ST. LOUIS — People from southern Illinois to Jefferson County, Missouri, called and wrote to 5 On Your Side recently about some remarkable lights in the sky.
They sent photos and video of a string of lights just after sunset that shone brightly and then blinked out all at once. They also sent their guesses: were these planes? An exploding satellite? A UFO? Santa's sleigh?
The Verify team asked the experts. There’s a simple explanation for these lights, but it doesn’t make the footage any less amazing.
THE QUESTION
Is there an explanation for the string of fast-moving lights that appeared over the St. Louis area Dec. 3?
THE SOURCES
Rich Fefferman, a member of the St. Louis Astronomical Society
Michael Swartwout, a professor of aerospace engineering at Saint Louis University’s Parks School of Engineering
THE ANSWER
Yes, the lights are a known phenomenon related to the Starlink satellite train.
WHAT WE FOUND
The experts say these lights are a network of satellites called Starlink. They circle the planet every 90 minutes.
“At first glance, it looked like a jet contrail in the sky, kind of a very spooky-looking contrail. But then, when you look close or took out binoculars, you can see all the individual satellites looking like dim stars all lined up,” said Fefferman.
The satellite “train” is run by SpaceX to provide broadband internet all over the globe. There are already more than 1,600 satellites in the Starlink train overhead.
The satellites that the St. Louis area saw on Dec. 3 just happen to be some of the latest additions, which were still in a lower orbit. Eventually, scientists set them on a course for a higher orbit, and they’re much harder to see.
“None of these spacecraft are shining their own lights or firing an energetic thruster where you would see them on their own," said Swartwout. "And so it only works when you can see the sunlight reflecting off of them.”
In the videos sent to 5 On Your Side, the lights travel quickly across the southwest sky and then blink out of sight before reaching the other horizon. The experts told the Verify team that they reflected sunlight from the setting sun just over the horizon, and then passed into Earth’s shadow, causing the unusually bright lights followed by darkness.
There are almost 50 satellites in this particular line, and they’re each about the size of a kitchen table, Swartwout said.
His students work on satellites that are even smaller, called Cubesats. They have the advantage of being adaptable to ride along with many different kinds of launched vehicles, wherever there’s just enough space for a standardized Cubesat container.
The satellites in Starlink travel the same speed and direction because they were all dispersed the same way from a single launch vehicle.
Fefferman says if you want to see Starlink yourself, there are websites that tell you when to look up.
Both experts recommended Find Starlink to specifically predict when there will be good visibility for the satellite train, and Heavens Above for historical data and for identifying any other objects in the sky. Heavens Above has a mobile app that also lets users view a live sky map based on their location.
Fefferman recommends that night sky observers find a location with clear views to the horizon on a clear night and, if possible, put any bright lights in the opposite direction of what they’re trying to find, or find a building to block the light pollution.
He added that there’s another exciting reason to look to the sky right now: Three planets are visible in the night sky low to the west through December.
