Something moving in 47 Tuc?

[Atmos]

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 (https://cdn.astrobin.com/images/57732/2021/467b7167-702e-4b85-a9bb-b626bded3219.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?:help:

[N1]

Foreground red dwarf? Congrats if you turn out to be its discoverer :D

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.

[xelasnave]

Find the earliest image and compare.
Alex

[Stonius]

Is it moving, or just changing magnitude dramatically? Carbon stars are also variables. Just a thought.


Markus

[multiweb]

That's pretty cool Colin. :thumbsup:

[bojan]

Looks like moving to me...

[leon]

Yep, seems to be moving to me as well, nice job.

Leon

[Stonius]

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

[bojan]

Good point.

It could be the red channel is shifted just a tad...

[Atmos]

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 ;)

[gaseous]

Still a very interesting spot Colin, sharp eyes!

[gary]

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



"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

[Atmos]

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.

[N1]

Movement in opposite directions - parallax effects from Earth orbit maybe?
I still think it's much closer than the cluster.

[Atmos]

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 :lol:
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.

[gary]

Hi Collin,

Good stuff.

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

[Sunfish]

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.

[Rick Petrie]

I can see three stars moving Gary. Two up and one down.

[gary]

Thanks Rick,

I see three moving now too. :)

Are yours the same three as circled in the image below?

[Sunfish]

Ah yes. I can see that too now. More and more interesting.

[Sunfish]

So a long way closer than Tuc 47 and part of some other structure?

[johnnyjetski]

Very interesting find Colin.
Looks like those 3 moving stars are in our foreground.
John

[Atmos]

Just as a side note for anyone who isn't sure, the last blink images that I posted are Hubble data, the field is tiny compared to what I've been able to capture, even on a tight crop.


I got my original field wrong, only by a tiny amount but I spotted the wrong moving star. I also may have misread the DR2 data for the parallax measurement but I'm not sure. It wouldn't be unusual to spot a small star (brown dwarf) between us and 47 Tuc as it is estimated that there is a bucket load of them out there... Yes, bucket load is a scientific amount! :lol:

As for having a parallax of 1.1 arc seconds, that would potentially make it within the Oort Cloud which I suppose could be a possibility considering it is Hubble tanking the images.

[Sunfish]

Beyond 47 Tuc?( not that I understand much of this)

https://iopscience.iop.org/article/10.3847/1538-4357/aae089

[Stonius]

You're right - good find! Given that there are now three moving stars, would the same thing occur almost anywhere? Like could you expect to see the same thing in any part of the sky given a survey that goes deep enough and is repeated after a long enough interval?


Markus