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Streak in sky
Keri Brooke, vice president of product marketing for Salesforce Analytics Cloud, snapped this picture of the bright streak. “What the heck is this in the sky?” she asked on Facebook. (Keri E. Brooke Photo via Facebook)

Rocket fans in California may have been disappointed by tonight’s scrub of a Delta 4 Heavy launch from Vandenberg Air Force Base, but they received a nice consolation prize: a fireball that left what looked like a contrail hanging in sunset skies.

The bright squiggle in the sky may have mystified some, but savvy folks who spotted the flash recognized it as the signature of an exploding meteor, also known as a bolide.

It was pure coincidence that the fireball flashed at 5:34 p.m. PT, just before United Launch Alliance called off the launch of a classified spy satellite known as NROL-71 for the National Reconnaissance Office, due to elevated hydrogen levels that were detected during the countdown.

Video views captured from cars traveling in locales including Sacramento, Stockton and the San Francisco Bay Area helped solve the celestial mystery. Here are a few of the best clips:

And here are more views from social media:

A bright meteor was visible in the skies over the Bay Area shortly after sunset this evening, leaving a bright trail…

Posted by Lick Observatory on Wednesday, December 19, 2018

SETI Institute senior planetary astronomer Franck Marchis was wrong about the airplane exhaust, but he was right about the intriguing nature of the meteor trail. German science writer Daniel Fischer pulled together a lot of the imagery — and pieced together a sensible explanation:

The NROL-17 launch had to be put off until Dec. 30 at the earliest so that United Launch Alliance could address the Delta 4 Heavy rocket’s accumulation of excess hydrogen.

SpaceX’s scheduled launch of an Air Force GPS III satellite from Florida was also postponed today, due to weather, and it may be postponed again on Thursday for the same reason. But today wasn’t a total washout for rocket fans.

India sent up a GSLV rocket with the Indian Air Force’s GSAT-7A remote-sensing satellite, while Arianespace launched the French CSO-1 spy satellite from its spaceport in French Guiana with a Russian-built Soyuz rocket.

Who knows? Maybe there’ll be another sunset fireball to celebrate a successful Delta 4 Heavy launch — after what are now four postponements.

Fireball sighting reports can be filed with the American Meteor Society, which has already received more than 100 reports (and scores of photos).

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