(meteorobs) Earth-grazer definition question
Roberto Gorelli
md6648 at mclink.it
Fri Nov 20 03:31:18 EST 2015
On Thu, 19 Nov 2015 23:34:28 +0000 (UTC)
LEO STACHOWICZ <l.stachowicz at btinternet.com> wrote:
> I'm afraid I can't answer, but I do have a related question that has
>been on my mind: For the purposes of observation, if we are talking
>about sporadics (or if the shower is unknown), how many degrees of
>sky does a meteor have to travel before it can be called an
>earth-grazer? Also, in the case of a known shower member, how far
>from the radiant does the meteor have to start to be called an
>earth-grazer?
> Clear skies,Leo
>
>
>
> On Thursday, 19 November 2015, 23:21, Thomas Ashcraft
><ashcraft at heliotown.com> wrote:
>
>
> Definition of an earth-grazing fireball from wiki:
> https://en.wikipedia.org/wiki/Earth-grazing_fireball
>
> " An Earth-grazing fireball (or Earth-grazer)[2] is a fireball, a
>very bright meteor that enters Earth’s atmosphere and leaves again."
>
> Does an earth-grazer have to leave earth's atmosphere to be called
>an earth-grazer? Can it skim and ablate or burn up entirely and
>still be termed an earth-grazer?
>
> Thanks in advance.
>
> Thomas
Sorry for the bad English.
It's to remember that there isn't a scientific definition of a
"earth-grazer" in the same way that there isn't a scientific
definition of "bolid".
An earth-grazer should to be the meteors/bolids that cross the entire
sky from an horizon to the other in the opposite side, but this it's
only the apparent view from a single observer in a single locality.
In the all day observations we can to said, IHMO, that a meteor/bolid
was an earth-grazer when crossed over 90° of the sky, in this way each
observer can to said a number of that events in its observer live.
Only the bolid of 10 August 1972, and perharps some others (not more
of 5-10 in the past century), that entered and exit from the Earth
atmophere, was a real earth-grazer, then if only it can to be
denominated "earth-grazer" probably we never shall see in our live a
similar phaenomena (earth-grazer).
Then the question is: do we are speaking of a apparent or of a real
earth-grazer?
Best greetings.
Roberto Gorelli
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