A starburst of bright lights was seen tearing across California's sky, mystifying onlookers. It was actually flaming chunks of space debris, says an astrophysicist.

• Bright lights streaking across the sky in Sacramento, California, mystified onlookers on Friday.
• Astrophysicist Jonathan McDowell said the lights were likely flaming pieces of space debris.

A series of streaking lights across California's skies had onlookers speculating about aliens and UFOs. It turned out to be bits of flaming space debris re-entering the atmosphere.

For 40 seconds on Friday, people in Sacramento, California, saw what looked like a group of shooting stars, per the Associated Press.

Jaime Hernandez, who was celebrating St. Patrick's Day at the King Cong Brewing Company in Sacramento, told the AP that it was unlike like anything he had seen before.

"Mainly, we were in shock, but amazed that we got to witness it," Hernandez told the AP. "None of us had ever seen anything like it."

He filmed the phenomenon, and the brewery posted his video on its Instagram page.

"This flew over the brewery tonight," the brewery wrote in its caption. "What do you guys think? #UFO"

But astrophysicists had a scientific explanation for the lights.

Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, told The New York Times that the lights were likely pieces of communication equipment that were thrown out from the International Space Station in February 2020.

The pieces, which were traveling across the sky at 17,000 miles per hour, were part of a discarded 700-pound communications antenna, McDowell said. They burst into flames upon re-entering the atmosphere at high speeds, he added.

"What you're seeing is some actually very small objects releasing a lot of energy, very high up, traveling extremely fast," McDowell told The Times.

Space debris falling back to earth is a more common occurrence than most would think, he said. Pieces of space debris that size have been falling back to earth every few weeks for over 50 years.

"They don't happen very often over any one given place, so it's always new to the people who see it," McDowell told The Times. "For me, it's just another Tuesday."

He predicts that these pieces seen over California will land in the area around Yosemite National Park.

Privateer, a company that tracks about 48,000 man-made objects in space, told The Times that there is a lot of man-made waste material in space. He says that of all the objects that his company tracks, 90% are garbage.

"Humanity is not slowing down in launching stuff into space," the company's co-founder Moriba Jah told The Times. "On average, right now we're launching more than 12 satellites every week."

McDowell and representatives for NASA and the King Cong Brewing Company did not immediately respond to Insider's requests for comment outside regular business hours.