[meteorite-list] re: meteor velocity
From: GeoZay_at_aol.com <GeoZay_at_meteoritecentral.com>
Date: Thu Apr 22 10:27:46 2004 Message-ID: <78.4a12c085.2cdfa729_at_aol.com> -------------------------------1068387625 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit I just noticed that I sent a reply to Jose, but didn't include adding the meteorite-list. So...resending my response again, but to the list only this time. GeoZay --------------------------------------------- >>Take the Leonids, for instance, (Nov 14-20), they are known to be associated to P/comet Tempel-Tuttle and they are described as "very fast"; However, the E Taurids, associated to comet P/Encke, are described as "slow" meteors (Oct 10-Dec 5), so it seems that the visual perception of a meteor's velocity is not a reliable indicator that the meteor has,or has not a cometary origin?<< Hello Jose, I believe it's more reliable than most people realize and you are right partially...But there are a number of guidelines that one can refer to in regards to the parentage of meteors that I wouldn't disregard. The following are some guidelines that I've formulated from my experience in recording meteor data that you might find useful? a) if a meteor appears very fast, it is reasonably certain that it is of cometary origin and not asteroidal. If one should happen to be traveling that fast for some unknown reason, it most likely won't be producing any meteorites. A good bet that it will terminal burst and nothing to be found, but dust. b) if a meteor appeared very slow and non fireball status, I'd be inclined to think of it as also being cometary...particularly if no sonic booms were reported. This is based on asteroidal material being made up of denser material than the typical cometary meteoroid whose texture is pretty much like fluff. Even a small piece of asteroidal material (such as rock or iron) will appear quite brite. Only with the micrometeorites(visible and non-visible) will there be any doubt, but I think for the typical meteorite hunter they aren't too concern about micrometeorites? c) if a meteor appeared very slow and had fireball status accompanied by reports of sonic booms, It's no doubt of asteroidal(or moon/mars) origin. d) if a Meteor was a fireball, Very slow and not associated with a cometary shower thru radiant alignment, I'd be inclined to consider it likely being asteroidal....provided the event occurred between noon and midnight. The closer the event occurred to 6 pm local with the above circumstances, the more I'd be inclined to think of it as an asteroidal object. e) If a meteor appeared very slow and lasted a minute or two, most likely re-entering satellite. f) A fireball lasting only a few seconds is highly unlikely to be a satellite re-entry. g) if a fireball occurred with any velocity(Very Slow thru Very Fast) after midnight and before 9 am local, I'd be incline to think of it being cometary. I think that's all the guidelines I'd use in classifying whether a meteor was generally cometary or asteroidal and thus a possible meteorite dropper. I've never written them down before, but these are what I look for instinctively. As for the Taurids you mentioned above, I've only watched for the North and South Taurids. I'm not familiar with "E Taurids". Maybe a typo perhaps? The N. and S. Taurids active period is considered to be from Oct 1 thru Nov 25 with a peak for the N. Taurids on Nov 12. The S. Taurids peak occurs on Nov 5. If you are referring to either or both of these Taurids, their entry velocity is between 27 and 29 km/s. Visually I'd consider these velocities as being Slow to Medium....Very distinct looking compared to the typical asteroidal object entering usually with velocities less than 23 km/s. I'm pretty certain if I seen something with a velocity like that of a N. Taurid, I'd be highly inclined to think of it being cometary. However, out of the 40 meteor showers recognized as being active enough to warrant watching, only 6 have entry velocities that might cause confusion due to their velocites. And these can usually be eliminated or considered if they should happen to be active or not at the time a suspect fireball was observed. It may seem like a lot of if's and but's, but once these guidelines are firmly implanted, a suspect fireball can be quickly and reasonably judged as to whether it's worth chasing down meteorite potentials or not. George Zay -------------------------------1068387625 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable <HTML><HEAD> <META charset=3DUTF-8 http-equiv=3DContent-Type content=3D"text/html; charse= t=3Dutf-8"> <META content=3D"MSHTML 6.00.2800.1106" name=3DGENERATOR></HEAD> <BODY style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial; BACKGROUND-COLOR: #fffff= f"> <DIV>I just noticed that I sent a reply to Jose, but didn't include