APOD: Hoags Object: A Strange Ring Galaxy (2010 Aug 22)

[bystander]

Click to view full size image

Sorry, I don't see the M104 hypothesis. I see spiral arms all the way into the center. But here is UGC 7388 which appears to be a Hoags in the making. In this case it appears the process has just begun. Could it not be that the Hoags collider culprit is behind the central mass of yellow stars since we are looking down the tube so to speak.

UGC 7388 seems to me to be an example of a polar ring galaxy, which, in my opinion, is rather different from ring galaxies such as Hoag's.

[neufer]

Then we shall agree to disagree (once again).

Hey, what if I don't want to agree to disagree? <g>

The inability to look at any galaxy (including our own) from more then one viewpoint
is sure a serious limitation in studying them, at least using images.

So you disagree to agree to disagree? (Have we done that before?)

• -------------------------------------------------
  Gree, n. [F. gré. See Grateful, and cf. Agree.]
  
  1. Good will; favor; pleasure; satisfaction; -- used esp. in such phrases as:
  to take in gree; to accept in gree; that is, to take favorably. [Obs.] Chaucer.
  
  __ Accept in gree, my lord, the words I spoke. Fairfax.
  
  2. Rank; degree; position. [Obs. or Scot.] Chaucer.
  
  __ He is a shepherd great in gree. Spnser.
  
  3. The prize; the honor of the day; as, to bear the gree, i. e., to carry off the prize. [Obs. or Scot.] Chaucer.
  -------------------------------------------------

[Chris Peterson]

So you disagree to agree to disagree? :shock: (Have we done that before?)

• -------------------------------------------------
  Gree, n. [F. gré. See Grateful, and cf. Agree.]
  
  1. Good will; favor; pleasure; satisfaction; -- used esp. in such phrases as:
  to take in gree; to accept in gree; that is, to take favorably. [Obs.] Chaucer.
  
  __ Accept in gree, my lord, the words I spoke. Fairfax.
  
  2. Rank; degree; position. [Obs. or Scot.] Chaucer.
  
  __ He is a shepherd great in gree. Spnser.
  
  3. The prize; the honor of the day; as, to bear the gree, i. e., to carry off the prize. [Obs. or Scot.] Chaucer.
  -------------------------------------------------

Don't just quote a bunch of literary characters. Are you offering me your gree or not?

[neufer]

Don't just quote a bunch of literary characters.
Are you offering me your gree or not?

Then I'll misquote (or, at least, paraphrase) a movie character:

• “Gree, for lack of a better word, is good. Gree is right. Gree works. Gree clarifies, cuts through, and captures, the essence of the evolutionary spirit. Gree, in all of its forms; Gree for life, for money, for love, knowledge, has marked the upward surge of mankind."

Sure, you are welcome to all my gree, Chris. (That is a girl's name isn't it?)

[Chris Peterson]

Sure, you are welcome to all my gree, Chris. (That is a girl's name isn't it?)

Thank you. (It can be a girl's name, but in my case it's short for Christopher, which is usually not.)

[JohnD]

Hoag's object has features of a comet.

Balderdash! Baloney! You outa yur tree, I hear you cry.
But it returns, regularly as does a comet, to feature as the APOD:
http://antwrp.gsfc.nasa.gov/apod/ap020909.html
http://antwrp.gsfc.nasa.gov/apod/ap040815.html
and
http://antwrp.gsfc.nasa.gov/apod/ap100822.html
But, mirabus mirabile! It has changed its period! So it can't be a comet


No matter, Hoag's Object is extraordinary enough to appear more than thrice.
When it appeared earlier, I suggested my own 'little theory', that a black hole orbited in the matter free gap, and had swallowed up all the material there. Its gravity was stirring up the outer ring by tidal effects to cause the new star formation.
I was pointed then to papers that showed that such an orbit would soon decay, and that the orbiting black hole would 'fall' into the centre.
But it's a nice theory, one of my best!

