I'm glad to see an APOD galaxy that is not M31, LMC, M33, M81, M82, M51, M101 or M104!
M96 is indeed a weird-looking galaxy. You have to wonder what could have caused the dust lane at about 3 o'clock to be so strange-looking and lopsided, and what could have caused the strange dust pattern near the center to emerge. It is almost as if someone had used a sort of windup key on this galaxy, and wound it up too hard.
M96 has a large yellow bulge, and when I look at it I get the impression that it is a quite yellow galaxy. But its colors are "normal", with a B-V index of 0.86 and a U-B index of 0.31. Its far infrared magnitude is about 0.4 magnitudes fainter than its B magnitude. Normal. Compare that with the Andromeda galaxy, which is considerably redder: B-V is 0.92, U-B is 0.50, and its far infrared magnitude is 1.3 magnitudes fainter than its B magnitude.
While today's APOD is interesting and beautiful, I wish that an Ha filter had been used when acquiring the data for the image. Now it is hard to spot the emission nebulas that must be there. Fascinatingly, a very blue bubble can be seen at close to 11 o'clock. No other gaseous blue structures can be seen in the galaxy, as far as I'm aware. Could that blue bubble be an OIII structure?
Some deep orange-red spots are visible all over the disk of M96. (But not really in the bulge.) An 814 nm infrared filter has been used for the red channel for this image, and since red giants are always bright in infrared light, I guess the red spots are just red giants. But there are two extended red "blisters" which are yellow in the middle, located in dust lanes at about 9 o'clock and 7 o'clock, which look like regions of star formation to me. (They also look a bit like pimples ready to burst, but don't tell anyone.)
There are a few other red spots with yellow middles which look more like tremendous red supergiants to me. And there is an extended red spot at about 12 o'clock which looks more like a background galaxy. Indeed, don't miss the background galaxies! The one at 1 o'clock is a barred beauty, brimming with star formation!
Ann wrote:M96 contains the background galaxy of all background galaxies, a beautifully edge-on, largish, flat, reddish spiral galaxy perfectly aligned with a spiral arm of M96!
That's a good one, but I must respectfully disagree about the superlative. There's, umm, NGC 3314 itself, and the gigantic edge-on galaxy behind SDSS 1336+62 in this recent Hubble red-light image:
(But these are matters perhaps to be explored in future APODs, maybe when the STARSMOG Hubble survey of such things wraps up...)
NGC3314 wrote:(But these are matters perhaps to be explored in future APODs, maybe when the STARSMOG Hubble survey of such things wraps up...)
Is there a website of some sort for STARSMOG? It's actually pretty difficult to find info on. Best I can do is Benne's little blurb on it here: http://home.strw.leidenuniv.nl/~holwerda/STARSMOG.html
Of course, there is also an assortment of slightly enigmatic tweets from yourself as well.
Just call me "geck" because "zilla" is like a last name.
No (and if there were one I would have had to write it). I have Tweeted pretty much all the images as they came in, and the program status information can be seen here. "Proposal information" and "visit status" links are, to my mind, the most helpful.
54 targets so far, but no more in the next 2 weeks or so from the long-range schedule. I'm not completely clear on whether snapshot targets stay in the queue for one of two years (one year runs out in late November).
The "examining the edges" in the "Galaxies far in the background can be found by examining the edges of the picture" sentence is a link to a cute image of a cat looking round the corner of a building. I've no problem with such cute images though I still expected that there would be fairly obviously seen such galaxies in the image but I however only see one probable one (to the top right) and at best (on enlarging the image) a very few very faint objects that may or may not be galaxies. I think the final sentence is misleading and should be removed.
DavidLeodis wrote:
The "examining the edges" in the "Galaxies far in the background can be found by examining the edges of the picture" sentence is a link to a cute image of a cat looking round the corner of a building. I've no problem with such cute images though I still expected that there would be fairly obviously seen such galaxies in the image but I however only see one probable one (to the top right) and at best (on enlarging the image) a very few very faint objects that may or may not be galaxies. I think the final sentence is misleading and should be removed.
Thanks, NGC 3314 and starsurfer! I knew about NGC 3314, of course, but I didn't know about SDSS 1336+62. And starsurfer, I knew about 2MASX J00482185-2507365, but I had forgotten that it is so conveniently located near NGC 253. And I didn't know about Burbidge's Chain. What a splendid chain of spiral and starbursting galaxies!
I would be grateful if someone could please produce an annotated version of the image that shows the positions of the "Galaxies far in the background" that are "found by examining the edges of the picture", as I have a feeling that it is only me that is having trouble spotting them! Thanks .
