A mesmerizing display of lights streaking in the night sky over Northern California on Friday was caused by the re-entry of flaming space debris into Earth’s atmosphere, experts said.
Specifically, flaming chunks 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 orbit of the equipment had shrunk over the past couple of years until it got low enough to break apart and burn up.
“What you’re seeing is some actually very small objects releasing a lot of energy, very high up, traveling extremely fast,” he said.
The retired 700-pound communications antenna, called the Inter-orbit Communication System-Exposed Facility, went into space on a 2009 shuttle flight. About 10 percent of equipment like that might fall to Earth in small pieces, rather than melt on the way, Dr. McDowell said.
The equipment came down in an uncontrolled re-entry, which means experts cannot predict where exactly the objects will land. Dr. McDowell said that pieces likely landed somewhere around Yosemite National Park. By contrast, the destination of equipment in a controlled de-orbit can be specified using rocket engines, he said.
Equipment the size of the one that created Friday night’s 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 over any one given place, so it’s always new to the people who see it,” Dr. McDowell said. “For me, it’s just another Tuesday.”
On Instagram, King Cong Brewing Company in Sacramento posted a video of the streaking lights, adding: “This flew over the brewery tonight. What do you guys think? #UFO.”
Debris that falls at night with clear skies can create a captivating light display for observers, said Moriba Jah, an associate professor of aerospace engineering and engineering mechanics at the University of Texas at Austin.
But as the equipment burns, it can pollute the upper layers of the atmosphere, he said. Upon reaching Earth’s surface, the equipment can also contaminate oceans and land — and even injure people, though that scenario happens infrequently.
Privateer, a company co-founded by Dr. Jah, tracks about 48,000 human-made objects, ranging in size from a cellphone to the International Space Station itself. But only about 10 percent of those are functional, he said.
The rest is garbage.
“Humanity is not slowing down in launching stuff into space,” he said. “I remember a busy year was a launch a month, and, on average, right now we’re launching more than 12 satellites every week.”
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