When a sudden streak of light flashes across the night sky, it is often called a “shooting star.” This common term is misleading because the object is not a star. The scientific term for this atmospheric phenomenon, caused by space debris entering Earth’s atmosphere at high velocity, is a meteor. Correct terminology requires differentiating between the space rock, the light it produces, any remnant that reaches the ground, and human-made objects in orbit.
The Primary Phenomenon: The Meteor
The bright streak of light visible from Earth is named a meteor. This fleeting display is caused by a tiny piece of space debris, often no larger than a grain of sand or a pebble, colliding with the upper atmosphere. The tremendous speed of entry (11 to 72 kilometers per second) rapidly compresses the air in front of the object. This compression generates intense heat, causing the air and the surface of the space rock to glow brightly through incandescence.
The light show typically occurs between 75 and 120 kilometers above the ground, and most meteors disintegrate completely before falling below 50 kilometers in altitude. Meteors are characterized by their extreme brevity, usually lasting only a fraction of a second to a few seconds, and moving extremely fast. The color of the streak offers clues about the chemical composition of the space rock, as different elements vaporize at different temperatures.
A blue-green hue indicates the presence of magnesium, while a yellow color suggests iron or sodium. Red colors are produced by the excited nitrogen and oxygen atoms within the surrounding atmosphere. If a meteor is particularly bright, outshining Venus, it is classified as a fireball. An exceptionally bright fireball that explodes is called a bolide.
Understanding the Meteoroid-Meteor-Meteorite Continuum
The terminology for these cosmic objects is based entirely on the object’s location in space. Before the piece of rock enters the atmosphere, it is known as a meteoroid. Meteoroids are small fragments of asteroids or comets, generally ranging from a dust particle up to about 10 meters in diameter.
The moment a meteoroid enters Earth’s atmosphere and creates the visible streak of light, its name changes to a meteor. The term meteor refers to the luminous trail itself, not the physical object creating it. The meteor stage ends when the object is fully vaporized or stops glowing, usually tens of kilometers above the surface.
If any part of the original meteoroid survives the fiery descent and lands on Earth’s surface, it is designated a meteorite. Because of the intense heat and speed, few meteoroids are durable enough to complete this journey. When Earth passes through the orbital path of a comet’s debris, the result is a meteor shower—a predictable, recurring increase in the number of meteors seen.
Identifying Streaks Caused by Human Activity
Distinguishing a natural meteor from a human-made streak of light relies on observing speed, duration, and angle of travel. Meteors move incredibly fast, are gone in one to three seconds, and often plunge into the atmosphere at a steep angle. Human-made objects exhibit significantly different characteristics regarding speed and duration.
Satellites and high-altitude aircraft are the most common source of confusion. A satellite, such as the International Space Station, appears as a steady, slow-moving point of light that can take several minutes to cross the sky. Satellites are only visible when they reflect sunlight, primarily around dawn or dusk, since they do not generate their own light. Occasionally, a tumbling satellite can appear to blink as its flat surfaces alternately catch and reflect the sun’s light.
Re-entry debris from defunct rockets or satellites presents a slower sight than a meteor. This debris typically enters the atmosphere at a shallower, more horizontal angle and a much slower speed, meaning the event lasts for 20 seconds or more. The tell-tale sign is often the object breaking up into a tight cluster of multiple glowing fragments moving in parallel, sometimes with a long, dazzling tail.
Aircraft are easily identified by their consistent, relatively slow speed and the presence of flashing or blinking navigational lights. A meteor will never have rhythmically blinking lights or follow the predictable, shallow flight paths of commercial air travel. If the light persists for more than a few seconds and shows any sign of blinking, it is almost certainly an airplane.