DavidLeodis wrote:I would be grateful if someone could please produce an annotated version of the image that shows the positions of the "Galaxies far in the background" that are "found by examining the edges of the picture", as I have a feeling that it is only me that is having trouble spotting them! Thanks .
Here you go.
Attachments
Larger circles are surely background galaxies. A few smaller circles are likely background galaxies.
Just call me "geck" because "zilla" is like a last name.
Thanks geckzilla for your help which is greatly appreciated . Without your help I would not have known where the galaxies were, nor perhaps have even spotted many of them!
1. To me it looks like a big swath of dust is in a prominence above the plane of the main body of the spiral, above the main star-filled arm of the galaxy. Is this how other professional observers see it?
2. What is the conventional explanation for why all matter in the presence of a black hole in the case of galaxies is supposed to be present as a flat spiral instead of a sphere?
3. Why is it unexpected or outside the conventional model to have this swath of dust that does NOT lay in the plane of the spiral?
That object showed up with obvious dust absorption in the ANGST Hubble survey of halo stars in nearby galaxies including NGC 253. ANGST principal investigator Julianne Danton chased Benne Holwerda and me down at a meeting to show us, knowing we did such occulting galaxy things, and thereby hangs a paper with detailed analysis. Such small galaxies with dust tendrils extending very far into their outskirts are rare but would explain some features of the far-IR statistics of galaxies, so one goal of projects such as the STARSMOG Hubble survey is finding more (we think we see a few more to date).
And that example has just been sitting there in many images of NGC 253 all along.
sallyseaver wrote:1. To me it looks like a big swath of dust is in a prominence above the plane of the main body of the spiral, above the main star-filled arm of the galaxy. Is this how other professional observers see it?
I'd be cautious trying to infer any 3D structure from images like this. Our visual systems did not evolve to analyze such scenes, and we can fall victim to many illusions that paint a distorted view of reality.
2. What is the conventional explanation for why all matter in the presence of a black hole in the case of galaxies is supposed to be present as a flat spiral instead of a sphere?
Black holes have nothing to do with it. All that matters is gravitational attraction and the density of orbital material. If the density is high enough that the material can interact via electromagnetic forces, that material will flatten out (just like spinning pizza dough). If not, it won't, and will eventually settle into a spherical cloud. That's what's happening to all galaxies over time- whether or not they have a black hole at the center.
3. Why is it unexpected or outside the conventional model to have this swath of dust that does NOT lay in the plane of the spiral?
It isn't. The asymmetry suggests a previous interaction with another galaxy, and such interactions can draw material out of the original plane.
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory https://www.cloudbait.com
Chris Peterson wrote:
All that matters is gravitational attraction and the density of orbital material. If the density is high enough that the material can interact via electromagnetic forces, that material will flatten out (just like spinning pizza dough). If not, it won't, and will eventually settle into a spherical cloud. That's what's happening to all galaxies over time-
Just to be clear...when Chris talks about "density" he means GAS "density"
and "interact via electromagnetic forces" includes collisions of neutral gas particles:
https://en.wikipedia.org/wiki/Outer_space#Interstellar_space wrote:
<<Interstellar space is the physical space within a galaxy beyond the influence of each star on the plasma. These atoms are ejected into the interstellar medium by stellar winds or when evolved stars begin to shed their outer envelopes such as during the formation of a planetary nebula. The cataclysmic explosion of a supernova will generate an expanding shock wave consisting of ejected materials. The density of matter in the interstellar medium can vary considerably:
1) the average is around 106 particles per m3 [: mean free path ~ 109 km],
2) but cold molecular clouds can hold 108–1012 per m3 [: mean free path ~ 107 - 103 km].
Note: The mean free path is the average distance traveled by a moving particle (such as an atom, a molecule, a photon) between successive impacts (collisions), which modify its direction or energy or other particle properties.>>
The Andromeda Galaxy. NASA's Wide-field Infrared Survey Explorer
I think the best answer is that there is no such thing as a "typical" spiral galaxy. Andromeda certainly isn't typical. Andromeda is a "ring galaxy" rather than a spiral galaxy, as you can see in this infrared image at left.
Like M96, Andromeda has in all probability been shaped by the mergers and collisions it has undergone. For Andromeda, (repeated) collisions with its small elliptical satellite galaxy M32 are probably responsible for creating rings like ripples in a pond. But the collisions and mergers that M96 has undergone have been different from those of Andromeda, and these two galaxies have also evolved differently.
