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    On February 15, 2013, a meteor exploded in the air over Chelyabinsk, a region in southern Russia. Unlike many space rocks, which astrophysicists can predict will enter Earth’s atmosphere, the Chelyabinsk meteor was undetected before it screamed across the sky.
     
    The Chelyabinsk meteor was part of the Apollo group of asteroids, about 240 space rocks that orbit the sun between Mercury and Earth. The meteor was fairly small, between 17 and 20 meters (56 and 66 feet) in diameter with a mass of about 11,000 metric tons (12,125 short tons) when it entered Earth’s atmosphere. It raced through the atmosphere at about 66,960 kilometers per hour (41,000 miles per hour)—nearly 60 times the speed of sound. This speed led to most of the meteor burning up in the sky, causing a fireball briefly brighter than the sun. The largest chunk of charred Chelyabinsk meteorite, recovered from the icy waters of Lake Cherbarkul, was only 654 kilograms (1,442 pounds).
     
    Most of the 1,400 injuries associated with the Chelyabinsk meteor were not a direct result of the meteor, but of the shock wave that followed. The shock wave caused windows, roofs, and walls to shatter and collapse.
  • Term Part of Speech Definition Encyclopedic Entry
    asteroid Noun

    irregularly shaped planetary body, ranging from 6 meters (20 feet) to 933 kilometers (580 miles) in diameter, orbiting the sun between Mars and Jupiter.

    astrophysicist Noun

    person who studies the relationship between matter, energy, motion, and force outside the Earth's atmosphere.

    atmosphere Noun

    layers of gases surrounding a planet or other celestial body.

    Encyclopedic Entry: atmosphere
    char Verb

    to burn.

    meteor Noun

    rocky debris from space that enters Earth's atmosphere. Also called a shooting star or falling star.

    Encyclopedic Entry: meteor
    meteorite Noun

    type of rock that has crashed into Earth from outside the atmosphere.

    Encyclopedic Entry: meteorite
    orbit Verb

    to move in a circular pattern around a more massive object.

    Encyclopedic Entry: orbit
    region Noun

    any area on Earth with one or more common characteristics. Regions are the basic units of geography.

    Encyclopedic Entry: region
    shock wave Noun

    moving, measurable change in pressure and density of a material.