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Old 10-06-2021, 08:03 AM
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Atmos (Colin)
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Something moving in 47 Tuc?

I was doing an image comparison with the Chart32 image of 47 Tuc last night and noticed something interesting…. What appears to be a moving red dot (star).
Link to the GIf

Given that there is only about half a decade between these two images having been captured and the distance of 47 Tuc I’m a little dubious as to whether it is actual stellar motion.

Any thoughts?
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Old 10-06-2021, 01:13 PM
N1 (Mirko)
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Foreground red dwarf? Congrats if you turn out to be its discoverer

Not likely to be part of the 13kly distant cluster in any case I reckon. You'd need longer intervals to see anything moving at that distance & resolution.
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Old 10-06-2021, 01:53 PM
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Find the earliest image and compare.
Alex
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Old 10-06-2021, 02:01 PM
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Stonius (Markus)
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Is it moving, or just changing magnitude dramatically? Carbon stars are also variables. Just a thought.


Markus
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Old 10-06-2021, 02:40 PM
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That's pretty cool Colin.
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Old 10-06-2021, 02:47 PM
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Looks like moving to me...
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Old 10-06-2021, 03:15 PM
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Yep, seems to be moving to me as well, nice job.

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Old 10-06-2021, 03:32 PM
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Quote:
Originally Posted by bojan View Post
Looks like moving to me...
Maybe I'm not seeing what you guys are. The colour balance between the shots is very different which makes the red star 'centre' appear to blink, but unless I'm crazy, there is still a star in that position in the less saturated version.


It would be interesting to see a comparison where the colours were matched, or of only blue channels for example.


I also recognise I'm far less experienced than some of you guys, so very happy to retract if I'm wrong.



Markus
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Old 10-06-2021, 03:41 PM
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Quote:
Originally Posted by Stonius View Post
..It would be interesting to see a comparison where the colours were matched, or of only blue channels for example.
Good point.

It could be the red channel is shifted just a tad...
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Old 10-06-2021, 04:50 PM
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Atmos (Colin)
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Thanks for the comments everyone. I am using a OSC with no UV/IR filter so there WILL be some IR bloat around the redder stars. I’ll have a go at restacking only the best subs but from memory this only has 40 minutes of data as it is.

I’ll check out the individual colour channels after debayering and see if checking the blue channel makes a difference.

Might also go back through some archival stuff around, Hubble can be a good reference point
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Old 10-06-2021, 07:05 PM
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Still a very interesting spot Colin, sharp eyes!
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Old 10-06-2021, 09:09 PM
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Hi Colin,

If you are interested in following up, you might want to check if this star is in the Gaia DR2 data set :-
https://www.cosmos.esa.int/web/gaia/dr2

If so, there might even be proper motion data for it.

This paper, "Gaia unveils the kinematics of multiple stellar populations in 47 Tucanae" by Milone et. al. July 2018, may be of interest :-
https://arxiv.org/pdf/1807.03511.pdf

Quote:
Originally Posted by Milone et. al.
ABSTRACT
The series of events, which occurred at high redshift and originated multiple stellar populations in Globular Clusters (GCs) are still poorly understood.
Theoretical work suggests that the present-day dynamics of stars in nearby GCs, including the rotation and velocity dispersion, may retain important clues on the formation of multiple populations.

So far, the dynamics of multiple populations have been investigated either from radial
velocities of a relatively-small sample of stars, or from relative proper motions of stars in the
small field of view provided by the Hubble Space Telescope. In this context, Gaia provides
the unique opportunity to investigate the dynamics of thousands GC stars over a wide field of
view.
For the first time, we combine Gaia DR2 proper motions and multi-band photometry to
study the internal motions of the two main stellar populations of 47 Tucanae in a wide field of
view. We confirm that this cluster exhibits high rotation on the plane of the sky and find that
both stellar generations share similar rotation patters. Second-generation stars show stronger
anisotropies and smaller tangential-velocity dispersion than the first generation, while there
is no significant difference between their radial-velocity dispersion profiles. We discuss the
impact of these results in the context of the formation scenarios for multiple stellar populations
in GCs.
"HST PROPER MOTIONS AND STELLAR DYNAMICS IN THE CORE OF THE GLOBULAR CLUSTER 47 TUCANAE" by . MCLAUGHLIN et. al. Sept 2006, may
also be of interest :-
https://arxiv.org/pdf/astro-ph/0607597.pdf
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Old 10-06-2021, 09:21 PM
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Okay so I can all but confirm that there is some movement around a star very close to the coordinates of 00 23 53 -72 02 00. It has thrown up some more questions than answers. I really struggled to find a cooperative field when going through the HLA but I did use StarCatalogGenerator in PI and found a difference between Gaia DR1 and Gaia DR2. Gaia DR1 and Chart-32 appear to be virtually identical and from what I can gather would have been captured fairly close together time wise.