That object showed up with obvious dust absorption in the ANGST Hubble survey of halo stars in nearby galaxies including NGC 253. ANGST principal investigator Julianne Danton chased Benne Holwerda and me down at a meeting to show us, knowing we did such occulting galaxy things, and thereby hangs a paper with detailed analysis. Such small galaxies with dust tendrils extending very far into their outskirts are rare but would explain some features of the far-IR statistics of galaxies, so one goal of projects such as the STARSMOG Hubble survey is finding more (we think we see a few more to date).
And that example has just been sitting there in many images of NGC 253 all along.
I forgot to mention that not only is it an interesting background galaxy but that it is also an overlapping pair. Another point to mention about Burbidge's Chain is that two of the galaxies might be connected together by a tidal bridge. These types of systems are quite rare and also visually striking.
Just to be clear...when Chris talks about "density" he means GAS "density"
and "interact via electromagnetic forces" includes collisions of neutral gas particles:
And dust, although in most environments gas is by far the dominant player.
Collisions of dust with gas certainly...
with mean free paths dependent only upon the gas density.
Dust/dust collisions would be rather rare by comparison I would think...
with mean free paths comparable to red light photon mean free paths with dust:
Thank you Chris, Ann and Neufer. Your answsers are very helpful.
Chris Peterson wrote:
sallyseaver wrote:1. To me it looks like a big swath of dust is in a prominence above the plane of the main body of the spiral, above the main star-filled arm of the galaxy. Is this how other professional observers see it?
I'd be cautious trying to infer any 3D structure from images like this. Our visual systems did not evolve to analyze such scenes, and we can fall victim to many illusions that paint a distorted view of reality.
More regarding #1
Chris, you said to be cautious about trying to infer 3D structure, but you can see the light from the middle of 96M shining through the swath of dust, the dust that is making the image look asymmetrical, what I will call the dust prominence. If the dust prominence was in the plane of the galaxy, then I don't think the central illumination would be able to shine through it given the angle the picture was taken in.
So maybe you are saying that even though it looks like the light from the center is illuminating some of the dust rising up from the outer ring, that experienced observers are highly skeptical that this is the case, yes? Rather, the thinking is that the dust just is naturally a lighter color while lying flat in the plane of orbit?
Chris Peterson wrote:
sallyseaver wrote:2. What is the conventional explanation for why all matter in the presence of a black hole in the case of galaxies is supposed to be present as a flat spiral instead of a sphere?
Black holes have nothing to do with it. All that matters is gravitational attraction and the density of orbital material. If the density is high enough that the material can interact via electromagnetic forces, that material will flatten out (just like spinning pizza dough). If not, it won't, and will eventually settle into a spherical cloud. That's what's happening to all galaxies over time- whether or not they have a black hole at the center.
More regarding #2
Chris, your answer is very interesting and this satisfies some of my curiosity on this matter. But I have a couple follow-up questions.
a.)
Where does the original angular momentum come from? My understanding is that the original matter started like the big nebulae we see in other parts of the cosmos, like The Great Nebula (APOD Jan 19, 2015) or Gamma Cygni Nebula (APOD April 22, 2015) or the Carina Nebula. [from Big Bang TO stars TO the nebula material after stars die, i.e. planetary nebulae] Then if matter accretes around a denser part of the big nebula, it seems to me that the accretion would tend to be spherical. How does the angular momentum get started according to current thinking?
Angular momentum shows up for spiral and ring galaxies, also for the discs of material involved with star formation. The answers I have read might, in a wild stretch of imagination, produce angular momentum in one or two systems, but not the wide spread occurrence that is witnessed in the cosmos of going from no angular momentum to a system with angular momentum. What is the answer that has satisfied you?
b.) IF there is a dust prominence in the absence of interacting with a different galaxy, then it could mean that the dust is primarily iron (an abundant element) with it's own magnetic properties so that it does not interact in the same way as the other orbital material? Would this be an acceptable explanation? This paper indicates that 90% or more of the iron in a planetary nebula is deposited in dust grains [arXiv:0812.1578v2 [astro-ph] 31 Mar 2009: "The Iron Abundance in Galactic Planetary Nebulae"]
sallyseaver wrote:
Where does the original angular momentum come from? My understanding is that the original matter started like the big nebulae we see in other parts of the cosmos, like The Great Nebula (APOD Jan 19, 2015) or Gamma Cygni Nebula (APOD April 22, 2015) or the Carina Nebula.
No, the original matter did not start as a big nebula. Everything that exists in the universe was originally created in the Big Bang. The Big Bang was the sudden appearance and the immediate, violent expansion of the universe. From the beginning the universe was incredibly tiny, hot and dense. In the beginning it was far too hot and dense for matter and energy to be separate at all. When the universe had expanded and cooled to a certain degree, matter and energy could "decouple". That is when hydrogen first came into existence, the simplest form of ordinary matter. Helium, too, the second element, was created in the Big Bang, and also some lithium. This matter existed as a hot, dense, but expanding "soup".
