Starship Asterisk*

Thanks for the replies everyone. I had not been getting any email notifications even after I posted something and thought I was being ignored. :) Now I'll have to go back to see what other replies I missed.

Not sure what changed, but how do I resubscribe to this board? I did it once over a year ago.

EDIT: I figured it out: I had accidentally flagged all "concam" emails as SPAM!

[quote=johnnydeep post_id=321585 time=1648137467 user_id=132061]
...
Fourth: where the heck is neufer?
[/quote]
[url=https://asterisk.apod.com/viewtopic.php?p=321004#p321004]neufer's last post[/url] was on 2022 Mar 01.
Looking back at his previous posts, I see no reasons for his absence.

[quote=johnnydeep post_id=321585 time=1648137467 user_id=132061]
...
Third, the last link in the text - http://heritage.stsci.edu/2016/13/fast_facts.html - doesn't lead anywhere specific.
...
[/quote]
Hubble Heritage was absorbed by HubbleSite and STScI has not been very faithful in maintaining previous links while reorganizing. I'm not sure exactly where that was pointing but it can probably be found here https://hubblesite.org/contents/media/images/2016/13/3725-Image.html . This is the Hubble Heritage Release 2016-13, Bubble Nebula (NGC 7635).

[quote=johnnydeep post_id=321585 time=1648137467 user_id=132061]
I'm a say late and a dollar short...

First, what does AVAO mean above by the statement that "But I'm not sure if the scales are comparable for stars with stellar wind bubbles.". What scales are being compared here? Stellar wind bubbles and some other type of bubble?[/quote]

Well, let me put it like this: [b][color=#FF0000]In the case of the Rosette Nebula, the nebula created the stars[/color][/b], [b][color=#0040FF]but in the case of the Bubble Nebula, the star created the nebula[/color][/b].

Okay, that is an oversimplification and not quite correct. Nevertheless, in the case of the Rosette Nebula, there was a large molecular cloud that "collapsed" - Chris may have a better word for it - and started forming stars. In the case of the Bubble Nebula, the star itself, a mass-losing Wolf-Rayet star, blows a continuous furious stellar wind that removes a lot of mass from it and deposits it in a nebula.

Take a look at another Wolf-Rayet star, WR 31a, that is up to the same tricks as the central star of the Bubble Nebula:


[float=left][img3="Wolf-Rayet star WR 31a and its bubble. Credit: ESA/Hubble & NASA. Acknowledgement: Judy Schmidt"]https://cdn.spacetelescope.org/archives/images/screen/potw1608a.jpg[/img3][/float]
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Let's consider the Rosette Nebula. This is what Wikipedia says about it:

[quote][url=https://en.wikipedia.org/wiki/Rosette_Nebula]Wikipedia[/url] wrote:

The cluster and nebula lie at a distance of 5,000 light-years from Earth and measure roughly 130 light years in diameter. The radiation from the young stars excites the atoms in the nebula, causing them to emit radiation themselves producing the emission nebula we see. [b][color=#FF0000]The mass of the nebula is estimated to be around 10,000 solar masses[/color][/b].[/quote]

Let's compare that with what Wikipedia says about the Bubble Nebula, NGC 7635:

[quote][url=https://en.wikipedia.org/wiki/NGC_7635]Wikipedia[/url] wrote:

NGC 7635, also known as the Bubble Nebula, Sharpless 162, or Caldwell 11, is an H II region emission nebula in the constellation Cassiopeia. It lies close to the direction of the open cluster Messier 52. [b][color=#FF0000]The "bubble" is created by the stellar wind from a massive hot, 8.7 magnitude young central star[/color][/b], SAO 20575 (BD+60°2522). The nebula is near a giant molecular cloud which contains the expansion of the bubble nebula while itself being excited by the hot central star, causing it to glow. It was discovered in 1787 by William Herschel. [b][color=#0040FF]The star BD+60°2522 is thought to have a mass of about 44 M☉[/color][/b].[/quote]

So the mass of the Rosette Nebula is believed to be 10,000 solar masses, but the mass of the star that has created the Bubble Nebula is believed to be 44 solar masses. Even if the star, BD+60°2522, started out with twice that mass and lost perhaps half of due to its furious stellar wind and its enormous mass loss, it is still unlikely that the mass of the Bubble Nebula itself is a lot more than, say, 50 solar masses. So the Rosette Nebula probably outweighs the Bubble Nebula by some 200 times to 1.


