Three different viewers contacted KGW to say they had seen it just before 6 a.m.
"I was out walking my dog this morning around 5:55 a.m. and saw what looked like someone lit a tennis ball on fire and threw it," viewer John Kisling said. "It took a couple seconds to traverse the sky."
An expert told KGW it was a piece of an asteroid burning up when it hit the atmosphere.
"Fireballs are not uncommon," said Dick Pugh of the Portland State University Meteorite Labratory. "The question is: Did it make it all the way down?"
Comment: No, the question is: why are they now common?
Pugh said most pieces of "space debris" burn up when they hit the atmosphere. But some push through and hit the ground, becoming meteorites. Those are accompanied by a loud sound.Witnesses in the Portland area Wednesday agreed the fireball was silent.
Pugh said several other sightings in San Francisco earlier this week and other "major fireballs" around the world show that Earth is likely going through a debris field from a leftover comet.
Comment: Possibly... or multiple comets!
Portlander Tony King told KGW he saw it from his back porch and it took several seconds to move "across the whole sky, from east to west, along the horizon line."
One Twitter user posted a photo of the fireball over the Netherlands last night and another caught the phenomenon over Scotland. And someone in Colombia caught a fireball on cell phone video last Friday.
Good times with #EN95 #Benningbrooek. Beautiful -10 #fireball last night! pic.twitter.com/cZldqkdF4T
- Jos Nijland (@Jos_Nijland) October 30, 2013
Fireball for Outer Space Scotland. pic.twitter.com/zjNtyEotAZ