APOD: Unexpected Clouds Toward the Galaxy... (2023 Jan 17)

[APOD Robot]

Unexpected Clouds Toward the Andromeda Galaxy

Explanation: Why are there oxygen-emitting arcs near the direction of the Andromeda galaxy? No one is sure. The gas arcs, shown in blue, were discovered and first confirmed by amateur astronomers just last year. The two main origin hypotheses for the arcs are that they really are close to Andromeda (M31), or that they are just coincidentally placed gas filaments in our Milky Way galaxy. Adding to the mystery is that arcs were not seen in previous deep images of M31 taken primarily in light emitted by hydrogen, and that other, more distant galaxies have not been generally noted as showing similar oxygen-emitting structures. Dedicated amateurs using commercial telescopes made this discovery because, in part, professional telescopes usually investigate angularly small patches of the night sky, whereas these arcs span several times the angular size of the full moon. Future observations -- both in light emitted by oxygen and by other elements -- are sure to follow.

<< Previous APOD

This Day in APOD

Next APOD >>

[jks]

Very impressive discovery!

[ill]

At first i thought they'd simply captured a tiny whisp of noctilucent cloud in their image, but obviously they've multi-checked their findings; the cloud does appear to be simply a line of sight effect though with the cloud being significantly closer to us than Andromeda, perhaps being a remnant of an ancient star outburst?

Stunning image nonetheless!

[ill]

...or it could simply be an outstretched whisp of spiral arm of Andromeda

[Ann]

Hanny's Voorwerp and IC 2497 taken by Wide Field Camera 3 of the Hubble Space Telescope. Credit: NASA, ESA, W. Keel (University of Alabama), and the Galaxy Zoo Team

---

Unexpected clouds toward the Andromeda Galaxy. Image Credit & Copyright: Yann Sainty & Marcel Drechsler

---

The strange OIII cloud right next to Andromeda is slightly similar to the (admittedly quite differently shaped and also starforming) feature known as Hanny's Voorwerp near galaxy IC 2497. Hanny's Voorwerp may have formed as a tidal tail was drawn out of IC 2497 by a passing galaxy, and the tidal tail was later illuminated and ionized (and compressed so that it started forming stars) by a jet from the black hole of IC 2497, when the black hole became a quasar as gas fell into it as a consequence of IC 2497's encounter with another galaxy.

Astronomers found that Hanny's Voorwerp is the only visible part of a 300,000-light-year-long gaseous streamer stretching around the galaxy. The greenish Voorwerp is visible because a searchlight beam of light from the galaxy's core illuminated it. This beam came from a quasar, a bright, energetic object that is powered by a black hole. An encounter with another galaxy may have fed the black hole and pulled the gaseous streamer from IC 2497. Illustration: NASA, ESA, and A. Feild (STScI)

---

Andromeda has a very massive black hole, much more massive than the one in the Milky Way. I have also read somewhere, although I don't know where to find it, that Andromeda has had more encounters with other galaxies than the Milky Way.

Note that the OIII cloud seen in today's APOD is almost perfectly aligned with the disk of Andromeda, and it is centered smack dab above the core and central black hole of Andromeda. It sure looks as if this green cloud "belongs" to Andromeda.

On the other hand... it is also possible to see the OIII cloud as located above the apparent OIII outflows from the disk of Andromeda just next to the position of small but ultra-compact dwarf galaxy M32. Do you think there could be a connection between the outflows in the disk and the large cloud located well above the disk over Andromeda?

Well, I guess not after all. Almost certainly it must be the core and central black hole of Andromeda that shaped and ionized the OIII cloud seen in the APOD, if the cloud indeed belongs to Andromeda. But maybe possibly maybe the interactions between Andromeda and M32 caused some upheavals in the past that created the cloud over Andromeda.

Consider the OIII outflows in the disk of Andromeda near M32 (and a few other interesting things) in this image:

M32 in optical light. You can just barely guess at a few little disturbances in the dust lanes in the disk of Andromeda near M32. Credit: Fabrizio Francione

---

Ann

[Knight of Clear Skies]

Interesting stuff. Looking at the linked paper, an ongoing spectrographic study will help determine if this object is outside our galaxy.

"A spectrum of the [O iii] emission arc would offer radial velocity information which could establish an association with M31 and its halo. A follow-up spectroscopic study of this emission arc is ongoing."

As I understand it, an extra-galactic object would show a much larger velocity distribution than an object inside our galaxy.

If it is a Voorwerp-like object do we have any idea why it's only visible in OIII? Has the oxygen become concentrated somehow, are there processes that differentiate gas clouds by atomic weight? Or has the OIII been selectively ionized?

