Interesting objects at Galaxy Zoo forum

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Nereid
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Interesting objects at Galaxy Zoo forum

Post by Nereid » Mon Mar 19, 2012 7:43 pm

No doubt many people who hang out here know of the Galaxy Zoo citizen science project. Probably many have also signed up, and spent a pleasant hour or two classifying galaxies.

But did you know that there's a forum associated with Galaxy Zoo? It was on this forum that the object which became known as Hanny's Voorwerp has first announced. This APOD, from over a year ago, covers some recent observations of it. Another discovery, also stemming from posts on that forum, is Green Peas (covered here by this post by bystander).

So, I was idly browsing the forum the other day, and came across a thread entitled An enigma wrapped in a riddle (surrounded by emptiness?). It's about a galaxy with a strange shape; here's the SDSS thumbnail image:

Image

It seems no one over at the GZ forum really knows why it has such an odd shape (though several zooites - as they call themselves - have posted some suggestions). And I wondered if anyone here has seen it before, and whether anyone has any idea what it might be?

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Ann
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Re: Interesting objects at Galaxy Zoo forum

Post by Ann » Tue Mar 20, 2012 4:57 am

[idle speculation] Well, surely it must be a galaxy.
Image
Image credit: NASA/JPL-Caltech
It reminds me ever so slightly of NGC 4725, which is a one-armed galaxy, whose arm is wrapped around its yellow center.









Image
NASA, ESA, the Hubble Heritage, (Aura-STScI)-ESA/Hubble Collaboration,
and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)
Of course, the arm in the Zoo object doesn't fit too well around its yellow center. But it appears that galaxies can suffer "knocks" that may partly separate some parts of them from other parts of them. Arp 148, Mayall's Object, may be a galaxy whose yellow bar has been knocked free of its ring.




An objection here is that Mayall's Object is obviously chaotic, while the Galaxy Zoo object seems so "calm". Well, I still believe that it is a galaxy! How else would it get that general shape and that general, typical color distribution - yellow center, blue periphery?

You may also want to check out this page of the Bear Paw Galaxy. Talk about strange.

I'm a believer in the wonderful strangeness of some galaxies!
[/idle speculation]

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Re: Interesting objects at Galaxy Zoo forum

Post by Nereid » Wed Mar 21, 2012 3:47 pm

Thanks Ann (awfully quiet here, isn't it?).

Being disturbed - by another galaxy that's now hidden (e.g. behind the core of this one) or long gone (e.g. has moved so far away that's it's not visible in the immediate vicinity) or dark (e.g. a galaxy composed almost entirely of dark matter) - is certainly a possibility.

Evolving towards becoming a ring, or ringed, galaxy is much less likely I think; such objects are 2-dimensional (confined pretty much to a plane), but this one looks like it has two prominent arms in inclined planes which intersect in (or near) the nucleus.

The galaxy almost certainly has far too small a mass for it to produce gravitational lens arcs as large as the two prominent arms.

The suggestion, by elizabeth (in the Galaxy Zoo forum), that it might be a polar ring galaxy seems the least far-fetched explanation.

But what to make of Jean Tate's observation, that the [NII] lines are far too prominent, in the spectrum, compared with the [OIII], [SII], and [OII] ones? The Balmer lines look odd too (though it's hard to tell at this resolution): H-alpha is in emission, and has a relatively broad base; H-beta is weak (not clear if there's a weak emission in a broader absorption base), H-gamma and H-delta are nice and normal narrow absorption lines.

If you're into strange objects, there's another Object of the Day (I guess they borrowed the term from APOD! :ssmile: ) which is really fun: Ashes of Worlds. It's about a star which a zooite named Mitch came across, and noticed that its spectrum is really, really strange. It turns out that it's an extreme example of a class of white dwarfs called DZ, and that what we're very likely looking at is the ground up remains of an asteroid which the star ate, quite recently (hence the title, Ashes of Worlds).

A quick search of APODs did not turn up any on this kind of interesting fate for asteroids (or planets).

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Re: Interesting objects at Galaxy Zoo forum

Post by Ann » Thu Mar 22, 2012 1:30 am

Thanks for the additional input, Nereid! Very interesting!