John

[biddie67]

Ann - if you aren't already a teacher professionally, you definitely have the natural skills to be one!! Thanks for gathering all the pictures and info on a level that I could understand it.

After reading it, and at the mention of some analogies to the behavior of stars, I couldn't help wonder if black holes might have some extraodinary ends to their overall cycle that might be compared to the stars and their red giant or supernova phases ??

Please don't jump on me folks for creating theories - I'm probably guilty of having a lot more "what if" imagination than solid technical knowledge .....

[Ann]

Ann - if you aren't already a teacher professionally, you definitely have the natural skills to be one!! Thanks for gathering all the pictures and info on a level that I could understand it.

After reading it, and at the mention of some analogies to the behavior of stars, I couldn't help wonder if black holes might have some extraodinary ends to their overall cycle that might be compared to the stars and their red giant or supernova phases ??

Please don't jump on me folks for creating theories - I'm probably guilty of having a lot more "what if" imagination than solid technical knowledge .....

Thanks for the praise, Biddie! Actually I am a teacher.

This will have to be a quickie, though, since I'm pressed for time.

Astronomers believe that black holes are created from massive stars. They aren't sure how supermassive black holes like the ones we find at the centers of galaxies got started, but bystander posted a theory about that in the Breaking News folder recently. Go search for it there.

Anyway, astronomers believe that "normal" black holes are created from massive stars at the end of their lives. During its lifetime, a star will shed mass. The Sun is doing that right now in a so called stellar wind. All stars do it, but the more massive a star is, the more violent is the stellar wind and the more mass it will lose during its lifetime.

However, the mass that stars lose is mass in their outer layers. The cores of stars will generally get more massive as long as the stars live.

The Sun now weighs one solar mass (what a surprise). The Sun now shines by converting hydrogen in its core into helium, but about a billion years from now the Sun will have exhausted the hydrogen in its core. The core will now be all made of helium. When that happens the Sun will become extremely unsettled. Its core will shrink, releasing heat, and this heat will make the Sun's outer parts expand prodigiously. The Sun will grow huge, definitely huge enough to swallow Mercury and Venus. The shrinking core will keep heating until it gets hot enough to start converting the helium in its core into carbon and oxygen. When that happens the outer layers of the Sun will shrink a bit, but the Sun will still be huge compared with its size today. As long as the helium supply in its core lasts, the Sun will shine moderately steadily as a "red" (really yellow) giant.

But the Sun will exhaust its central helium, too, just as it must exhaust its central hydrogen. When that happens the Sun will not again be able to shine steadily. In fact, it will not be able to generate heat in its core and protect its core from shrinking even further. The Sun will get the hiccups, so to speak, and it will get more and more unbalanced. It will expand and shrink, shine brighter and fainter, and eventually it will just shed all its outer envelope and turn its core into a white dwarf, a tiny, hot but cooling stellar ember. Eventually it will have radiated all its heat into space and become dark and cold.

The end of the Sun will be relatively undramatic because the Sun is not very massive (even if it is, believe it or not, more massive than more than 90% of the stars in our galaxy). But if a star starts out with a lot more mass than the Sun, it may build up a core that weighs more than 1.4 times as much as the Sun weighs today. Such a massive star will be able to fuse the carbon and oxygen that it builds up in its core into even heavier elements. I don't have the strength or the time to look up the sequence of elements that will be produced, but if a star is sufficiently massive it will build silicon in its core, and after silicon, iron. The iron is the end of the line for the star. The reason why the star builds up heavier and heavier elements in its core is that the fusion of elements releases energy and protects the core from collapsing under its own weight. But once the star has reached the "iron stage" the fusion must stop, because iron will not release energy if you try to fuse it into heavier elements. In other words, the core has run out of energy supplies once it has turned itself into iron. Therefore, the iron core must shrink catastrophically, releasing a shock wave of heat. The star will explode as a supernova.

