Notes on NGC891, The Outer Limits Galaxy
Some misc notes on Ed's picture of NGC891 (Caldwell 23), The Outer Limits Galaxy http://www.utahastronomy.com/album24/NGC891_Mew_1_6x4_150dpi Distance: 31 M l/yr Diameter: 100,000 l/yr - similar to the Milky Way Discovered: Caroline Herschel, 1784 Coordinates: RA 02h22.6m Dec +42h21m S&T Article: Block, Adam. Nov. 2004. Galaxy NGC 891 in Andromeda. S&T 108(5):136. 2004S&T...108e.136B Analogues: Milky Way; NGC4565 in Coma B (Caldwell 38) Ed's picture images a couple of the distinguishing features of this edge-on spiral: vertical chimneys aka galactic fountains. These are dark nebula "sticks" extending perpendicular to NGC's galactic disk. In Ed's picture a prominent one is seen set-off against the galactic bulge. These chimneys are thought to be the result of nova or supernova heating gas and supporting the dark nebula gas tube against galaxy's gravity. In our own Milky Way, these chimneys are identified as low velocity molecular clouds (LVMC) and/or galactic fountains. These chimney clouds continue to rise, cool and slow. Eventually, gravity becomes dominate and then the clouds fall as high-velocity molecular clouds (HVMC). When HVMC's crash back into the gas and dust of the galactic disk, they set off a burst of stellar birth - snr's and novae that create bubbles. Sol is currently transiting the 500-1000 parsec diameter Local Bubble, which is believed to probably be the result of this process (Olano 2000). Sol is also transiting the smaller 50 parsec diameter Local Chimney, a vertical tube of thin hydrogren gas, which is also believed to be the result of a nova remanent of unknown origin. Like most galaxies, we see only a visible fraction of its total extent. The rotational curve of the NGC 891 galaxy implies an enveloping disk of hydrogren gas extending out many times it's visible diameter. A radio-astronomy contour map of HI gas super-imposed on an optical black/white picture of NGC 891 can be seen in Figure 1 of this article: Swaters, R.A. 12/1997. The HI Halo of NGC 891. 1997ApJ...491..140S http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v491n1/36835/36835.p... Because NGC 891 distance is 31 M l/yr, it is foreground to and not part the more distant (200+ M /yr) Perseus-Pisces supercluster at RA 03h19m and the nearly the same declination (see Caldwell 24, NGC1275). NGC 891 is a member of group of galaxies defined by Tully (1988) as the Triangulum Spur. In popular TV culture NGC 891 was the galaxy shown in the opening credits of the original 1960s "Outer Limits" TV series. For a blast from the past, listen to "Outer Limits" intro using the link "Listen to Samples," at: http://www.amazon.com/exec/obidos/tg/detail/-/B000001P19/002-9010935-6813669... - Canopus56 Other sources: O'Meara, S. 2002. The Caldwell Objects. Sky Pub. pp. 96-99. __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com
Wow! There is sure a lot more to these images than the images themselves. What a complete write-up you have provided. In IC 410 there are a couple of gas formations known as the "tadpoles". Are these other examples of vertical chimneys? I am planning to image IC 410 in the next week or so. It will be interesting to see what the camera comes up with. BTW-Would you mind if I used your write-up as part of my permanent image album? I would certainly appreciate it. Ed L --- Canopus56 <canopus56@yahoo.com> wrote:
Some misc notes on Ed's picture of NGC891 (Caldwell 23), The Outer Limits Galaxy
http://www.utahastronomy.com/album24/NGC891_Mew_1_6x4_150dpi
Distance: 31 M l/yr Diameter: 100,000 l/yr - similar to the Milky Way Discovered: Caroline Herschel, 1784 Coordinates: RA 02h22.6m Dec +42h21m S&T Article: Block, Adam. Nov. 2004. Galaxy NGC 891 in Andromeda. S&T 108(5):136. 2004S&T...108e.136B Analogues: Milky Way; NGC4565 in Coma B (Caldwell 38)
Ed's picture images a couple of the distinguishing features of this edge-on spiral: vertical chimneys aka galactic fountains. These are dark nebula "sticks" extending perpendicular to NGC's galactic disk. In Ed's picture a prominent one is seen set-off against the galactic bulge. These chimneys are thought to be the result of nova or supernova heating gas and supporting the dark nebula gas tube against galaxy's gravity.