I have to keep saying that it is so obviously a galaxy. Just look at that yellow bulge! Not only is it yellow, as we expect from a galactic bulge, but it is brightest in the more-or-less middle, too.

I agree with elizabeth at the Galaxy Zoo forum that this could very easily be a polar ring galaxy. The shape of the blue arm (arms?) is weird. It does indeed look as if it was wrapped around the yellow bulge of the galaxy, but at some distance away from the yellow bulge. But that is about what polar ring galaxies look like, so that might be the explanation here.

There is something "sticking out behind" the galaxy at nine o'clock. How about that is a dwarf galaxy that has helped disturb the larger galaxy? Admittedly that could just be a part of the larger galaxy's arm system.

I would assume that the small object that we see at lower right is at another redshift. Otherwise, we might assume that it was a dwarf galaxy affecting the larger galaxy.

I'm pretty sure that if we could see this object at higher resolution, we would understand it better. I have a low-resolution image of "the Mice", NGC 4676, in a James D Wray's Color Atlas of Galaxies at home. In the atlas, Wray writes about one of the "Mice":
The morphological nature of the inner region of NGC 4676a is nothing less than baffling.
But there is nothing strange about NGC 4676a. In this Hubble image, we can see that there is just a clump of dust hiding the nucleus of NGC 4676a from our point of view.

Another galaxy that looks quite weird in James D Wray's Atlas is NGC 5994. It looks as if it had spouted a pair of horns! But on this page, probably from the Arp Catalogue of peculiar galaxies, we can see that the "horns" of NGC 5994 are just the brightest parts of a large "loop" of stars. (NGC 5994 is the galaxy in the second picture on this page.) The Arp Catalogue also links to an SDSS image of NGC 5994. The color data from SDSS makes it ever more obvious that we are seeing a galaxy with a bright yellow bar and a lot of bright blue star formation in various structures around the bar.

So I think that the hugely interesting galaxy that you have posted here might make more sense if we saw it at higher resolution.

But thank you, Nereid, for posting that galaxy here! I'm a sucker for galaxies. I love galaxies, as long as they have some obvious features. I tried doing some galaxy classification myself, but there were too many yellow fuzzies there for me, so I grew tired of it. But please come back with some more strange galaxies here - I, at least, will appreciate it! :D

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Re: Interesting objects at Galaxy Zoo forum

Post by Nereid » Thu Mar 22, 2012 7:41 pm

I don't doubt that it's a galaxy Ann! :D

And yes, the various blobs close and not-so-close could be related satellite or dwarf galaxies, and they could be responsible for the odd appearance of this object.

A higher resolution image would surely make its nature much more clear! So would, I suspect, long-slit spectroscopy, or better, IFU spectroscopy. Unfortunately, neither of these things can be done by amateurs. :(

I'm glad that you like galaxies (and by not responding to what I wrote about the Ashes of Worlds thread, I guess you aren't much interested in white dwarfs). If I come across some other interesting galaxies, posted in the GZ forum, I'll write a post about them here.

This page has been viewed quite a few times (well, relatively speaking); I wonder what the others who read the posts here thought?

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Re: Interesting objects at Galaxy Zoo forum

Post by rstevenson » Thu Mar 22, 2012 8:03 pm

This page has been viewed quite a few times (well, relatively speaking); I wonder what the others who read the posts here thought?
Since you asked...

I looked at the first pic and thought, "It's a galaxy." Full stop. If we had a better picture we'd be able to say more than that about it, but then if we had a better picture, it wouldn't be an interesting object in the same way that it is now, where "interesting" equates to "unclear".

Rob

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Re: Interesting objects at Galaxy Zoo forum

Post by Ann » Fri Mar 23, 2012 4:50 am

Nereid wrote:

I'm glad that you like galaxies (and by not responding to what I wrote about the Ashes of Worlds thread, I guess you aren't much interested in white dwarfs).
I'm afraid that's it, pretty much. :(

Two things trigger my interest in astronomy. The first of those is that things in space are so humongously far away. It is so amazing that they can be so far away in the first place (and that space can be so big), and it is so amazing that our science is good enough to tease out facts about what they are. Astronomy at its best is better than any detective story, and it is the twin siblings, Observation and Mathematical modelling, which are doing the amazing detective job.

