Satellite or Meteor? Dissecting Light Trails in Your Sky Photos

As ever more night-sky images pop up on social media, I see more and more artificial satellites misidentified as meteors. So many satellites crisscross my own pictures — especially when photographing meteor showers — I sometimes scratch my head trying to tell one from the other. Whether we like it or not, the proliferation of Earth-orbiting satellites in recent years has compelled us all to contend with the increasing mechanization of the night sky. To that end, here are several ways to distinguish meteors from their machine imitators.

Profile and shape

When sifting through meteor shower images, as I did recently with the Lyrids, the first thing I pay attention to is the trail’s shape. Satellite trails often begin and end abruptly and display a consistent width from start to finish. They look like straight lines drawn with a ruler and snipped at the ends with scissors.

A meteor trail in contrast exhibits a different profile — faint at first as the particle first encounters the atmosphere, then becoming much brighter as its kinetic energy is rapidly converted to heat via ram pressure (air compression). When the particle is completely vaporized and/or slows down, it quickly fades. The sequence creates a faint-bright-faint profile resembling a narrow, toothpick-like spindle with sharp, pointed ends — distinct from typical satellite trails. While the difference can be a useful indicator in telling the two apart, flaring satellites make even better meteor mimics.

Flares occur when the angle between the satellite, observer, and the Sun results in a brilliant, specular reflection from a shiny surface like a solar panel array or antenna. In our everyday lives we witness similar glints from metal and glass surfaces as we move about our environment. Most satellite flares brighten, climax, and fade, similar to a meteor but lasting for several seconds or more. If you see it with your eye, there’s no doubt about it being a satellite. But if you only capture a photo of it, examine the trail for squared-off ends and evidence of color. Also, many flaring satellites continue to leave a track after flaring, while most meteors quickly come to an end.

Color vs. monochrome

Satellites reflect sunlight and often appear white (colorless) to the eye and in photos. There are exceptions. The ISS glows pale yellow from the amber-colored Kapton film used in solar panels and as insulation for the spacecraft. Newer Starlink satellites shine with a blue tint because they’re coated with a special film to reduce their brightness so they’re less bothersome to astronomers.

All but faint meteors show color in time-exposures. But their color profiles are quite different from the occasional colorful satellite. Satellite color is mostly consistent throughout its trail length. A blue Starlink leaves a blue streak. Meteors on the other hand not only exhibit a different set of colors, typically green, pink, orange, and red, but the color often varies across the trail length as different chemical elements vaporize and emit light.

The most common color profile I’ve noticed in shower meteors is a green-to-pink transition. Excitation of atmospheric oxygen when the object first enters the atmosphere is often responsible for the green color, which changes to pink/red as it slows down. Magnesium and nickel, both of which are common materials in meteorites, can also tint a meteor green. Speeds vary, too, with red more commonly seen in slower-moving meteors.

Continuity across frames and trail length

When photographing meteor showers, you’re often taking hundreds of consecutive images in the hope of catching as many meteors as possible. While searching each frame for a streak with that telltale faint-bright-faint profile or one that ends in a bright terminal burst, you’re sure to find copycats. You can weed them out by looking for color and squared-off ends as previously discussed. But there’s another way — check to see if the trail appears on multiple frames. If so, you can completely ignore it. Meteors rarely last longer than a second (average is 0.4 seconds), so capturing the same one in two frames almost never happens.

I get a lot of these pseudo-meteors in longer, sequential time exposures. In the first frame, the satellite might be uniformly bright but then fades during the next exposure. In that second frame, the imposter will appear to have a bright, meteor-like head and fainter trail.

A typical low Earth-orbit (LEO) satellite moves about 0.5° to 1° per second, or 15° to 30° in a 30-second exposure. Meteor trails vary greatly in length, with brighter ones typically longer than fainter. But the most are no more than about 10° long, considerably shorter than many satellite trails.

A night at the races

Starlink satellites frequently flare one after another low in the northwestern sky (approximately 10° to 15° high) for a couple hours after the end of dusk and again in the southeastern sky in the wee hours, following similar paths like cars on a racetrack. The photo at the top of this story best illustrates this so-called Racetrack effect. They’re dim to start but quickly brighten, sometimes rivaling Jupiter and Venus, before fading away.

While Starlinks often exhibit the faint-bright-faint profile of meteors, their lack of color, long trail lengths, and clustering behavior expose them as artificial. Newcomers to astrophotography who happen to stumble across them may think a meteor shower is underway. Either that or an alien invasion. I’m not kidding. A concerned skywatcher once called me, convinced the UFOs he watched night after night in the northwestern sky were up to no good.

Direction of travel

When photographing a meteor shower, you have an additional way of weeding out satellites from meteors. Random, or sporadic, meteors appear anywhere in the sky, but the paths of shower members point back to the radiant. While helpful in distinguishing between the two kinds of meteors, you can also use this criterion as yet another way of to filter out machine imitators.

Look it up

If you think you’ve captured a satellite, you can often determine its identify if you know its location, direction of movement, and when you took the photo. Go to Heaven-Above.com and select your city, then click on the blue link, Daily Predictions for Brighter Satellites. Scan the pass times, then click a satellite-suspect link for a map to compare against your observation.

My hope is that by applying each of these criteria, you’ll be able to tell a meteor from a satellite most of the time. Occasional trails resist my best efforts, especially when I’m shooting single frames of sky phenomena like aurora and conjunctions, but I soldier on.

Some observers may discover that being a meteor detective has its small joys. Who doesn’t like solving a puzzle? If so, I’ve got good news. Tens of thousands more satellites will be launched in the next decade, guaranteeing tons of maddening fun!