Mysterious light in Philly sky wasn’t aliens or a meteor. Here’s what it likely was.

It wasn’t a bird or a plane, an alien spacecraft or a wayward meteor, but people in several states, including Pennsylvania and New Jersey, witnessed quite an amazing celestial sight Tuesday night.

“It was inexplicable,” said Nicholas McAlister, a fundraiser at the University of Pennsylvania who witnessed it in the night sky from his Bella Vista rooftop about 10:30 p.m. Tuesday. “It looked like a slow-moving cyclone, with a lit-up glowing white center.”

Like others, he captured a video image of what resembled a glowing hand weight or dog bone with propellers on either end rotating in the sky. McAlister said it was visible for a good five minutes, and keep in mind that South Philly is not one of the nation’s dark-sky capitals.

It was the peak night of the annual Perseid meteor showers. But it had nothing to do with meteors.

The celestial puzzle stumped stargazers, and theories abounded. One guess was that it was related to the ULA Vulcan rocket launched in Florida. However, anything Vulcan-related most likely would have been visible over the Atlantic Ocean.

According to the experts at the popular astronomy site EarthSky, in all likelihood what people saw was connected to Europe’s Ariane 6 rocket, which was launched from South America.

The show over the Northern and Eastern United States was the result of a fuel dump from Ariane 6, whose trajectory took it over the mainland toward the Arctic.

While fuel-dumping is a common practice, it doesn’t often result in such high drama.

In this instance, said Derrick Pitts, chief astronomer at the Franklin Institute, given the launch time and altitude it is likely that some sunlight still was shining on the spacecraft, even though it was night in South Philly.

Also, the fuel would have been frozen — it’s mighty cold up there — and the sunlight on the icy particles would have created the dramatic effects. Think of contrails from jets.

The net result was a spectacular cosmic ballet for those lucky enough to be looking up. That would include legions of disappointed Perseid fans, who had to contend with the interfering moonlight.

McAlister, who describes himself as a casual skywatcher, said he hadn’t been on his rooftop hunting Perseids.

“I like rainbows, moon events, solar eclipses, celestial phenomenon, but I don’t know much about the sky,” he said.

The visit that he and his wife made to their rooftop had more do about the weather, and the overall oppressive mugginess this summer.

“My wife and I go on the roof a lot,” he said, “but it’s been so hot this summer we haven’t had a chance. We’re trying to make up for it at the end of summer.“

For those who did see the magical fuel dump, it was a matter of good fortune, said Pitts, who was among those who didn’t.

“They don’t schedule these things,” he said.