APOD: The Star Streams of NGC 5907 (2008 Jun 19)

Sputnick · Post by **Sputnick** » Thu Jun 19, 2008 4:32 pm

Photo June 19 http://antwrp.gsfc.nasa.gov/apod/ap080619.html

I see the faint trails of stars at the extremities of the galaxy curve off in directions opposing each other. This suggests to me that the galaxy is tumbling as it travels .. first time I've had the thought of tumbling galaxies .. and I think to myself, 'why wouldn't galaxies tumble ever so slowly? They move in every other direction.'

https://apod.nasa.gov/apod/ap080619.html

neufer · Post by **neufer** » Thu Jun 19, 2008 4:56 pm

Sputnick wrote:Photo June 19 http://antwrp.gsfc.nasa.gov/apod/astropix.html

I see the faint trails of stars at the extremities of the galaxy curve off in directions opposing each other. This suggests to me that the galaxy is tumbling as it travels .. first time I've had the thought of tumbling galaxies .. and I think to myself, 'why wouldn't galaxies tumble ever so slowly? They move in every other direction.'

Pluto has an Orbital Inclination 17.14175° but one probably wouldn't say that the solar system was "tumbling."
---------------------------------------
http://antwrp.gsfc.nasa.gov/apod/ap030607.html

<<How did spiral galaxy ESO 510-13 get bent out of shape? The disks of many spirals are thin and flat, but not solid. Spiral disks are loose conglomerations of billions of stars and diffuse gas all gravitationally orbiting a galaxy center. A flat disk is thought to be created by sticky collisions of large gas clouds early in the galaxy's formation. Warped disks are not uncommon, though, and even our own Milky Way Galaxy is thought to have a small warp. The causes of spiral warps are still being investigated, but some warps are thought to result from interactions or even collisions between galaxies. ESO 510-13 is about 150 million light years away and about 100,000 light years across.>>
---------------------------------------
http://adsabs.harvard.edu/cgi-bin/nph-b ... .185.2209H
.
<<The warp of our galaxy was discovered by Kerr (1957) and has since been found at many wavelengths such as CO (Wouterloot et al 1990), young stars (Stenholm 1975) and 1.25 microns (Freudenreich 1994). Explanations for the warp started with the hypothesis of tidal creation by the Magellanic Clouds by Hunter and Toomre (1969) who found that a close approach of 20 kpc by the Magellanic clouds was required. Simulations by Spight and Grayzeck (1978) confirmed the 20 kpc close approach distance. The discovery of the Magellanic Stream (Mathewson et al 1974) and simulation studies of its creation via a tidal encounter with our galaxy (e.g. Fujimoto and Murai 1984, Lin 1993) indicate that the Clouds are near their perigalactic point at their present distance of 52 kpc (not 20 kpc!). The general conclusion is that ``It is unlikely that the tidal pull of the Magellanic Clouds is responsible for the warp (Sparke 1993)." Since new measurements have been made of the proper motion of the Clouds (Jones et al 1994, Lin 1993) which improve our knowledge of the Clouds' orbit and since the 1978 study of tidal warping by Spight and Grayzeck was done when the extent and mass of dark matter halos of galaxies were not fully appreciated, we have conducted new simulations of the tidal effect of the Magellanic Clouds on the disk of our galaxy.>>
---------------------------------------

dduggan47 · Post by **dduggan47** » Thu Jun 19, 2008 5:07 pm

Here's what strikes me about this picture. Consider a sun like star out in that "stream" which has an earth-like planet in orbit. One of us, having evolved there, would look into the night sky and see ... the Milky Way on steroids???

I want to go there and see.

Freefall74 · Post by **Freefall74** » Thu Jun 19, 2008 5:26 pm

I was wondering, if I were on a planet in one of the "outer loops" of this image, what the night sky would look like? If I were this close to a galaxy, how big would it look? Could I distinguish its structure? Would it get as dark (at night) as it does here on Earth?

orin stepanek · Post by **orin stepanek** » Thu Jun 19, 2008 5:54 pm

Freefall74 wrote:I was wondering, if I were on a planet in one of the "outer loops" of this image, what the night sky would look like? If I were this close to a galaxy, how big would it look? Could I distinguish its structure? Would it get as dark (at night) as it does here on Earth?

http://apod.nasa.gov/apod/ap080619.html

I had similar thoughts. I'M sure it would be quite impressive! I bet some denizens of some dwarf galaxies may have similar views.

iamlucky13 · Post by **iamlucky13** » Thu Jun 19, 2008 8:21 pm

That would rock!

