Scientists have solved the mystery of a spinning orb of bluish light that slowly flashed across the sky over Alaska last month, stealing the show from the famous Northern Lights: The unusual ball was most likely debris from a Chinese rocket that flew overhead.
Eyewitnesses across the state spotted the strange phenomenon around 5 a.m. local time on March 29. “It seemed like something was spinning around in it,” Leslie Smallwood, a Fairbanks resident who witnessed the event, told the local news station KUAC (opens in new tab)† The sphere seemed much larger than a full Moon and moved from the northeast to the southwest, he added.
An automatic camera trap captured images of the orb streaking in front of the northern Lights (also called the aurora borealis). The camera trap, operated by The Aurora Chasers (opens in new tab) Ronn Murray and Marketa Murray, a husband-and-wife duo in Fairbanks who organize Northern Lights photography tours, take regular photos of the sky every 45 seconds so that people can experience the Northern Lights in near real time. The camera took six pictures of the orb, suggesting it was visible for at least four and a half minutes.
“It’s not like it was shot through the air,” Smallwood told KUAC. “It was like taking my time.”
The orb came and went without any real explanation. However, after analyzing the photos, scientists determined that the large blue ball was likely the result of a photobombing by Chinese missile.
“I’m very confident that what people saw was dumping fuel from a Chinese rocket stage,” Jonathan McDowell, an astronomer at the Harvard Smithsonian Center for Astrophysics in Massachusetts, told KUAC. The sphere matched the flight path of a Chinese rocket that put two satellites into orbit, he added. The missile was a two-stage Long March 6 launcher launched from Taiwan, according to a tweet (opens in new tab) by McDowell.
The rocket likely released leftover fuel into space, where the fuel froze and spread into a large ball lit by sunlight, McDowell told KUAC. “This cloud is probably hundreds of kilometers wide, which is why it seems so big,” he added.
Other scientists agree with McDowell’s explanation. “A glowing cloud of gas illuminated by the sun would look like this,” Mark Conde, a physicist at the University of Alaska Fairbanks, told KUAC.
The sphere appeared to be spinning because, when rockets dump their fuel, they enter a controlled tumble to maintain the rocket’s orbit. The rocket would have “turned end over end spewing this fuel like a garden hose,” McDowell said.
This is not the first time this phenomenon has occurred. In October 2017, an even larger blue sphere was seen in the sky over Siberia, according to Science Alert (opens in new tab)† On that occasion, the frozen fuel was left behind by Russian military missile tests in the area.
Originally published on Live Science.