APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

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Expand view Topic review: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Anthony Barreiro » Thu Feb 06, 2014 5:55 pm

geckzilla wrote:If it was direct response to "Chinese occupation and subjugation" it would be a lot more different, don't you think? Unless you suppose they were just a little upset by such actions and decided that rabbits were out and cats were in.
We're getting further from astronomy than I usually like to wander on the starship asterisk, but ... . The relationship between Vietnam and China is very complicated and ambivalent. A lot of learning came from China to Vietnam. Many people whose families have lived in Vietnam for many generations are ethnically Chinese.

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by geckzilla » Thu Feb 06, 2014 5:48 pm

If it was direct response to "Chinese occupation and subjugation" it would be a lot more different, don't you think? Unless you suppose they were just a little upset by such actions and decided that rabbits were out and cats were in.

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Anthony Barreiro » Thu Feb 06, 2014 5:42 pm

Cousin Ricky wrote:...My tropical sign = Taurus = bull = what I think of astrology. In the avatar, north is 30° clockwise from vertical.
My year of birth = 1963 CE = Chinese year of the rabbit = Lepus.
My year of birth = 1963 CE = Vietnamese year of the cat = Lynx. ...
I didn't know that Vietnamese astrology uses different animals than Chinese astrology for some years. According to http://www.asiafinest.com/forum/index.p ... pic=254721, there are three differences:

Chinese........Vietnamese
Rabbit..........Cat
Ox..............Water buffalo
Sheep..........Goat

Given the history of Chinese occupation and subjugation of Vietnam, I guess it makes sense that the Vietnamese would want to customize the zodiac for their own land.

And by the way, not everyone who was born in 1963 is a Rabbit (or a Cat). Lunar new year (Tet) was on January 25, 1963, so Western Capricorns and Aquarians born before that date are Tigers. Imagine being a Tiger in a grade school class full of Rabbits!

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Chris Peterson » Thu Feb 06, 2014 3:32 pm

Tumbleweed wrote:Dark Matter and ordinary matter may affect each other, but to say they are gravitationally bound is a stretch. Ordinary matter affects other ordinary matter in gravity but they are not bound .. if so rockets could not leave earth's gravity field.
Rockets don't leave Earth's gravity field. Bodies are gravitationally connected even if they aren't in closed orbits... that is, even if their relative velocity exceeds their escape velocity. The material in a galaxy is certainly gravitationally bound, and that includes both the ordinary matter and the dark matter halo. In the case of galaxies, they are certainly bound by any reasonable definition, being in mutually closed orbits.
How do you account for the warped edges clearly visible in many galaxies?
Collisions. Possibly internal tidal interactions. But not interactions with some sort of tenuous intergalactic medium.
Did you look into the urls I posted?
Yes.

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Tumbleweed » Thu Feb 06, 2014 3:25 pm

Chris Peterson wrote:
Tumbleweed wrote:So you don't believe that the vast majority of the universe (Dark Matter) through which the galaxies move, or in which the galaxies move, is a reality?
Dark matter and ordinary matter are gravitationally bound. There's nothing to suggest that galaxies are moving through larger fields of dark matter. The exception is in galaxy clusters, where the entire cluster supports a dark matter halo. But I've seen nothing to suggest any morphological impact on the galaxies within those clusters (e.g. warped edges or tumbling).

And while galaxies might (and it's far from certain) show motion on more than a single axis, I wouldn't characterize them as tumbling, and I'd certainly not associate it with the influence of any intergalactic medium.
Dark Matter and ordinary matter may affect each other, but to say they are gravitationally bound is a stretch. Ordinary matter affects other ordinary matter in gravity but they are not bound .. if so rockets could not leave earth's gravity field.

How do you account for the warped edges clearly visible in many galaxies?

Did you look into the urls I posted?

