The experience of looking up and seeing an unexpected light or object in the night sky is universal, often sparking confusion or wonder. Before concluding that a sighting is truly unknown, a systematic look at the common origins of aerial phenomena reveals that the vast majority of strange lights have logical explanations. These sources fall into distinct categories, ranging from natural astronomical events to routine human-made technology and a small collection of genuinely unexplained observations. Investigating these categories provides a clear framework for understanding these visual mysteries.
Natural Celestial and Atmospheric Explanations
Many reports of lights moving erratically or changing color can be traced to the interplay between distant celestial bodies and Earth’s turbulent atmosphere. Stars appear as pinpricks of light because of their immense distance, and their light must travel through many layers of air with varying temperatures and densities. This process, known as atmospheric scintillation, causes the light to be refracted multiple times, resulting in the familiar “twinkling” effect, which can be particularly intense when the star is low on the horizon.
Planets like Venus or Jupiter are closer, making them appear as small discs rather than points of light, which averages out the atmospheric distortion so they shine more steadily. However, when a bright planet is near the horizon, its light passes through a greater volume of atmosphere, and the refraction can be significant enough to cause apparent erratic movement or dramatic color shifts, leading observers to believe they are seeing an accelerating or decelerating object.
Other natural phenomena include the rapid, bright streaks caused by space debris entering the atmosphere. A meteor, commonly called a shooting star, is the light produced by a small piece of rock burning up upon entry. A much brighter version, called a fireball, is defined as a meteor that reaches a visual magnitude brighter than the planet Venus. If this larger object explodes in a terminal flash, it is referred to as a bolide, which can sometimes be mistaken for an aerial explosion. Rarely observed, high-altitude electrical discharges known as sprites are also sometimes reported, appearing as massive, reddish-orange flashes that occur in the mesosphere above thunderstorms, at altitudes between 30 and 60 miles.
Conventional Aircraft and Satellite Systems
The modern night sky is increasingly populated by human technology, which is responsible for a large percentage of lights reported as unusual. Among the most commonly misidentified objects is the International Space Station (ISS), which appears as a steady, very bright light moving rapidly across the sky, usually visible shortly after sunset or before sunrise. Satellite mega-constellations, such as SpaceX’s Starlink, have also introduced a new visual signature.
When a new batch of Starlink satellites is deployed, they often appear as a distinctive “train” or “string of pearls”—a line of dozens of bright, evenly spaced lights moving in unison. These satellites are only visible when the observer is in darkness but the satellites are still illuminated by the sun high above the horizon. As they ascend to their operational orbits of approximately 340 miles (550 kilometers), they spread out and become much fainter.
Military aircraft maneuvers also generate lights that can appear highly anomalous, particularly flares. These are pyrotechnic decoys made of a hot-burning metal compound, such as magnesium, designed to burn hotter than a jet engine’s exhaust to divert heat-seeking missiles. When deployed, these flares create a brilliant, descending light that can be mistaken for a falling fireball or a crashing object, especially during training exercises. High-altitude weather balloons or scientific instruments, especially when reflecting sunlight, can also appear stationary or move with an unpredictable drift, often mistaken for slow-moving, hovering craft.
Genuinely Unidentified Aerial Phenomena
After ruling out all conventional explanations—celestial, atmospheric, and human-made technology—a small residual category of observations remains unexplained. The official term for these is Unidentified Anomalous Phenomena (UAP), a designation used by the United States government that has replaced the older “Unidentified Flying Object” (UFO). This updated terminology is broader and encompasses objects detected in the air, sea, and space, including “transmedium” objects that move seamlessly between these environments.
The US Department of Defense, through the All-domain Anomaly Resolution Office (AARO), is tasked with systematically collecting and analyzing reports of UAP, primarily for national security reasons. The focus is on objects that demonstrate performance characteristics beyond the known capabilities of any nation’s technology. A tiny fraction of reports exhibit what investigators call the “Five Observables,” which defy current understanding of physics and aeronautics.
These reported characteristics include instantaneous acceleration or deceleration, with some sensor data suggesting objects moving from a standstill to thousands of miles per hour in seconds, implying forces far exceeding the structural limits of known aircraft. They also involve hypersonic velocities—speeds exceeding Mach 5—without producing the expected signatures of a sonic boom or an incandescent plasma sheath. These truly unidentified sightings are not automatically assumed to be extraterrestrial but represent a small pool of data that warrant continued scientific investigation.