In our own Milky Way, these chimneys are identified as low velocity molecular clouds (LVMC) and/or galactic fountains. These chimney clouds continue to rise, cool and slow. Eventually, gravity becomes dominate and then the clouds fall as high-velocity molecular clouds (HVMC).
When HVMC's crash back into the gas and dust of the galactic disk, they set off a burst of stellar birth - snr's and novae that create bubbles. Sol is currently transiting the 500-1000 parsec diameter Local Bubble, which is believed to probably be the result of this process (Olano 2000). Sol is also transiting the smaller 50 parsec diameter Local Chimney, a vertical tube of thin hydrogren gas, which is also believed to be the result of a nova remanent of unknown origin.
Like most galaxies, we see only a visible fraction of its total extent. The rotational curve of the NGC 891 galaxy implies an enveloping disk of hydrogren gas extending out many times it's visible diameter. A radio-astronomy contour map of HI gas super-imposed on an optical black/white picture of NGC 891 can be seen in Figure 1 of this article:
Swaters, R.A. 12/1997. The HI Halo of NGC 891. 1997ApJ...491..140S
http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v491n1/36835/36835.p...
Because NGC 891 distance is 31 M l/yr, it is foreground to and not part the more distant (200+ M /yr) Perseus-Pisces supercluster at RA 03h19m and the nearly the same declination (see Caldwell 24, NGC1275). NGC 891 is a member of group of galaxies defined by Tully (1988) as the Triangulum Spur.
In popular TV culture NGC 891 was the galaxy shown in the opening credits of the original 1960s "Outer Limits" TV series. For a blast from the past, listen to "Outer Limits" intro using the link "Listen to Samples," at:
http://www.amazon.com/exec/obidos/tg/detail/-/B000001P19/002-9010935-6813669...
- Canopus56
Other sources:
O'Meara, S. 2002. The Caldwell Objects. Sky Pub. pp. 96-99.
__________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com
http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
Visit the Photo Gallery: http://www.utahastronomy.com
__________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com
--- Edward Lunt <lunco@yahoo.com> wrote:
In IC 410 there are a couple of gas formations known as the "tadpoles". Are these other examples of vertical chimneys?
I don't know that much about IC 410. It's the smaller nebulosity about a degree west of IC 405, the Flaming Star nebula (C31). The "tadpoles" in IC 410 are easily seen in this SEDs image - http://www.seds.org/~spider/ngc/ngcdss.cgi?obj=IC!410&r=5:22.6&d=+33:31&e=J2... These appear to be small globular clouds near a bright star or PN remnant. The solar wind from the bright star or PN remanent is blowing on the molecular clouds and form the characteristic "cometary knot" shape. IC405 and 410 are part of the Orion cloud complex and are about 1,500 l/yr (500 parsecs) away. Similar blown molecular globule clouds can be seen inside this famous 1994 Hubble photo of the Helix Nebula: http://hubblesite.org/newscenter/newsdesk/archive/releases/1996/13/ This small cloud group (IC 405 and 410) is local phenomena involving few light years (< 1 parsec) of volume. Vertical chimneys or galactic fountains are on an entirely different scale. The whole Orion cloud complex sits on the edge of and is a small part of band of molecular clouds that define the boundaries of our 500 x 300 parsec Local Bubble. Sol is slighty off-center of this relatively gas free area.
BTW-Would you mind if I used your write-up as part of my permanent image album? I would certainly appreciate it.
Please do. I'm just resummarizing other secondary sources. Enjoy - Canopus56(Kurt) __________________________________ Start your day with Yahoo! - Make it your home page! http://www.yahoo.com/r/hs
Kirt, Many thanks!!! Your information (although some of it is beyond my understanding at this point) is most interesting and adds a great deal to my understanding. Thanks again, Ed L --- Canopus56 <canopus56@yahoo.com> wrote:
--- Edward Lunt <lunco@yahoo.com> wrote:
In IC 410 there are a couple of gas formations known as the "tadpoles". Are these other examples of vertical chimneys?
I don't know that much about IC 410. It's the smaller nebulosity about a degree west of IC 405, the Flaming Star nebula (C31). The "tadpoles" in IC 410 are easily seen in this SEDs image -
http://www.seds.org/~spider/ngc/ngcdss.cgi?obj=IC!410&r=5:22.6&d=+33:31&e=J2...
