March 31, 2009 11 Comments
The past 10 days have seen 2 extremely bright fireballs over the East Coast of the US. Both fireballs also were accompanied by loud sonic booms.
The latest meteor occurred on Sunday night, March 29, at ~9:50 EDT. Observed from Pennsylvania to North Carolina, the fireball seems to have ended over the Norfolk/Virginia Beach area of southeast Virginia. A loud noise similar to an aircraft sonic boom or distant thunder was heard and felt ~2 minutes after the fireball last disrupted.
According to many press stories, the Naval Observatory is reporting that the fireball was caused by the reentry of part of a Russian Soyuz rocket booster. Last Thursday this rocket launched 1 American astronaut, 1 Russian Cosmonaut and an American paid passenger to the International Space Station. Reports from the Joint Space Operations Center at Vandenberg AFB and the US Strategic Command both state that the fireball was not caused by the Soyuz booster and was most likely due to a small asteroid (see here and here).
Below is a map showing the location of some of the fireball reports. Yellow circles denote fireball sightings but no sound. Red circles are locations that heard sonic booms or concurrent noises. It is obvious from the maps that the fireball detonated over southeast Virginia.
Little over a week earlier on March 20 at ~2:30-3:00 am EDT, another bright and loud fireball was seen and heard. As the map below shows, the fireball was seen over a 4 state area from Virginia to Georgia. Similar to the map above, red circles show were the fireball was heard. The concentration of sound reports in the Augusta area on the border of Georgia and South Carolina pinpoints where this fireball detonated.
[NOTE: This paragraph has been edited since it was originally posted.] There are 2 different ways a fireball can produce sound. The sound heard over southeast Virginia and the GA/SC border was a sonic boom caused by the fireball’s shock wave. This shock wave is the natural result of a fast moving solid object moving through the atmosphere. Since this usually occurs at a height of 20 or more miles it can take the sound a few minutes to travel to the observer. This is why the sound was heard ~2 minutes after the fireball was no longer visible.
The second way fireballs create sound is via EMF radiation. In this case, the high temperature fireball produces radiation at all wavelengths. Sometimes objects such as a metal frame or even a tree can convert the EMF waves into audible sounds. Since the EMF waves travel at the speed of light, these sounds can be heard at the exact same time the fireball is visible. It is possible these EMF sounds were heard by the March 20th fireball observer in Traxton, Virginia.