[float=left][img2]https://image.shutterstock.com/image-photo/angry-huge-business-man-lokking-260nw-410055622.jpg[/img2][c][size=85][color=#0040FF]The Rosette Nebula and the Bubble Nebula?[/color][/size][/c][/float]
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[quote]Second, in the APOD text, I found this phrasing odd: "...has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud". What does "against denser material" mean?[/quote]

The denser material in this case is the interstellar medium, which is always thicker in some directions than in others. Simply put, our galaxy is filled with a thin soup of gas and dust, which is thicker in some parts than in others. Consider the California Nebula:


[float=left][img3="The California Nebula in narrowband. The gas is swept up by O-type star Xi Persei and is piling up on the opposite site due to resistance from the interstellar medium. Image: Remidone at wikimedia."]https://upload.wikimedia.org/wikipedia/commons/thumb/d/d2/NGC_1499_%28California_Nebula%29_narrowband.jpg/1188px-NGC_1499_%28California_Nebula%29_narrowband.jpg?20180824132038[/img3][/float][float=right][img3="A galactic jet is being bent by resistance from the intergalactic medium."]https://www.mendozza.org/sergio/phdthesis/phdlatex2html/img973.png[/img3][/float]
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The California Nebula is being swept up by the tremendous stellar wind of O-type star Xi Persei. You can see the star at upper left in the image at left. But note the tall "ridge" in the foreground. What makes the gas pile up? I'd say it is the resistance caused by the interstellar medium.

[quote]Third, the last link in the text - http://heritage.stsci.edu/2016/13/fast_facts.html - doesn't lead anywhere specific.[/quote]

That's right. The Hubble Heritage pages are "dead".

[quote]Fourth: where the heck is neufer?
[/quote]

I wish I knew.

Ann

I'm a say late and a dollar short...

First, what does AVAO mean above by the statement that "But I'm not sure if the scales are comparable for stars with stellar wind bubbles.". What scales are being compared here? Stellar wind bubbles and some other type of bubble?

Second, in the APOD text, I found this phrasing odd: "...has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud". What does "against denser material" mean?

Third, the last link in the text - http://heritage.stsci.edu/2016/13/fast_facts.html - doesn't lead anywhere specific.

Fourth: where the heck is neufer?

[quote=AVAO post_id=321579 time=1648069922 user_id=144694]

Thanks Ann
for your exciting explanations - like always.
But I'm not sure if the scales are comparable for stars with stellar wind bubbles.
For me, the comparison with NGC 2359 - Thor's Helmet - would also make sense.

Jac

[img]https://noirlab.edu/public/media/archives/images/screen/noaoann10014a.jpg[/img]
[size=85][url]https://noirlab.edu/public/images/noaoann10014a/[/url][/size]
[size=85]Image Credit: SSRO/PROMPT/CTIO[/size]
[img]https://science.nasa.gov/science-red/s3fs-public/styles/image_gallery_scale_960w/public/atoms/BubbleNebHST_kakitsev1024.jpg[/img]
[size=85][url]https://science.nasa.gov/ngc-7635-bubble-nebula[/url][/size]
[size=85]Image Credit: NASA, ESA, Hubble Heritage Team - Reprocessing by Maksim Kakitsev[/size]
[/quote]

Very good point, Jac! :D

Note that the entire bubble of Thor's Helmet appears to be made of "blue OIII fluff".

Maybe the horns of Thor's Helmet are the remnants of a bubble that burst?

Ann

[quote=Ann post_id=321575 time=1648056796 user_id=129702]
Let's have a look at some details:
..
I think that the Bubble Nebula can be compared to the Rosette Nebula, because the Rosette Nebula is a sort of Bubble Nebula too. Of course, the ionizing cluster NGC 2244 (which, if I remember correctly, contains at least three O-type stars) is more energetic than the lone but powerful ionizing star of NGC 7635, [url=https://simbad.u-strasbg.fr/simbad/sim-id?Ident=SAO+20575]O6.5-type star SAO 20575[/url].

The Rosette Nebula is older, too, because the Bubble Nebula is very young, much younger than its ionizing star. I would guess that the Bubble Nebula formed when SAO 20575 had some sort of outburst. By contrast, the Rosette Nebula is probably just the remnant of the molecular cloud that gave rise to cluster NGC 2244.

