A meteor is the visible streak of light seen when a small piece of space debris, called a meteoroid, enters the Earth’s atmosphere at high speed and vaporizes. This phenomenon, commonly referred to as a shooting star, is not a star but the glowing air and material created by the object’s rapid entry. Most meteoroids are tiny, often no larger than a grain of sand, yet they produce a striking visual event when they collide with air molecules high above the ground. The light is generated by the intense compression of air, causing both the air and the meteoroid’s surface to heat up and glow brightly through incandescence and ionization.
The Brief Flash Speed and Duration
The appearance of a meteor is defined by its extreme speed and fleeting nature. Meteoroids enter the atmosphere at velocities ranging from about 27,000 to over 160,000 miles per hour (12 to 72 kilometers per second) relative to Earth. This immense speed means the entire visible event occurs very quickly, typically at altitudes between 47 and 75 miles (75 to 120 kilometers).
The average meteor flash lasts for only a fraction of a second, often closer to 0.4 seconds. For brighter, larger objects, known as fireballs, the visible streak may persist for up to two or three seconds. This brief duration is a direct consequence of the object’s rapid entry and instantaneous vaporization due to atmospheric drag and heat.
In rarer cases, if a meteoroid grazes the atmosphere at a shallow angle, its path can be extended, making the visible event last up to five or more seconds. The combination of high velocity and the physical process of ablation—the erosion and vaporization of the outer layers—is what creates the momentary line of light that disappears almost as soon as it appears.
Color Brightness and Appearance
A meteor’s visual appearance is highly variable, largely determined by the object’s chemical composition and speed. The brightness is measured on the magnitude scale, where lower numbers indicate greater brightness. Faint meteors are barely visible, but brighter ones, known as fireballs, can rival the brightness of Venus or the Moon. An exceptionally bright fireball that explodes in the atmosphere is called a bolide.
The color observed in a meteor’s streak provides a clue about the elements vaporizing from the meteoroid. An orange-yellow hue often indicates sodium, while pure yellow light suggests iron is the dominant element. Magnesium tends to produce a distinct blue-green color. Violet light can be attributed to calcium, and a red color is usually caused by the excitation of atmospheric molecules like nitrogen and oxygen.
Fast-moving meteors tend to have a greater atmospheric plasma component, sometimes resulting in a more blue-green color due to ionized magnesium. Slower meteors may show more yellow-orange from sodium. The light from a typical meteor can combine these different element emissions, often resulting in an overall bright white appearance to the unaided eye.
The Aftermath Persistent Trails
Following the flash of the meteor, some of the brightest events may leave a residual effect known as a persistent train. This is distinct from the momentary streak of light that follows the meteoroid’s head. The persistent train is a glowing column of ionized gas and vaporized meteoroid material left along the path of entry.
The glowing train can linger for several seconds, or for several minutes in the case of very bright fireballs, sometimes twisting as upper atmosphere winds move the material. This afterglow is caused by a chemical reaction where metals from the meteoroid, such as sodium and iron, react with ozone and oxygen atoms. This reaction releases light, sustaining the glow long after the initial passage. Persistent trains have been documented to last up to an hour, providing an opportunity for scientists to study high-altitude wind patterns.
How to Distinguish Meteors from Other Objects
Distinguishing a meteor from other moving lights in the night sky requires observing a few key characteristics. The most telling feature is its speed: it moves across the sky in a blindingly fast, straight line that lasts for less than a few seconds, appearing as a momentary flash. A meteor’s light often brightens and tapers quickly at its ends as the object vaporizes.
Satellites and space junk move much more slowly and steadily across the sky, maintaining a constant brightness. They do not flash or leave a brief, luminous trail, but instead appear as a continuous streak of light reflecting sunlight. If the light source persists for more than a few seconds, it is almost certainly a satellite or an aircraft.
Airplanes are usually easy to distinguish because they move at a slower speed than meteors and typically display blinking or strobing navigation lights. Unlike the high-altitude, silent event of a meteor, aircraft may also be accompanied by the sound of their engines.