Unexplained sighting in the night sky. Credit for base image: Nayu Kim
Unexplained sighting in the night sky. Credit for base image: Nayu Kim

Ever seen something in the sky that was unusual, and which you couldn’t explain? I’ve received calls from some of you and have done my best to suggest explanations. Many of you have thanked me for my second-hand appraisals (second-hand, because I wasn’t present to see what you saw). A few have rejected the “mundane” possibilities I offer, insisting what they saw wasn’t what I proposed at all.

So this post is a condensed version of, “My Guide To Identifying Unexplained and Unidentified Apparitions in the Night Sky”–just a peek at my process of armchair evaluation of unexplained sightings.

Disclaimer: While I do believe that life is probably common in the universe, and that if one planet (ours) could develop intelligent life that in turn developed a technological, space-faring civilization, so could others. But in my experience as an astronomical observer of the world around me and the sky above, I have never seen anything for which my only possible explanation is a flying saucer. My process is to look for the simplest, most natural or human-related explanations first when possible.

The easiest ones are planets—in particular, Venus and Jupiter. Since planets move around in the sky, they regularly appear in different locations at different times in spots people didn’t see them before. And, being so bright at times, these two often get questioned: is it a plane? Is it the International Space Station? Has a star gone supernova?

Fortunately, we know where the planets are at all times, so when I get a call asking about the brilliant white light shining in the west just after sunset, for example, it’s easy to finger the culprit.

This happens with some bright stars on occasion, like Sirius. In fact, when I was a teenager, I had the personal experience of walking outside one night, looking up and seeing a brilliant, flickering prismatic apparition that I swore I’d never seen before. It took me some time to figure out that it was merely the brightest star in the night sky and it was supposed to look that way! I always think back to this experience when listening to your descriptions of the fantastic and strange things you’ve seen in the sky.

By the way, stars twinkle, planets don’t (much). That’s another way to tell them apart, other than consulting an app on your smart phone.

What about things that move–that is, with speed and direction different from normal “diurnal” motion (motion caused by Earth’s rotation)? When you observe something moving, relative to the background stars or horizon, there are generally three (mundane) things it is likely to be: an aircraft, a spacecraft, or a meteor/meteorite.

Spacecraft (let’s start with artificial satellites, the International Space Station, and in times of yore the Space Shuttle) can appear to move like a plane, but with the defining feature that they are always a single point of white light. Depending on how far from Earth they orbit they will move at different paces (just like aircraft at different altitudes), but since they are at least 150-200 miles above Earth’s surface, they’re too small to be seen as anything more than a point of light. And as the light they shine is actually reflected sunlight, they will be white. Some of them may flash, or pulse, as reflective surfaces like solar panels turn in the sunlight. Also, because they are in orbit in a ballistic trajectory, you won’t be seeing them change direction.

An aircraft—or more correctly, at night, an aircraft’s wing and fuselage lights—can appear as more than a single point of light, and these lights can bear color. Typical aircraft (commercial and private alike) have a lighting configuration in common: green for starboard, red for port, and blinking white at wingtips, tailtop, and tailtip. And if they’re heading directly at you with their landing lights on, they may appear to flare up and barely move at all.

The shape the wing and fuselage-lights form (what kind of triangle or diamond they make) depends on the style of aircraft (where the wingtips are relative to the tail, etc.), but I’d say green, red, and flashing white are a dead giveaway for an airplane (or a flying saucer trying to look like one.)

Military aircraft can look unusual, depending on what they are and what kind of maneuvers they’re on. They can even fly without lights on at all. In Flagstaff, Arizona, I once saw a simple triangle of steady, white lights fly over and have always assumed it was a stealth fighter on night maneuvers.

Meteors and meteorites (bits of interplanetary metal and rock that burn up in our atmosphere, or that are large enough to hit the ground before burning up completely, respectively) also have their hallmark behaviors and appearances.

Fainter ones will appear white, while brighter ones can show some color—blue, green, orange, depending on their composition and how hot they get. Most leave smooth, straight streaks, but some can exhibit “flame-like” raggedness, like long luminous gashes in the night. Some can even explode. But all of them move very fast, lasting only a couple seconds or typically less, yet crossing a good portion of sky in the process. You’ll only see an airplane moving that fast if it passes thirty feet over your head.

If none of this helps you sort out what you’ve seen aloft, try this chart. And remember, if you’re not sure what it is, it doesn’t hurt to smile and make no aggressive moves….

  • sean greenwalt

    “Smile and make no aggressive moves” has done a lot for me in many situations. Good advice.

  • Burressrex

    Good, logical, story, Ben. I thought it was funny about the recent story of the airline pilot taking a 15 minute nap while his co-pilot controlled, and when he woke and took control, looked out the window and saw a bright light dead ahead, he went into a dive to avoid hitting what he thought was a plane, but was only Jupiter, or maybe Venus! Everyone was all shook up and he returned to the airport.

    • Ben Burress

      Too bad airline pilots don’t learn basic Celestial Navigation anymore; if so that pilot might have been better tuned in…. :) I understand even the Navy stopped teaching Celestial Navigation….

      • whitetidelinedesigns

        My father was taught to navigate by the stars by his father, Capt. Robt. Wilson of the Union Steamship Co of B.C. When WWII came round, my father had his father sign him off – to join the Merchant Marines. As a lad, of just 15, my Dad would be called to the bridge of his ship to quietly navigate the ship into European & African ports during the night – with all lights/machinery off lest they be seen/heard by the enemy. Celestial navigation is a lost art & skill indeed.

  • tkharmon

    last night i was standing outside my house in Houston tx
    and i saw a greenish blue bright light just shine in the sky it was shaped
    like the sun.it stayed for a blink of an eye and left.

    • Ben Burress

      Cool! The way I look at it, it’s not necessarily a downside if a particular unusual sighting goes unidentified. As with my own experience (as I described in my Flashes in the Night blog), it just adds a little mystery to an already awesome and mysterious Universe!

  • Ben Burress

    BTW, I swear I had no fore-knowledge of the meteorite that just streaked across California and Nevada, visible in the daytime with accompanying sonic boom! I swear!

  • http://twitter.com/GabrielRoybal Gabriel Roybal

    now im gonna stay up staring at the sky!

  • msandram

    yea just saw about 10 and more lights flying all over the place, one went that way and than one would go another way , lasted for about an hour befor the sun came out wierd , omg what are they


Ben Burress

Benjamin Burress has been a staff astronomer at Chabot Space & Science Center since July 1999. He graduated from Sonoma State University in 1985 with a bachelor’s degree in physics (and minor in astronomy), after which he signed on for a two-year stint in the Peace Corps, where he taught physics and mathematics in the African nation of Cameroon. From 1989-96 he served on the crew of NASA’s Kuiper Airborne Observatory at Ames Research Center in Mountain View, CA. From 1996-99, he was Head Observer at the Naval Prototype Optical Interferometer program at Lowell Observatory in Flagstaff, AZ. Read his previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.

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