APOD: Hoag's Object: A Nearly Perfect Ring... (2019 Nov 27)

[BDanielMayfield]

In Dr. Smethurst's video she states that ring galaxies make up 'less than one tenth of one percent of all galaxies'. Also in that video a paper discussed well explained the existence of the gap in Hong's ring as a zone of gravitational orbital instability, explaining both it's clearness and uniformity. The ring inside the ring can't be at the same distance because it would then be inside a region where it would be shredded in short (astronomical) order. The consensus view is that this inner ring is just what it looks like; a very distant background galaxy.

So then how unlikely is this "coincidental" alignment? What are the odds of the inner ring's perfect positioning right in the dead center of Hoag's galaxy's ring gap? I just can't buy it that this is just total chance.

Bruce

[neufer]

In Dr. Smethurst's video she states that ring galaxies make up 'less than one tenth of one percent of all galaxies'. Also in that video a paper discussed well explained the existence of the gap in Hong's ring as a zone of gravitational orbital instability, explaining both it's clearness and uniformity. The ring inside the ring can't be at the same distance because it would then be inside a region where it would be shredded in short (astronomical) order. The consensus view is that this inner ring is just what it looks like; a very distant background galaxy.

So then how unlikely is this "coincidental" alignment? What are the odds of the inner ring's perfect positioning right in the dead center of Hoag's galaxy's ring gap? I just can't buy it that this is just total chance.

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To be clear: I am suggesting that Hoag's Object resembles the Cartwheel galaxy in there being two disturbed ring galaxies: one small one behind another larger one. The small ring galaxy (Piglet?) is noticeably reddened by a trail of (cold) dust left in its own "wake" caused by the explosion of numerous recent short lived supernovae.
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The Cartwheel galaxy in different light spectra (X-ray, ultraviolet, visible, and infrared). The image combines data from four different space-based observatories: the Chandra X-ray Observatory (purple), the Galaxy Evolution Explorer (ultraviolet/blue), the Hubble Space Telescope (visible/green), and the Spitzer Space Telescope (infrared/red). Image is 160 arcsec across. RA 00h 37m 41.10s Dec −33° 42′ 58.80″ in Sculptor. Credit: NASA/JPL/Caltech/P.Appleton et al. X-ray: NASA/CXC/A.Wolter & G.Trinchieri et al.

[sillyworm 2]

Not that I have knowledge to back up my claim..but I'm agreeing with Ann's idea that these 2 ring galaxies are not related or have had any influence on each other.Hoag's Object is a fascinating mystery.

[Chris Peterson]

So then how unlikely is this "coincidental" alignment? What are the odds of the inner ring's perfect positioning right in the dead center of Hoag's galaxy's ring gap? I just can't buy it that this is just total chance.

Only because you choose to place significance on something which is striking to your senses. Something which lacks any natural significance. You could as well be astonished by the alignment of two stars with measurably identical temperatures lying within a few arcseconds of each other, or any other extremely unlikely things. Yet all these unlikely things exist. Indeed, virtually everything we observe in the Universe is the end result of a massively long sequence of unlikely events. You could say that everything borders on impossible. Yet everything is.

[neufer]

So then how unlikely is this "coincidental" alignment?
What are the odds of the inner ring's perfect positioning right in the dead center of Hoag's galaxy's ring gap?
I just can't buy it that this is just total chance.

Hoag's Object apparent diameter is 0.28′ and therefore
covers just 1/600,000,000th (=[1.0-cos(0.28′)]/2) of the sky.

If there are ~N ring galaxies within 600 Mly of the sun then there are
~30,000N ring galaxies within 18.6 Gly (=31 x 600 Mly) of the sun and therefore
~30,000N ring galaxies at least 1/31st the apparent diameter of Hoag's Object.

The probability that the center of one of these ring galaxies lies
within Hoag's Object is ~30,000N/600,000,000 or N chances in 20,000.

A partial list of known ring galaxies within 600 Mly
suggests that N in this case is probably on the order of ~20.

Hence, the probability that Hoag's Object coincidentally contains a distinct
though more distant "Piglet" is certainly no more than ~1 in 1,000
(and considering "Piglet's" large size could be more like ~1 in 30,000).