The second thing that gives me a kick about space is that many things in space are so beautiful. They may be beautiful because of their shapes. They can be even more beautiful because of their colors. My favorite color by far is blue.

In what ways are white dwarfs interesting to me? Well... they are often blue. That's nice. But the white dwarf you showed me had a spectrum which suggests to me that it is cool and non-blue. That makes its color uninteresting to me. Its general shape is, of course, also uninteresting to me.

The spectrum you showed me was odd. Sibling number one, Observation, has done a good job observing it. Now we need Sibling number two, Mathematical modelling, to do its job and explain that spectrum. When Mathematical modelling has done its job, I'll listen. But up until then... no, I'll leave that dead yellow cinder of a star to its own devices and wait for Mathematical modelling to explain why it has those strange peaks and valleys in its spectrum.

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Re: Interesting objects at Galaxy Zoo forum

Post by Nereid » Fri Mar 23, 2012 9:05 pm

rstevenson wrote:
This page has been viewed quite a few times (well, relatively speaking); I wonder what the others who read the posts here thought?
Since you asked...

I looked at the first pic and thought, "It's a galaxy." Full stop. If we had a better picture we'd be able to say more than that about it, but then if we had a better picture, it wouldn't be an interesting object in the same way that it is now, where "interesting" equates to "unclear".

Rob
Thanks.

Yes, I certain appreciate that it simply looks like a galaxy with arms, and is otherwise unclear.

I guess I'm prepared to give zooites - or at least some zooites - more credit; if they say it's quite unusual, with respect to the (tens of) thousands of galaxies they've looked at, I can but agree. Subsequent posts in the forum thread bear this out: no zooite has come along and said, in effect, "oh boring; these are a dime a dozen, for example ...".

What might be more telling - in the "it's just an unclear galaxy, no need to get excited" department - is that none of the professional astronomers who regularly hang out in that forum have chimed in. Or not; at least until recently they seem to have been willing to jump in, within a day or so, posting a highly informative comment about whatever object was the Object of the Day. This time, no one has (so far).

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Re: Interesting objects at Galaxy Zoo forum

Post by Nereid » Fri Mar 23, 2012 9:20 pm

Ann wrote:
Nereid wrote:

I'm glad that you like galaxies (and by not responding to what I wrote about the Ashes of Worlds thread, I guess you aren't much interested in white dwarfs).
I'm afraid that's it, pretty much. :(
Well, OK. Horses for courses, and all that.
Two things trigger my interest in astronomy. The first of those is that things in space are so humongously far away. It is so amazing that they can be so far away in the first place (and that space can be so big), and it is so amazing that our science is good enough to tease out facts about what they are.
May I ask if you've joined any of the various Citizen Science astronomy projects? Like Galaxy Zoo, or Planet Hunters?

I've been classifying galaxies since shortly after the original Galaxy Zoo went up. When they started serving up images from the Hubble (I think they called it Hubble Zoo), I was astonished! Almost every second galaxy looked strange, nothing like the vast majority of galaxies I'd classified in Galaxy Zoo!!
Astronomy at its best is better than any detective story, and it is the twin siblings, Observation and Mathematical modelling, which are doing the amazing detective job.
Yes it is, isn't it?
The second thing that gives me a kick about space is that many things in space are so beautiful. They may be beautiful because of their shapes. They can be even more beautiful because of their colors. My favorite color by far is blue.
I love blue too!

Do you find yourself keeping an eye out for different shades of blue, among the galaxies? I don't just mean intensity (pale to brilliant, for example), but the blues that shade into green, or violet.
In what ways are white dwarfs interesting to me? Well... they are often blue.
That's certainly true!
That's nice. But the white dwarf you showed me had a spectrum which suggests to me that it is cool and non-blue. That makes its color uninteresting to me. Its general shape is, of course, also uninteresting to me.

The spectrum you showed me was odd. Sibling number one, Observation, has done a good job observing it. Now we need Sibling number two, Mathematical modelling, to do its job and explain that spectrum. When Mathematical modelling has done its job, I'll listen. But up until then... no, I'll leave that dead yellow cinder of a star to its own devices and wait for Mathematical modelling to explain why it has those strange peaks and valleys in its spectrum.

