Can Anyone explain

[tytower]

Here we see two galaxies interacting -these are real taken by Hubble.

Material is flowing from one to the other ,I am assuming into the spiral galaxy.

So they get close to each other -the gravity pulls part of the second galaxy toward the spiral. Probably with explosions at the source.

Material is headed straight for the spiral galaxy which I assume is spinning.

Now what I don't understand is why the material acquires a spin around the spiral galaxy. What makes it fall in a spiral way and not straight to the center. It has forward momentum created by the explosion or by the gravity exerted on it but wherever that is from I would have thought the gravity would act straight on the material regardless of spin.

[muddy0409]

Well, obviously it bumps into stuff and gets deflected??

[M3ZMN]

is this really happening? could the larger galaxy spiral arm merely be superimposed over the smaller galaxy which is actually big but further away?

[trash]

Yes, Blue's got it right. The two galaxies are actually far apart, they just look close because one is behind the other.
The second galaxay may be interacting, but the guts are not being sucked out of it.

Have a search for pictures of galaxies colliding, stars and gas tend to be thrown out rather than sucked in.

Eventually colliding galaxies merge into a single galaxy over millions of years and most of the material does not escape.

The reason for galaxies spinning is the same as it is for Cyclones. The coriolis effect. Material is drawn towards the galaxy because of gravity. But the galaxy is not stationary, it's moving. So material is constantly moving to where the galaxy was, not where it is now.

Once the material is captured by the galaxy's gravity and has an angular momentum, it sets up a galactic current, much like an electric current.
Where there is current, there's a magnetic flux. Everything in the spinning galaxy contributes to the galaxy's magnetic field as well as having it's own magnetic moment. The field is tiny, but it's enough to push all the rotating material into a rotating disc rather than something like we picture in a atom with electrons orbiting in all directions. It takes millions of years, but that's short in universal terms.

Rings around planets also form in relation to a planet's magnetic field.
Also the reason why planets orbit the sun in a narrow plane.

Neutron Stars with companion stars suck the matter out of their neighbours and the gas also forms an accretion disc.


Not all galaxies rotate. The spiral galaxy in the picture does, but the globular companion galaxy does not. Irregular galaxies also tend not to rotate.

In the case of galaxies merging, the stars do not explode. The galaxy is made up of mostly nothing. Stars interact by gravity. Even though the galaxies may be ripped apart, most solar systems will remain in tact.
If stars pass through a nebula of the other galaxy, then all kinds of cool things can happen. A star can go nova (not supernova), it's a bit like throwing petrol on a fire. Rather than explode, it can just flare up.

Because of the huge amounts of space between stars, very few of them actually collide. Some solar systems may pass very close to each other in which case, some of the planets in either solar system may be ejected or captured. Two stars actually colliding would be spectacular, the collision would probably look something like two snowballs colliding in flight.

Galaxies colliding is not something that happens overnight.
Andromeda galaxy is on a collision course with the Milky Way.
It'll be about 500,000 million years before it gets here and the collision and merge will probably go on for a billion years after that before the new bigger galaxy settles down. The mangellanic clouds (irregular galaxies) will probably also be absorbed or they may be ejected or torn apart by the gravity of the two large spiral galaxies.

[tytower]

Well, obviously it bumps into stuff and gets deflected??

Thats a lot of star stuff coming out or in as the case may be and I wouldn't think there would be enough matter that far out to make it spiral -but I don't know

is this really happening? could the larger galaxy spiral arm merely be superimposed over the smaller galaxy which is actually big but further away?

Yes I suppose so which means the matter would be going the other way but does not explain why it spirals?

[tytower]

I keep losing the edit button with this new setup

I notice some sites say"The impact between the Milky way and Andromeda is predicted to occur in about 2.5 billion years."


Either should give me enough time to get ready

If material flows out then, from the foreground galaxy , and the galaxy moves ,the outward flowing material still has the momentum from its source?-so it leaves in a straight line ,galaxy turns a little ,why would it affect the straight line if that material in that line is pulled out by the larger galaxy behind .

