The (amateur) astronomy pictures of the year have been announced:

https://www.bbc.co.uk/news/in-pictures-66807814

The most stunning is the very deep M31 image showing a gas plasma cloud
in the same field which it seems from the blurb has not been noticed
until now!

Mars setting behind the moon and the sprites are my other favourites.

The other stunning image is of a comet disconnection event:

https://www.bbc.co.uk/news/science-environment-62916234

Online source at the RGO with slightly more info.

https://www.rmg.co.uk/whats-on/astronomy-photographer-year/galleries/overall-winners-2023

--
Martin Brown

On Friday, September 15, 2023 at 9:01:11 AM UTC+1, Martin Brown wrote:
> The (amateur) astronomy pictures of the year have been announced:
>
> https://www.bbc.co.uk/news/in-pictures-66807814
>
> The most stunning is the very deep M31 image showing a gas plasma cloud
> in the same field which it seems from the blurb has not been noticed
> until now!
>
> Mars setting behind the moon and the sprites are my other favourites.
>
> The other stunning image is of a comet disconnection event:
>
> https://www.bbc.co.uk/news/science-environment-62916234
>
> Online source at the RGO with slightly more info.
>
> https://www.rmg.co.uk/whats-on/astronomy-photographer-year/galleries/overall-winners-2023
>
>
> --
> Martin Brown

Astrophotographers are such cool people and the effort they make to create these images for enjoyment.

There is an emerging way to advance imaging with more enjoyable perspectives.

On 9/15/23 4:01 AM, Martin Brown wrote:
> The (amateur) astronomy pictures of the year have been announced:
>
> https://www.bbc.co.uk/news/in-pictures-66807814
>
> The most stunning is the very deep M31 image showing a gas plasma cloud
> in the same field which it seems from the blurb has not been noticed
> until now!
>
> Mars setting behind the moon and the sprites are my other favourites.
>
> The other stunning image is of a comet disconnection event:
>
> https://www.bbc.co.uk/news/science-environment-62916234
>
> Online source at the RGO with slightly more info.
>
> https://www.rmg.co.uk/whats-on/astronomy-photographer-year/galleries/overall-winners-2023
>
>

Seems suspect that the "plasma arc" near M31 oddly has not been noticed
until recently. The write up mentions that "scientists are now
investigating" so it must really exist. Hard to believe that with as
many images of M31 of varying exposures and filtration that something
like that would be missed.

On 15/09/2023 13:43, Will Peters wrote:
> On 9/15/23 4:01 AM, Martin Brown wrote:
>> The (amateur) astronomy pictures of the year have been announced:
>>
>> https://www.bbc.co.uk/news/in-pictures-66807814
>>
>> The most stunning is the very deep M31 image showing a gas plasma
>> cloud in the same field which it seems from the blurb has not been
>> noticed until now!
>>
>> Mars setting behind the moon and the sprites are my other favourites.
>>
>> The other stunning image is of a comet disconnection event:
>>
>> https://www.bbc.co.uk/news/science-environment-62916234
>>
>> Online source at the RGO with slightly more info.
>>
>> https://www.rmg.co.uk/whats-on/astronomy-photographer-year/galleries/overall-winners-2023
>>
>>
>
> Seems suspect that the "plasma arc" near M31 oddly has not been noticed
> until recently.  The write up mentions that "scientists are now
> investigating" so it must really exist.  Hard to believe that with as
> many images of M31 of varying exposures and filtration that something
> like that would be missed.

I'm inclined to agree. I'm also a bit puzzled why it hasn't shown up on
various 21cm hydrogen line observations. It isn't like M31 hasn't been
observed in all wavebands and lots of times.

However, their image frame is larger and deeper than most.

--
Martin Brown

On Fri, 15 Sep 2023 14:06:32 +0100, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:

>On 15/09/2023 13:43, Will Peters wrote:
>> On 9/15/23 4:01 AM, Martin Brown wrote:
>>> The (amateur) astronomy pictures of the year have been announced:
>>>
>>> https://www.bbc.co.uk/news/in-pictures-66807814
>>>
>>> The most stunning is the very deep M31 image showing a gas plasma
>>> cloud in the same field which it seems from the blurb has not been
>>> noticed until now!
>>>
>>> Mars setting behind the moon and the sprites are my other favourites.
>>>
>>> The other stunning image is of a comet disconnection event:
>>>
>>> https://www.bbc.co.uk/news/science-environment-62916234
>>>
>>> Online source at the RGO with slightly more info.
>>>
>>> https://www.rmg.co.uk/whats-on/astronomy-photographer-year/galleries/overall-winners-2023
>>>
>>>
>>
>> Seems suspect that the "plasma arc" near M31 oddly has not been noticed
>> until recently.  The write up mentions that "scientists are now
>> investigating" so it must really exist.  Hard to believe that with as
>> many images of M31 of varying exposures and filtration that something
>> like that would be missed.
>
>I'm inclined to agree. I'm also a bit puzzled why it hasn't shown up on
>various 21cm hydrogen line observations. It isn't like M31 hasn't been
>observed in all wavebands and lots of times.
>
>However, their image frame is larger and deeper than most.

It's an [O III] emission region, with no H-alpha and apparently no
neutral H (so no radio emission).

Quite a few interesting objects and regions have been discovered in
recent years by amateur imagers, using widefield instruments that are
largely absent in professional observatories outside of a few survey
instruments... and they are usually not using narrowband or long
exposure times.

