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APOD: Milky Way and Exploding Meteor (2017 Aug 06)
Posted: Sun Aug 06, 2017 4:06 am
by APOD Robot
[img]https://apod.nasa.gov/apod/calendar/S_170806.jpg[/img] Milky Way and Exploding Meteor
Explanation: Next weekend the
Perseid Meteor Shower reaches its maximum. Grains of icy rock will
streak across the sky as they evaporate during entry into
Earth's atmosphere. These grains were shed from
Comet Swift-Tuttle. The
Perseids result from the annual crossing of the Earth through
Comet Swift-Tuttle's orbit, and are typically the most active
meteor shower of the year. Although it is hard to predict the level of activity in
any meteor shower, in a clear dark sky an observer might see a
meteor a minute. This year's
Perseids peak nearly a week after
full Moon, and so some faint meteors will be lost to the
lunar skyglow.
Meteor showers in general are best be seen from a
relaxing position, away from lights.
Featured here is a meteor caught
exploding during the 2015 Perseids above
Austria next to the central band of our
Milky Way Galaxy.
[/b]
Re: APOD: Milky Way and Exploding Meteor (2017 Aug 06)
Posted: Sun Aug 06, 2017 4:27 am
by Chris Peterson
This is actually less dramatic than it appears. The meteor isn't so much "exploding" as it is disintegrating. The parent body (probably less than a centimeter in diameter) reached deep enough into the atmosphere (50-100 km high) that the aerodynamic pressure on it exceeded the material strength of the stone. It broke apart, exposing a lot more surface area, which resulted in the bright flare and rapid loss of most mass as dust. The heat also ionized both meteoritic gas and atmospheric gas. This left a small cloud which was subsequently spread by high altitude winds and remained visible for several minutes as it dissipated. The motion of the cloud is unrelated to any "explosion" of the meteoroid itself.
Re: APOD: Milky Way and Exploding Meteor (2017 Aug 06)
Posted: Sun Aug 06, 2017 6:41 am
by keesscherer
It is the same picture as the 12 aug 2015 APOD:
https://apod.nasa.gov/apod/ap150812.html
I was not aware that APOD used the same image more than once. It is an awesome image though!
Re: APOD: Milky Way and Exploding Meteor (2017 Aug 06)
Posted: Sun Aug 06, 2017 10:11 am
by heehaw
Wow! Best meteor picture(s) I have EVER seen!
Re: APOD: Milky Way and Exploding Meteor (2017 Aug 06)
Posted: Sun Aug 06, 2017 11:22 am
by neufer
Chris Peterson wrote:
This is actually less dramatic than it appears. The meteor isn't so much "exploding" as it is disintegrating. The parent body (probably less than a centimeter in diameter) reached deep enough into the atmosphere (50-100 km high) that the aerodynamic pressure on it exceeded the material strength of the stone. It broke apart, exposing a lot more surface area, which resulted in the bright flare and rapid loss of most mass as dust. The heat also ionized both meteoritic gas and atmospheric gas. This left a small cloud which was subsequently spread by high altitude winds and remained visible for several minutes as it dissipated. The motion of the cloud is unrelated to any "explosion" of the meteoroid itself.
So it was either a "meteor" or "meteoroid" when it "exploded" and the small cloud is a "
meteorite"
Re: APOD: Milky Way and Exploding Meteor (2017 Aug 06)
Posted: Sun Aug 06, 2017 12:57 pm
by rstevenson
The Sunday APOD image is almost always a repeat; it has been so for many years.
Rob
Re: APOD: Milky Way and Exploding Meteor (2017 Aug 06)
Posted: Sun Aug 06, 2017 1:43 pm
by Chris Peterson
neufer wrote:Chris Peterson wrote:
This is actually less dramatic than it appears. The meteor isn't so much "exploding" as it is disintegrating. The parent body (probably less than a centimeter in diameter) reached deep enough into the atmosphere (50-100 km high) that the aerodynamic pressure on it exceeded the material strength of the stone. It broke apart, exposing a lot more surface area, which resulted in the bright flare and rapid loss of most mass as dust. The heat also ionized both meteoritic gas and atmospheric gas. This left a small cloud which was subsequently spread by high altitude winds and remained visible for several minutes as it dissipated. The motion of the cloud is unrelated to any "explosion" of the meteoroid itself.
So it was either a "meteor" or "meteoroid" when it "exploded" and the small cloud is a "
meteorite" :?:
During the luminous phase "meteor" usually includes both the parent meteoroid and the secondary phenomena of energy release. Technically, the body itself remains a "meteoroid". The dust particles in the cloud are, indeed, "meteorites" ("any solid object which survived the meteor phase in planetary atmosphere without being completely vaporized"), and are more specifically "meteoritic smoke particles" ("solid object which recondensed in planetary atmosphere from material vaporized during the meteor phase"). Other acceptable terms called out in the definition are "meteoritic dust" and "micrometeorite".
Re: APOD: Milky Way and Exploding Meteor (2017 Aug 06)
Posted: Sun Aug 06, 2017 10:16 pm
by FLPhotoCatcher
If you look closely, you will see that the two meteor streaks in the first two frames do not line up. Are one of them added for effect, or is it a piece of the meteor that changed direction when the meteor broke up?
Also, the orangeish stuff (plasma?) around the streak in the first frame had to have propagated from the meteor faster than the speed of sound (based on the idea that the camera's shutter closed before the 2nd frame starts, and the location of the streak in the 2nd frame). Does anyone know what the orange glow is, if not just the normal ionized gas that meteors make?
Re: APOD: Milky Way and Exploding Meteor (2017 Aug 06)
Posted: Sun Aug 06, 2017 10:29 pm
by Chris Peterson
FLPhotoCatcher wrote:If you look closely, you will see that the two meteor streaks in the first two frames do not line up. Are one of them added for effect?
Almost certainly, the meteor in the second frame is a completely different one.
Also, the orangeish stuff (plasma?) around the streak in the first frame had to have propagated from the meteor faster than the speed of sound (based on the idea that the camera's shutter closed before the 2nd frame starts, and the location of the streak in the 2nd frame).
No, the cloud dissipated slowly. These are long exposures- I'd guess perhaps 30 seconds each.
Does anyone know what the orange glow is, if not just the normal ionized gas that meteors make?
It's a photochemical process that primarily involves sodium, and also iron if it's present in the meteoroid. Both elements react with upper atmpospheric ozone to produce a sustained release of light- 589 nm for sodium, and a range of lines between red and green for iron.
Re: APOD: Milky Way and Exploding Meteor (2017 Aug 06)
Posted: Tue Aug 08, 2017 2:11 am
by avdhoeven
Before people start to dissect the images and saying it's faked I want to make clear these are all original as I shot them. The answers are quite simple.
1) the exposure times were three minutes, so the total time was about 9 minutes, so it was not that fast in motion
2) the stripe in the second image has nothing to do with the meteor. It was a satellite passage if I remember correctly. I think in that time I even looked it up, but don't remember exactly.
Re: APOD: Milky Way and Exploding Meteor (2017 Aug 06)
Posted: Wed Aug 09, 2017 12:16 pm
by Knight of Clear Skies
Chris Peterson wrote:No, the cloud dissipated slowly. These are long exposures- I'd guess perhaps 30 seconds each.
The exposures were 180 seconds each and there are four frames, 12 minutes in total. There are some more details in
this thread. I suggested submitting it to APOD but if I hadn't I'm sure someone else would have, it's a great capture.
There is
another version here which includes the meteor in a wider mosaic.
