Those bright lights marching slowly in a straight line across the sky this week aren't comets or meteors -- although there was also-- but the second batch of SpaceX Starlink broadband satellites.
60 of the small internet routers aboard a Falcon 9 rocket Monday and within hours they were being spotted around the world, flying in formation. The sight looks like a train of staggered lights or bright stars, moving in a straight line through space.
Spotters from California to Maryland to Japan uploaded video evidence of the odd spectacle, which again raised concerns from astronomers.
SpaceX launched its, and a number of scientists that the company's plans to launch thousands of the reflective objects could have an adverse effect on astronomical observations.
It soon became clear the satellites become much less visible as they gain altitude and orient themselves for operation. SpaceX has pledged to coordinate with astronomers to minimize impacts and also paint the satellites to make them less reflective, although the batch that went up Monday was unpainted like the first group.
However, since the May launch,through regulatory filings that seek to launch up to 42,000 of the satellites in coming years. And SpaceX is just one of a handful of companies looking to launch such mega-constellations.
With this new information in the background, the reappearance of a new Starlink train in the sky this week has brought up concerns from astronomers once again.
Astronomer Jonathan McDowell from the Harvard-Smithsonian Center for Astrophysics keeps a close eye on satellites in orbit. He thinks Starlink and constellations like it don't pose a problem now, but their growth rate concerns him.
"It's an overstatement to say they are disrupting (astronomy)," he wrote on Twitter. "They are bright enough that if there were thousands of them they would."
SpaceX says it will work with astronomers and can adjust the orbit of satellites to keep the constellation from interfering with observations.
The company plans to continue ramping up launches of Starlink satellites, including another batch of 60 within the next few months.
Originally published at 10 a.m. PT. Updated at 4 p.m. with response from SpaceX.