APOD: Bright Meteor, Starry Sky (2021 Aug 19)

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APOD: Bright Meteor, Starry Sky (2021 Aug 19)

Post by APOD Robot » Thu Aug 19, 2021 4:05 am

Image Bright Meteor, Starry Sky

Explanation: Plowing through Earth's atmosphere at 60 kilometers per second, this bright perseid meteor streaks along a starry Milky Way. Captured in dark Portugal skies on August 12, it moves right to left through the frame. Its colorful trail starts near Deneb (alpha Cygni) and ends near Altair (alpha Aquilae), stars of the northern summer triangle. In fact this perseid meteor very briefly outshines both, two of the brightest stars in planet Earth's night. The trail's initial greenish glow is typical of the bright perseid shower meteors. The grains of cosmic sand, swept up dust from periodic comet Swift-Tuttle, are moving fast enough to excite the characteristic green emission of atomic oxygen at altitudes of 100 kilometers or so before vaporizing in an incandescent flash.

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Ann
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Re: APOD: Bright Meteor, Starry Sky (2021 Aug 19)

Post by Ann » Thu Aug 19, 2021 5:17 am

Very nice APOD!

Okay, let's try to annotate...

BrightMeteorPerseids2021-7337-crop-net1024[1].jpg
Cygnus with a bright Perseid. Photo: Miguel Claro.
Cygnus with meteor annotated Miguel Claro.png

1) At the tip of this dust lane, we find the Cocoon Nebula (I think). See this image of the Cocoon Nebula by Keesscherer at Wikimedia Commons.

2) The North America Nebula, NGC 7000. See this image of the North America Nebula by Oliver Stein at Wikimedia Commons.

3) Deneb, Alpha Cygni.

4) Sadr, Gamma Cygni.

5) Epsilon Cygni.

6) Zeta Cygni.

7) Delta Cygni.

8) Iota2 Cygni.

9) Albireo, Beta Cygni. The colors in the picture are saturated.

10) The Coathanger asterism.

11) Altair, Alpha Aquila.

12) Tarazed, Gamma Aquila.

13) Constellation Delphinus.

Ann
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Re: APOD: Bright Meteor, Starry Sky (2021 Aug 19)

Post by orin stepanek » Thu Aug 19, 2021 11:49 am

BrightMeteorPerseids2021-7337-crop-net1024.jpg
A tiny grain; a lot of light;
Burns up quickly in the night!
Burns up fast;
Doesn't last;
Out shines Deneb, and Altair;
And suddenly it will Disappear!
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Re: APOD: Bright Meteor, Starry Sky (2021 Aug 19)

Post by Chris Peterson » Thu Aug 19, 2021 12:34 pm

APOD Robot wrote:
Thu Aug 19, 2021 4:05 am
Image Bright Meteor, Starry Sky

Explanation: Plowing through Earth's atmosphere at 60 kilometers per second, this bright perseid meteor streaks along a starry Milky Way. Captured in dark Portugal skies on August 12, it moves right to left through the frame. Its colorful trail starts near Deneb (alpha Cygni) and ends near Altair (alpha Aquilae), stars of the northern summer triangle. In fact this perseid meteor very briefly outshines both, two of the brightest stars in planet Earth's night. The trail's initial greenish glow is typical of the bright perseid shower meteors. The grains of cosmic sand, swept up dust from periodic comet Swift-Tuttle, are moving fast enough to excite the characteristic green emission of atomic oxygen at altitudes of 100 kilometers or so before vaporizing in an incandescent flash.
Given the fragmentation event and continuing material still ablating, the parent body here was likely a few centimeters in size. Larger than sand. And the degree to which it outshone the bright stars around it is more than might be initially apparent. The exposure time of the stars was somewhere from 30 seconds to a few minutes. The exposure time of the meteor (at any given pixel) was tens of milliseconds. Most of the visible trail here is brighter than the brightest stars.
Chris

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Re: APOD: Bright Meteor, Starry Sky (2021 Aug 19)

Post by johnnydeep » Thu Aug 19, 2021 3:39 pm

Is the fact that Perseids typically begin green due primarily to their speed when entering the upper atmosphere? I might guess meteors of different speeds would excite different atmospheric elements, and probably their own material as well.
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Re: APOD: Bright Meteor, Starry Sky (2021 Aug 19)

Post by Chris Peterson » Fri Aug 20, 2021 4:20 am

johnnydeep wrote:
Thu Aug 19, 2021 3:39 pm
Is the fact that Perseids typically begin green due primarily to their speed when entering the upper atmosphere? I might guess meteors of different speeds would excite different atmospheric elements, and probably their own material as well.
Slowest (11 km/s) to fastest (71 km/s) are all fast enough to ablate, and will basically be the same as far as colors. There is some contribution from the elemental makeup of the parent. And the colors produced by the body itself (as opposed to the atmosphere, which contributes most of the color) change, as the more volatile, lower melting point elements tend to burn off first. The color also changes along the path as the meteor descends deeper into the atmosphere, and the gas density changes.
Chris

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Ann
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Re: APOD: Bright Meteor, Starry Sky (2021 Aug 19)

Post by Ann » Fri Aug 20, 2021 5:09 am

I was wrong! I have to change my mind about where to find the Cocoon nebula in this APOD!