It wouldn't be much brighter than the Milky Way, however. We'd still need long exposures to capture the brilliant details like we see in the iconic galaxy pictures.

bystander · Post by **bystander** » Thu Jun 19, 2008 8:37 pm

Sputnick wrote:Photo June 19 - http://antwrp.gsfc.nasa.gov/apod/astropix.html

I think this is the link you wanted. The one you posted will be different tomorrow, and the next day, and every day after that.

http://antwrp.gsfc.nasa.gov/apod/ap080619.html
APOD: 2008 June 19 - The Star Streams of NGC 5907

bystander · Post by **bystander** » Thu Jun 19, 2008 8:59 pm

Sputnick wrote:I see the faint trails of stars at the extremities of the galaxy curve off in directions opposing each other. This suggests to me that the galaxy is tumbling as it travels .. first time I've had the thought of tumbling galaxies .. and I think to myself, 'why wouldn't galaxies tumble ever so slowly? They move in every other direction.'

I suppose they could tumble. But I think most astrophysicists would explain the warp as interaction with the dwarf galaxies that left the tidal streams of stars. There would have to be some effect apparent in the larger galaxy long after it had absorbed the satellites.

d2386n · Post by **d2386n** » Thu Jun 19, 2008 9:22 pm

[color=blue][/color]I think it would be awesome to live in the halo. I'll bet the night sky would be one huge pinwheel of stars; I guess it would be at least as bright as our Milky Way at night only seen face-on. Maybe it would be much brighter if you lived right near the disk rather than farther out at the end of the halo.

Maybe a math-friendly person can tell us just how bright and how much disk one would see.

d2386n · Post by **d2386n** » Thu Jun 19, 2008 9:23 pm

I think it would be awesome to live in the halo. I'll bet the night sky would be one huge pinwheel of stars; I guess it would be at least as bright as our Milky Way at night only seen face-on. Maybe it would be much brighter if you lived right near the disk rather than farther out at the end of the halo.

Maybe a math-friendly person can tell us just how bright and how much disk one would see.

Sputnick · Post by **Sputnick** » Thu Jun 19, 2008 10:02 pm

Neufer .. speak plain English for God's sake. Just kidding, even though I need a dictionary to follow you sometimes (strike sometimes insert often.) But the effect I was talking about had nothing to do with orbit of anything, just the resistance caused by the 'dark matter or dark energy or whatever fills the void ouside the galaxy .. that resistance is, I think, what is bending the streams. But thanks for the mind expanding possibilities.

Bystander, thanks for the 'I suppose they could tumble' .. yes, it is an obvious possibility, and my suggestion is just as valid as more complicated possibilities .. and perhaps more likely to be real as it's based on smple observation of natural effects. Just because the galaxy is so many light years away does not place it outside the real of simple nature. I think too much study in theoretical whatsismaybes can pull a mind away from the simplicity of observation, the effects of a breeze on a leaf can be understood without mathematical equations, but if a mind is concentrated on revealing the effect of the breeze on the leaf before and after the breeze has touched other leaves, well, the possibilities are endless because of temperature variations, moisture content in each individual leaf, eddies of the breeze around the roughness or smoothness of the trunk's bark, temperature of the trunk's sunlight and shadowed patches .. endless. No computer could do a realistic simulation.

danbonnick · Post by **danbonnick** » Thu Jun 19, 2008 10:15 pm

Great picture. Been a fan for years.
It made me curious as to why the 'filaments' of stars look so flimsy - shouldn't there be a lot more resitance to moving them, caused by the galaxy's dark matter halo? Does this pic provide some sort of limit on the amount of gravitational influence from the halo?

just curous.

)

jgabany · Post by **jgabany** » Fri Jun 20, 2008 12:51 am

Hello danbonnick:

These are good questions- thank you for asking!