Ann
Well, I'm different, in this regard.

I find the thought that the spectrum of this star can tell us that this is a tiny star, perhaps not much bigger than Earth in size. A whole Sun's worth of matter squished into such a small volume! Held from collapsing by physics that's very similar to what makes metals metals!!

But in this case the spectrum is telling the story of the passing of an asteroid, perhaps even a dwarf planet. An orb that was, once, like Vesta, or Ceres, or even our own Moon. And it's a passing that is fleeting; in the blink of astronomical time, all spectral evidence of the shredded asteroid/dwarf planet will be gone (the heavier elements will sink below the white dwarf's atmosphere, and so lines due to Mg, Cr, etc will disappear), leaving nothing to tell that it had once existed ...

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rstevenson
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Re: Interesting objects at Galaxy Zoo forum

Post by rstevenson » Fri Mar 23, 2012 10:37 pm

Nereid wrote:I guess I'm prepared to give zooites - or at least some zooites - more credit; if they say it's quite unusual, with respect to the (tens of) thousands of galaxies they've looked at, I can but agree. Subsequent posts in the forum thread bear this out: no zooite has come along and said, in effect, "oh boring; these are a dime a dozen, for example ...".
I see your point. My reaction reflects my own experience, of course -- I've only looked at a few hundred galaxies. Also my own preferences -- I'm extremely interested in good clear images of galaxies and am willing to wait until there is a clear one available before thinking too much about any particular galaxy. Which brings up a question ...

Is there a way -- Hubble perhaps, or some other current telescope -- to get a better image? The image everyone has been looking at shows a galaxy that is only about 160 pixels wide at it's widest, so there's not much information to go on there. How wide, in degrees (or minutes or even seconds), is this galaxy? Will we have to wait for the James Webb telescope before we get a better look?

Rob

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Re: Interesting objects at Galaxy Zoo forum

Post by Ann » Sat Mar 24, 2012 6:19 am

Neried wrote:

May I ask if you've joined any of the various Citizen Science astronomy projects? Like Galaxy Zoo, or Planet Hunters?
I did join Galaxy Zoo for a while, and I tried classifying galaxies. The spirals and irregulars were a lot of fun. Some of the brighter and better-resolved ellipticals were OK, too. But in the end there were just too many yellow blobs. How was I to know if they were elliptical galaxies of artifacts? Well, I thought they were ellipticals, but in some cases their color profiles were weird enough that I didn't know. In any case, they were boring to look at.

And how was I to know if the galaxies were barred? I recognize the peanut-shaped bulge of edge-on barred galaxies, but how could I see if the bulges were peanut-shaped if the bulge was just a blur anyway? Then later, someone at the Galaxy Zoo talked about a picture of a galaxy and said that the galaxy was clearly barred. I would never have guessed that it was barred. And then I felt that I just wasn't qualified to do the galaxy classification.

I'm not sufficiently interested to join the planet hunt, sorry. Let me put it like this: I just don't believe that any planet I might find that way will be sufficiently beautiful-looking to justify the effort I have to make trying to find it.
Do you find yourself keeping an eye out for different shades of blue, among the galaxies? I don't just mean intensity (pale to brilliant, for example), but the blues that shade into green, or violet.
Absolutely. Anything that is blue interests me. I want to know not only if it is blue, but how it is blue and why it is blue. In SDSS images, I know that a shade of aqua usually means blue starlight mixed with red Ha light, which is mapped as green in SDSS images. In other words, a shade of aqua means that there are very young stars here, whose light is mixed with the light of emission nebulae. Admittedly, though, I don't know what it means if the blue color shades into violet in SDSS images.

I'm very frustrated at obviously false-color shades of blue, i.e., objects that are completely non-blue but are shown as blue anyway. I once saw a good-looking infrared picture of a portion of the starry Eta Carina region. Two stars stood out by being enormously large and bright as well as brilliantly blue. I decided I had to find what stars they were. Identifying them was incredibly difficult, but in the end I managed. They were two red supergiant stars! They looked so blue because they really were so red! (No, really, they looked so blue because their photospheres are so large, and the red light they emit all over those huge photospheres was mapped as blue.) But since then, I don't like looking at infrared pictures of stars.

