A mesmerizing display of lights streaking across the night sky over northern California on Friday was caused by burning space debris re-entering Earth’s atmosphere, experts said.
Specifically, burning fragments of communications equipment, which were jettisoned from the International Space Station in February 2020, streaked across the sky at 17,000 miles per hour, said Jonathan McDowell, an astrophysicist at the Smithsonian and Harvard Center for Astrophysics.
The team’s orbit had been reduced over the past two years until it was low enough to break and burn.
“What you’re seeing are some really very small objects releasing a lot of energy, very high, traveling extremely fast,” he said.
The retired 700-pound communications antenna, called the Inter-orbit Communication System-Exposed Facility, went into space on a shuttle flight in 2009. About 10 percent of equipment like that could fall to Earth in small pieces, in instead of melting along the way, Dr. McDowell said.
The team fell into uncontrolled re-entry, which means experts can’t predict where exactly the objects will land. Dr. McDowell said the pieces likely landed somewhere around Yosemite National Park. Rather, the team’s fate in a controlled deorbit can be specified using rocket engines, he said.
The team the size of the one that created the Friday night light show re-enters Earth’s atmosphere every few weeks and has been doing so for the past 50 years, he said.
“They don’t happen very often in any one place, so it’s always new to people who see it,” said Dr. McDowell. “For me, it’s just another Tuesday.”
On Instagram, King Cong Brewing Company in Sacramento He posted a video of the lights, adding: “This flew over the brewery tonight. What do you think? #UFO.”
Debris falling at night under clear skies can create a captivating light display for observers, said Moriba Jah, an associate professor of aerospace engineering and mechanical engineering at the University of Texas at Austin.
But as the equipment burns, it can contaminate the upper layers of the atmosphere, he said. Upon reaching the Earth’s surface, the equipment can also contaminate the oceans and land, and even injure people, although that scenario occurs infrequently.
Privateer, a company co-founded by Dr. Jah, tracks around 48,000 human-made objects, ranging in size from a cell phone to the International Space Station itself. But only about 10 percent of them are functional, he said.
The rest is garbage.
“Humanity is not slowing down in launching things into space,” he said. “I remember a busy year was one launch a month, and on average right now we’re launching more than 12 satellites a week.”