The universe was certainly at least 400,000 years old, and possibly many million years old, before the first stars appeared. The first stars probably emerged out of nebulas, but the first nebulas were certainly very different from the typical nebulas of today. For one thing, the original nebulas contained no dust at all. Dust is made of elements more complex than hydrogen and helium (and lithium), but all such elements are created inside stars as rest products of their fusion of hydrogen and helium. Before the stars existed, there was no dust.
Where does the angular momentum come from? I'm not the correct person to answer that at all, but you must remember that the universe has always been teeming with energy, motion and outward expansion. Remember that the universe was always a place were outward expansion and inward-pressing gravity fought with one another. The distribution of matter and energy was always very slightly "uneven", encouraging the flow of matter away from more rarefied locations into more densely packed parts. Why should there not be angular momentum in such a dynamic place? What force could actually stop the angular momentum in the universe?
In any case, stars appears when a nebula shrinks and condenses under the influence of its own gravity. In other words, the nebula becomes smaller (or at least the part of the nebula that gives rise to the star becomes smaller). If the nebula is not perfectly "still", but contains some inherent rotation at all, this rotation will become much more pronounced as the nebula shrinks. Compared this with what figure skaters do to rotate, and to rotate faster. When they spin, they have to create their own initial rotation, but then they speed their rotation up by making themselves "smaller", by holding their arms and legs close to their "axis of rotation":
Click to play embedded YouTube video.
IF there is a dust prominence in the absence of interacting with a different galaxy, then it could mean that the dust is primarily iron (an abundant element)
Iron is not particularly abundant at all, compared with many other elements in the universe like oxygen, carbon and silicon. You can be sure that the dust in the universe is mostly made up of other elements than iron.
sallyseaver wrote:
Where does the original angular momentum come from? My understanding is that the original matter started like the big nebulae we see in other parts of the cosmos, like The Great Nebula (APOD Jan 19, 2015) or Gamma Cygni Nebula (APOD April 22, 2015) or the Carina Nebula.
No, the original matter did not start as a big nebula. Everything that exists in the universe was originally created in the Big Bang.
Ann, I am sorry for the misunderstanding. I know about the Big Bang theory, this is why I used the word "matter" and not the "precursors to matter." I was talking about the stage of development just prior to a galaxy forming, not from the very beginning of time. According to the current standard theory for the development of the universe, as I understand it, there have to be many stars formed and decayed before we get to the matter in a nebula which is a precursor to a galaxy. The idea is that elements heavier than hydrogen and helium had to be formed through the decay of stars. When a star dies it gives off a burst of electrons, helium nuclei (alpha particles) and a small percentage of high-z nuclei. Then through some mechanism, the output of the dying stars collect to form the a nebula. I know that nebulae are precursors to stars. I would think that a star-studded nebula would be a precursor to a galaxy.
Angular momentum is a conserved physical quantity. In the example of the skater, the skater uses force to create the initial angular momentum (as you say), then decreases the moment of inertia so that the angular speed increases. [magnitude of angular momentum = magnitude of moment-of-inertia x angular speed] The areas of the cosmos that turn into stars or galaxies are very big, we would see even a little bit of angular momentum around a common axis, like you can see the skater turning slowly at first. Also, the gases and dust are so sparse that there is a problem for getting a proper moment of inertia which is usually associated with a rigid moment-arm of some kind (e.g. skater's legs). The atomic and dust components are free to rotate in three dimensions, but to get to a big spiral, you have to get all components to orbit in such a way that they all have the same axis of rotation.
Ann wrote:
sallyseaver wrote: IF there is a dust prominence in the absence of interacting with a different galaxy, then it could mean that the dust is primarily iron (an abundant element)
Iron is not particularly abundant at all, compared with many other elements in the universe like oxygen, carbon and silicon. You can be sure that the dust in the universe is mostly made up of other elements than iron. Ann
The paper that I referred to says that Si and Mg can have similar contributions to dust grains as iron [Fe]; C and O can be even higher. Iron [Fe] is the 6th most abundant element according to current observations (which may be biased towards local observations/measurements). Admittedly this is only .11% of the total ON AVERAGE. But with heterogeneity of elements in nebulae, there can be a higher percent in localized regions. And IF iron is a strong component of the brown dust clouds in our APOD picture of M96, then in cold space the microscopic domains would line up to have a macroscopic magnetic field that would influence its interaction with the other constituents of the outer ring of M96.
Spiral Galaxy M96 from Hubble
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