[Chris Peterson]

Not that I have knowledge to back up my claim..but I'm agreeing with Ann's idea that these 2 ring galaxies are not related or have had any influence on each other.Hoag's Object is a fascinating mystery.

A not unreasonable view given that if these objects are of similar size, they are separated by about 10 billion light years.

[neufer]

Not that I have knowledge to back up my claim..but I'm agreeing with Ann's idea that
these 2 ring galaxies are not related or have had any influence on each other.

A not unreasonable view given that if these objects are of similar size,
they are separated by about 10 billion light years.

Only a very small percentage of galaxies are ring galaxies facing us.

So where are all the other types of prominent galaxies inside of Hoag's Object

Simple logic suggests that these galaxies are indeed related unless redshift measurements exclude that possibility.

[Chris Peterson]

Not that I have knowledge to back up my claim..but I'm agreeing with Ann's idea that
these 2 ring galaxies are not related or have had any influence on each other.

A not unreasonable view given that if these objects are of similar size,
they are separated by about 10 billion light years.

Only a very small percentage of galaxies are ring galaxies facing us.

So where are all the other types of prominent galaxies inside of Hoag's Object :?:

Simple logic suggests that these galaxies are indeed related unless redshift measurements exclude that possibility.

You've already demonstrated a 1:1000 probability, which is quite high, actually. Logic does not suggest they are related at all, but it would be interesting to know the redshift of the smaller object.

Here's the actual probability of this thing existing as it does: unity. We get fooled by things that are improbable. What are the odds of your genome existing as it does? Well, it's such a vanishingly small probability that we might nearly say it's impossible. But yet... you exist. Go figure. Depending on how we structure the question, almost everything has only the tiniest probability of existing.

[geckzilla]

the funny thing is that if you didn't look at it with high resolution and notice the ring shape, none of you would have any doubt about whether or not they're related:
http://legacysurvey.org/viewer?ra=229.3 ... r8&zoom=15

so obviously an unrelated background galaxy you wouldn't even question it.

[Chris Peterson]

the funny thing is that if you didn't look at it with high resolution and notice the ring shape, none of you would have any doubt about whether or not they're related:
http://legacysurvey.org/viewer?ra=229.3 ... r8&zoom=15

so obviously an unrelated background galaxy you wouldn't even question it.

Very true. But humans are pattern seekers, and we'll find them even when they don't actually exist. It's a bias we have to make a conscious effort to avoid. Coincidences are real, and they are common.

[neufer]

the funny thing is that if you didn't look at it with high resolution and notice the ring shape,
none of you would have any doubt about whether or not they're related:

http://legacysurvey.org/viewer?ra=229.3 ... r8&zoom=15

so obviously an unrelated background galaxy you wouldn't even question it.

If we don't look at it with high resolution and notice the ring shape:
it wouldn't be surprising to see one "Piglet" sized galaxy within Hoag's Object.

It *IS*, however, surprising to see one "Piglet" sized RING GALAXY pointing at us within Hoag's Object.

RING GALAXIES pointing at us are quite rare

Humans are pattern seekers, and we'll find them even when they don't actually exist.
It's a bias we have to make a conscious effort to avoid.
Coincidences are real, and they are common.

Scientists are pattern seekers who put forth conjectures that can be tested.

I see a pattern between Hoag's Object and the Cartwheel galaxy that can be tested with one Doppler shift measurement:

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I am suggesting that Hoag's Object resembles the Cartwheel galaxy in there being two disturbed ring galaxies: one small one behind another larger one. The small ring galaxy (Piglet?) is noticeably reddened by a trail of (cold) dust left in its own "wake" caused by the explosion of numerous recent short lived supernovae.
.......................................................................
The Cartwheel galaxy in different light spectra (X-ray, ultraviolet, visible, and infrared). The image combines data from four different space-based observatories: the Chandra X-ray Observatory (purple), the Galaxy Evolution Explorer (ultraviolet/blue), the Hubble Space Telescope (visible/green), and the Spitzer Space Telescope (infrared/red). Image is 160 arcsec across. RA 00h 37m 41.10s Dec −33° 42′ 58.80″ in Sculptor. Credit: NASA/JPL/Caltech/P.Appleton et al. X-ray: NASA/CXC/A.Wolter & G.Trinchieri et al.