The streams seen in this picture represent the remains of a long lost satellite galaxy that was gravitationally torn to shreds and digested by the large spiral, seen edge on in this image. Very little of the former companion remains. Measurements by the team of researchers who studied this galaxy and its rings had difficulty finding any traces of stellar activity. The rings appear to be comprised mostly of dust.

One of the researchers used a powerful computer to prepare an animation that illustrates how the rings were formed. Here's a link that you may find interesting:

http://www.cosmotography.com/images/ngc ... ation.html

As the animation depicts, the small satellite was orbiting the larger companion (not shown) and, over time, was simply stretched by tidal forces originating from the spiral's center. It is interesting to note that the rings are elliptical in shape- the NGC 5907's central region lies at one of the foci.

Dark matter most likely played a part in the events that destroyed the original satellite- to what extent, I can only speculate.

I hope this, at least partially, answers your questions.

Jay

Nerull · Post by **Nerull** » Fri Jun 20, 2008 1:13 pm

And obviously, the sun goes around the Earth. Look, its obvious! And its just as valid as the possibilities that actually agree with, you know, basic physics.

bystander · Post by **bystander** » Fri Jun 20, 2008 1:35 pm

Nerull wrote:And obviously, the sun goes around the Earth. Look, its obvious! And its just as valid as the possibilities that actually agree with, you know, basic physics.

ROFLMAO

Sputnick · Post by **Sputnick** » Fri Jun 20, 2008 2:18 pm

Which 'basic laws of plhysics' is the author talking about, the basic laws which have proven themselves so easily violated by not so basic laws of physics? Or the basic laws which are violated by as yet unknown laws of physics? Or the not so basic laws which are so easily violated by the basic laws? Please errudicate.

https://apod.nasa.gov/apod/ap080619.html

henk21cm · Post by **henk21cm** » Fri Jun 20, 2008 8:47 pm

Suppose the galaxy is tumbling. If so, than it must be tumbling rather slowly, compared to the rotational period of the stars. At least an order of magnitude slower.

Why? We know that in most spiral arm galaxies the rotational speed of the stars is constant, apart from the central region of the galaxy. In an area about 10% of the radius of a galaxy the rotational speed increases roughly linear with the distance to the center. Further away (than 10% of the radius) from the center the speed is constant.

We see NGC5907 flat, in its main rotational plane, so we can not see any spiral arms, if any. Nevertheless it looks much like a spiral galaxy, since it is not so 'fat' in its center as an elliptical galaxy. If the galaxy was tumbling fast, the same effect that causes the constant rotational speed in its main rotational plane, would have bend the stars in the galaxy opposite to the direction of its tumbling. So it would have formed spiral arms opposite to the direction of its tumbling motion. And that would have been perpendicular to the direction in which we see 5907. It must have had some characteristics of M51.

I do not see such spiral arms, so the assumption that it is tumbling fast, is likely to be false. What remains is, that, if it is tumbling, it tumbles rather slowly.

BMAONE23 · Post by **BMAONE23** » Fri Jun 20, 2008 9:34 pm

Could tumbling help explain some warp edged galaxies?
Like this one http://antwrp.gsfc.nasa.gov/apod/ap030607.html

Animation · Post by **Animation** » Fri Jun 20, 2008 9:39 pm

How do galaxy orientations generally occur, anyway?

What I mean is, if you take any 2 galaxies, are their angles or tilts or relative position to each other more likely to be perfectly random? Or do galaxies in vague proximity tend to be parallel or tend to be aligned to the same plane? If I look towards the galaxies in one direction from ours and then to some other direction, do i find the same percentages, and even distributions, of galaxies in every angular position?

Do galaxies on massive scales do anything cool like align like iron flakes in magnetic fields or do they just splosh and spin out at all angles in evenly distributed ways?

Just curious.

Lewis

Sputnick · Post by **Sputnick** » Fri Jun 20, 2008 11:37 pm

Speed. Relative to the size of the universe, most motion in nature occurs at slow speeds .. like an acorn growing into an Oak. The speed of light may seem startlingly quick to us, but in the cosmic scheme of things it's merely a placid stroll meandering around and through gravity fields much as we might divert our peaceful Sunday path to examine a flower. The speed of thought, though, may be instantaneous acros the universe.