These appear to be small globular clouds near a bright star or PN remnant. The solar wind from the bright star or PN remanent is blowing on the molecular clouds and form the characteristic "cometary knot" shape.
IC405 and 410 are part of the Orion cloud complex and are about 1,500 l/yr (500 parsecs) away. Similar blown molecular globule clouds can be seen inside this famous 1994 Hubble photo of the Helix Nebula:
http://hubblesite.org/newscenter/newsdesk/archive/releases/1996/13/
This small cloud group (IC 405 and 410) is local phenomena involving few light years (< 1 parsec) of volume.
Vertical chimneys or galactic fountains are on an entirely different scale. The whole Orion cloud complex sits on the edge of and is a small part of band of molecular clouds that define the boundaries of our 500 x 300 parsec Local Bubble. Sol is slighty off-center of this relatively gas free area.
BTW-Would you mind if I used your write-up as part of my permanent image album? I would certainly appreciate it.
Please do. I'm just resummarizing other secondary sources.
Enjoy - Canopus56(Kurt)
__________________________________ Start your day with Yahoo! - Make it your home page!
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com
http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
Visit the Photo Gallery: http://www.utahastronomy.com
__________________________________ Start your day with Yahoo! - Make it your home page! http://www.yahoo.com/r/hs
--- Edward Lunt <lunco@yahoo.com> wrote: <snip>
--- Canopus56 <canopus56@yahoo.com> wrote:
These (IC410 "tadpoles") appear to be small globular clouds near a bright star or PN remnant. The solar wind from the bright star or PN remanent is blowing on the molecular clouds and form the characteristic "cometary knot" shape.
Ed, Looks like I got that one wrong on first impression. IC 405 is surrounded by open cluster NGC 1893. This is a stellar birthing area. A better image of the "tadpoles" - http://www.skyhound.com/sh/archive/jan/NGC_1893.html - shows them to be newly born hot stars. The solar wind from the hot stars are blowing away the surrounding gas that gave birth to the star. Because these new born stars are in a stellar nursery, the surrounding less dense gas of the larger nebula keeps the gas blown from the new stars condensed into the smoke-like trailer or cometary tail. Although solar wind is the causative agent of the cometary knot cloud form in both cases, the setting is different. IC 405 involves stellar birth; the cometary knots in the Helix Nebula involve stellar death. - Canopus56(Kurt) __________________________________ Yahoo! FareChase: Search multiple travel sites in one click. http://farechase.yahoo.com
Thanks Kirt, I think I'll put this on my list of objects to look at over Thanksgiving. (I'll be giving thanks that the moon will be out of the way by then.) Ed L --- Canopus56 <canopus56@yahoo.com> wrote:
--- Edward Lunt <lunco@yahoo.com> wrote: <snip>
--- Canopus56 <canopus56@yahoo.com> wrote:
These (IC410 "tadpoles") appear to be small globular clouds near a bright star or PN remnant. The solar wind from the bright star or PN remanent is blowing on the molecular clouds and form the characteristic "cometary knot" shape.
Ed,
Looks like I got that one wrong on first impression.
IC 405 is surrounded by open cluster NGC 1893. This is a stellar birthing area. A better image of the "tadpoles" -
http://www.skyhound.com/sh/archive/jan/NGC_1893.html
- shows them to be newly born hot stars. The solar wind from the hot stars are blowing away the surrounding gas that gave birth to the star. Because these new born stars are in a stellar nursery, the surrounding less dense gas of the larger nebula keeps the gas blown from the new stars condensed into the smoke-like trailer or cometary tail.
Although solar wind is the causative agent of the cometary knot cloud form in both cases, the setting is different.
IC 405 involves stellar birth; the cometary knots in the Helix Nebula involve stellar death.
- Canopus56(Kurt)
__________________________________ Yahoo! FareChase: Search multiple travel sites in one click. http://farechase.yahoo.com
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com
http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
Visit the Photo Gallery: http://www.utahastronomy.com
__________________________________ Yahoo! FareChase: Search multiple travel sites in one click. http://farechase.yahoo.com
participants (2)
-
Canopus56 -
Edward Lunt