You know I am trying to visualise the changes over small periods of time, differentiate it. I need time to think about the flux and electrical current comparison though. I would guess thats probably the answer though

[fandtm666]

awesome pic , just found my new desktop for the week

[trash]

Yeah, I don't remember the period of time allocated to a Milky Way - Andromeda collision.

I can't also remember which way the galaxy rotates in relation to the spiral pattern. It helps to remember that eveything in the galaxy is attracted to everything else, so spiral arms tend to be clusters of stars grouped together by gravity. Motion of individual stars in the galaxy is also somewhat random.
They oscillate through the disc and at regular periods.

Matter moving out from a galaxy moves in a curve again for coriolis effect.
The same way that air spirals out of a high pressure system here on earth.
Not that mater is escaping the gravitational pull of its parent galaxy.

In the case of say a planet that is ejected from it's parent solar system due to solar systems colliding. The planet may have enough velocity to escape even the parent galaxy. (that's a lot of energy).

As the planet leaves the galaxy, the galaxy's gravity is trying to pull it back, and once again the galaxy is moving. So the trajectory even as it escapes is curved. If gravity is great enough, the curve is less than unity and the body never escapes.

I'm trying to think of an experiment that can be performed to demonstrate the (FBI) relationship between movement, electricity and magnetic fields.

The best I can come up with off the top of my head is a cyclotron.
Ok, not a large particle accellerator type, but rather a glass of water.

Place a magnet underneath a glass of water and another above the water to create a magnetic field through the water from top to bottom. This is the galactic poles.
Now place a wire in the center of the glass and another at the edge.
Sprinkle some sawdust on the water so you can see it moving.

Now connect a battery to the wires and the water in the glass will start to move. Reverse the current or the magnetic field and the water will rotate in the other direction.

[tytower]

Yep OK worth a try . I understand that principal but have just been looking at another galaxy picture taken recently through the haze of the Milky Way galaxy (our own) .



This has no external galaxy acting on it and still has the red material in the spirals . Perhaps in the first image of two galaxies colliding the material of the first is not in the influence of the second yet and only the outer extremities are being affected .

[admin]

Tytower re your post report about attachment problems. We are aware of the problem and in the meantime you are enouraged to use the Image Shack photo uploader box under the quick reply box at the bottom of the page.

[mickc]

the rotation depends on if you are in front or behind it

[trash]

hehe ... yes, but the spiral image is also reverse if your behind it giving the same impression. I'm sure that they rotate in the direction that makes them look like the matter is flowing inwards, not being flung out like a catherine wheel. So in tytowers last picture, the rotation is anti-clockwise.

I saw Centaurus A was on the news the other night again. This is the same Black Hole that I posted reference too in the other thread. The one with the X-ray jets illuminating gas clouds.

[tytower]

Yep more on that The latest post at that same site is here



Now it shows what trash was trying to tell me with the Xrays being visible if the picture is coloured to show up Xrays as a colour ie white for very strong . They dont give the frequencies so I will have to look further for this. Interestingly it shows no jets in the visible light spectrum

[trash]

I saw another picture of it today in the Infra Red Spectrum, and it looks good.
They're some nice pictures.

Anyhow... the book I saw it in today was called "BANG". You should be able to find it at any good bookshop. Its got a holographic flicker picture of the big bang on the front cover, pretty hard to miss and it is full of some really really cool astronomy photos. Including Centaurus A in IR. It also had a picture with the rotation of galaxies and how they form. Rotation is confirmed as I mentioned above.

I had some time to burn and was looking through a big bookshop. There were heaps of books that I know you'd like. But BANG was the best. I almost bought it myself. But I was short on cash.

I also passed by the usual quantum and particle physics books. Plenty of Hawking stuff there. But the was another new one there that caught my eye.
Another recomendation for you.
"A briefer History of Time". It's the same book as his first one, but it's a LOT more friendly to the average reader. Some of his original work was some pretty heavy going for the average person of the street.
But this book is much simpler and has some very good illustrations.

Pop down to your local angus & robertson and have a peak in their science section for these books. You wont regret it.


Ah, I remember a picture of a Quasar called 3C175 in the book too. some more links

[tytower]

The only thing we can see is the optical view . This is the true light frequencies we see in a strong telescope.

