A bright streak of light flashing across the night sky is commonly known as a “shooting star.” This fleeting phenomenon naturally sparks curiosity about whether the fiery object represents material that will eventually strike the ground. The streak itself is a spectacular display of physics, but it is not a star, and the answer to whether it lands depends entirely on the size and composition of the original object.
Defining the Phenomenon
The common name “shooting star” is a misnomer for what is actually a three-part celestial event. The initial object, existing in space, is called a meteoroid, and it is a piece of rock or metal ranging in size from a grain of sand up to a small asteroid. Most meteoroids originate from the asteroid belt between Mars and Jupiter, while others are tiny fragments of dust shed by comets as they orbit the Sun.
The light streak that people observe is the second stage, called a meteor. This is the visible atmospheric phenomenon caused by the meteoroid entering the Earth’s atmosphere at high speed. The light is not the rock burning itself, but rather the air around it glowing intensely from the extreme heat generated by the entry process.
Only if a piece of the original space rock survives the fiery passage through the atmosphere and impacts the Earth’s surface does it earn the third designation: a meteorite. This terminology clarifies that the “shooting star” (the meteor) is just the light show, while the space rock (the meteoroid) must survive to become the physical object found on the ground.
The Physics of Atmospheric Entry
A meteoroid begins its journey into the atmosphere traveling at extreme velocities, often between 11 and 72 kilometers per second. As the object slams into the atmosphere, it compresses the air in front of it rapidly, which generates a shock wave and tremendous heat. This effect is so intense that the surface of the meteoroid can reach temperatures of several thousand Kelvin.
This intense heat causes the meteoroid’s outer layers to vaporize in a process called ablation, which continually removes mass from the object. The light seen from the ground is produced by the heated air and the glowing, ionized particles of the meteoroid’s vaporized material. The majority of visible meteors are caused by objects no larger than a grain of sand or a small pebble, and these small particles completely vaporize at altitudes between 80 and 120 kilometers.
The intense thermal and mechanical stresses often cause larger, less dense meteoroids to fragment and break apart high in the atmosphere. This destruction is why almost all of the roughly 44,000 kilograms of material that enters Earth’s atmosphere daily is vaporized.
When Material Reaches the Ground
The material from a “shooting star” does reach the ground, but only when the original meteoroid was large and durable enough to withstand the atmospheric burn. If the initial object is sufficiently massive, it can retain a core that punches through the lower atmosphere after the blinding light of the meteor phase has ended. These surviving pieces are then classified as meteorites.
For a portion to survive the atmospheric entry, the meteoroid generally needs to be at least the size of a marble. Once the object slows down enough in the denser air, the intense light ceases, and the meteorite continues in a dark flight until it impacts the surface.
Meteorites fall indiscriminately across the planet, but they are most easily found and recovered in barren environments like the cold, dry ice sheets of Antarctica or the expansive, rock-free plains of hot deserts. These environments prevent the meteorites from being quickly weathered or hidden by vegetation, allowing scientists to recover these valuable samples of extraterrestrial matter.