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Beyond » Thu Feb 06, 2014 2:03 pm

Thanks for the explanation. I try to ignore all that kinda stuff whenever possible. :lol2:

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Cousin Ricky » Thu Feb 06, 2014 6:15 am

Beyond wrote:You've got all that stuff in that small space? No wonder i couldn't tell anything. But even if i did recognize some of it, i still wouldn't have known what you were talking about, even though i spent almost a year and a half in Vietnam. And what's those two gray rectangles??
It's no good if you have to explain it.
My tropical sign = Taurus = bull = what I think of astrology. In the avatar, north is 30° clockwise from vertical.
My year of birth = 1963 CE = Chinese year of the rabbit = Lepus.
My year of birth = 1963 CE = Vietnamese year of the cat = Lynx.
And yes, the equal sign is slacktivist support for marriage equality, but rather than completely replace my avatar, I just worked the equal sign into the design.

The Whetstone of Witte

by neufer » Thu Feb 06, 2014 5:27 am

geckzilla wrote:
Beyond wrote:
And what's those two gray rectangles??
=

How to use the =

2+2=4
http://en.wikipedia.org/wiki/Robert_Recorde wrote: <<Robert Recorde (ca. 1512–1558) was a Welsh physician & mathematician.

Recorde: 1) invented the "equals" sign (=),
  • 2) introduced the pre-existing "plus" sign (+) to English speakers and
    3) popularized the name zenzizenzizenzic to represent the eighth power of a number
In his 1557 work _The Whetstone of Witte_ Recorde recorded that
zenzizenzizenzic "doeth represent the square of squares squaredly" Image.

(The root word for Recorde's notation is zenzic, which is a German spelling of the medieval Italian word censo, meaning "squared".)>>

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Nitpicker » Thu Feb 06, 2014 5:02 am

I thought they were monoliths from 2001: A Space Odyssey. Either that or a statement saying that starsigns are bull.

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by geckzilla » Thu Feb 06, 2014 4:46 am

Beyond wrote:And what's those two gray rectangles??
=

How to use the =

2+2=4

This was a bit of a social movement on Facebook a while back and changing your profile picture to an equal sign was originally support for marriage equality but it may have branched out beyond just that.

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Beyond » Thu Feb 06, 2014 2:57 am

Cousin Ricky wrote:The Hyades and the Pleiades didn't give it away? (OK, maybe the bits of Auriga and Orion in the field might be confusing.)
You've got all that stuff in that small space? No wonder i couldn't tell anything. But even if i did recognize some of it, i still wouldn't have known what you were talking about, even though i spent almost a year and a half in Vietnam. And what's those two gray rectangles??

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Ann » Thu Feb 06, 2014 2:15 am

MarkBour wrote:
Ann wrote: . . . This galaxy is somewhat bland and poor in star formation. Or, to put it somewhat differently, this flying saucer lacks its red nebulae brake lights.
Ann --
Just wondering. Do edge-on galaxies show us less nebulae in general, or can we see them fine in most edge-on galaxies? I'm wondering if this galaxy is perhaps more rich in them than we can see, just that the dust lanes block our view.
Edge-on galaxies are not all the same, of course, just like face-on galaxies are not all the same. Some have a lot of bright and obvious red emission nebulae, while others have none that we can see.

Like Rob Gendler pointed out, NGC 2683 probably doesn't have a lot of emission nebulae at all. At least not in the part of it that we can see. But the very regular shape of NGC 2683 suggests, to me at least, that the galaxy likely doesn't contain a lot of star formation overall.

Ann

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Cousin Ricky » Thu Feb 06, 2014 2:12 am

Anthony Barreiro wrote:I don't understand what flying saucers have to do with Vietnamese skylore, nor what connection you have to Vietnam.
My Vietnamese sign is the cat, and NGC 2683 is in Lynx. I have no connection to Vietnam, but I do like the Al Stewart song, “Year of the Cat.”

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Chris Peterson » Thu Feb 06, 2014 12:47 am

Tumbleweed wrote:So you don't believe that the vast majority of the universe (Dark Matter) through which the galaxies move, or in which the galaxies move, is a reality?
Dark matter and ordinary matter are gravitationally bound. There's nothing to suggest that galaxies are moving through larger fields of dark matter. The exception is in galaxy clusters, where the entire cluster supports a dark matter halo. But I've seen nothing to suggest any morphological impact on the galaxies within those clusters (e.g. warped edges or tumbling).

And while galaxies might (and it's far from certain) show motion on more than a single axis, I wouldn't characterize them as tumbling, and I'd certainly not associate it with the influence of any intergalactic medium.