When a supernova explodes, it is the outer layers that are blasted into space. The core will not explode, because it has already shrunk and become incredibly dense. The core is left behind as the rest of the star explodes, and most very massive stars will turn themselves into neutron stars as an end product. A neutron star is incredibly small and dense, much, much smaller and denser than a white dwarf. A typical white dwarf is the size of the Earth, but a typical neutron star may be the size of Manhattan (okay, that was probably an exaggeration). But the neutron star still weighs more than a white dwarf. A neutron star must weigh more than 1.4 solar masses.

If the core that the star has built up is still more massive - and astronomers are not sure exactly how massive - the core can't even settle down as a neutron star. The general hypothesis is that a neutron star can't weigh more than six to eight solar masses. If it is still more massive, it must collapse into a black hole.

A black hole can be regarded as "mass point" that has all the mass of the core that collapsed, but it has zero volume. (It does have something called the event horizon which indeed extends some distance from the black hole and which marks the boundary beyond which nothing can't escape the gravity of the black hole, but we don't need to discuss that here.)

After a black hole has formed it is very stable. However, Stephen Hawking has shown that black holes must eventually evaporate. However, the lifetime of a massive black hole, the kind that you find at the centers of galaxies, is believed to be trillions of years, much, much longer than the current age of the universe. Smaller black holes evaporate faster, but they still live so long that you aren't likely to see a mighty explosion in the universe caused by the final, catastrophic evaporation of a black hole.

Ann

[Henning Makholm]

This will have to be a quickie, though, since I am pressed for time.

If this is a quickie, I think I dread the day you decide to post a slowie.

Smaller black holes evaporate faster, but they still live so long that you aren't likely to see a mighty explosion in the universe caused by the final, catastrophic evaporation of a black hole.

In particular, a black hole large enough to have been formed by a collapsing star will be evaporating so slowly that it gains more mass by being hit by the cosmic microwave background than it loses to evaporation. So it won't be going anywhere anytime soon.

If we ever do see a black hole explode catastrophically, it must be a small variant arising from some other process than stellar collapse, and nobody have been able to propose a plausible mechanism that could produce them. Some extremely tenuous speculation posits that they could have came into being somehow during the Planck-stage big bang, and that their explosive evaporation could be responsible for some observed gamma-ray bursts. But that seems to be in the realm of idle speculation, not even reaching the level of "sort-of interesting hypothesis".

[Ann]

[I'm not sure about your "little theory" , "Boomer12k" , but I do agree
that the Hoag's Object is just a distant example of M104 seen face on.

I don't see that at all. M104 is a slightly unusual spiral galaxy- the dust lane is more pronounced than usually seen, the central bulge is larger, but it is still pretty obviously a spiral, not far from normal. Hoag's object is structurally very different. It has a broad region almost completely devoid of normal matter. It has a dense central section like an elliptical galaxy, nothing like the halo seen on M104. And its outer ring is obviously evolved from (or evolving to) a spiral, and shows lots of star formation.

If I had to pick two galaxies that had less in common, I'd be hard pressed.

I disagree.

Well, I agree that that M104 doesn't seem a lot like Hoag's Object. I was carried away by neufer's arguments, but I have changed my mind. I agree the disk of M104 extends all the way into the massive bulge, leaving no obvious "hole" between the ring and the bulge.

However, I disagree that M104 shows a lot of star formation. I apologize for posting such a massive file in another post, and I realize now that I shouldn't have done it, but my purpose for doing it was to demonstrate that M104 does not show a lot of star formation.

Here are my arguments for why M104 is poor in star formation:

1) It looks monocolored in almost all images.

2) Its color indexes are B-V = 0.97 and U-B = 0.52. Both color indexes are "red" and indicate little or no star formation. Such color indexes are actually typical of non-starforming elliptical galaxies.

3) It is faint in the far infrared, fainter than in blue light. Vigorously starforming galaxies are typically brighter in the far infrared than in blue light. For M104, B = 9.075 and far infrared is 10.925.

4) GALEX shows that M104 is faint in the far ultraviolet. Vigorously starforming galaxies are typically bright in the far ultraviolet.

