OT: Lost in the Galaxy? No wonder.
 

Turns out the Milky Way isn't a Spiral galaxy, it's a Barred Spiral! Hoorah.

http://www.space.com/scienceastronom...milky_way.html

Re: OT: Lost in the Galaxy? No wonder.
 

Oh my God..... So they actually know that there's a supermassive black hole at the center of the galaxy? I've been telling people that we don't know squat about the center of the galaxy for years now, and now it appears that we are not only part of the accretion disk of a supermassive black hole, but that there is a bar - a bar of ancient red supergiants near what is apparently the event horizon?

Oh my God. So..... if we have evolved on a world orbiting a star in the accretion disk - accretion disk - of a black hole, then wouldn't that mean that other spiral galaxies - and I use that term lightly now - are merely accretion disks? And what about non-spiral galaxies, like the Magellanic Clouds?

I think my brain has just burnt out.

Re: OT: Lost in the Galaxy? No wonder.
 

You think THAT's weird? Well, humans (as well as pretty much everything alive except bacteria) are really symbiotic organisms, much like the CueCappa - but not on the organismic level, but on the CELLULAR Level - about a billion years ago, some protozoa decided to absorb these other protozoa with whom they had this symbiotic relationship - we now call those second set of protozoa "mitochondria" and "chloroplasts"! http://forum.shrapnelgames.com/images/smilies/eek.gif
Well OK, maybe the galaxy stuff IS more impressive... "bar of ancient red supergiants" sounds almost like something you'd find in a vault in Angband, too http://forum.shrapnelgames.com/image...ies/tongue.gif

Re: OT: Lost in the Galaxy? No wonder.
 

Ahhh, but did you know that the Milky Way may in fact be twice as large in diameter as originally thought? Up to 200,000 light years, or if you prefer more familiar measurements, 2.0 x 10^18 km across?

Here's the article I read that in: Astronomy.com link

Re: OT: Lost in the Galaxy? No wonder.
 

*fizzle*

Re: OT: Lost in the Galaxy? No wonder.
 

Which is not what you want your nuclear bomb to do.

Re: OT: Lost in the Galaxy? No wonder.
 

The Bar of Ancient Red Super Giants! What time is Happy Hour?
And we're actually made up of many individual living things that take my DNA? Think they would like a drink too?

Re: OT: Lost in the Galaxy? No wonder.
 

http://anywherebb.com/noctis.html
Just in case you want to visit those stars.

Re: OT: Lost in the Galaxy? No wonder.
 

I don't understand galaxies. Especially elliptical ones. I can sort of see how a spiral galaxy works, it rotates around so the spiral arms orbit around the center and the rotation and the gravitational pull towards the center balance each other out. So the galaxy doesn't collapse or fly apart.

So why doesn't an elliptical galaxy collapse under its own gravity? If it's spinning, that will stop it from collapsing in the plane of rotation but not at right angles to the rotation.

Also, I wonder how a barred spiral galaxy can form. What happened when the galaxy was forming? The bars full of stars extended outwards from the middle, straight, in opposite directions, and then after the bars grew to a certain length, the whole galaxy started to rotate so that the arms bent into a spiral? How can that happen, I just don't understand!

Re: OT: Lost in the Galaxy? No wonder.
 

I believe that all rotating objects and all orbital paths are elliptical. The earth, the sun, the earth's orbit around the sun, everything. It has something to do with off-center focal points and centers of mass, but I can't remember it just now... And plenty of wobbling.

Re: OT: Lost in the Galaxy? No wonder.
 

Pretty much, yeah. That sums it up. Also, elliptical galaxies are believed to form from mergers between two or more galaxies. These mergers could disrupt the spiral arms of either galaxy, due to the new gravitational forces that have to be compensated for. Thus, in many cases the spiral arms collapse, unless the merger is between a really small galaxy and a much larger one. Mergers like this have taken place many times in the Milky Way's history, but the galaxies that have been absorbed have seemingly been small enough to not significantly disrupt the spiral arm structure of our galaxy. Though it is difficult to tell, since we can't exactly take a nice little picture of our galaxy from the outside looking in to see what the structure actually is like. http://forum.shrapnelgames.com/image...ies/tongue.gif

