Early Monday afternoon, a bright object flashed across the sky before vanishing with a flash, according to scores of eyewitnesses from Virginia to Massachusetts.

The likeliest explanation is that a large meteor - a space rock hurtling through the atmosphere - passed eastward over the North Jersey-New York City area.

© MIKE HANKEY / www.mikesastrophotos.com
It might have been 5 feet in diameter with a weight of more 5 metric tons, judging from reports that it blazed as bright as a full moon, said NASA scientist Bill Cooke of the Marshall Space Flight Center.

He based his estimate on "a reasonable speed" of 33,500 m.p.h. Good thing it didn't hit anything.

"My crude estimate of the energy of this fireball is about 100 tons of TNT, which means it was capable of producing a crater 125 feet in diameter and about 15 feet deep, assuming an impact into sandstone," Cooke said.

The Earth's atmosphere, is strafed by such rocks about once a month, usually over the oceans, and a similar event may have happened near Jackson, Miss., on Jan. 11, he said.

Apparently, this intruder was much larger than the typical debris in shooting stars or meteor showers. At night, even a grain of sand can cause a bright streak across the sky.

Cooke said a better estimate would be available in a few days, after data is collected from "infrasound stations to try to determine the meteor's energy from the sound waves emitted as it flew through the atmosphere."

Eyewitness reports put the time of Monday's fireball around 12:35 to 12:45 p.m. Eastern time.

Here's a sampling from reports to Meteor/Meteorite News:

-- "Egg Harbor, NJ. Silvery ball like 'shooting star' for about a second or so across good portion of sky. Heard a bit of a woosh and then it flashed out. Definitely a little intimidating but cool!"

-- "I saw the meteor that came down in Philly. Spectacular, bright came Almost straight down. Positioning reported by news inaccurate though."

-- "I saw a meteorite today in Bayonne, New Jersey between noon and 1pm. It appeared out of nowhere in my line of sight coming down toward the shoreline, and disintegrated about 100 feet above the ground in an instant!"

-- "Old Bridge, NJ Driving on Route 34- Saw a circular meteor appear with long red flare ending- it was there for a seconds and gone instantly- it glided like a shooting star -1pm in the afternoon- red as can be!!"

Among more than 50 reports to the American Meteor Society were these:

-- "It fluxed all the colors of the rainbow akin to a ... oil sheen on water. It was moving at breakneck speed. ... I don't want to sound weird but it looked magical," wrote one New York City man.

-- "A true spectacle. Top 5 coolest things I have ever ... seen. I will remember this fireball till death :) Love, Kurt," wrote a Unionville, Pa., observer.

The accompanying map, created by Mike Hankey of Mike's Astro Photos, used early reports to approximate the fireball's path.

Shoot a photo or video of the fireball? Please contact the Inquirer Online News Desk at 215-854-2443 or online@phillynews.com.