Cygnus with meteor annotated Miguel Claro.png
Miguel Claro's image of Cygnus with Perseid, where I put the
Cocoon Nebula in the wrong place.
Cocoon widefield arrow Tommy Knutsen.png
A part of Tommy Knutsen's picture of Cygnus. Note the Cocoon Nebula (arrow).

As you can see, I placed the Cocoon Nebula mostly north of the North America Nebula. The position I gave to the Cocoon Nebula is marked as 1. But the Cocoon Nebula is really located far more east-northeast of the North America Nebula than I gave it credit for.

The approximate coordinates for the North America Nebula are 20h 59m, +44 29'. For the Cocoon Nebula, the approximate coordinates are 21h 53m, +47 17'.

Ann
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Re: APOD: Bright Meteor, Starry Sky (2021 Aug 19)

Post by johnnydeep » Fri Aug 20, 2021 12:29 pm

Chris Peterson wrote:
Fri Aug 20, 2021 4:20 am
johnnydeep wrote:
Thu Aug 19, 2021 3:39 pm
Is the fact that Perseids typically begin green due primarily to their speed when entering the upper atmosphere? I might guess meteors of different speeds would excite different atmospheric elements, and probably their own material as well.
Slowest (11 km/s) to fastest (71 km/s) are all fast enough to ablate, and will basically be the same as far as colors. There is some contribution from the elemental makeup of the parent. And the colors produced by the body itself (as opposed to the atmosphere, which contributes most of the color) change, as the more volatile, lower melting point elements tend to burn off first. The color also changes along the path as the meteor descends deeper into the atmosphere, and the gas density changes.
So the statement in the description that the "initial greenish glow is typical of the bright perseid(s)" isn't trying to say that the Perseids' colors look any different than other meteor showers?
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Re: APOD: Bright Meteor, Starry Sky (2021 Aug 19)

Post by Chris Peterson » Fri Aug 20, 2021 1:03 pm

johnnydeep wrote:
Fri Aug 20, 2021 12:29 pm
Chris Peterson wrote:
Fri Aug 20, 2021 4:20 am
johnnydeep wrote:
Thu Aug 19, 2021 3:39 pm
Is the fact that Perseids typically begin green due primarily to their speed when entering the upper atmosphere? I might guess meteors of different speeds would excite different atmospheric elements, and probably their own material as well.
Slowest (11 km/s) to fastest (71 km/s) are all fast enough to ablate, and will basically be the same as far as colors. There is some contribution from the elemental makeup of the parent. And the colors produced by the body itself (as opposed to the atmosphere, which contributes most of the color) change, as the more volatile, lower melting point elements tend to burn off first. The color also changes along the path as the meteor descends deeper into the atmosphere, and the gas density changes.
So the statement in the description that the "initial greenish glow is typical of the bright perseid(s)" isn't trying to say that the Perseids' colors look any different than other meteor showers?
Most meteors look very similar in images. Differences are more likely to be visual, and a consequence mostly of how our eyes and brains process these events.
Chris

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Re: APOD: Bright Meteor, Starry Sky (2021 Aug 19)

Post by johnnydeep » Fri Aug 20, 2021 2:07 pm

Chris Peterson wrote:
Fri Aug 20, 2021 1:03 pm
johnnydeep wrote:
Fri Aug 20, 2021 12:29 pm
Chris Peterson wrote:
Fri Aug 20, 2021 4:20 am


Slowest (11 km/s) to fastest (71 km/s) are all fast enough to ablate, and will basically be the same as far as colors. There is some contribution from the elemental makeup of the parent. And the colors produced by the body itself (as opposed to the atmosphere, which contributes most of the color) change, as the more volatile, lower melting point elements tend to burn off first. The color also changes along the path as the meteor descends deeper into the atmosphere, and the gas density changes.
So the statement in the description that the "initial greenish glow is typical of the bright perseid(s)" isn't trying to say that the Perseids' colors look any different than other meteor showers?
Most meteors look very similar in images. Differences are more likely to be visual, and a consequence mostly of how our eyes and brains process these events.
Thanks. Good to know.
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