A brilliant fireball in the Virginia sky on Sunday was likely a natural meteor event and not the remnants of a Russian rocket, scientists now say, a reversal from yesterday's initial analysis.
On Monday, Geoff Chester of the U.S. Naval Observatory told SPACE.com that the loud boom and flash of light seen in the skies over Norfolk and Virginia Beach was likely the second stage of the Soyuz rocket that launched Expedition 19 to the International Space Station last Thursday.
However, U.S. Strategic Command has since reported that the rocket re-entered Earth's atmosphere near Taiwan, on the other side of the world, several hours after the reports of the fireball. So both its timing and entry location rule out the rocket as the explanation for the fireball.
"Well, we're all entitled to a 'mulligan' now and then, right," Chester wrote SPACE.com in an email, adding that he deferred Strategic Command. (A mulligan is a do-over in golf.)
"However, it is still a remarkable coincidence that a random rock would fall out of the sky along a path that is very similar to the ground-track of a decaying rocket body," Chester added. "But this is what makes science fun!"
The evidence now suggests, he said, that the loud boom and streak of light was created by a natural meteor, or bolide, burning up as it plummeted through Earth's atmosphere.
"I'm confident that this was a meteoric event," Bill Cooke of NASA's Marshall Space Flight Center in Alabama said this morning.
Sunday night light show
Residents of the areas around Norfolk and Virginia Beach, Va., began calling 911 Sunday night with reports of hearing a loud boom and seeing a streak of light that lit up the sky, according to news reports. Some said their houses shook.
The difficulty in distinguishing the cause of such a fireball lies in getting accurate reports with the right kinds of information.
"Most of the eyewitness accounts don't mention altitudes and azimuths. They just describe the light show," Chester explained.
Chester said he received "credible reports" from amateur astronomers that, when combined with the area from which reports of the fireball originated, "fit the ground-track of the rocket body with remarkable similarity."
"The only problem is that the time the rocket was predicted to pass over the area differs by some 10 minutes from the reported times that the fireball was seen," Chester said. The difference could be the result of an error in his prediction software or could be 'real,'" he said.
But, "based on the evidence I have at hand now, I have to lean more toward the 'natural' explanation," Chester said.
Space rocks the size of small cars plunge into Earth's atmosphere several times a year, typically burning up before reaching the ground. Most go unreported since they fall over uninhabited areas (our planet's surface is two-thirds ocean).
Cooke agreed that tracing the fireball's source is tricky given the paucity of information available.
"It's very hard to do given only eyewitness accounts," Cooke said in a telephone interview. He plans to look at sound measurements (meteors make sounds below human hearing as they travel through the atmosphere) taken that could reveal the energy of the bolide and in turn give a rough estimate of its size.
Video of the object, if any surfaces, could also shed light on the trajectory of the fireball. Such video often comes from the dashboard cameras in police cars, Cooke said. "They're out that time of night, and the camera is always running."
But, he said, "It's going to be very hard to get more information" on the nature of the bolide.
Whether or not any fragments of the meteor might have made it to Earth's surface is uncertain. "Most bolides do not," Cooke said. "The atmosphere is very good at protecting us from falling rocks."
A few space rocks do occasionally make it to the surface though. In recent years, pieces of a bolide were found after a meteor event in western Canada, Chicago and Peekskill, NY, Cooke said. Fragments of a meteor that originated from an asteroid that blew up over the skies of Africa last October were also recovered in the Sudanese desert.