Conclusion: M104 has little star formation. Hoag's Object may have more of it.

Ann

[mexhunter]

Hi to all:
The universe is more prolific than our imagination.
Beautiful view and excellent photo.
Greetings
Cesar

[Chris Peterson]

Well, I agree that that M104 doesn't seem a lot like Hoag's Object. I was carried away by neufer's arguments, but I have changed my mind. I agree the disk of M104 extends all the way into the massive bulge, leaving no obvious "hole" between the ring and the bulge.

However, I disagree that M104 shows a lot of star formation. I apologize for posting such a massive file in another post, and I realize now that I shouldn't have done it, but my purpose for doing it was to demonstrate that M104 does not show a lot of star formation.

You disagree with whom? I said that Hoag's shows star formation, and that is one of the ways it differs from M104, which does not. Seems to me we're in complete agreement here.

[maloohoo]

Awesome image!!!! I love this stuff!!

I am no expert but this looks to me like a soon-to-be spiral galaxy. The central red stars will collapse as they die creating a black hole and speeding up the spiral motion that has already started. It's like the start of a whirlpool.

Anybody else see that??

[neufer]

The Sombrero Galaxy (M104) as observed by the Spitzer. Credit: HST/NASA/ESA.

---

I'm not sure about your "little theory" , "Boomer12k" , but I do agree that the Hoag's Object is just a distant example of M104 seen face on.

I don't see that at all. M104 is a slightly unusual spiral galaxy- the dust lane is more pronounced than usually seen, the central bulge is larger, but it is still pretty obviously a spiral, not far from normal. Hoag's object is structurally very different. It has a broad region almost completely devoid of normal matter. It has a dense central section like an elliptical galaxy, nothing like the halo seen on M104. And its outer ring is obviously evolved from (or evolving to) a spiral, and shows lots of star formation.

Hoag's object's outer ring has obviously evolved from a highly symmetric dust ring similar to that of M104.

M87, M104 and Hoag's object are all basically the same animal at different stages of evolution, IMO.

[Chris Peterson]

Hoag's object's outer ring has obviously evolved from a highly symmetric dust ring similar to that of M104.

That's not at all obvious to me. You can't really compare an image in IR to one in visible light. Your IR image of M104 looks exactly like you'd expect, with the dust having a strong IR signal. Most of the mass of the galaxy is hotter stars, with only a weak IR signal. Since the dust is in a ring, that's what you see at the long wavelength. Hoag's has an actual zone free of normal matter; M104 pretty obviously does not.

[Beyond]

The Sombrero Galaxy (M104) as observed by the Spitzer. Credit: HST/NASA/ESA.

---

I'm not sure about your "little theory" , "Boomer12k" , but I do agree that the Hoag's Object is just a distant example of M104 seen face on.

I don't see that at all. M104 is a slightly unusual spiral galaxy- the dust lane is more pronounced than usually seen, the central bulge is larger, but it is still pretty obviously a spiral, not far from normal. Hoag's object is structurally very different. It has a broad region almost completely devoid of normal matter. It has a dense central section like an elliptical galaxy, nothing like the halo seen on M104. And its outer ring is obviously evolved from (or evolving to) a spiral, and shows lots of star formation.

Hoag's object's outer ring has obviously evolved from a highly symmetric dust ring similar to that of M104.

M87, M104 and Hoag's object are all basically the same animal at different stages of evolution, IMO.

Neufer, do you have any idea what that cute little double red spot is over the last part of the word "Sombrero?"

[Ann]

Well, I agree that that M104 doesn't seem a lot like Hoag's Object. I was carried away by neufer's arguments, but I have changed my mind. I agree the disk of M104 extends all the way into the massive bulge, leaving no obvious "hole" between the ring and the bulge.

However, I disagree that M104 shows a lot of star formation. I apologize for posting such a massive file in another post, and I realize now that I shouldn't have done it, but my purpose for doing it was to demonstrate that M104 does not show a lot of star formation.