[AVAO]

In view of the "perceived" 2,537,000 photos of the Andromeda galaxy by astrophotographers on the internet, the photo and the discovery of the so-called "STROTTNER-DRECHSLER-SAINTY OBJECT 1" (the large blue structure) is an absolute sensation. It is the culmination of a search by this group for several years for as yet undiscovered nebulae in the Milky Way galaxy, as their astrobin side impressively shows. The collaboration with several university organizations and professional astrophysicists and researchers in this context for verification and in-depth research is also exciting. This shows that amateur astronomy can now represent an absolutely essential addition to the large observatories such as HUBBLE or WEBB, since their focus is mostly on smaller areas of the sky and shorter exposure times.

Congratulations on this success!


https://www.astrobin.com/1d8ivk/#rH

https://www.astrobin.com/1d8ivk/H/rawthumb/qhd/?sync

[Ann]

In view of the "perceived" 2,537,000 photos of the Andromeda galaxy by astrophotographers on the internet, the photo and the discovery of the so-called "STROTTNER-DRECHSLER-SAINTY OBJECT 1" (the large blue structure) is an absolute sensation. It is the culmination of a search by this group for several years for as yet undiscovered nebulae in the Milky Way galaxy, as their astrobin side impressively shows. The collaboration with several university organizations and professional astrophysicists and researchers in this context for verification and in-depth research is also exciting. This shows that amateur astronomy can now represent an absolutely essential addition to the large observatories such as HUBBLE or WEBB, since their focus is mostly on smaller areas of the sky and shorter exposure times.

Congratulations on this success!


https://www.astrobin.com/1d8ivk/#rH

https://www.astrobin.com/1d8ivk/H/rawthumb/qhd/?sync

Thank you for the links, AVAO!

I love this RGB + OIII (no Hα) version of today's APOD. All the OII features become to incredibly obvious. There is also a hint of a jet, emerging not from the core of Andromeda but not too far away from it:

Note all the little green planetary nebulas along the outer dust lane of Andromeda! Fantastic!

Yes, and do note the tiny little green jet that seems to point at the amazing Strottner-Drechsler-Sainty Object 1! Could that green jet possibly, possibly have something to do with the large green OIII feature?

Ann

[johnnydeep]

Firstly, this is indeed a triumph of amateur astronomy and an incredible image in itself!

But in contrast to Ann, it sure looks to me like these linearly wispy OIII clouds are much closer to us than to Andromeda. I also don't agree that Andromeda's central blackhole is having (or ever had) any effect on it, even if it is "close" to Andromeda, since close here is still probably at least 50,000 ly away.

On another topic, the paper linked to has this to say:

The vector of M31's proper motion measured by GAIA points roughly to the [O iii] emission arc suggesting a possible interaction of M31 with the Milky Way. But the arc seems much too close to M31 to fit that picture.

But I don't understand what this means. How does M31's motion pointing in the apparent direction of the arc suggest anything about how M31 is interacting with the Milky Way?

[AVAO]

In view of the "perceived" 2,537,000 photos of the Andromeda galaxy by astrophotographers on the internet, the photo and the discovery of the so-called "STROTTNER-DRECHSLER-SAINTY OBJECT 1" (the large blue structure) is an absolute sensation. It is the culmination of a search by this group for several years for as yet undiscovered nebulae in the Milky Way galaxy, as their astrobin side impressively shows. The collaboration with several university organizations and professional astrophysicists and researchers in this context for verification and in-depth research is also exciting. This shows that amateur astronomy can now represent an absolutely essential addition to the large observatories such as HUBBLE or WEBB, since their focus is mostly on smaller areas of the sky and shorter exposure times.

Congratulations on this success!


https://www.astrobin.com/1d8ivk/#rH

https://www.astrobin.com/1d8ivk/H/rawthumb/qhd/?sync

Thank you for the links, AVAO!

I love this RGB + OIII (no Hα) version of today's APOD. All the OII features become to incredibly obvious. There is also a hint of a jet, emerging not from the core of Andromeda but not too far away from it:


Strottner Drechsler Sainty Object 1 OIII no Hα.png


Note all the little green planetary nebulas along the outer dust lane of Andromeda! Fantastic!

Yes, and do note the tiny little green jet that seems to point at the amazing Strottner-Drechsler-Sainty Object 1! Could that green jet possibly, possibly have something to do with the large green OIII feature?

Ann

ThanX Ann

I see more similarities with NGC 4651 than with IC 2497.



"...The jet-like feature is strikingly coherent and narrow. This feature was previously reported by Vorontsov-Velyaminov (1959) but never interpreted as a stellar tidal stream. Moreover, our deep image shows an additional spectacular crescent shaped shell surrounding the east side of the galaxy that corresponds to the apocenter of the dwarf galaxy. Interestingly, a possible second arc on the western side of the galaxy can also be seen in this image. This structure is less obvious because it is partially hidden by the galaxy's disk. This suggests we are observing a moderately inclined structure projected into the halo of NGC 4651..." https://www.cosmotography.com/images/st ... ights.html

[Ann]

Firstly, this is indeed a triumph of amateur astronomy and an incredible image in itself!