The rest is somewhat fictional because somebody has taken natural real emissions and chosen a colour scale to apply to each range of frequencies.

It is very useful because say the radio picture shows not reflected emissions but original emissions coming from what must be matter at its source. Likewise the xrays . At least there will be some reflected emissions but I would expect the majority would be source emissions just as is the case with normal light .

The radio picture indeed shows a balanced plume both sides of the central black star. The xrays are a large beam toward our direction and a much smaller one in the other direction from the black star. Light frequencies show nothing .

So take the radio picture . This shows us that this galaxy is balanced fairly evenly as we would expect. It tells us particles of some sort are emitting vibrations ,some in xray ,some in light and all in radio in the vibrations we have chosen to look for.

It can not tell us if these are single particles of a few atoms or less or sun size.

My question is " at what point does matter ejected from a black star start to act like a sun so it can be seen"

There are going to be stages it will pass through as it re-expands -would these be sudden or gradual? What would be the emissions at each phase?
If small particles they will do the same but will then have to combine with other particles to get to a sun size again.

Interesting stuff ..for me anyway

[Terracon]

In my opinion I would say that a black hole would be the brightest thing in the sky, just like the first pic of the spiral galaxy.

Light from every other star in the universe passing by this black hole would be bent by the huge gravitational force and so and so it only seems like a huge cluster of stars but it’s actually an optical illusion

Its internal gravity would cause it to be flat not a sphere form because of the high speed of the gravity ….more than light….any thing moving towards the speed of lights flattens in that direction…

[tytower]

Terracon- can you explain a bit more . A black star typically is said to have the mass of one million of our suns. Light is bent by gravity and the theory is light is bent so much passing a black star it does not come out. That is out to a certain distance from the black star ,an event horizon for light.

[trash]

It's not really that trivial to translate X-rays and radio into colours.
It's just a matter of interpretation. X-rays and radio do behave in the same way that light does. We tend to think of X-rays passing through things, but they reflect, refract and absorb just like light does. X-rays aren't just one frequency either, they are a whole spectrum just like light.

Colour adds a lot of information that cannot otherwise be easy to interpret.
In electron mircoscopes where colour becomes a mathematical impossibility because of the scale. Colouring Hydrogen atoms Red, Oxygen White, Carbon Black and so on has no relivance to the atom itself, but it adds meaning.

Even false colouring of light can be very useful.

It can not tell us if these are single particles of a few atoms or less or sun size.

I'm not sure what you mean ?

Matter - Well we need to look at the order that things happen as things get close to the black hole.

Lets deal with our own solar system. The first thing that happens is solar systems are drawn closer together, the gravity each start system being flung around like grains of sand in a vacuum cleaner. Gravity of a neighbouring system will make planet's orbits erractic and eventually rip them from their orbits and flung into intersteller space, eventually they too will evenutally end up in the black hole.

Now we're left with just stars. The gravitational pull of the black hole is going to distort them. Nasty things will happen, the stars magnetic fields will be drawn and streched. The star itself will elongate and eventually its own gravity will be overcome by that of the black hole and the star will go nova (explode - not supernova) the material will still be VERY hot at this point, and it will be accellerated even further as it ends on in the accretion disk.
It will no longer be undergoing fusion, but it will still be so hot that it's a plasma and it will visibly glow white hot like a furnace. As particles collide at high speed, some of them may undergo fusion, but it is more likely that the collisions will cause X-rays.
This is where it helps to think of eletromagnetic radiation as one form with different energy levels.
If you rub a material, it heats up.
If you heat it enough, it emits IR radiation.
If you continue heating it, it starts to glow red hot.
If you continue heating it, it glows white hot.
continue heating it and it will emit very high energy and glow UV light.
continue heating it and it will glow emitting X-rays.

As solid objects get closer to the black hole, gravity rips them apart physically and then down at the atomic level and litterally disintergrates it to atoms.
So all the material is now nothing but a very hot gas (plasma) orbiting the black hole like a very large syncrotron. Where we use magnetic fields to steer the particles, the black hole holds them with gravity.
Whenever you have high velocity particles changing velocity, you get Bremsstrahlung emiting even more X-rays.
Each type of interaction of matter causes different types of X-rays and spectrum, and we can see what this matter is made of and or how fast it is moving by the spectra emited.