[Chris Peterson]

I see a pattern between Hoag's Object and the Cartwheel galaxy that can be tested with one Doppler shift measurement:

I don't see much resemblance. I don't see a second ring galaxy. I don't see any obvious more distant galaxies. This is a galaxy cluster, which is how we commonly encounter galaxies. Hoag's Object is unusual in its isolation. In the case of the cluster containing the Cartwheel, all are at about the same distance and have the same redshift. (And that's primarily cosmological redshift, not Doppler. The several decimal places out variation in redshift in the cluster members is a tiny Doppler shift superimposed on the cosmological redshift.) And structurally, the Cartwheel looks very different, an obvious spiral and a structure readily explained by a collision, whereas the structure of Hoag's Object can't seem to be explained by a collision.

It seems as if the best understanding here is that the category of "ring galaxy" contains objects with entirely different production mechanisms. And that the distant galaxy seen in the gap is entirely unrelated.

[geckzilla]

Another thing about the little ring galaxy behind Hoag's is that it has just enough details for you to know there is some sort of ring there, and your brain is automatically like wow, another one just the same, almost facing us, incredible! But if you could see it in even further detail, closer up, it's not likely to be that similar to Hoag's at all. Galaxies wrap their arms around and form ring-like structures all the time.

♬ Great big globs of blurry, blobby galaxies
blurry, blobby galaxies
blurry, blobby galaxies ♬

[neufer]

Click to play embedded YouTube video.

the funny thing is that if you didn't look at it with high resolution and notice the ring shape, none of you would have any doubt about whether or not they're related: so obviously an unrelated background galaxy you wouldn't even question it.

But if you could see it in even further detail, closer up, it's not likely to be that similar to Hoag's at all. Galaxies wrap their arms around and form ring-like structures all the time.

I'm going to make a resolution to stop replying
to all the arm waving going on here
and wait for science to clarify what's going on.

[geckzilla]

Go on and get some Keck time and look at it with their fancy adaptive optics to get a morphology study on it, and throw some spectroscopy in while you're there.

[Chris Peterson]

Go on and get some Keck time and look at it with their fancy adaptive optics to get a morphology study on it, and throw some spectroscopy in while you're there.

That would, of course, be interesting. But not terribly necessary given the strong evidence that Hoag's object wasn't created by a collision, and that the two objects are much too separated to have any effect on each other, and that there's no proposed mechanism which would make the bodies related, and by the statistical reasonableness of coincidences like this. You know... the existing science.

[geckzilla]

What do you mean "to settle an argument on the Internet" isn't necessary? Hmph.

[Chris Peterson]

What do you mean "to settle an argument on the Internet" isn't necessary? Hmph.

Now, Geck... I know that you know that arguments are never settled on the Internet!

[geckzilla]

Maybe there's another ring inside the background ring. Maybe it's rings all the way down.

[Chris Peterson]

Maybe there's another ring inside the background ring. Maybe it's rings all the way down.

For the sake of argument, let's just take that as a fact. Why not? The science hasn't demonstrated otherwise!

It's a good theory. Here's mine: the topology of the Universe is such that we're seeing right around the horizon in that direction. We're not seeing a different galaxy inside Hoag's Object, we're seeing Hoag's Object itself, whose light has made one complete orbit around the Universe. So there will be another ring inside the inner ring. It will be rings all the way down. But they'll all be the same object. It's the Barbershop Mirror Theory of Cosmology. (Not to be confused with the Barbershop Mirror Theory of Cosmetology.)

[geckzilla]

It happens often enough that I see a weird, seemingly unique galaxy, and then find an oddly similarly unique galaxy just behind it in Hubble imagery that I am nearly willing to accept that light has looped around, and at least in some places the galaxies remained parallel to the light path.

[Fred the Cat]

Following this bit of lively discussion, I ran across this bit of info regarding a spectroscopic evaluation. Anything with such symmetry should garner a vast circle of curiosity seekers.

[sebastian.echeverry2]

Guys is it possible to know where to find information of planets and stars in Hoag's object?. thanks.

[Chris Peterson]

Guys is it possible to know where to find information of planets and stars in Hoag's object?. thanks.

We can't detect planets around stars in other galaxies (although there are a handful of candidates based on suggestive, but far from definitive, evidence).