But in contrast to Ann, it sure looks to me like these linearly wispy OIII clouds are much closer to us than to Andromeda. I also don't agree that Andromeda's central blackhole is having (or ever had) any effect on it, even if it is "close" to Andromeda, since close here is still probably at least 50,000 ly away.

On another topic, the paper linked to has this to say:

The vector of M31's proper motion measured by GAIA points roughly to the [O iii] emission arc suggesting a possible interaction of M31 with the Milky Way. But the arc seems much too close to M31 to fit that picture.

But I don't understand what this means. How does M31's motion pointing in the apparent direction of the arc suggest anything about how M31 is interacting with the Milky Way?

Doesn't it at least suggest that the green arc is quite close to M31, and not a feature intrinsic to the Milky Way?

Ann

[Balky]

Obviously where species 10C resides...

[Ann]

I see more similarities with NGC 4651 than with IC 2497.



"...The jet-like feature is strikingly coherent and narrow. This feature was previously reported by Vorontsov-Velyaminov (1959) but never interpreted as a stellar tidal stream. Moreover, our deep image shows an additional spectacular crescent shaped shell surrounding the east side of the galaxy that corresponds to the apocenter of the dwarf galaxy. Interestingly, a possible second arc on the western side of the galaxy can also be seen in this image. This structure is less obvious because it is partially hidden by the galaxy's disk. This suggests we are observing a moderately inclined structure projected into the halo of NGC 4651..." https://www.cosmotography.com/images/st ... ights.html

Very good comparison, AVAO!

I found a link to that picture of NGC 4651, and I'm wondering about the insert and the small blue star in brackets. Could that possibly be the core of the small galaxy that was broken up to create that umbrella-like structure of NGC 4651? Although I really wouldn't expect a galactic core to be blue.

And if we are seeing anything even remotely similar in Andromeda, what could the intruding galaxy be? Not, say, M32?

Ann

[johnnydeep]

Firstly, this is indeed a triumph of amateur astronomy and an incredible image in itself!

But in contrast to Ann, it sure looks to me like these linearly wispy OIII clouds are much closer to us than to Andromeda. I also don't agree that Andromeda's central blackhole is having (or ever had) any effect on it, even if it is "close" to Andromeda, since close here is still probably at least 50,000 ly away.

On another topic, the paper linked to has this to say:

The vector of M31's proper motion measured by GAIA points roughly to the [O iii] emission arc suggesting a possible interaction of M31 with the Milky Way. But the arc seems much too close to M31 to fit that picture.

But I don't understand what this means. How does M31's motion pointing in the apparent direction of the arc suggest anything about how M31 is interacting with the Milky Way?

Doesn't it at least suggest that the green arc is quite close to M31, and not a feature intrinsic to the Milky Way?

Ann

Why? We know from other measurements that M31 is approaching the Milky Way, so if this green cloudy wisp WAS close to the M-W, M31 would naturally be approaching it as well, right?

Oh, and as for the tiny green "jet" apparently emanating from near M31's core and apparently pointing in the direction of the green cloudy wisps, MAYBE it means the two are related, and maybe not. But we don't really know how far that tiny jet is from M31 either.

[Chris Peterson]

Why? We know from other measurements that M31 is approaching the Milky Way, so if this green cloudy wisp WAS close to the M-W, M31 would naturally be approaching it as well, right?

As noted in the paper, what's really needed is a spectroscopic measurement of the cloud, so its Doppler shift can be compared to that of M31. If the two are physically associated, it's likely they will share the same common motion.

[johnnydeep]

Why? We know from other measurements that M31 is approaching the Milky Way, so if this green cloudy wisp WAS close to the M-W, M31 would naturally be approaching it as well, right?

As noted in the paper, what's really needed is a spectroscopic measurement of the cloud, so its Doppler shift can be compared to that of M31. If the two are physically associated, it's likely they will share the same common motion.

I guess that's right, provided the shared motion is not just direction but velocity as well! Although if the cloud is close to the M-W and shares the M-W's motion, both would also share the same motion with respect to M31.

[AVAO]

I see more similarities with NGC 4651 than with IC 2497.



"...The jet-like feature is strikingly coherent and narrow. This feature was previously reported by Vorontsov-Velyaminov (1959) but never interpreted as a stellar tidal stream. Moreover, our deep image shows an additional spectacular crescent shaped shell surrounding the east side of the galaxy that corresponds to the apocenter of the dwarf galaxy. Interestingly, a possible second arc on the western side of the galaxy can also be seen in this image. This structure is less obvious because it is partially hidden by the galaxy's disk. This suggests we are observing a moderately inclined structure projected into the halo of NGC 4651..." https://www.cosmotography.com/images/st ... ights.html

Very good comparison, AVAO!

