NGC4725 (1SEP05)

Chip · Post by **Chip** » Thu Sep 01, 2005 3:43 pm

I'm no astronomer so please excuse any really dumb statements.

NGC4725 is interesting to me in that it seems to be a single arm spiral. An observation and some questions. First of all the galaxy seems to have a bar within it. Wouldn't this intimate another arm somewhere? Would it be possible for the galaxy to have sped up it's rotation or the outer portion slowed down (through, possibly, resistance from unseen dust, dark matter, etc.) so that the second arm is actually there but has "run into" the first? The relative thickness of one part of the visible arm compared to other portions may give more creedence to this rather far out idea. Dumb idea? Thanks for listening.

orin stepanek · Post by **orin stepanek** » Thu Sep 01, 2005 4:47 pm

Do you suppose the rate of spin of the black hole may have something to do with the number of arms a galaxy has??
Orin

Aqua · Post by **Aqua** » Thu Sep 01, 2005 4:53 pm

APOD rocks... Pretty easy to see that in this galaxy (NGC4725), the spinning core has two opposing jets. Together, they look like the product of a 'horizontally' rotating torus. (DEEP images of our galactic core posted in an earlier APOD, clearly show a perpendicular torus! ) The high speed jets eventually slow as they plow through galactic scale electro-gravitational forces. Passing thru those fields appears to 'densify' energy into matter? Mostly dust and gas.... urp... then matter accumulates and gravity takes over! BIG question though... Is the matter shooting out one jet right handed chirality and the other jet left handed? Shore would 'mix' things up' a bit! Note that the jet on the right hand side of the image appears to be plowing into previously ejected matter from the other jet and there's some SERIOUS mixing going on!

BMAONE23 · Post by **BMAONE23** » Thu Sep 01, 2005 7:12 pm

If you download the image into photoshop and invert the colors it looks really cool. it also causes the appearance of more arms in the outer region of the galaxy. If I knew how to import pictures into the BB and have them work, I would post it but for some reason my PC won't do it

Aqua · Post by **Aqua** » Fri Sep 02, 2005 4:58 pm

In your 'profiles' selection, choose preferences and scroll down to click on 'Always allow HTML'. Maybe that'll do the deed? I noted that in the Options Selections, below left, the 'HTML is OFF' is not active and does not change when you enable 'Always allow HTML'.... I have a few shots of the moon taken with my lil ol 4" Meade SCT. Not really worth posting. BUT, it would be neat to post previous APOD images to demonstrate rotating horizontal tourus' ejecting left and right handed chirality jets! HO! ~@; )

Aqua · Post by **Aqua** » Fri Sep 02, 2005 5:04 pm

Its easy enough to make an active link to an image... or a URL with the above boxes.

BMAONE23 · Post by **BMAONE23** » Fri Sep 02, 2005 7:26 pm

Thanks Aqua, I'll try it.
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Bad Buoys · Post by **Bad Buoys** » Sat Sep 03, 2005 5:27 am

Don't forget that any image you wish to post must have a URL.

There are a number of free image hosts. One being at:

http://www.tripod.lycos.com/

Sign up for their free account then upload your image and they will issue a URL for the storage location. Use that between the tags.

bandi · Post by **bandi** » Tue Sep 13, 2005 8:32 am

I too have photoshop and that invert is a very interesting image. It does confirm that there is a large line of stars in the area you might expect an arm to be. Because the stars are all but invisible in the infrared shot, perhaps it can be assumed that the stars are so old that they are not generating enough heat to significantly indicate. It could be that there hasn't been any star formation there for longer than the lifespan of the stars so that in time the entire arm will fade from existence. It might be that the equivalent arm on the other side is an even worse state.
Why no star formation for eons? They've run out gas or at least the gas has run out on them. Gas is light and so could be pulled rather sharpishly towards the center by the black hole. If so, it has coagulated thereabouts and with plenty accrueing, star clusters are forming.
Meanwhile very few stars in the halo while millions of solar masses are packed into the core so go figure!
I've taken the liberty of indicating the invert against spira mirabilis. That is where it occurs with consistancy in the spiral galaxies. The line of outlying stars is a spira mirabilis arc but as usual it is as if the stars have formed further out and then been gradually moved inwards. They approach the core as a front with a direct inward shift along the entire length of this arc. The lines of stars hint at an ancient time but spira is still acitve. Can you see it? It's snaking through the nebula at the left of the image, infusing it with energy, heating that gas up and there will be a new line of stars right there.
Very exciting so thanks for that -I'd never considered how an entire arm could become extinct before.
Try
http://homepages.ihug.co.nz/~bandicoot