APOD: Geminid of the North (2021 Dec 17)

Comments and questions about the APOD on the main view screen.
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APOD: Geminid of the North (2021 Dec 17)

Post by APOD Robot » Fri Dec 17, 2021 5:05 am

Image Geminid of the North

Explanation: An arid expanse of the Tengger Desert in north-central China, planet Earth fills the foreground of this starry scene. A widefield panoramic view, it was recorded shortly after moonset in the local predawn hours of December 14. Pictured in the still dark sky, stars of the northern winter hexagon surround a luminous Milky Way. Seen near the peak of the annual meteor shower, the startling flash of a bright Geminid fireball meteor was also captured on that night. Above the western horizon and just below bright star Capella, its dagger-like trail points back to the meteor shower's radiant in Gemini. Of course, the constellation Gemini is easy to spot. Its twin bright stars, bluish Castor and yellowish Pollux are near top center in the frame.

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Re: APOD: Geminid of the North (2021 Dec 17)

Post by orin stepanek » Fri Dec 17, 2021 2:08 pm

GeminidFireball_AlvinWu.jpg
Best Geminid so far this season? Well for me it is!
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Re: APOD: Geminid of the North (2021 Dec 17)

Post by neufer » Fri Dec 17, 2021 2:52 pm

https://en.wikipedia.org/wiki/Tengger_Desert wrote:
<<The Tengger Desert (Mongolian: Тэнгэр цөл, lit. 'Sky Desert') is an arid natural region that covers about 36,700 km2 and is mostly in the Inner Mongolia Autonomous Region in China. The expansion of the Tengger and its neighbour, the Badain Jaran Desert, has been apparent since the 1950s, when large volumes of water were diverted from rivers to feed agricultural expansion and huge tracts of forest :tree: were removed.>>
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Re: APOD: Geminid of the North (2021 Dec 17)

Post by hypatia » Fri Dec 17, 2021 9:54 pm

What are the three blue 'stars' right above Rigel?

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Re: APOD: Geminid of the North (2021 Dec 17)

Post by johnnydeep » Fri Dec 17, 2021 10:02 pm

hypatia wrote: Fri Dec 17, 2021 9:54 pm What are the three blue 'stars' right above Rigel?
Those would be the belt of Orion! Which from left to right are named: Alnitak, Alnilam and Mintaka!
https://en.wikipedia.org/wiki/Orion's_Belt wrote:Orion's Belt or the Belt of Orion, also known as the Three Kings or Three Sisters,[1] is an asterism in the constellation Orion. It consists of the three bright stars Alnitak, Alnilam and Mintaka.

Looking for Orion's Belt is the easiest way to locate Orion in the night sky. The stars are more or less evenly spaced in a straight line, and so can be visualized as the belt of the eponymous hunter's clothing. They are best viewed in the early night sky during the Northern Winter/Southern Summer, in particular the month of January at around 9:00 pm.[2]
And here are some of the other stars in Orion and the nearby nebula:

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Re: APOD: Geminid of the North (2021 Dec 17)

Post by johnnydeep » Fri Dec 17, 2021 10:09 pm

I'll note that if you follow the "straight" line from the meteor trail up, it badly misses Castor, which is very near the radiant, but I presume that is only because of the panoramic view, and the fact that the normally "straight" trail appears curved here, and it is that (slight) curve that must be followed back, maintaining the curve, in order to intersect the radiant.
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"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."

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Re: APOD: Geminid of the North (2021 Dec 17)

Post by hypatia » Sat Dec 18, 2021 11:24 pm

johnnydeep wrote: Fri Dec 17, 2021 10:02 pm
hypatia wrote: Fri Dec 17, 2021 9:54 pm What are the three blue 'stars' right above Rigel?
Those would be the belt of Orion! Which from left to right are named: Alnitak, Alnilam and Mintaka!
https://en.wikipedia.org/wiki/Orion's_Belt wrote:Orion's Belt or the Belt of Orion, also known as the Three Kings or Three Sisters,[1] is an asterism in the constellation Orion. It consists of the three bright stars Alnitak, Alnilam and Mintaka.

Looking for Orion's Belt is the easiest way to locate Orion in the night sky. The stars are more or less evenly spaced in a straight line, and so can be visualized as the belt of the eponymous hunter's clothing. They are best viewed in the early night sky during the Northern Winter/Southern Summer, in particular the month of January at around 9:00 pm.[2]
And here are some of the other stars in Orion and the nearby nebula:

Thank you.

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Re: APOD: Geminid of the North (2021 Dec 17)

Post by alter-ego » Sun Dec 19, 2021 3:28 am

johnnydeep wrote: Fri Dec 17, 2021 10:09 pm I'll note that if you follow the "straight" line from the meteor trail up, it badly misses Castor, which is very near the radiant, but I presume that is only because of the panoramic view, and the fact that the normally "straight" trail appears curved here, and it is that (slight) curve that must be followed back, maintaining the curve, in order to intersect the radiant.
That's true.
Generally speaking, meteors travel in a straight line, which become great circles when projected onto a sphere. Imaged onto a plane, the curvatures vary depending on the projection method, and where and what direction in the field of view the meteors travel.
Below I've replicated the APOD FoV and projection good enough to show the appearance of a great-circle arc originating near the meteor trail and extending to the radiant about 57°away. I intentionally directed this arc to the radiant, and don't know the exact curvature of the trail. As you say, the larger the FoV, the larger the curvature.
 
stellarium-006.jpg
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Re: APOD: Geminid of the North (2021 Dec 17)

Post by johnnydeep » Sun Dec 19, 2021 3:49 pm

alter-ego wrote: Sun Dec 19, 2021 3:28 am
johnnydeep wrote: Fri Dec 17, 2021 10:09 pm I'll note that if you follow the "straight" line from the meteor trail up, it badly misses Castor, which is very near the radiant, but I presume that is only because of the panoramic view, and the fact that the normally "straight" trail appears curved here, and it is that (slight) curve that must be followed back, maintaining the curve, in order to intersect the radiant.
That's true.
Generally speaking, meteors travel in a straight line, which become great circles when projected onto a sphere. Imaged onto a plane, the curvatures vary depending on the projection method, and where and what direction in the field of view the meteors travel.
Below I've replicated the APOD FoV and projection good enough to show the appearance of a great-circle arc originating near the meteor trail and extending to the radiant about 57°away. I intentionally directed this arc to the radiant, and don't know the exact curvature of the trail. As you say, the larger the FoV, the larger the curvature.
 
stellarium-006.jpg
Nice.
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"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."