What is this long green structure fanning out from M51?

[BrendanC]

Hi all,

I recently imaged M51. On using the range selector tool in PixInsight, I could see that there was a large structure fanning out from the object, mostly in the green channel. I thought it was a problem with calibration or light pollution, but the more I looked and played around with the data, the more I became convinced it was an actual thing.

So, I stretched it out a bit more, and here it is - the green cloud going to the top right corner.

My question is: what is this? I haven't seen it in any other images. If I've discovered it I'm going to call it Cooper's Cone or something.

Any takers?

Thanks
Brendan

[bomberbaz]

To me it looks like it could possibly be gas (HB and OIII spring to mind) that has been blown off during the merger and left behind as the merging galaxies have moved away from it. 

A lot of imaging programmes remove excessive green noise and this would point to why it hasn't been picked up before.

Was this done under dark skies or were you subject to LP at the location?

I would try gathering data again from another location and see if you can recreate this phenomena. If it is recreated with the same amount of data and processing techniques, you may have discovered a new nebula! 

[BrendanC]

Bortle 4 skies, not very much light pollution.

It was shot broadband, which is why I was surprised something would appear in what seems to be O3.

I can't really give it another shot elsewhere because my rig is static.

Edited March 27 by BrendanC

[ONIKKINEN]

There is a 254 hour image of M51 on Astrobin :https://www.astrobin.com/7hwtz0/?q=M51&camera=

Doesnt quite look like the nebulosity matches, but some of it is definitely the extended halo around M51. Field of view is smaller in that one too, so hard to say for sure.

Maybe a bit of high cloud and background noise coupled with actual dust?

[BrendanC]

Yep, checked out that image too.

I have no idea what it could be. I guess I could go through the subs, say, every half hour or so, and if it's persistent then it isn't clouds.

Don't know what the 'background noise' could be? It's a definite structure.

[Earl]

I think you have started to pick up the dust clouds which are all over the place.

[Ratlet]

Could be integrated flux nebula?

[ONIKKINEN]

6 minutes ago, BrendanC said:

Yep, checked out that image too.

I have no idea what it could be. I guess I could go through the subs, say, every half hour or so, and if it's persistent then it isn't clouds.

Don't know what the 'background noise' could be? It's a definite structure.

Im thinking some of it may be high cloud and background extraction produced some blotches. If you look through your subs youll see if there was something extra.

Could be wrong and its just dust. Plenty of dust at this declination.

[BrendanC]

6 minutes ago, Earl said:

I think you have started to pick up the dust clouds which are all over the place.

I guess so, I was just surprised that one particular dust cloud seemed so definitely to emanate from M51.

[Hals]

Definitely Cooper's Cone ! No doubt about it 😉

[assouptro]

Aurora? 

[ollypenrice]

This is a good one for comparison. https://www.cloudynights.com/topic/616189-m51-how-far-can-i-push-until-it-breaks/

Olly