Gaia DR2 which was taken after has movement in the opposite direction to what mine does which was captured mid Sept last year.

As another side note, when comparing just the blue channel of mine and the Chart-32 team it does give the appearance of the smaller red star at 10:30 (almost touching) moving in the opposite direction as if they're circling one another.

It's something that's proving difficult to track down comparison images for as most don't have the required resolution to resolve the individual stars in the region.
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Old 11-06-2021, 01:14 PM
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Movement in opposite directions - parallax effects from Earth orbit maybe?
I still think it's much closer than the cluster.
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Old 14-06-2021, 12:19 AM
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Been digging through the DR3 archive and from what I can figure, there is a star in that region that has a parallax of 5.2 was (milliarcseconds) which equates to about 627 light years from us. I've been digging through images on the interwebs trying to find whether it is parallax but it's been a struggle.

And after spending an hour or two digging into Hubble Legacy Archive I've managed to track down the offending star. From counting pixels it has a movement of 1.11 arcseconds (~22 pixels at 0.05 arcsec/pixel) between 2002-04-05 19:13:39 & 2002-10-09 08:15:15.

So yes, it is definitely parallax.... Or is it....

Just as an FYI, I've been writing this one post for a couple of hours now so as another discovery... I was tracking the wrong star
I'm back on the stellar motion band wagon! What has been bugging me for a little while is that the DR2 stars were seeming to be before 2002 position as I have been comparing 2002 & 2013 images from Hubble. Then... BAM... It occurred to me that I was possibly using the DR2 catalog in J2000 and not current date so I recreated the time stamp for 2020 and damn near every star has moved compared to the 2000 time stamp.... DR2 catalog in PI takes into consideration proper motion.
Between 2002 and 2013 there is a 1 arc second movement so it is about 0.1 arcseconds per year.
In one of my previous posts I mentioned that it appeared that in the blue channel that the smaller star very close to the main mover was moving a little bit.... Well... it is! It had moved ~0.12 arc seconds between when Chart32 had taken their image and when I did.
Attached Thumbnails
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Old 14-06-2021, 01:23 PM
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Quote:
Originally Posted by Atmos View Post
Just as an FYI, I've been writing this one post for a couple of hours now so as another discovery... I was tracking the wrong star .
Hi Collin,

Good stuff.

In your latest blinked images, there appears to be two stars moving there??
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Old 14-06-2021, 02:48 PM
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Very interesting result. Those stars definitely appear to be moving a large distance past each other. In the earlier images one is quite red compared to the bulk of stars.
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Old 14-06-2021, 08:48 PM
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Quote:
Originally Posted by gary View Post
Hi Collin,

Good stuff.

In your latest blinked images, there appears to be two stars moving there??

I can see three stars moving Gary. Two up and one down.
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Old 14-06-2021, 10:59 PM
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Quote:
Originally Posted by Rick Petrie View Post
I can see three stars moving Gary. Two up and one down.
Thanks Rick,

I see three moving now too.

Are yours the same three as circled in the image below?
Attached Thumbnails
Click for full-size image (IceInSpace Images - Something moving in 47 Tuc - Google Chrome_2021-06-14_22-51-58.jpg)
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Old 14-06-2021, 11:06 PM
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Ah yes. I can see that too now. More and more interesting.

Quote:
Originally Posted by Rick Petrie View Post
I can see three stars moving Gary. Two up and one down.
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