Hubble gazes on one ring to rule them all

Mar 18, 2013
Credit: ESA/Hubble and NASA

(Phys.org) —Galaxies can take many forms—elliptical blobs, swirling spiral arms, bulges, and disks are all known components of the wide range of galaxies we have observed using telescopes like the NASA/ESA Hubble Space Telescope. However, some of the more intriguing objects in the sky around us include ring galaxies like the one pictured above—Zw II 28.

Ring galaxies are mysterious objects. They are thought to form when one galaxy slices through the disk of another, larger, one—as galaxies are mostly empty space, this collision is not as aggressive or as destructive as one might imagine. The likelihood of two stars physically colliding is minimal, and it is instead the gravitational effects of the two galaxies that cause the disruption.

This disruption upsets the material in both galaxies, and redistributes it forming a dense central core, encircled by bright stars. All this commotion causes clouds of gas and dust to collapse and triggers new periods of formation in the outer ring, which is full of hot, young, blue stars and regions that are actively giving rise to new stars.

The sparkling pink and purple loop of Zw II 28 is not a typical due to its lack of a visible central companion. For many years it was thought to be a lone circle on the sky, but observations using Hubble have shown that there may be a possible companion lurking just inside the ring, where the loop appears to double back on itself. The galaxy has a knot-like, swirling ring structure, with some areas appearing much brighter than others.

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triplehelix
4.2 / 5 (5) Mar 18, 2013
I am not too well read on Galaxies but...

If one small galaxy went through the middle bulbous bit of the larger galaxy, wouldn't this smaller galaxy get eaten up by the supermassive black hole at the centre of the larger galaxy? Instead it seems in this picture to rip right through it vaccuuming up stars or displacing them so the galaxy is now ring shaped...Wouldn't these stars be drawn back in due to the pull of the SM black hole?

I'm not trying to dispute anything here, I just don't know and wondering if someone here does?
Lurker2358
1 / 5 (9) Mar 18, 2013
If one small galaxy went through the middle bulbous bit of the larger galaxy, wouldn't this smaller galaxy get eaten up by the supermassive black hole at the centre of the larger galaxy?


The real answer is YES, eventually, in spite of what the bozo scientists keep saying. The claim that no collisions occur in this article contradicts their own computer models, but it apparently makes them look smart to most people so they keep spitting it out.

The collision may take a few passes, but eventually the galaxies will merge, and most of the material will end up in a very large SMBH.

While much material will be ejected, the final galaxy will be more massive than the large one was originally, and will also be much, much more dense.

In fact, collisions are what slows the galaxies' motion down, due to conservation laws.
nEc
5 / 5 (4) Mar 18, 2013
Indeed, galaxies and galaxy interactions, are best explained with fluid dynamics and specially in this case - with impulsive approximation, using gravipotentials. This type of galaxy collision, results in density "shock" wave, which is responsible for star formation in the plane of passing galaxy disk.
This is despite some comments from ppl, who seem to have nothing to do with the field of Astronomy :)
Silverhill
5 / 5 (5) Mar 18, 2013
@Lurker2358
The claim that no collisions occur in this article contradicts their own computer models
Read the article more carefully:
The likelihood of two stars physically colliding is minimal
Minimal ≠ 0.
Fleetfoot
5 / 5 (3) Mar 19, 2013
I am not too well read on Galaxies but...

If one small galaxy went through the middle bulbous bit of the larger galaxy, wouldn't this smaller galaxy get eaten up by the supermassive black hole at the centre of the larger galaxy?


While the BH has a very high mass, it is still only a small fraction of the mass of the host galaxy and importantly it is also very small. The SMBH in the Milky Way has a mass about 4.3 million times that of the Sun (or about 0.34% of the galaxy) but its diameter is smaller than some large stars.
Mix2This
not rated yet Mar 19, 2013
Curious... Is it not the gravitational effect of a SMBH rather than its relative size that matters? Not sure why the diameter is mentioned when that is just the event horizon?

I've often wondered what processes would occur when two central black holes merge (possible you could have one SMBH orbiting another?). Do such central SMBH play in the role in how the new galaxy forms? Would it be inevitable that they would merge? If they didn't would you be able to see two distinct SMBH (by reference of nearby gas and stars)?



Mix2This
not rated yet Mar 19, 2013
Oh internet how you answer my questions:

NGC 6240 - Possible galaxy with orbiting binary SMBH forming a double nuclei.

The merger of two black holes isn't as clear. In all likelihood that the black holes will be of much dissimilar mass and spin. There was one read where it would be possible for a central SMBH to be ejected from the galaxy via angular momentum. Leaving such a SMBH just spinning out in the inky blackness of space, might be difficult to find such an object.

A another picture of this forms with pebbles on two blankets with a small rock in the center of each. Looking on the underside you can see the distortion based on weight (similar to flatten shuttlecock). Its not likely that these galaxies will be on a even plane. Would it be wrong to envision that, despite distances and the other mass of lesser objects, the two SMBH would be attracted to each other once the galaxies came into close proximity?
Fleetfoot
5 / 5 (1) Mar 19, 2013
Curious... Is it not the gravitational effect of a SMBH rather than its relative size that matters? Not sure why the diameter is mentioned when that is just the event horizon?


The gravity would deflect any stars passing too close but if they came from the merging galaxy, they would be moving faster than escape velocity so would simply pass by unless they were close enough to be disrupted by the tidal effects. Generally the BH is too small a target. The original question was "wouldn't this smaller galaxy get eaten up by the supermassive black hole at the centre of the larger galaxy?", that wouldn't happen though the stars will be scattered and eventually merge into a single larger elliptical galaxy. The mass of the SMBH isn't too important either because it is such a small fraction of the total galaxy mass.
Fleetfoot
5 / 5 (1) Mar 19, 2013
I've often wondered what processes would occur when two central black holes merge (possible you could have one SMBH orbiting another?).


As the galaxies merge, their gas tends to fall to the centre and turn the SMBH into a quasar so do a search for "binary quasar" and you should find images. Most are at high redshift because galaxies were smaller and more numerous so mergers more frequent.

http://phys.org/n...sar.html

Do such central SMBH play in the role in how the new galaxy forms?


The quasar can emit far more radiation than the whole of the rest of the galaxy and the pressure of that can push so much gas out of the galaxy that it kills star formation.

Would it be inevitable that they would merge?


That depends on how close they pass. If the galaxies merge, so will their SMBH due to gravitational radiation.

would you be able to see two distinct SMBH (by reference of nearby gas and stars)?


We do, as binary quasars!
Mix2This
5 / 5 (1) Apr 08, 2013
Thanks for the responses to the many questions.