An elliptical galaxy won't collapse under its own gravitational attraction due to the fact you mentioned; spin. What stops the collapsing at right angles (or any angle) to the rotation is the fact that a lot of galaxies are essentially two-dimensional. They may be hundreds of thousands of light years across, but they're only a few thousand ly thick. So there basically aren't many stars at right angles to the rotation, and ones that are, yes could be pulled in...but bear in mind we're talking distances of thousands of light years, and stars travelling at a very low percentage of light speed. It would take a LONG time for them to reach the galactic center. Also, just because they're in the same galaxy as the majority of the stars that are spinning one way, doesn't mean they aren't rotating contrary to the rest of the stars. So even if they are at a right angle to the plane of the galaxy, the stars that aren't in the plane could have a different rotation that results in a stable 'orbit' around the galactic nucleus.

Barred spirals are probably, again, the result of galactic mergers disrupting things. For one thing, galactic mergers can cause "bow shocks" that compress interstellar gases in an area, causing a burst of star formation. This would result in stars of approximately the same age, and sort of "strung out" in a line. I suppose that strung out line of stars could form the bar of the barred spiral, but I'm really not very familiar with the finer points of galactic formation. The bar of the barred spiral galaxy could actually even be the remnants of the smaller galaxy that was absorbed!

Please bear in mind that I'm by no means an expert in astronomy or cosmology, all of what I have said is merely from the viewpoint of a very interested amateur. Most of it is taken from what I can remember having read in astronomy books, etc. and since my memory is fallible, the information is probably at least partly incorrect. http://forum.shrapnelgames.com/images/smilies/wink.gif But hopefully I could clear a little confusion.

Re: OT: Lost in the Galaxy? No wonder.
 

Again, *fizzle*

Re: OT: Lost in the Galaxy? No wonder.
 

I've always been amazed at how we can't see the dense center area of stars (sans black hole of course). You'd think that with all those stars, the brightness would be obvious. Someone told me we can't all the light from the center because of all the interstellar dust in the way. I hope he wasn't B.S.ing me.

Re: OT: Lost in the Galaxy? No wonder.
 

He wasn't BSing you, that is the currently accepted and most plausible theory.

Re: OT: Lost in the Galaxy? No wonder.
 

The dust and because of how Earth is placed, the milky way we see is actually the converging point of the... Persius and... Some other arm for the galaxy. Sol is right between those arms

Re: OT: Lost in the Galaxy? No wonder.
 

And the Orion arm I believe. Or was it Saggitarius...

Re: OT: Lost in the Galaxy? No wonder.
 

Renegade 13, thanks for the explaination about galaxies. http://forum.shrapnelgames.com/images/smilies/smile.gif

Re: OT: Lost in the Galaxy? No wonder.
 

No problem at all, I love talking about stuff like that http://forum.shrapnelgames.com/images/smilies/laugh.gif But bear in mind, it might be partly wrong!

Re: OT: Lost in the Galaxy? No wonder.
 

What makes things more interesting, the matter we see is only smaller part of the matter of the galaxy. Dark matter is unseen matter, which has about 10 times more mass in our own galaxy than we have matter we can see.

A quotation from Wikipedia article:
For those who say it is/may be untrue: This same conclusion about dark matter you can make from various different places in the internet, including BBC site and Berkeley university. http://forum.shrapnelgames.com/images/smilies/cool.gif

Re: OT: Lost in the Galaxy? No wonder.
 

http://forum.shrapnelgames.com/images/smilies/happy.gif I love astronomy. Look at all the fascinating things you learn!

Dark matter is still, technically, a theory, but it is a theory that is nearly universally accepted today. There simply isn't enough baryonic ("normal") matter to account for all the gravitational effects we observe. If the visible matter was the only stuff there was, the large scale structures would not/could not exist, since the gravity required for them to form and stay formed simply would not be present. By the way, large scale in this context means larger than the solar system. Without dark matter, structures like galaxy clusters and superclusters wouldn't exist, even galaxies may not have enough gravity to stay together.

Scientists recently discovered a particle that makes up part of dark matter; neutrinos. Neutrinos are a by-product of nuclear fusion, among other things I'm certain, and so are hugely abundant. However, until recently, scientists didn't think they had any mass at all, that they were a "massless" particle. However, they recently have determined the mass, which although it is vanishingly small, it does exist. Neutrinos do make up a percentage of dark matter, but it is a quite small percentage.

