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The following image is a map of the area surrounding the Local Bubble. One side of the image is 1700 lightyears. From the Sun to the Hyades (immediately below the sun) it is 150 lightyears.

The local bubble, with the sun in its center, has three immediate neighboring bubbles, numbered in roman numerals, Loop I, II, and III. At the lower right edge we can see a section of the Orion-Eridanus-Superbubble.

What is the name of the area marked in green?

Image of Local the Bubble at a scale of 50 Lightyears

Image source: Henbest/Couper, The Guide to the Galaxy. Found online at http://www.astronomy.ohio-state.edu/~pogge/TeachRes/Ast162/ISM/Local500pcAnn.gif

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  • A guess (not enough for a definitive answer) is that it is the Orion Molecular Cloud Complex. – HDE 226868 Aug 12 '14 at 12:44
  • As far as I know the Orion Molecular Cloud Complex centers at the lower right end (as this image is presented) of the Orion-Eridanus-Superbubble (here "O-E-Loop"), outside the image, approximately where the line of your comment ends (if viewed not in the mobile version). That's where the Orion Nebula, Barnard Loop, Orion OB1 Association and so on lie. I'm not sure if the O-E-Superbubble is part of the Orion Molecular Cloud Complex, but I believe so. In anyway, the region I seek the name for lies outside the Orion Molecular Cloud, and (at least partly) between it an the Local Bubble. –  Aug 12 '14 at 13:16
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    Okay, so much for that idea. I haven't been able to find much about the region you're talking about. – HDE 226868 Aug 12 '14 at 16:32
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    The situation kind of stinks, really. I love your question, but I can't seem to find anything on it. – HDE 226868 Aug 12 '14 at 18:35

1 Answers1

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I wonder if the area I am looking for is GSH 238+00+09.

In the color image quoted in my question, the galactic core lies beyond the top center. This would be 0° galactic longitude. Going counterclockwise, 238° is somewhere around Beteigeuze.

Here is a "[p]rojection of the Local Cavity onto the Galactic plane":

Figure 9 from Lallement et al. (2003)

Figure 9 from Lallement et al. (2003)

But if you try to superimpose this image on the other one (I matched the positions of the Sun, the Ophiuchus clouds and the Pleiades bubble, the Lupus cloud is a bit off), it seems as if the area marked in green was actually part of our Local Bubble! And GSH 238+00+09 then appears to be identical to the Orion-Eridanus-Superbubble:

Superimposed images

I'm sure I didn't match this correctly. Especially Loop III would be in totally the wrong place. But I found an article that used the same black and white image to illustrate possible locations of Loop III, and the second alternative to the one shown here was in the upper right hand corner, where it would then overlap with "Loop II" of the color image. But probably we should not worry too much over Loops II and III. The creator of the 3D Galaxy Map writes: "I haven't added Loop II, III or IV because I couldn't find any accurate information about their size and location." I'm sure he has been looking more thoroughly than I have, so I feel the mismatch of Loop III is not a problem.

But then the color image is from 1994, and understanding and cartography of our Galactic neighborhood has advanced quite a bit in the ten years between the two publications, so maybe the placement of the Local Bubble in the color map is only a rough equivalent and the mismatch between the two images is not my fault but a result of scientific progress.

Here is another image (rotated 180° in relation to the color image from my question) of local loops, bubbles, and superbubbles, where it becomes clear that GSH 238+00+09 (termed "New Superbubble" (NSB) in this image) is not identical to the Orion-Eridanus-Superbubble:

Figure 8 from Heiles et al., (1998)

Figure 8 from Heiles et al., (1998)

If you compare the scales of this last and my first color image, you will note that the color image falls completely inside the circle denoting the Local Bubble, supporting the thought that the green area lies within it (and not within GSH 238+00+09 or the Orion-Eridanus-Bubble). But this second image also supports the insight that the color image might not be that accurate, and that maybe the area whose name I am looking for does not exist in that shape at all.

In the following image (which shows Loop I as the Scorpius-Centraurus Shells and the Orion-Eridanus-Loop as the Orion Shell) the red blot immediately rimward (lower right) of the sun is the Taurus Dark Cloud. This is not from a scientific but a popular publication (just as my color image), so we should not expect it to be totally accurate, but it still suports the notion that the green area might be part of the Local Bubble.

Unnumbered 3rd figure from Frisch (2000)

Unnumbered 3rd figure from Frisch (2000)

Here is a final image, apparently a different rendering of the image from Lallement et al. (2003), the first image given in this answer. In this image the location of some important stars is marked. Most notably ε CM, which is the scientific name for the Arab name Adhara, with which the same star is marked in the color image from my question and there lies far out in the green area, **lies still within the Local Bubble in this image, close to the edge.

Figure 3 from Sfreir et al. (1999)

Figure 3 from Sfreir et al. (1999)

Here I overlayed the previous image and the image from my question. I matched the sun an Adhara. Other objects are still a bit off, but not much, and we get a good idea of where the Local Bubble ends.

Second overlay image

So it seems the local bubble extends to a bit beyond the star Adhara, halfway from the Sun to the right edge of the image in my question and does indeed include the closer part of the green area.

This thought is supported in the abstract of Heiles (1998), where it says: "[GSH 238+00+09] is at least partially responsible for the apparent extreme elongation of the Local Bubble toward l ~ 230° ..." (my emphasis).

I'll leave my first thoughts and the badly matched image in this answer, to document how I came to the final conclusion.

I'd welcome any thoughts and corrections of this attempt at an answer.

Sources:

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  • This paper (http://iopscience.iop.org/0004-637X/498/2/689/pdf/0004-637X_498_2_689.pdf) seems to suggest it lies somewhere nearer to the Linblad Ring and the Eridanus Loop. See the picture on page 698. Also, what is your scale in the original picture? – HDE 226868 Aug 13 '14 at 13:06
  • Part of the problem here probably lies in the fact that we are looking at 2D projections of 3D space. – called2voyage Aug 13 '14 at 14:01
  • @called2voyage Since all images are projected onto the Galactic plane, that should not be a problem (if done correctly). –  Aug 13 '14 at 14:39
  • @HDE226868 You mean in the color image in my question? From the Sun to the Hyades it is 150 lightyears (according to the scale that's below that image in my book). Note that scale in some of the other images is in parsecs. –  Aug 13 '14 at 14:44
  • @called2voyage brings up an interesting point. I agree that it might not be a huge issue, but it could influence some distance measurements. – HDE 226868 Aug 13 '14 at 15:19
  • Also, what looks like the boundary of a bubble from a 2D perspective may not actually be the boundary. In your original image, the orange-yellow strip between Hyades and Betelgeuse where the "Local Bubble" label rests may not be a boundary. There may be a cavity above and/or below that line of density which connects the cavities on either side of it. Notice in this 3D representation of the Local Bubble that it is has an amorphous boundary. – called2voyage Aug 13 '14 at 15:31
  • @called2voyage Yes, but the idea that the local bubble does not have spherical form (but rather looks like an hourglass open at the bottom and top) is more recent that the book that contained that color illustration. I actually read the article that proposed the non-sphericality during my research. That is why I emphasized the age of the book. In it, the loops are round. It is only recently that we have come to understand the true form of the Local Bubble, which, in more recent texts, is being called the "Local Cavity" or "Local Tube" (since it is open at both vertical ends). –  Aug 13 '14 at 15:38