Now we're in the final stages, just metres above the event horizon, traveling very very fast. The gas is so hot, it's ionised. Fusion is also occuring as atoms slam into each other at very high speed. The galactic (electric) current huge at this point. The orbiting material sets up a massive magnetic field and all of the atoms magnetically polarise further completeing the magnetic circuit and aliging more particles for the cause.
This polisation of matter is probably why the jets are aligned magnetically.

At this point, if we could get close enough for a look, the black hole will still optically look like a big brightly glowing star with a bright glowing ring or super hot gas all of it emitting lots of X-rays.

The final few moments, the atoms themselves begin to distort as gravity rips them apart as well. The potential across just a single atom becomes enoumous. Imagine time running three times faster at your head than your feet. As the elementry particles cross the event horizon, huge amounts of energy are released. The matter has aquired so much energy because it is traveling so fast, this energy cannot just be distroyed.
We're now down on the level of Hawking Radiation. Some of this energy contributes to the mass of the black hole, some of it escapes.
Information theory becomes important at this time as we now have to consider the memory of the matter absorbed. Does the black hole remember what it swallowed or did it vanish forever or did that energy become so compressed, it can now only be measure in gravitational accelleration.

An example is....
Matter is swallowed by the black hole. It's gravity pulls in new matter.
This matter emits X-rays all the way down to the black hole.
Where did this energy come from ? The potential energy of the atom or the gravity of the black hole (the same thing). So it could be looked as if, the energy of the orginal matter escaped the black hole through gravity to the particle and then as X-rays into space.

Small black holes evaporate. If find it confusing that a black hole can become so small that it just ceases to exist and pull in new material.
It's not confusing that it can happen mathematically, it's confusing that the remaining mass of a tiny black hole could gravitationally hold itself together at such a low point.

Anyhow.... They are still revising all this theoretical physics. Steven Hawking's latest books are usually up to date.

[trash]

Light from every other star in the universe passing by this black hole would be bent by the huge gravitational force and so and so it only seems like a huge cluster of stars but it’s actually an optical illusion

The effect is relative. You need to be a long way away from the source of the gravity to notice such a huge lensing effect. If you're close in, the gravitational lens appears to be physically much smaller.

Its internal gravity would cause it to be flat not a sphere form because of the high speed of the gravity ….more than light….any thing moving towards the speed of lights flattens in that direction…

But space isn't flat, it's three dimensional and gavity works in all directions equally. A sphere is the minimalist shape in three dimensions.

The "speed of gravity" is not faster than the "speed of light". It is the same (3x10^8ms^-1).

[Terracon]

-trash-

According to contemporary astronomical theory, a ray of light passing near the surface of a black hole is deflected (bent) greatly by the gravitational field of the black hole. In fact for every star or galaxy in the universe there are an infinite number of light paths which will pass near or circle the black hole and arrive at our viewing position (see for example...Ohanian, The black hole as a gravitational lens, Am .J. Phys, 55(5), May, 1987)

Only a few of these light paths result in detectable light being deflected to our telescopes, but in fact a detectable light path can be found from every visible star and galaxy in the universe which will pass near a black hole and appear to come from it or from near it...

Moderate Mass Black Hole
If the black hole has only moderate mass... say up to 20 times that of the sun, or is very distant, all of the deflected rays of light will appear to come from the black hole itself... Individual images cannot be identified, and will blend together to form a single image. There will be at least one path of light coming from the black hole from every visible object in the universe! The black hole will be one of the brightest objects in the sky!


Massive Black Hole

When the black hole is very massive (i.e. has a large gravitational force) or is very nearby, a telescope on earth would be able to distinguish some individual deflected images. The black hole would itself appear to be bright from light "borrowed" from every other star or galaxy in the universe, but it would be surrounded by star images. These are "false" images.... images of distant stars whose light has been deflected by the gravitational force of the black hole so as to appear to be around the black hole. What would it look like? How about this!

Globular cluster 47 Tucanae




Now lets say that this black hole was spinning......what would it look like then.?