Another candidate for dark matter is the Higgs Boson particle. This one hasn't even been detected, only theorized. But if it does exist, it should account for a large portion of dark matter, since it would have a large mass. Higgs Boson Link The Large Hadron Collider, a particle accelerator that is, I think, already under construction at CERN, should prove or disprove the existance of the Higgs.

Things get a lot more strange however, when you think of things like dark energy, a theoretic form of energy that is sort of "anti-gravitational", and so is causing the expansion of the universe to accelerate. It appears dark energy rules the vast inter-galactic spaces, and gravity rules the on the galactic scale. In other words, dark energy is powerful enough to continue to force galaxies apart from one another, but not powerful enough to rend the galaxies apart.

Scientists now predict that "normal" baryonic matter, of which you and I are all made, composes merely 4 or 5% of the universe. Dark matter, either baryonic dark matter, or hot/cold dark matter makes up another 25%, with dark energy taking the other 70%. Dark Energy Link

But I'm sure I've totally gone beyond the point of interest here, so I'll shut up http://forum.shrapnelgames.com/images/smilies/wink.gif And I just realized most of what I said about dark matter is already in the link Karibu posted http://forum.shrapnelgames.com/image...es/redface.gif But hopefully the links I provided are interesting http://forum.shrapnelgames.com/images/smilies/happy.gif

Re: OT: Lost in the Galaxy? No wonder.
 

I found it interesting.

Re: OT: Lost in the Galaxy? No wonder.
 

But if, as the original post says, there's twice as much baryonic matter in galaxies as previously thught, then you don't need as much dark matter to make all the gravitational calculations add up. Make that 4%-10% of the universe made up of baryonic matter.

Re: OT: Lost in the Galaxy? No wonder.
 

Good point! http://forum.shrapnelgames.com/images/smilies/cool.gif

Narf: I'm glad you found it interesting http://forum.shrapnelgames.com/images/smilies/smile.gif

Re: OT: Lost in the Galaxy? No wonder.
 

So, I was just thinking; Dark Matter must be invisible because if there is so much of it, why doesn't it interfere with our observation of other stellar objects like other galaxies. You don't hear someone say "I was watching Mars last nite when suddently an orb of dark matter blocked my view"

Dark Matter, Anti-Matter,and little lambs eat ivy.

Re: OT: Lost in the Galaxy? No wonder.
 

Possibilities for dark matter: It interacts very little or not at all with normal matter. Or it is composed more of particles than large "blobs" of matter like an asteroid or planet or star. Neutrino's for example are hugely abundant, but very hard to detect, and also make up a portion of dark matter. If there's more particles like the neutrino out there, they possibly wouldn't be easily detected but could make up a large part of dark matter.

Anti-matter is another subject, but I'll save that for another time http://forum.shrapnelgames.com/images/smilies/happy.gif

Re: OT: Lost in the Galaxy? No wonder.
 

Look up 'Anti-Protons'. Basically, protons with a negative charge. Apparently, if you smash a proton and an anti-proton, there's a 100% energy release, or really close to it.

Re: OT: Lost in the Galaxy? No wonder.
 

Anti-particles also have a different spin (I think), due to certain factors that are beyond my comprehension.

Re: OT: Lost in the Galaxy? No wonder.
 

There's also this assumption, that dark matter in the galaxy is spread on far wider area than normal matter. Scientists call it the "dark matter halo" of galaxy. For example, the diameter of our galaxy is considered to be about 100 000 light years. The diameter of dark matter in our galaxy is assumpted to be around million light years. Which is effectively 10 times more than visible matter in our galaxy. Perhaps you know more of this, Renegade?

Re: OT: Lost in the Galaxy? No wonder.
 

Anti-particles have the same spin, but opposite charge. I'm not sure what all the details are about spin. It's a rather confusing subjuect to me at times. This helps a bit though.

http://en.wikipedia.org/wiki/Image:Particle_chart.jpg

I think Baryons, which are made up of 3 quarks have odd spins like 1/2 or 3/2 and so on. They make up normal matter like protons and neutrons.

