Source: Spaceweather.com

In Los Angeles and San Diego, millions of people watched it fragment into dozens of pieces high overhead. But what was it? Initial speculation focused on decaying space junk. The slow pace of the fireball combined with its fragmentation–as if parts of a satellite were breaking off in the atmosphere–suggested an orbital decay event. It appears, however, that the fireball was something else entirely.

Bill Cooke of NASA’s Meteoroid Environment Office has triangulated data from multiple cameras that picked up the fireball. His conclusion: It did not come from Earth. Instead, the fireball was a small asteroid or comet fragment belonging to the Apollo/Jupiter family. It was orbiting the sun when Earth got in the way, hitting our planet at a speed of 15.5 km/s (~35,000 mph). For comparison, manmade objects in low-Earth orbit typically hit at 7.9 km/s (17,700 mph) when they decay.

Source: Spaceweather.com