A brilliantfireball in the Virginia sky on Sunday was likely a natural meteor event andnot the remnants of a Russian rocket, scientists now say, a reversal fromyesterday's initial analysis.
On Monday,Geoff Chester of the U.S. Naval Observatory told SPACE.com that the loudboom and flash of light seen in the skies over Norfolk and Virginia Beach waslikely the secondstage of the Soyuz rocket that launched Expedition 19 to the InternationalSpace Station last Thursday.
However, U.S.Strategic Command has since reported that the rocket re-entered Earth'satmosphere near Taiwan, on the other side of the world, several hours after thereports of thefireball. So both its timing and entry location rule out the rocket as theexplanation for the fireball.
"Well,we're all entitled to a 'mulligan' now and then, right," Chester wrote SPACE.comin an email, adding that he deferred Strategic Command. (A mulligan is a do-overin golf.)
"However,it is still a remarkable coincidence that a random rock would fall out of thesky along a path that is very similar to the ground-track of a decaying rocketbody," Chester added. "But this is what makes science fun!"
Theevidence now suggests, he said, that the loud boom and streak of light wascreated by a natural meteor, or bolide, burning up as it plummeted throughEarth's atmosphere.
"I'mconfident that this was a meteoric event," Bill Cooke of NASA's Marshall Space Flight Center in Alabama said this morning.
Sundaynight light show
Residentsof the areas around Norfolk and Virginia Beach, Va., began calling 911 Sundaynight with reports of hearing a loud boom and seeing a streak of light that litup the sky, according to news reports. Some said their houses shook.
Thedifficulty in distinguishing the cause of such a fireball lies in gettingaccurate reports with the right kinds of information.
"Mostof the eyewitness accounts don't mention altitudes and azimuths. They justdescribe the light show," Chester explained.
Chester said he received "crediblereports" from amateur astronomers that, when combined with the area fromwhich reports of the fireball originated, "fit the ground-track of the rocketbody with remarkable similarity."
"Theonly problem is that the time the rocket was predicted to pass over the areadiffers by some 10 minutes from the reported times that the fireball wasseen," Chester said. The difference could be the result of an error in hisprediction 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 rocksthe size of small cars plunge into Earth's atmosphere several times a year,typically burning up before reaching the ground. Most go unreported since theyfall over uninhabited areas (our planet's surface is two-thirds ocean).
Cookeagreed that tracing the fireball's source is tricky given the paucity ofinformation available.
"It'svery hard to do given only eyewitness accounts," Cooke said in a telephoneinterview. He plans to look at sound measurements (meteors make sounds belowhuman hearing as they travel through the atmosphere) taken that could revealthe energy of the bolide and in turn give a rough estimate of its size.
Video ofthe object, if any surfaces, could also shed light on the trajectory of thefireball. Such video often comes from the dashboard cameras in police cars,Cooke said. "They're out that time of night, and the camera is alwaysrunning."
But, hesaid, "It's going to be very hard to get more information" on thenature of the bolide.
Whether ornot any fragments of the meteor might have made it to Earth's surface isuncertain. "Most bolides do not," Cooke said. "The atmosphere isvery good at protecting us from falling rocks."
A few spacerocks do occasionally make it to the surface though. In recent years, pieces ofa 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 blewup over the skies of Africa last October were also recovered in theSudanese desert.