I found a link to that picture of NGC 4651, and I'm wondering about the insert and the small blue star in brackets. Could that possibly be the core of the small galaxy that was broken up to create that umbrella-like structure of NGC 4651? Although I really wouldn't expect a galactic core to be blue.

And if we are seeing anything even remotely similar in Andromeda, what could the intruding galaxy be? Not, say, M32?

Ann

If I compare the red Hα structures of today's APOD with those of https://apod.nasa.gov/apod/ap221024.html, the red hallo around M31 is completely missing on today's APOD. the red Hα structure of today's APOD therefore seems to be rather detached from M31 in our galaxy. the OIII shell structure, in turn, does not show any interaction with the red Hα structure. For me, M31, the OIII shell structure and the Hα structure are rather far apart. the fine stripe structure of the OIII shell structure indicates that it could also be very close to us. Research will show in the future.

[NGC3314]

The strange OIII cloud right next to Andromeda is slightly similar to the (admittedly quite differently shaped and also starforming) feature known as Hanny's Voorwerp near galaxy IC 2497. Hanny's Voorwerp may have formed as a tidal tail was drawn out of IC 2497 by a passing galaxy, and the tidal tail was later illuminated and ionized (and compressed so that it started forming stars) by a jet from the black hole of IC 2497, when the black hole became a quasar as gas fell into it as a consequence of IC 2497's encounter with another galaxy.

I couldn't help wondering right away whether the newly found M31 cloud might be similar to Hanny's Voorwerp. Later work by Galaxy Zoo volunteers uncovered another 20 similar AGN-ionized clouds ("voorwerpjes") already reported, and another 36 have been spectroscopically confirmed but not yet published (some detected out to 100 kpc from the associated galaxy). Most of these are photoionized gas in tidal debris, and most likewise have lower heavy-element abundances than the reference solar value. Because of the nonintuitive fact that [O III] emission becomes relatively stronger for lower oxygen abundance until one gets to maybe 10% of solar, these have [O III]/H-alpha intensity ratios at least as high as 5. That may still be allowed by the limits on H-alpha from the M31 cloud. (The most effective way to get a spectrum might be to put a camera lens in front of a spectrograph and point it that way...)

Many of the Voorwerpje clouds are very filamentary. This is not very quantitative, but to my eye the filaments in the M31 images are smoother and there aren't the distinct clumps usually found in Voorwerpjes.

[starsurfer]

Marcel Drechsler is amazing! He and Xavier Strottner as well as Dana Patchick have made hundreds of new discoveries not to mention a few scientific papers!

I find it interesting the OIII arc looks a bit like some of the ionized emission jets in Centaurus A. Maybe M31's black hole had an outburst in the past?

[pjw]

As other have mentioned, the elephant in the room is the uncorrelated H-alpha data when compared to the earlier "deep M31" APOD. If the h-alpha data is real, there should be a good match between the two, but there is not.

As for the OIII no doubt others will be motivated to go deep here to verify these amazing structure.

[starsurfer]

As other have mentioned, the elephant in the room is the uncorrelated H-alpha data when compared to the earlier "deep M31" APOD. If the h-alpha data is real, there should be a good match between the two, but there is not.

As for the OIII no doubt others will be motivated to go deep here to verify these amazing structure.

The OIII structure has already been verified in this image.

[vbasile]

No relationship with a similarly looking feature present in APOD 19th January 23 (just below center right)?

[johnnydeep]

As other have mentioned, the elephant in the room is the uncorrelated H-alpha data when compared to the earlier "deep M31" APOD. If the h-alpha data is real, there should be a good match between the two, but there is not.

As for the OIII no doubt others will be motivated to go deep here to verify these amazing structure.

The OIII structure has already been verified in this image.

Nice. And I can see no sign of a "jet" emanating from near the core of M31 in that image. Hmm...

[johnnydeep]

No relationship with a similarly looking feature present in APOD 19th January 23 (just below center right)?

No, since the text says: "The prominent bluish arc below and right of center is a bow shock from runaway star FN Canis Majoris.", and there's no indication this is any sort of bow shock.

[JKLassitterJr]

The APOD for 1-17-23 is absolutely spectacular and looks almost like a painting. I've made it my desktop image.

Question: Why aren't there any light spikes -- that one usually sees in these kinds of photos -- around any of the local stars that are located within our Milky Way galaxy? Surprisingly, the stars in this view are perfect spheres of different sizes, and it is a pleasure to view them this way.

Was an app used to filter out the light spikes around the local stars?

JKLJ