adding t= he meteorite-list. So...resending my response again, but to the list only th= is time. </DIV> <DIV>GeoZay</DIV> <DIV>---------------------------------------------</DIV> <BLOCKQUOTE style=3D"PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue=20= 2px solid"> <DIV><FONT face=3DArial>>>Take the Leonids, for instance, (Nov 14-20),= they are known to</FONT></DIV> <DIV><FONT face=3DArial>be associated to P/comet Tempel-Tuttle and they are=20= described as "very fast";</FONT></DIV> <DIV><FONT face=3DArial>However, the E Taurids, associated to comet P/Encke,= are described as "slow" meteors (Oct 10-Dec 5), so it seems that the&n= bsp;visual perception of a meteor's velocity is not a reliable indicator tha= t the meteor has,or has not a cometary origin?<<</FONT></DIV></BLOCKQU= OTE> <DIV>Hello Jose,</DIV> <DIV> </DIV> <DIV>I believe it's more reliable than most people realize and you are right= partially...But there are a number of guidelines that one can ref= er to in regards to the parentage of meteors that I wouldn't disregard. &nbs= p;The following are some guidelines that I've formulated from my experi= ence in recording meteor data that you might find useful?</DIV> <DIV> </DIV> <DIV> a) if a meteor appears very fast, it is reasonably certain t= hat it is of cometary origin and not asteroidal. If one should happen t= o be traveling that fast for some unknown reason, it most likely won't be pr= oducing any meteorites. A good bet that it will terminal burst and noth= ing to be found, but dust.</DIV> <DIV> </DIV> <DIV>b) if a meteor appeared very slow and non fireball status, I'd be incli= ned to think of it as also being cometary...particularly if no sonic booms w= ere reported. This is based on asteroidal material being made up of de= nser material than the typical cometary meteoroid whose texture is pretty mu= ch like fluff. Even a small piece of asteroidal material (such as rock or ir= on) will appear quite brite. Only with the micrometeorites(visible and non-v= isible) will there be any doubt, but I think for the typical meteorite=20= hunter they aren't too concern about micrometeorites? </DIV> <DIV> </DIV> <DIV>c) if a meteor appeared very slow and had fireball status acc= ompanied by reports of sonic booms, It's no doubt of asteroidal(or moon/mars= ) origin. </DIV> <DIV> </DIV> <DIV>d) if a Meteor was a fireball, Very slow and not associated with a come= tary shower thru radiant alignment, I'd be inclined to consider it likely be= ing asteroidal....provided the event occurred between noon and midnight. The= closer the event occurred to 6 pm local with the above circumstances, the m= ore I'd be inclined to think of it as an asteroidal object. </DIV> <DIV> </DIV> <DIV> e) If a meteor appeared very slow and lasted a minute or two, mos= t likely re-entering satellite. </DIV> <DIV> </DIV> <DIV>f) A fireball lasting only a few seconds is highly unlikely to be a sat= ellite re-entry.</DIV> <DIV> </DIV> <DIV>g) if a fireball occurred with any velocity(Very Slow thru Very Fa= st) after midnight and before 9 am local, I'd be incline to think of it= being cometary. </DIV> <DIV> </DIV> <DIV> </DIV> <DIV>I think that's all the guidelines I'd use in classifying whether a mete= or was generally cometary or asteroidal and thus a possible meteorite d= ropper. I've never written them down before, but these are what I look= for instinctively. As for the Taurids you mentioned above, I've only watche= d for the North and South Taurids. I'm not familiar with "E Taurids". Maybe=20= a typo perhaps? The N. and S. Taurids active period is considered to be= from Oct 1 thru Nov 25 with a peak for the N. Taurids on Nov 12. The S. Tau= rids peak occurs on Nov 5. If you are referring to either or both of these T= aurids, their entry velocity is between 27 and 29 km/s. Visually I'd conside= r these velocities as being Slow to Medium....Very distinct looking compared= to the typical asteroidal object entering usually with velocities= less than 23 km/s. I'm pretty certain if I seen something with a velocity l= ike that of a N. Taurid, I'd be highly inclined to think of it being cometar= y. However, out of the 40 meteor showers recognized as being active enough t= o warrant watching, only 6 have entry velocities that might cause confu= sion due to their velocites. And these can usually be eliminated or consider= ed if they should happen to be active or not at the time a suspect fireball=20= was observed. It may seem like a lot of if's and but's, but once these guide= lines are firmly implanted, a suspect fireball can be quickly and=20= reasonably judged as to whether it's worth chasing down meteorite potentials= or not. </DIV> <DIV>George Zay</DIV></BODY></HTML> -------------------------------1068387625-- Received on Sun 09 Nov 2003 09:20:25 AM PST |
 StumbleUpon del.icio.us reddit Yahoo MyWeb
|