Mesons have 2 quarks and have even spin like 0 or 1. Some mesons can be their own anti-particle. Here is a quick site.
http://www2.slac.stanford.edu/vvc/theory/hadrons.html

Mesons also don't obey the "Pauli exclusion principle" which I think mostly says 2 particles can't occupy the same state. Thats part of what keeps electrons, which are Baryons, separated in their electron configurations. Here's more on that
http://education.jlab.org/qa/electron_config.html

I think I read somewhere that mesons, since they don't obey the Pauli exclusion principle, don't interact with most matter, and were hard to detect because of this. If dark matter is made up of these particles then it would be hard to find.

Black holes, now thats a whole other suject...

Anyway, I'm sure there is more I didn't say but my fingers are getting sore from typing for now. Hope some of you find this interesting.

Re: OT: Lost in the Galaxy? No wonder.
 

http://forum.shrapnelgames.com/image...es/biggrin.gif Nope, I don't really know more than that. Just that they call the hypothetical dark matter halo objects MACHO's (Massive Compact Halo Objects).

Oh, I just remembered something more. Some candidates for dark matter:

SIMP's (Strongly Interacting Massive Particles): They interact with normal matter strongly, but still are thought by some to form at least a part of dark matter. Hypothetical Particel! Not proven to exist yet. SIMP Link (not much info)

WIMP's (Weakly Interacting Massive Particles): Another hypothetical particle that only interacts with normal matter through the weak nuclear force and gravity. Since they (theoretically) don't interact through electromagnetism or the strong nuclear force, they can't be seen directly, or interact with atomic nuclei. NOTE: Most of the above paraphrased from Wikipedia. WIMP Info Link

Neither of the above have been proven to exist yet, to the best of my knowledge.

Don't you just love particle physics? http://forum.shrapnelgames.com/images/smilies/cool.gif

Thanks for correcting me Wolfman http://forum.shrapnelgames.com/images/smilies/happy.gif

Re: OT: Lost in the Galaxy? No wonder.
 

This one has more info on SIMP's.
http://www.news.uiuc.edu/scitips/02/0604darkmatter.html

Also taks a bit about WIMP's, and their interactions in the early universe.

Re: OT: Lost in the Galaxy? No wonder.
 

Thanks for the link Wolfman http://forum.shrapnelgames.com/images/smilies/laugh.gif http://forum.shrapnelgames.com/images/smilies/happy.gif

Re: OT: Lost in the Galaxy? No wonder.
 

Everything I don't know about dark matter I learned from
"Schlock Mercenary":

http://www.schlockmercenary.com/d/20031208.html

Re: OT: Lost in the Galaxy? No wonder.
 

OK, this might be a dumb question, but...

Why do astronomers have to introduce the idea of this mysterious "dark matter" to account for the gravity in the galaxies? Couldn't the extra mass simply be made up of planets, asteroids, dust, black holes and other objects that don't emit light and are therefore hard to detect? Do all planets have to orbit stars? Couldn't there be just lots of big planets in between the stars, independently orbiting the galactic center, so that they make up the missing mass?

Re: OT: Lost in the Galaxy? No wonder.
 

All those planets, asteroids, dust, black holes, etc. would by definition be dark matter. Dark matter isn't some wierd kind of exotic material, it's a general category for a whole lot of mass that astronomers calculate has to be there to account for certain gravitational effects but that is hard enough to detect that they haven't found it yet.

Re: OT: Lost in the Galaxy? No wonder.
 

Thanks, that makes sense. I was somehow under the impression that "dark matter" was composed of some sort of strange and unusual material that's not found on earth.

Re: OT: Lost in the Galaxy? No wonder.
 

The 'why' is that the universe is not behaving right for the observed material. It looks like there is more gravity than the currently known contents of the universe can account for. So, there are various ways to invent more mass -- either simply 'dark' but normal matter as already mentioned, or also as 'exotic' stuff that doesn't even interact with normal matter except through gravity.

It should be pointed out, though, that we might not have mastered how gravity actually works yet. There is a very detectable discrepancy in the movement of the Pioneer space probes (currently the furthest man-made objects from earth). They have not moved as far as they should have. Not by much, but by enough to make the NASA engineers and scientists wonder what is going on. And even though they are moving in opposite directions (i.e. on opposite sides of the solar system), they show the same degree of this discrepancy, too, so it's not easily explained by some hidden planet somewhere. There may be an extra 'fudge factor' in the way gravity works over great distances that would explain the movement of galaxies without requiring all that 'dark matter'.