NGC 7635: The Bubble Nebula; a question (APOD 18 Oct 2006)

harry · Post by **harry** » Wed Oct 18, 2006 8:55 am

Hello All

Re: http://antwrp.gsfc.nasa.gov/apod/ap061018.html

This bubble is 10 light years in diameter.

If my eye prove me right. I see other bubbles within the large bubble.

Other links

http://heritage.stsci.edu/1998/31/index.html
http://astrosurf.com/ericmouquet/galeri ... OL_600.htm
http://antwrp.gsfc.nasa.gov/apod/ap030617.html

http://adsabs.harvard.edu/cgi-bin/nph-b ... .295..509C

The complicated kinematic structure of the (approximately equal to 3 pc) diameter shell nebula NGC 7635 (itself part of a system of shells in the broader S162 area) has been revealed by observations of spatially resolved hydrogen alpha and (NII) line profiles. The observations were obtained with the Manchester echelle spectrometer on the William Herschel and Isaac Newton telescopes along NS lines of measurement distributed over the filamentary nebula. We propose a model where the stellar wind from the exciting star pressurises an ionized layer which is itself in pressure equilibrium with the molecular cloud. Irregular expanding shells are also produced by the breakout of the stellar wind from the surface of the cloud.

orin stepanek · Post by **orin stepanek** » Wed Oct 18, 2006 1:32 pm

APOD has shown this bubble before. It is very intriguing. I wonder if there are other bubbles in the universe as prominent as this one?

Orin

falcon99 · Post by **falcon99** » Wed Oct 18, 2006 1:36 pm

I've always wanted to ask what might be a rather simplistic question...

The Bubble nebula APOD shows the identified "source star" significantly to the right. The nebula is pretty small compared to others we've seen on APOD. Is the source star's relative velocity (or the nebula's) that high to result in such a misalignment? I would think the star would be closer to the center..

Falcon

BMAONE23 · Post by **BMAONE23** » Wed Oct 18, 2006 5:13 pm

I believe that the mentioned "Bright Hot Star" is actually outside the Bubble and is casting light and pressure on the bubble causing the glowing reflection nebula just below and left of the star. I believe that the source star is the faint centrally located star.

Andy Wade · Post by **Andy Wade** » Wed Oct 18, 2006 5:46 pm

BMAONE23 wrote:I believe that the mentioned "Bright Hot Star" is actually outside the Bubble and is casting light and pressure on the bubble causing the glowing reflection nebula just below and left of the star. I believe that the source star is the faint centrally located star.

Is there a chance that this is formed from a catastrophic explosion such as a supernova?
Or am I just wearing my 'thicky' head today?

BMAONE23 · Post by **BMAONE23** » Wed Oct 18, 2006 7:20 pm

I would imagine that it would take that or a similar event to cast off that which creates the bubble
http://antwrp.gsfc.nasa.gov/apod/image/ ... an_big.jpg
here is another great image from APOD

orin stepanek · Post by **orin stepanek** » Wed Oct 18, 2006 8:02 pm

http://www.noao.edu/outreach/aop/observers/n7635.html
I like this view also.
Orin

harry · Post by **harry** » Wed Oct 18, 2006 9:50 pm

Hello Orin

Your right.

Just put it in for the new comers.

Qev · Post by **Qev** » Thu Oct 19, 2006 8:15 am

BMAONE23 wrote:I believe that the mentioned "Bright Hot Star" is actually outside the Bubble and is casting light and pressure on the bubble causing the glowing reflection nebula just below and left of the star. I believe that the source star is the faint centrally located star.

As I understand from the caption, the 'source' star of the bubble is the bright star above and right of the center of the bubble. I imagine the bubble and star are 'misaligned', not necessarily due to the motion of the star, but rather due to variations in the density of the gas cloud in which the bubble is being blown.

astro_uk · Post by **astro_uk** » Thu Oct 19, 2006 12:03 pm

I think Qev is right, you can see that there is more material piled up towards the NE of the bubble
in this image.

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

I guess this is what you would expect if there is more gas in that direction so it takes longer for the ultraviolet photons from the star to ionise the material and blow out the bubble in that direction.

One interesting thing is that you can actually see that there is a larger bubble, (the part inside the orange regions). The double bubble if I remember my undegrad lectures is usually due to photons from the star of different energy being able to ionise helium (the smaller bubble) and lower energy photons ionising hydrogen (the larger one).