You disagree with whom? I said that Hoag's shows star formation, and that is one of the ways it differs from M104, which does not. Seems to me we're in complete agreement here.

Ah, sorry, Chris. I should have read your post more carefully.

Ann

[Ann]

Beyond wrote:

Neufer, do you have any idea what that cute little double red spot is over the last part of the word "Sombrero?"

That's a pair of distant galaxies. They are vigorously starforming and quite dusty, which is why they look red in this image, where dust shows up as red.

This is a true color image of M104 which shows the tiny galaxy pair at lower left. Note the white color of the starforming, interacting galaxies. They are considerably whiter than M104, even though they are much farther away and have had their light redshifted.

Click to view full size image

Ann

[Ann]

The Sombrero Galaxy (M104) as observed by the Spitzer. Credit: HST/NASA/ESA.

---

I'm not sure about your "little theory" , "Boomer12k" , but I do agree that the Hoag's Object is just a distant example of M104 seen face on.

I don't see that at all. M104 is a slightly unusual spiral galaxy- the dust lane is more pronounced than usually seen, the central bulge is larger, but it is still pretty obviously a spiral, not far from normal. Hoag's object is structurally very different. It has a broad region almost completely devoid of normal matter. It has a dense central section like an elliptical galaxy, nothing like the halo seen on M104. And its outer ring is obviously evolved from (or evolving to) a spiral, and shows lots of star formation.

Hoag's object's outer ring has obviously evolved from a highly symmetric dust ring similar to that of M104.

M87, M104 and Hoag's object are all basically the same animal at different stages of evolution, IMO.

Neufer, the fact that the dust doesn't extend all the way to the center of M104 doesn't mean that the yellow disk doesn't extend all the way to the nucleus. I agree with Chris that there is no gap between the ring and the nucleus in M104.

Ann

[neufer]

Hoag's object's outer ring has obviously evolved from a highly symmetric dust ring similar to that of M104.

M87, M104 and Hoag's object are all basically the same animal at different stages of evolution, IMO.

Neufer, the fact that the dust doesn't extend all the way to the center of M104 doesn't mean that the yellow disk doesn't extend all the way to the nucleus. I agree with Chris that there is no gap between the ring and the nucleus in M104.

Once the dust ring has formed it interacts gravitationally with the faster rotating stars within it much like a tidal ocean in reverse. The interior stars are slowed down and drop into the center while depositing their angular momentum into the dust cloud. It is roughly the same process that produced the outer giant planets in our own solar system accept that many new stars are generated in the Hoag's object ring rather than a few giant gas planets.

[Beyond]

Beyond wrote:

Neufer, do you have any idea what that cute little double red spot is over the last part of the word "Sombrero?"

That's a pair of distant galaxies. They are vigorously starforming and quite dusty, which is why they look red in this image, where dust shows up as red.

This is a true color image of M104 which shows the tiny galaxy pair at lower left. Note the white color of the starforming, interacting galaxies. They are considerably whiter than M104, even though they are much farther away and have had their light redshifted.

Click to view full size image

Ann

Thanks Ann. So whomever took the picture of the Sombrero galaxy also caught two other Galaxies in the background doing six. It's only in the white that with a magnifying glass i can see part of the left Galaxy's outer parts being deformed.

Neufer - forget your spellcheck when you got up this morning? - accept instead of except ?

[neufer]

Neufer - forget your spellcheck when you got up this morning? - accept instead of except ?

Touché. (The right & left halves of my brain don't talk to each other in the morning.)

[Chris Peterson]

Once the dust ring has formed it interacts gravitationally with the faster rotating stars within it much like a tidal ocean in reverse...

Maybe. But this assumes that there is enough mass in the dust to interact in the way you suggest. Gravitational effects of this sort require pretty high surface densities, but (appearances to the contrary) in reality these dusty zones are still very tenuous. I'd expect that the volume containing one stellar mass of dust would contain several actual stars. I think that surrounding stars are having more of an effect on the dust than the dust is having on the stars.