"If the galaxy was tumbling fast, the same effect that causes the constant rotational speed in its main rotational plane, would have bend the stars in the galaxy opposite to the direction of its tumbling. So it would have formed spiral arms opposite to the direction of its tumbling motion."

These are what I see the curving wisps as .. and they are curved opposite to each other because they are on opposite sides of the galaxy .. stars being pulled out from their spirals by the tumbling motion. The thought that galaxies might tumble is as easy for me to entertain as the thought that they travel and spin in many other directions .. I'm sure galaxies do not approach each other in straight lines, but in lines which can curve in any direction .. even, possibly, backwards.

Sputnick · Post by **Sputnick** » Fri Jun 20, 2008 11:40 pm

BMAONE23 wrote:Could tumbling help explain some warp edged galaxies?
Like this one http://antwrp.gsfc.nasa.gov/apod/ap030607.html

Wow, BMA .. that one's got a locomotion more peculiar than any tumble I've ever seen .. beyond my present ability to begin to explain .. unless galaxies can consume far too much alcohol.

starnut · Post by **starnut** » Sat Jun 21, 2008 3:43 am

jgabany wrote: Measurements by the team of researchers who studied this galaxy and its rings had difficulty finding any traces of stellar activity. The rings appear to be comprised mostly of dust.

Not really. If they were mostly dust, they would not be visible in the photograph, being too far from NGC 5907 to reflect the light from its disk. Here is a quote from the IAC press release

http://www.iac.es/divulgacion.php?op1=16&id=519&lang=en

According to the research team, the dwarf galaxy has lost the greater part of its mass in the form of stars, star clusters and dark matter, all of which has become strewn out along its orbit, giving rise to a complicated assembly of criss-crossing galactic fossils whose radius exceeds 150 000 light-years.

“Our results provide a fresh insight itno this spectacular phenomenon surrounding spiral galaxies and show that haloes contain fossil dwarf galaxies, thus providing us with a unique opportunity to study the final stages in the assembly of galaxies like ours,” maintains David Martínez, a researcher at the Instituto de Astrofísica de Canarias (IAC) leading the team that carried out the observations.

The astronomers’ search has not been able to find the main bodies of the devoured galaxies, which leads them to conclude that they have by now been completely destroyed. “These star streams are very difficult to detect and have a very low density of stars,” comments Martínez. “It is this that gives them their ghostly aspect.

Gary

jgabany · Post by **jgabany** » Sat Jun 21, 2008 5:29 am

Hello Starnut:

I apologize that my response implied there were no stars in the streams surrounding NGC 5907- I used a poor choice of words. You are correct, the streams are embedded with stars but they are widely dispersed with other material.

In fact, the team failed to find any concentrations of stars or evidence of new or significant stellar activity within the streams.

I will be more careful in the future and avoid being overly simplistic.

Jay

harry · Post by **harry** » Sat Jun 21, 2008 9:32 am

G'day from the land of ozzzzzzzzz

Here down under we can see the tumble, so to speak.

In general everything tumbles, our solar system tumbles around the arm of the Milky Way and spiralling towards the centre. Our milky way is tumbling towards Andromeda and as a group of galaxies with M87 at the centre are tumbling as a group of galaxies, towards the Great attractor forming a super cluster of groups of galaxies and in turn this cluster groups is tumpling towards, to form a cluster of groups of clusters and so on.

henk21cm · Post by **henk21cm** » Sat Jun 21, 2008 10:18 am

G'day L:ewis,

Animation wrote:How do galaxy orientations generally occur, anyway?

Random.

You can check whether it is random. Take a look at the apod of last monday and download (if you have a fast internet connection) the master image behind the one on the APOD page:

http://antwrp.gsfc.nasa.gov/apod/image/ ... ma_hst.jpg

It is huge, 33 MB. Apart from the few (dozen?) stars, most items are galaxies. Not astronomical numbers, maybe 1000. Good for simple statistical purposes.

Starship Asterisk*