But I trust SDSS. I trust that objects or parts of objects that look blue in SDSS images are at least moderately blue "in real life".
But in this case the spectrum is telling the story of the passing of an asteroid, perhaps even a dwarf planet. An orb that was, once, like Vesta, or Ceres, or even our own Moon. And it's a passing that is fleeting; in the blink of astronomical time, all spectral evidence of the shredded asteroid/dwarf planet will be gone (the heavier elements will sink below the white dwarf's atmosphere, and so lines due to Mg, Cr, etc will disappear), leaving nothing to tell that it had once existed ...
That's really very interesting! You mean that this white dwarf just ate one of its asteroids or dwarf planets? Actually, I just read an article about planet-eating white dwarfs in Astronomy Magazine (I think it was).
Image[c]Photo: ESO[/c]
I just said that I don't like infrared pictures of stars, and the sight of the blue stars in this picture doesn't make me happy. Most of these stars are likely non-blue, particularly the bluest-looking ones. The one really blue star in this picture, the white dwarf in the middle of this planetary nebula, looks no bluer than any other star here. :(

No, but the infrared portrait of the planetary nebula is interesting. There is clearly a lot of dust here. To me it is interesting to consider the possibility that all the dust that is produced during the final red giant phase of a star, which is then spread outwards during the planetary nebula phase, may in fact give rise to new-born asteroids or planets.

Obviously, judging from the spectra of white dwarfs, some white dwarfs also eat some of their own orbiting bodies, whether these orbs were "freshly minted" during the planetary nebula phase or if they had been there since soon after the formation of the sun that the white dwarf used to be. In any case, it's interesting.

Not sufficiently interesting for me to want to look at spectra of white dwarfs, though, I'm sorry.

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Re: Interesting objects at Galaxy Zoo forum

Post by Nereid » Sat Mar 24, 2012 2:33 pm

rstevenson wrote:
Nereid wrote:I guess I'm prepared to give zooites - or at least some zooites - more credit; if they say it's quite unusual, with respect to the (tens of) thousands of galaxies they've looked at, I can but agree. Subsequent posts in the forum thread bear this out: no zooite has come along and said, in effect, "oh boring; these are a dime a dozen, for example ...".
I see your point. My reaction reflects my own experience, of course -- I've only looked at a few hundred galaxies. Also my own preferences -- I'm extremely interested in good clear images of galaxies and am willing to wait until there is a clear one available before thinking too much about any particular galaxy. Which brings up a question ...

Is there a way -- Hubble perhaps, or some other current telescope -- to get a better image? The image everyone has been looking at shows a galaxy that is only about 160 pixels wide at it's widest, so there's not much information to go on there. How wide, in degrees (or minutes or even seconds), is this galaxy? Will we have to wait for the James Webb telescope before we get a better look?

Rob
Some time after Hanny's Voorwerp was discovered, Bill Keel (who goes by the handle NGC3314 in the Galaxy Zoo forum; he's a professional astronomer at the University of Alabama) went looking for more examples. They were given the name Voorwerpjes (Dutch for 'little objects', I think), and zooties quickly found many hundred candidates. From among those candidates a handful were chosen, and a proposal to look at them with the Hubble written. The project has begun, and the first object has been 'shot' by the Hubble.

Here it is, as seen by SDSS:
Image

And here is one of the raw Hubble images:
Image

When fully calibrated and processed - usually takes several months - the combined, multi-colour Hubble image of this galaxy will be extremely clear (Hubble's resolution is at least ten times better than the SDSS's). That gives some idea of how much more clearly "Aida's galaxy" ("Aida" is the zooite Lovethetropics, who posted the galaxy in the OP) could be seen by Hubble. I think a Hubble image would be more than sufficient to tell if there's something strange happening ...

Sources:
Hubble and Voorwerpje number 1 - a Galaxy Zoo forum thread
First look at Hubble’s first look at the first Voorwerpje - a Galaxy Zoo blog post (by Bill Keel)

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Re: Interesting objects at Galaxy Zoo forum

Post by Ann » Sat Mar 24, 2012 6:56 pm

Nereid, that new voorwerpje galaxy is really interesting. The outflows look blue-violet. I guess blue is from OIII radiation. What causes the violet tint?

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