A large, spent Russian rocket plummeted from space into the sky over the Southwest U.S., erupting into a fireball that was seen across much of the West.
Strategic Command spokesperson Julie Ziegenhorn told BuzzFeed News that teams at Vandenberg Air Force Base tracked the an SL-4 rocket body entering the atmosphere over Arizona at 7:08 p.m. MST.
Ziegenhorn did not have information on the history of the rocket or how long it had been in space. However, according to NASA SL-4 rockets have been used to carry satellites into orbit, and have previously been seen making fiery returns to earth.
According to the European Space Agency, they are used in the Soyuz spacecraft.
Witnesses across much of California and Nevada saw the rocket as it burned up in the atmosphere. The resulting bright lights prompted surprise and speculation that everything from a meteorite to an alien ship was descending to Earth.
Konstantin Batygin, an assistant professor of planetary science at Caltech, speculated the rocket had entered the atmosphere at an altitude of roughly 18 miles. Batygin — who spoke to BuzzFeed News before officials confirmed the object was a rocket — said the fireball didn't appear to be behaving like a meteorite.
"This thing is traveling slower than I wold expect a meteorite to travel," he said, "my intuition tells me this is on the larger side of space junk."
Batygin added that leftover debris in space has become a "huge problem" in recent years.
The fireball initially caused confusion and a scramble to figure out what could have burned up in the atmosphere.
Shortly after dozens of pictures and videos of the object appeared online, officials from the Federal Aviation Administration, the U.S. Air Force, and the National Weather Service all told BuzzFeed News they had no idea what the object might have been.
U.S. Strategic Command confirmed that it was a rocket around 11 p.m. MST.
Ultimately, after moving across the sky, the object appeared to break apart.
Ziegenhorn did not have information about the rocket's ultimate fate, but Batygin said he doubted any of it reached the surface of the Earth.
"I think this thing disintegrated in the atmosphere and just burned up," he said.