Note the blue fluff near the hot O-stars in both the Bubble Nebula and the Rosette Nebula. Since blue means OIII light in these SHO images, this blue fluff is really ionized oxygen structures.

Note the tiny pillars in the Bubble Nebula and the possible jet from a tiny newborn star. Also note the tiny [url=https://en.wikipedia.org/wiki/Bok_globule#/media/File:Bok_globules_in_IC2944.jpg]Bok globules[/url] (or Thackeray Globules) in the Bubble Nebula.

"True" bubble nebulas are unusual. I think it was David Malin who once said that it is hard for bubbles to form in the Milky Way, where the gas is both "constrained and turbulent". Bubbles form more easily in dwarf galaxies. Some great examples of bubble nebulas can be found in one of Milky Way's dwarf satellite galaxies, NGC 6822, and there is another one in another of our satellite galaxies, IC 1613:
...

Ann
[/quote]

Thanks Ann
for your exciting explanations - like always.
But I'm not sure if the scales are comparable for stars with stellar wind bubbles.
For me, the comparison with NGC 2359 - Thor's Helmet - would also make sense.

Jac

[img]https://noirlab.edu/public/media/archives/images/screen/noaoann10014a.jpg[/img]
[size=85][url]https://noirlab.edu/public/images/noaoann10014a/[/url][/size]
[size=85]Image Credit: SSRO/PROMPT/CTIO[/size]
[img]https://science.nasa.gov/science-red/s3fs-public/styles/image_gallery_scale_960w/public/atoms/BubbleNebHST_kakitsev1024.jpg[/img]
[size=85][url]https://science.nasa.gov/ngc-7635-bubble-nebula[/url][/size]
[size=85]Image Credit: NASA, ESA, Hubble Heritage Team - Reprocessing by Maksim Kakitsev[/size]

Let's have a look at some details:


[float=left][attachment=1]APOD 23 March Bubble Nebula annotated Hubble Mehmet Hakan Özsaraç.png[/attachment][c][size=85][color=#0040FF]Bubble Nebula in SHO. Image: Hubble/Mehmet Hakan Özsaraç[/color][/size][/c][/float][float=right][attachment=0]Rosette Nebula in SHO annotated by Sean.png[/attachment][c][size=85][color=#0040FF]Rosette Nebula in SHO. Image by Sean.[/color][/size][/c][/float]
[clear][/clear]


I think that the Bubble Nebula can be compared to the Rosette Nebula, because the Rosette Nebula is a sort of Bubble Nebula too. Of course, the ionizing cluster NGC 2244 (which, if I remember correctly, contains at least three O-type stars) is more energetic than the lone but powerful ionizing star of NGC 7635, [url=https://simbad.u-strasbg.fr/simbad/sim-id?Ident=SAO+20575]O6.5-type star SAO 20575[/url].

The Rosette Nebula is older, too, because the Bubble Nebula is very young, much younger than its ionizing star. I would guess that the Bubble Nebula formed when SAO 20575 had some sort of outburst. By contrast, the Rosette Nebula is probably just the remnant of the molecular cloud that gave rise to cluster NGC 2244.

Note the blue fluff near the hot O-stars in both the Bubble Nebula and the Rosette Nebula. Since blue means OIII light in these SHO images, this blue fluff is really ionized oxygen structures.

Note the tiny pillars in the Bubble Nebula and the possible jet from a tiny newborn star. Also note the tiny [url=https://en.wikipedia.org/wiki/Bok_globule#/media/File:Bok_globules_in_IC2944.jpg]Bok globules[/url] (or Thackeray Globules) in the Bubble Nebula.

"True" bubble nebulas are unusual. I think it was David Malin who once said that it is hard for bubbles to form in the Milky Way, where the gas is both "constrained and turbulent". Bubbles form more easily in dwarf galaxies. Some great examples of bubble nebulas can be found in one of Milky Way's dwarf satellite galaxies, NGC 6822, and there is another one in another of our satellite galaxies, IC 1613:


[float=left][img3="A striking bubble nebula in dwarf galaxy NGC 6822. Source: NASA/ESA."]http://www.astb.se/cassiopeiabloggen/wp-content/uploads/2015/09/Barnards_Galaxy-e1442060201589.jpg[/img3][/float][float=right][img3="A bubble nebula in IC 1613. Image: ESO, Acknowledgement: VST/Omegacam Local Group Survey"]https://cdn.eso.org/images/screen/eso1603a.jpg[/img3][/float]
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Off topic, but I can't resist comparing NGC 6822 and the Large Magellanic Cloud, so you can see how similar their "general makeup" is:


[float=left][img3="NGC 6822. Image Credit & Copyright: Data - Martin Pugh, Processing - Mark Hanson."]https://science.nasa.gov/files/science-red/s3fs-public/styles/image_gallery_scale_960w/public/atoms/NGC-6822_1024.jpg?itok=R_J_Vk1A[/img3][/float][float=right][img3="Ground-based image of the Large Magellanic Cloud. Credit: NASA & ESA"]https://cdn.spacetelescope.org/archives/images/large/opo9816c.jpg[/img3][/float]
[clear][/clear]


Ann

[quote="orin stepanek" post_id=321573 time=1648035776 user_id=100812]
[attachment=1]STScI-01EVVGYGRZGCQ8V7Q5P0S9PY8F.png[/attachment]
Do these bubbles ever burst? :?
[attachment=0]xxPkvxt.jpeg[/attachment]
"That knot looks like another dog!" :mrgreen:
[/quote]
And from its expression, I'd say it's been [url=https://www.youtube.com/watch?v=ppk3wop3SM0] naughty[/url]. :(

[attachment=1]STScI-01EVVGYGRZGCQ8V7Q5P0S9PY8F.png[/attachment]
Do these bubbles ever burst? :?
[attachment=0]xxPkvxt.jpeg[/attachment]
"That knot looks like another dog!" :mrgreen:

Congratulations, what a great composite image!
What is unclear to me, is how a single star can create such a bubble shape?

[size=85]...I especially like the "little ghost nebula" on the bottom right ...;-) [/size]
[img]https://live.staticflickr.com/65535/51956272439_fd9a6eb98e_w.jpg[/img]
[size=50]https://live.staticflickr.com/65535/51956272439_b9071565f1_k.jpg[/size]
[size=50]Jac Berne (flickr)[/size]

Stunning!

[url=https://apod.nasa.gov/apod/ap220323.html] [img]https://apod.nasa.gov/apod/calendar/S_220323.jpg[/img] [size=150]The Bubble Nebula from Hubble[/size][/url]

[b] Explanation: [/b] Massive stars can blow bubbles. The featured image shows perhaps the most famous of all star-bubbles, NGC 7635, also known simply as [url=https://hubblesite.org/contents/media/images/2016/13/3725-Image.html]The Bubble Nebula[/url]. Although it looks delicate, the 7-light-year diameter [url=https://www.exploratorium.edu/ronh/bubbles/bubbles.html]bubble[/url] offers evidence of violent processes at work. Above and left of [url=https://ui.adsabs.harvard.edu/abs/2002AJ....124.3313M/abstract]the Bubble[/url]'s center is a hot, [url=https://en.wikipedia.org/wiki/O-type_star]O-type star[/url], several hundred thousand times more luminous and some 45-times more massive than the Sun. A fierce [url=https://astronomy.swin.edu.au/cosmos/s/stellar+winds]stellar wind[/url] and intense radiation from that star has blasted out the [url=https://ui.adsabs.harvard.edu/abs/1995A%26A...295..509C/abstract]structure of glowing gas[/url] against denser material [url=https://apod.nasa.gov/apod/ap210925.html]in a surrounding[/url] [url=https://en.wikipedia.org/wiki/Molecular_cloud]molecular cloud[/url]. The [url=https://i.imgur.com/xxPkvxt.jpeg]intriguing[/url] Bubble Nebula and associated cloud complex lie a mere 7,100 [url=https://spaceplace.nasa.gov/light-year/en/]light-years[/url] away toward the boastful constellation [url=http://www.hawastsoc.org/deepsky/cas/index.html]Cassiopeia[/url]. [url=https://www.flickr.com/photos/mhozsarac/51838909434/in/dateposted-public/]This sharp, tantalizing view[/url] of the [url=https://apod.nasa.gov/apod/ap170531.html]cosmic bubble[/url] is a reprocessed composite of previously acquired [url=http://heritage.stsci.edu/2016/13/fast_facts.html]Hubble Space Telescope image data[/url].


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