On 15/09/2023 14:33, Chris L Peterson wrote:
> On Fri, 15 Sep 2023 14:06:32 +0100, Martin Brown
> <'''newspam'''@nonad.co.uk> wrote:
>
>> On 15/09/2023 13:43, Will Peters wrote:

>>> Seems suspect that the "plasma arc" near M31 oddly has not been noticed
>>> until recently.  The write up mentions that "scientists are now
>>> investigating" so it must really exist.  Hard to believe that with as
>>> many images of M31 of varying exposures and filtration that something
>>> like that would be missed.
>>
>> I'm inclined to agree. I'm also a bit puzzled why it hasn't shown up on
>> various 21cm hydrogen line observations. It isn't like M31 hasn't been
>> observed in all wavebands and lots of times.
>>
>> However, their image frame is larger and deeper than most.
>
> It's an [O III] emission region, with no H-alpha and apparently no
> neutral H (so no radio emission).

It is quite a peculiar cloud of plasma then. Normally you would expect
at least some neutral hydrogen in it simply because it is so common.

My guess would then be that it is something by way of a local planetary
nebula of lost CNO from some former large star that happens to be in the
same line of sight as M31 as opposed to a huge cloud near the galaxy.

> Quite a few interesting objects and regions have been discovered in
> recent years by amateur imagers, using widefield instruments that are
> largely absent in professional observatories outside of a few survey
> instruments... and they are usually not using narrowband or long
> exposure times.

Indeed - amateur capabilities have closed the gap a long way on
professional equipment in terms of basic imaging from dark skies.
Narrow band filters for deep sky have changed the game a lot.

Likewise for spotting things hitting the gas giants and supernovae.

--
Martin Brown

On Fri, 15 Sep 2023 15:26:34 +0100, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:

>On 15/09/2023 14:33, Chris L Peterson wrote:
>> On Fri, 15 Sep 2023 14:06:32 +0100, Martin Brown
>> <'''newspam'''@nonad.co.uk> wrote:
>>
>>> On 15/09/2023 13:43, Will Peters wrote:
>
>>>> Seems suspect that the "plasma arc" near M31 oddly has not been noticed
>>>> until recently.  The write up mentions that "scientists are now
>>>> investigating" so it must really exist.  Hard to believe that with as
>>>> many images of M31 of varying exposures and filtration that something
>>>> like that would be missed.
>>>
>>> I'm inclined to agree. I'm also a bit puzzled why it hasn't shown up on
>>> various 21cm hydrogen line observations. It isn't like M31 hasn't been
>>> observed in all wavebands and lots of times.
>>>
>>> However, their image frame is larger and deeper than most.
>>
>> It's an [O III] emission region, with no H-alpha and apparently no
>> neutral H (so no radio emission).
>
>It is quite a peculiar cloud of plasma then. Normally you would expect
>at least some neutral hydrogen in it simply because it is so common.
>
>My guess would then be that it is something by way of a local planetary
>nebula of lost CNO from some former large star that happens to be in the
>same line of sight as M31 as opposed to a huge cloud near the galaxy.

Indeed, most peculiar. The oxygen cloud is odd enough, but the absence
of an obvious source of ionizing radiation is what I find interesting.
It takes a good deal of energy to get [O III] emission.

On 15/09/2023 15:31, Chris L Peterson wrote:
> On Fri, 15 Sep 2023 15:26:34 +0100, Martin Brown
> <'''newspam'''@nonad.co.uk> wrote:
>
>> On 15/09/2023 14:33, Chris L Peterson wrote:

>>> It's an [O III] emission region, with no H-alpha and apparently no
>>> neutral H (so no radio emission).
>>
>> It is quite a peculiar cloud of plasma then. Normally you would expect
>> at least some neutral hydrogen in it simply because it is so common.
>>
>> My guess would then be that it is something by way of a local planetary
>> nebula of lost CNO from some former large star that happens to be in the
>> same line of sight as M31 as opposed to a huge cloud near the galaxy.
>
> Indeed, most peculiar. The oxygen cloud is odd enough, but the absence
> of an obvious source of ionizing radiation is what I find interesting.
> It takes a good deal of energy to get [O III] emission.

Although that is true O[III] is a forbidden transition so its time
constant for decay to the ground state is rather long. Perhaps it has
been flash illuminated in the distant enough past by a supernova and is
still in its excited state.

Problem with that is why isn't there some neutral hydrogen though.
Most odd!

--
Martin Brown

On Friday, September 15, 2023 at 6:43:38 AM UTC-6, Will Peters wrote:
> On 9/15/23 4:01 AM, Martin Brown wrote:

> Seems suspect that the "plasma arc" near M31 oddly has not been noticed
> until recently.

Although that's odd, what I found stranger about the caption to the picture
was... how do they know it's as distant as M31, and not instead something
that's in our own galaxy that just happens to be in front of it from our point
of view?

John Savard

On Sat, 16 Sep 2023 17:50:12 -0700 (PDT), Quadibloc
<jsavard@ecn.ab.ca> wrote:

>On Friday, September 15, 2023 at 6:43:38?AM UTC-6, Will Peters wrote:
>> On 9/15/23 4:01 AM, Martin Brown wrote:
>
>> Seems suspect that the "plasma arc" near M31 oddly has not been noticed
>> until recently.
>
>Although that's odd, what I found stranger about the caption to the picture
>was... how do they know it's as distant as M31, and not instead something
>that's in our own galaxy that just happens to be in front of it from our point
>of view?

This very recent paper, https://arxiv.org/pdf/2307.06308.pdf considers
various galactic and extragalactic explanations, and comes down
favoring (but with uncertainty) an association between the plasma
region and the galaxy.