superbolides.
Why Bolides Explode
On Earth, air slows down any moving object. An object’s terminal velocity is the fastest that object can free-fall before the resistance of the atmosphere prevents it from accelerating further. However, there is no atmosphere in outer space. Because of this, many objects in outer space move much faster than objects on Earth.
Meteors that enter Earth’s atmosphere are usually traveling much faster than their terminal velocity. Because of this, the atmosphere in front of the meteor is compressed, creating pressure and friction and causing the object to slow down. As the meteor slows, the air around it quickly heats up. This causes the meteor to burst into flames. When the heat and pressure become stronger than the meteor can bear, the meteor violently breaks apart.
Bolides and Humans
A few dozen bolides occur annually, but most are too small to reach the ground before they burn up. When bolides explode near humans, the results can be catastrophic. On February 15, 2013, a bolide exploded near Chelyabinsk, Russia. According to the National Aeronautics and Space Administration (NASA), the bolide exploded with almost five hundred kilotons of force. For comparison, the atomic bomb dropped at Hiroshima exerted only sixteen kilotons of force. The explosion injured about a thousand people and damaged about three hundred buildings.
More than a century earlier, an even larger bolide exploded over Russia’s Tunguska region. Scientists estimate that blast was one thousand times as powerful as the Hiroshima bomb. The Tunguska blast flattened trees for miles around the blast site and caused so much light and reflective dust to be thrown into the atmosphere that people as far away as western Europe reported glowing night skies.
PRINCIPAL TERMS
- asteroid: a minor planet in the inner solar system that orbits the sun.
- comet: an icy small solar system body that heats up and releases gas when it passes near the sun.
- fireball: a meteor that is unusually bright.
- meteor: a small body of rock or metal that enters Earth’s atmosphere and emits light.
- meteoroid: a small body of rock or metal that travels through space.
Bibliography
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Richardson, James, and James Bedient, comps. "Fireball FAQs." American Meteor Society. Amer. Meteor Soc., n.d. Web. 11 Mar. 2015.
"US Space Force Releases Decades of Bolide Data to NASA for Planetary Defense Studies." Jet Propulsion Laboratory, 7 Apr. 2022, www.jpl.nasa.gov/news/us-space-force-releases-decades-of-bolide-data-to-nasa-for-planetary-defense-studies. Accessed 13 June 2022.