APOD: Jets from Comet Churyumov-Gerasimenko (2015 Feb 03)

Comments and questions about the APOD on the main view screen.
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alter-ego
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Re: Stars and Blobs

Post by alter-ego » Sun Feb 08, 2015 7:05 am

There's a question about how many, if any, stars are visible in today's APOD, and among all those specks and blobs are any bits from the comet? Certainly, specks visible in the foreground, within shadowed regions are not stars, and it will remain a question which of those are artifacts or real objects. However, in the region surrounding the comet, It's not fully appreciated how many bona-fide stars there are. In the hover image I circled >230 specks that match catalogued star positions typically < 2 arcminutes. The positions aren't exact mainly because I had to scale and rotate a Stellarium star field to match the specks in the APOD. I'll say that this only works if a star field has been identified. Random speck positions will in no way map to the degree they do here.
  1. Clicking "image 1" should give you a full-size view. Not all circled stars may visible here because a higher magnification is required and/or my posted image is not as good as the original image I searched. However, in this view, there are roughly 50 to 100 specks that don't map to stars (including the foreground specks). So, about 75% of all the visible specs are stars, give or take.
  2. I like the blink-comparison viewing the hover-image after adjusting the browser magnification to 250% or higher.
Click to view full size image 1 or image 2
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geckzilla
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Re: APOD: Jets from Comet Churyumov-Gerasimenko (2015 Feb 03

Post by geckzilla » Sun Feb 08, 2015 8:36 am

Nice work, Sleuthhound.
Just call me "geck" because "zilla" is like a last name.

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alter-ego
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Re: APOD: Jets from Comet Churyumov-Gerasimenko (2015 Feb 03

Post by alter-ego » Sun Feb 08, 2015 8:33 pm

geckzilla wrote:Nice work, Sleuthhound.
Yeah, and a little bit o' luck!

Thanks geck! :)
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Ann
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Re: APOD: Jets from Comet Churyumov-Gerasimenko (2015 Feb 03

Post by Ann » Sun Feb 08, 2015 11:59 pm

Great work, alter-ego! :D

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FloridaMike
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Re: Stars and Blobs

Post by FloridaMike » Mon Feb 09, 2015 6:33 pm

alter-ego wrote:There's a question about how many, if any, stars are visible in today's APOD, ... ... there are roughly 50 to 100 specks that don't map to stars (including the foreground specks).
YOU MISSED ONE!
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alter-ego
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Re: Stars and Blobs

Post by alter-ego » Tue Feb 10, 2015 5:57 am

FloridaMike wrote:
alter-ego wrote:There's a question about how many, if any, stars are visible in today's APOD, ... ... there are roughly 50 to 100 specks that don't map to stars (including the foreground specks).
YOU MISSED ONE!
I admit I can get a terminator-like obsession for perfection, but what you say is true; most likely more the one. In fact, there were a few specks that I "deselected" because their change in position (still within the little yellow circle) I judged as anonymously high.
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Mattunes

Re: APOD: Jets from Comet Churyumov-Gerasimenko (2015 Feb 03

Post by Mattunes » Fri Feb 13, 2015 10:31 pm

Anybody have an explanation for the striations and clear curving/bending of the "jets"? They look suspiciously like being under magnetic field influence...

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alter-ego
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Re: APOD: Jets from Comet Churyumov-Gerasimenko (2015 Feb 03

Post by alter-ego » Sat Feb 14, 2015 6:32 am

Mattunes wrote:Anybody have an explanation for the striations and clear curving/bending of the "jets"? They look suspiciously like being under magnetic field influence...
The jet curvature direction looks consistent with the rotation axis. I'm not aware of any magnetic field and wouldn't expect one from it of any significance. Like you spinning in a circle holding a water hose, ejected particles from the rotating comet follow the same dynamics. The video shows the comet from the other side. It is rotating counter-clockwise whereas in the APOD view, it is rotating clockwise. Therefore the jets would appear to be curving to the left.
Click to play embedded YouTube video.
CometPlumes_Rosetta_2048.jpg
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