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Tumbleweed » Thu Feb 06, 2014 12:35 am

Chris Peterson wrote:
Tumbleweed wrote:
Tumbleweed wrote:A very slow clockwise tumble to this galaxy.
P.S. Comparing the mass of the galaxy, the rate of tumble, and the deflection of the leading and trailing edges will give the density of the medium the galaxy is tumbling in. Mathematicians, do your stuff.
Galaxies move in the intergalactic medium, which is far too tenuous to have any effect on the motion of any part of any galaxy. So there's nothing to see along the edges, and galaxies don't tumble at all.
So you don't believe that the vast majority of the universe (Dark Matter) through which the galaxies move, or in which the galaxies move, is a reality?

Tumbling Galaxies: http://adsabs.harvard.edu/full/1984ApJ...286...53D

Tumbling Galaxies: http://ned.ipac.caltech.edu/level5/Marc ... la4_2.html

Tumbling Galaxies: http://www.researchgate.net/publication ... e_Sequence

Tumbling Galaxies: http://www.cosmicastronomy.com/motions.htm

Tumbling Galaxies: https://www.google.ca/search?q=tumbling ... B350%3B322

It’s Barred, ‘cuz dem dar isophotes are boxy

by BDanielMayfield » Thu Feb 06, 2014 12:25 am

geckzilla wrote: ... you might be able to understand the paper linked to in the APOD description. Hmm, what are these mystical and arcane words?
Here’s what I think Geckzilla might mean by “mystical and arcane words”, with one exception:
Rachel, Matthew & Stacy wrote:We present optical long-slit and SparsePak Integral Field Unit emission line spectroscopy along with optical broadband and near-IR images of the edge-on spiral galaxy NGC 2683. We find a multi-valued, figure-of-eight velocity structure in the inner 45'' of the long-slit spectrum and twisted isovelocity contours in the velocity field. We also find, regardless of wavelength, that the galaxy isophotes are boxy. We argue that taken together, these kinematic and photometric features are evidence for the presence of a bar in NGC 2683. We use our data to constrain the orientation and strength of the bar.

Yes, I would say that that abstract is quite, well, abstract. Except for the word “boxy” which is quite understandable.

My apologies to Kuzio de Naray et al, the authors of Kinematic and Photometric Evidence for a Bar in NGC 2683.

Bruce

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Nitpicker » Wed Feb 05, 2014 8:49 pm

geckzilla wrote:Yes, what Art said, and for galaxies like NGC 2683 the stars stop becoming measurable when they blob together. If you can figure out what isovelocity contours and kinematics are you might be able to understand the paper linked to in the APOD description. Hmm, what are these mystical and arcane words? Astronomers are a little magical.
I haven't looked at the paper, but "isovelocity contours" sounds like redundant nomenclature. Contours of a velocity component are, by definition, iso-velocities, but maybe they are talking about velocity vector-potential, aka streamlines, showing the direction of motion (I'm probably wrong about what they are talking about). Kinematics is merely the study/description of motion without respect to the forces causing the motion. It is a general term.

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by FloridaMike » Wed Feb 05, 2014 8:49 pm

To a tumbleweed, the entire universe tumbles....

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Chris Peterson » Wed Feb 05, 2014 8:34 pm

Tumbleweed wrote:
Tumbleweed wrote:A very slow clockwise tumble to this galaxy.
P.S. Comparing the mass of the galaxy, the rate of tumble, and the deflection of the leading and trailing edges will give the density of the medium the galaxy is tumbling in. Mathematicians, do your stuff.
Galaxies move in the intergalactic medium, which is far too tenuous to have any effect on the motion of any part of any galaxy. So there's nothing to see along the edges, and galaxies don't tumble at all.

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Chris Peterson » Wed Feb 05, 2014 8:32 pm

FloridaMike wrote:If we can detect a bar in our own galay which is almost perfectly edge-on why is it hard to tell if near edge-on NGC 2683 has a bar?
Keep in mind that being barred isn't a binary option. There are galaxies that are obviously barred, there are galaxies that are obviously unbarred, and there is a range in between- including a region where it's pretty arbitrary what classification to apply.