BMAONE23 · Post by **BMAONE23** » Thu Oct 19, 2006 1:58 pm

If the larger star is in fact the source star, then I would imagine that the offset and brightness are caused by the Bow Shock effect of the material moving in that direction striking a more powerful source and therefore moving more slowly towards that source. The interaction heating up the gas in that area.

iamlucky13 · Post by **iamlucky13** » Thu Oct 19, 2006 7:35 pm

It seems to me bow shocks are supposed to be rather elongated, almost egg or teardrop in shape, but that thought occured to me, too while looking at the picture.

I'm having a hard time deciding if the apparently rough edges of the bubble are due to gas intruding into the bubble, or if it is an illusion caused by lack of gas around certain portions of the bubble perimeter. I suspect the latter.

Also, If I read the caption right, the little cloudy pillar near the star we think is source of the bubble is actually a reflection nebula outside the bubble. Any thoughts?

iamlucky13 · Post by **iamlucky13** » Thu Oct 19, 2006 7:44 pm

Andy Wade wrote:
Is there a chance that this is formed from a catastrophic explosion such as a supernova?
Or am I just wearing my 'thicky' head today?

My impression was that the center star just happened to be sitting in a rather hydrogen-dense region. It would have accrued matter from this for a while, but then as its output increased, radiation and particle pressure would have pushed the gas away from the star, forming the bubble. I could definitely be wrong though, and there's several examples of stars casting off shapes like this in supernova explosions. I think usually though the regions are much more turbulent in appearance and filled with a variety of heavier elements. The eskimo nebula is a pretty good example.

The clarity of the bubble perimeter is also interesting. It's like there's a buildup of matter right on the line. I would tend to think that more consistent with a shockwave than a relatively static heliosheath.

Andy Wade · Post by **Andy Wade** » Thu Oct 19, 2006 10:46 pm

iamlucky13 wrote:
Andy Wade wrote:
Is there a chance that this is formed from a catastrophic explosion such as a supernova?
Or am I just wearing my 'thicky' head today?
My impression was that the center star just happened to be sitting in a rather hydrogen-dense region. It would have accrued matter from this for a while, but then as its output increased, radiation and particle pressure would have pushed the gas away from the star, forming the bubble. I could definitely be wrong though, and there's several examples of stars casting off shapes like this in supernova explosions. I think usually though the regions are much more turbulent in appearance and filled with a variety of heavier elements. The eskimo nebula is a pretty good example.

The clarity of the bubble perimeter is also interesting. It's like there's a buildup of matter right on the line. I would tend to think that more consistent with a shockwave than a relatively static heliosheath.

Thanks for that, it helps a lot, I did wonder why they posed the question "What created this huge space bubble?", in the APOD text.
If there are a few possible explanations then it's quite understandable.
I suppose without the gas clouds to outline it, we wouldn't be able to see it at all?
If that was true, then I wonder if there are lots more of these out there than can't be seen very easily.
Oh... 'heliosheath'? Now that's a great word! I like it.

iamlucky13 · Post by **iamlucky13** » Fri Oct 20, 2006 1:18 am

Andy Wade wrote:Oh... 'heliosheath'? Now that's a great word! I like it.

Hehe...glad to give you a chuckle. It's a real term, even:

http://en.wikipedia.org/wiki/Heliosheath

Also, the eskimo nebula I mentioned before:
http://antwrp.gsfc.nasa.gov/apod/ap031207.html

I was wrong about it before. The Eskimo is a planetary nebula, which are formed by matter lost by stars during their red giant phase, as opposed to a supernova. However, supernova remnants and planetary nebulae can often look similar in structure.

Nereid · Post by **Nereid** » Fri Oct 27, 2006 2:20 am

Threads merged.

svs95 · Post by **svs95** » Fri Oct 27, 2006 1:05 pm

orin stepanek wrote:APOD has shown this bubble before. It is very intriguing. I wonder if there are other bubbles in the universe as prominent as this one?
Orin

I believe the Orion Nebula is a "bubble" nebula of very similar structure to this one, albeit somehwat degraded by a multitude of forces over time.

Does anybody else see the structural similarity? Maybe start with this image.

The Orion Nebula is specifically the "bubble" in the upper right part of this deep field image.

svs95

Starship Asterisk*

NGC 7635: The Bubble Nebula; a question (APOD 18 Oct 2006)

NGC 7635: The Bubble Nebula; a question (APOD 18 Oct 2006)

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