|
|
|
Rapport fra Trondheim Astronomiske Forening om ildkule over Nord-Trøndelag sendt til International Meteor Organisation (kopi til Metorgruppen i Norsk Astronomisk Selskap) 2. juni 1999. Svar fra IMO på denne henvendelsen finner du her. Dear Mr. Arlt, Initial report and questions to the International Meteor Society (IMO). A plus full moon fireball was seen from several locations in Mid-Norway on May 24th about 5:20pm local time. This far, I have heard of 6 independent sightings form different locations in Norway and rumours of sightings reported in the Swedish press. I am in the process of collecting reports. All refer to the fireball as brighter than the full moon. I have spoken to two of the observers on phone. They must have seen two different fragments. Both observers saw the bright "blank" light for about 2 or 3 seconds. Observer A, Dan Leo Totland, saw the light starting 25-30 deg. above the horison in direction 170 deg (360 deg. full circle with east = 90 and south = 180). It went straight down as seen from his site at Soerli (the "oe" is an o with a slash ,/, on top) approx. 64.26 deg. north and 13.75 deg east. The brightness increased untill the fireball suddenly disappeared about 20-25 deg above the horizon. The fireball left a train that looked like the train from an airliner at high altitudes seen from some distance (i.e somewhat dimmer than if the plane had been in zenith). The train was visible for 30-60 seconds, he believed. It deformed during this time due to different winds up in the atmosphere. There were no fragmentation seen. "Only" a brighter than full moon fireball of white/yellowish blank light. There were serveral people seeing the fireball and the train since they were in the middle of an out door party. About 90-120 seconds after the sighting, they all heard a thunderlike rumbeling sound lasting for an estimated 10-15 seconds. Yesterday, Mr. Totland told me that he had heard that a Swedish paper (in the city of Oestersund - same "oe" thing) had reported sightings which could well have been the same fragment. Observer B, Molly Grongstad from Hoeylandet (same "oe" thing), saw something that must have been in a direction approx. 290-310 degrees if seen from Soerli, Hence, it can't have been the same fragment. The time was given as "about 15 minutes after I left a cabin at about 5pm". The sighting was done close to the mountain top called Skarlandsfjell at about 64.62deg. north and 12.43 deg east. She was close to the top of this mountain which she claims is the highest in the area. Then she heard a deep rumbeling sound that lasted about 4-7 seconds. During the last 2 or 3 seconds of this period she saw an extremley bright fireball. "It was", she told me on telephone, "white (white/yellow ?) and very blank and bright at the front, and I could see flickering flames from the back of it." It came in on a fairly flat trajectory (I'll check out what that means and the exact location of the sighting when I and at least 3 others from the Trondheim Astronomical Society visit her the upcoming weekend. We will then go to the site and she will show us and tell in detail what happened. It is 2 1/2 hours walk from the nearest road. She knows the area as were it her own home. She also told me that at one time, the fireball was so low that she saw it projected against the mountains in the background. She isn't 100% sure about this, but the more thinks about what she saw; "it must have". This sounds incredible to me in the light of what I read yesterday in my IMO - Handbook Visual Meteor Observastion (1987 edition, page 4 & 5) that most meteorites have lost their "cosmic" velocity about 20 km above ground level, and then cools rapidly off to invisibility. Do you have any comments to this ? The fireball then seemed to "fall to ground" straight behind the top the mountain she stood on. She thought it was a plane crashing, but heard no sound after it disappeard from the field of view. She was scared, and had a long way back, so she did not look for it on the other side of the mountain. She was even reluctant to speak of it back home, except for the husband and a couple of close friends untill she saw other reports in the local newspaper "Namdalsposten" on monday 31st. That's where she got my name from. As I said, several people will go up there to speak to her and examine the area where she thought it might have fallen. We would really appreciate some guidance from you or others in the IMO. What is a possible size range for the fragment ? I have not even a clue. I am the former leader of the Meteor Section (1982 - 1986 or something like that) of the Norwegian Astronomical Society. Hence, I know the basic things about meteors and meteorites. I have the IMO handbook and a geological book with pictures and description of common type meteorites. And of course other literature like 10 years of WGN (1982-1992). What I know little about is impacts, sizes trajectories etc. The basic question is : From the description above (sound and light at the same time, possible projection against mountain background, individual flames seen from the back of it), it seems possible to me that the impact site is close to where she was. But then again, people may get twisted impressions of such incredible events, and this thing about meteorites going invisible in the last 20 km (?) of their trajectories pulls me down from the sky to the earth as far as expectations of a recovery are concerned. A recovery would be the 12th ever in Norway. The largest is 77.5 kg from Alta (1902), and the last is from Sogn in 1978 (1.513kg). Nine are stone meteorites, one is a iron meteorite and the eleventh is a iron/stone meteorite. A sighting of the fireball from observer B's home town about 10-20 km (?) away tells about a bent trajectory (two straight lines with a bend at the intersection ?). I will try to get drawings of this and also of other the sightings in the days that come. Some of the first reports were collected by Arnulf Loekken (again this "oe") from UFO Norway, who notified me about the first two sightings last friday. He will send me reports and drawings as he gets them. And if we find it, what can we do right and wrong ? I look forward to hearing from you soon. Regards Birger Andresen _________________________ Sist oppdatert : 02. juni 1999.
|