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by Anthony Barreiro » Wed Feb 05, 2014 7:25 pm

Cousin Ricky wrote:The other day on another forum, someone asked if there were any atheists who lent credence to astrology. Of course, the answer is “yes” (however few). If you look at my avatar, you’ll know what my astrological (tropical?) sign is. However, you’ll also know what I think of astrology. :wink:

Someone mentioned Chinese astrology, and I responded that if I had a Chinese background, I might use an image of Lepus, although it wouldn’t have the built-in clever pun. But I found myself wondering what constellation I would use if my background were Vietnamese.

Today’s APOD possibly answers that question.
Yes, Western astrology uses the tropical zodiac. And Tauruses never believe in astrology. :wink: I believe traditional Vietnamese culture used the Chinese system of dividing the sky into 28 lunar mansions, and the 12-year cycle of Jupiter through the zodiac to give us the 12 animals. I don't understand what flying saucers have to do with Vietnamese skylore, nor what connection you have to Vietnam.

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by geckzilla » Wed Feb 05, 2014 6:37 pm

Yes, what Art said, and for galaxies like NGC 2683 the stars stop becoming measurable when they blob together. If you can figure out what isovelocity contours and kinematics are you might be able to understand the paper linked to in the APOD description. Hmm, what are these mystical and arcane words? Astronomers are a little magical.

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by neufer » Wed Feb 05, 2014 6:34 pm

FloridaMike wrote:
If we can detect a bar in our own galay which is almost perfectly edge-on why is it hard to tell if near edge-on NGC 2683 has a bar?

conversely...

If we cannot tell if near edge-on NGC 2683 has a bar how do we detect a bar in our own galaxy which is almost perfectly edge-on ?
Astronomers can determine the distances of certain bright stars to within ~10%.

This is just sufficient to detect a bar like structure in the Milky Way
though not so for the more distant NGC 2683

http://asterisk.apod.com/viewtopic.php? ... 82#p216382
http://en.wikipedia.org/wiki/Galactic_Center wrote:
<<The nature of the Milky Way's bar which extends across the Galactic Center is actively debated, with estimates for its half-length and orientation spanning between 1–5 kpc (short or a long bar) and 10–50°. Certain authors advocate that the Milky Way features two distinct bars, one nestled within the other. The bar is delineated by red-clump stars (see also red giant), however, RR Lyr variables do not trace a prominent Galactic bar. The bar may be surrounded by a ring called the "5-kpc ring" that contains a large fraction of the molecular hydrogen present in the Milky Way, as well as most of the Milky Way's star formation activity. Viewed from the Andromeda Galaxy, it would be the brightest feature of the Milky Way.>>

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by FloridaMike » Wed Feb 05, 2014 6:12 pm

APOD Robot wrote:Image NGC 2683: Edge On Spiral Galaxy

Explanation: Does spiral galaxy NGC 2683 have a bar across its center? Being so nearly like our own barred Milky Way Galaxy, one might guess it has. Being so nearly edge-on, however, it is hard to tell.....
If we can detect a bar in our own galay which is almost perfectly edge-on why is it hard to tell if near edge-on NGC 2683 has a bar?

conversely...

If we cannot tell if near edge-on NGC 2683 has a bar how do we detect a bar in our own galaxy which is almost perfectly edge-on ?

Re: APOD: NGC 2683: Edge On Spiral Galaxy (2014 Feb 05)

by rgendler » Wed Feb 05, 2014 6:06 pm

geckzilla wrote:
MarkBour wrote:
Ann wrote: . . . This galaxy is somewhat bland and poor in star formation. Or, to put it somewhat differently, this flying saucer lacks its red nebulae brake lights.
Ann --
Just wondering. Do edge-on galaxies show us less nebulae in general, or can we see them fine in most edge-on galaxies? I'm wondering if this galaxy is perhaps more rich in them than we can see, just that the dust lanes block our view.
Puffs of hydrogen alpha typically extend beyond dust lanes, ballooning out over time. I'm not sure they're not there. I think this image may simply lack narrowband data.

Yep, neither Subaru or Hubble had any narrowband h-alpha. After studying many other images on the web I decided that the HII clouds were so few and bland it wasn't worth the trouble.

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