APOD: The Tarantula Zone (2014 Jun 12)

[APOD Robot]

The Tarantula Zone

Explanation: The Tarantula Nebula is more than 1,000 light-years in diameter, a giant star forming region within our neighboring galaxy the Large Magellanic Cloud (LMC). That cosmic arachnid lies toward the upper left in this deep and colorful telescopic view made through broad-band and narrow-band filters. The image spans nearly 2 degrees (4 full moons) on the sky and covers a part of the LMC over 8,000 light-years across. Within the Tarantula (NGC 2070), intense radiation, stellar winds and supernova shocks from the central young cluster of massive stars, cataloged as R136, energize the nebular glow and shape the spidery filaments. Around the Tarantula are other violent star-forming regions with young star clusters, filaments, and bubble-shaped clouds. In fact, the frame includes the site of the closest supernova in modern times, SN 1987A, just above center. The rich field of view is located in the southern constellation Dorado.

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[Ann]

This is a great picture, and the combination of RGB and narrowband filters produces a splendid result. Note the bluish nebulas, which are dominated by high-energetic OIII-emission. Look at the high-mass stellar associations, which are dominated by bright blue stars, but there are also orange supergiants among them.

Note the bar at lower right in the picture. Most of the bar is dominated by relatively modest red giants and relatively modest main sequence stars. The contrast between the "fuzzy", "quiescent" bar and the sparkling supergiants and "flaming" nebulas in and around the Tarantula Nebula is striking.

Ann

[BDanielMayfield]

The contrast between the "fuzzy", "quiescent" bar and the sparkling supergiants and "flaming" nebulas in and around the Tarantula Nebula is striking.

Yes it is very striking. I also note how lopsided the LMC is as far as nebulas are concerned. I guess that's why it's called an irregular galaxy. Is there a known or suspected cause for so much more star birth activity on one side/end of the LMC's "bar" as opposed to the other?

Does it really look like a tarantula when viewed though a small scope? I hope to see it with my own eyes someday.

[Boomer12k]

Nebula, Clusters, and Stars....Oh, MY!!!!!

A terrific look at a fantastic area of one of our nearest Galactic Neighbors.

:---[===] *

[Ann]

BDanielMayfield wrote:
Is there a known or suspected cause for so much more star birth activity on one side/end of the LMC's "bar" as opposed to the other?

Actually, the LMC has more star formation on the other side of the bar (along the bar) than we might think. Look at this image of LMC by Robert Gendler. The second largest nebula in the LMC, after the Tarantula Nebula, is actually the nebular complex at 10 o'clock in the image. It isn't altogether easy to find out its name, although it may go by the designation NGC 1760.

Clearly, most of the star formation of the LMC is on one side of the bar, as can be seen from Robert Gendler's picture. But some galaxies are just lopsided, for example NGC 5474. NGC 5474 is affected by the strong tidal forces of giant galaxy M101 (which is in itself lopsided), and the LMC may well be affected both by its small "sibling", the SMC, and by our own quite large galaxy, the Milky Way.

But in my opinion, it is even more interesting to try to understand the star formation in the Large Magellanic cloud by bearing in mind that it is a barred galaxy. It really has a very obvious and quite long bar. Is there a place in a barred galaxy where conditions are often particularly suitable for star formation? Actually, yes, there is, at the ends of the bar. Take a look at this watercolor painting of a barred spiral by Harriet Rex Smith, and note the blue blobs of star formation at the ends of the bar. Reality is often like that, although there is usually more star formation at one end of the bar than at the other. A good example is M66, where you can see that most of the bright red nebulas are at one end of the bar. NGC 5908, on the other hand, has enhanced star formation on both sides of the bar, as does NGC 1530. I find NGC 4450 very interesting. It has almost no star formation at all, except at the end of a dust lane which terminates at one end of the bar.

The way I understand it, a galactic bar tends to channel gas outwards, towards the ends of the bar. Here the gas runs into the more circular motion of the disk, and here we often find enhanced star formation. And that is how I think we should see the pattern of star formation in the LMC.

Ann

[starsurfer]

The LMC is an amazing galaxy and Marco Lorenzi has produced one of the greatest images of the most well known region of it!! Some of the nebulae with OIII are Wolf Rayet nebulae such as the bubble near the top right corner. In fact, there is a lot of OIII in many nebulae in the LMC! Also you can see a labeled version here.

[Ann]

I just found this picture of how gas is channeled to the ends of a galactic bar, leading to star formation there.

Ann

[Chris Peterson]

I just found this picture of how gas is channeled to the ends of a galactic bar, leading to star formation there.

Is there some explanatory text? I doubt that there is any channeling of gas as suggested, and note that the image is posted on a pseudoscience site.

[Ann]

I just found this picture of how gas is channeled to the ends of a galactic bar, leading to star formation there.

Is there some explanatory text? I doubt that there is any channeling of gas as suggested, and note that the image is posted on a pseudoscience site.

Unfortunately, yes, I saw that when I visited the page.

Nevertheless, if you look at a large number of barred galaxies, it is quite obvious that star formation, in those cases when it is occurring at all, is often particularly strong near the bar ends. Clearly there must be an explanation. Of course, the explanation might just be that the motion of the stars in the bar and the motion of the stars in the spiral arms and disk "collide" at the bar ends, which may lead to enhanced star formation for reasons that may have something to do with the fact that collisions between galaxies also often lead to enhanced star formation.

Ann

[Chris Peterson]

Nevertheless, if you look at a large number of barred galaxies, it is quite obvious that star formation, in those cases when it is occurring at all, is often particularly strong near the bar ends. Clearly there must be an explanation. Of course, the explanation might just be that the motion of the stars in the bar and the motion of the stars in the spiral arms and disk "collide" at the bar ends, which may lead to enhanced star formation for reasons that may have something to do with the fact that collisions between galaxies also often lead to enhanced star formation.

Right, that would be my thinking, that the same process that creates the inflection at the end of the bars allows for an environment where you have colliding gas clouds, which of course produces new stars.

I don't think in any galaxy (outside those in the process of collision or strong tidal interaction) that there's any significant radial transport of material, either inward or outward.