APOD: Star-Forming Eagle Nebula without Stars (2022 Oct 04)

[APOD Robot]

Star-Forming Eagle Nebula without Stars

Explanation: The whole thing looks like an eagle. A closer look at the Eagle Nebula's center, however, shows the bright region is actually a window into the center of a larger dark shell of dust. Through this window, a brightly-lit workshop appears where a whole open cluster of stars is being formed. In this cavity tall pillars and round globules of dark dust and cold molecular gas remain where stars are still forming. Paradoxically, it is perhaps easier to appreciate this impressive factory of star formation by seeing it without its stars -- which have been digitally removed in the featured image. The Eagle emission nebula, tagged M16, lies about 6500 light years away, spans about 20 light-years, and is visible with binoculars toward the constellation of the Serpent (Serpens). Creating this picture involved over 22 hours of imaging and combining colors emitted specifically by hydrogen (red), and oxygen (blue).

<< Previous APOD

This Day in APOD

Next APOD >>

[Ann]

Star-Forming Eagle Nebula without Stars
Image Credit & Copyright: Yannick Akar

I was wondering why today's APOD was showing us so much stuff "below" the Eagle Nebula. But when you look closely, you can see that there are gigantic "fronts" or "arcs" or "waves" in the molecular gas associated with the Eagle Nebula which seem to be the remnants of large outbursts of some sort from the massive cluster at the center of the nebula, or from the convulsions of star birth.

If you look at the picture that I have annotated, you can see that there is a bright blue star "above" one of the most obvious large waves (at lower left). I was wondering if that star had something to do with the shaping of the arc. Not so, however. The star, HD 167812, is a modest very late B-type star (B9.5V) which is quite similar to Sirius, and it is incapable of causing any light-year-long shock fronts in space.

What we are seeing is the convulsions of the interstellar medium (or in this case, the convulsions of a part of a molecular cloud) because of massive star formation going on in another part of the cloud. Such fronts and such compression could presumably lead to new star formation.

The Omega Nebula, M17, is located very close to M16, the Eagle Nebula, and my amateur guess is that these two nebulas might be, if not siblings, at least second cousins ultimately emanating from the same general molecular cloud. In M17, we see a very interesting case of triggered multi-generation star formation:

The Eagle Nebula, M16, at left, and the Omega Nebula, M17, at right. Photo: Kees Scherer.

---

Star formation in M17.

---

The gas around M17 is being recycled into new generations of stars. The same thing is probably happening in M16, too, although the "arcs" or "fronts" seen in the APOD may be too "mild" to compress the gas enough to trigger new star formation. More likely, the new star formation in M16 is happening where the gas and dust is more thick and dark.

Anyway. Speaking about arcs and waves in nebulas and molecular clouds. NGC 2264, the Cone Nebula and Christmas Tree Cluster, is one of my favorite regions for looking at billowing waves as a consequence of the lighting of furiously massive stars. Thar she blows, S Mon(ocerotis) - and she blows, and blows, and blows, and blows, and....

Until she really blows, as a supernova. But she won't do that yet, not for a couple of million years. Until then, she just blows, and she makes mighty waves in her sea of gas.

The Cone Nebula and Christmas Tree Cluster and all the billowing gas surrounding them. Photo: Graem Lourens.

---

Ann

[orin stepanek]

Nice! I'm glad stars are still being created

Kitty has stars in her eyes!

[XgeoX]

Looking at the middle of the nebula…



I can’t help but think of a resemblance to Michelangelo’s “Creation of Adam”…



And for Orin …



Eric

[orin stepanek]

Looking at the middle of the nebula…



I can’t help but think of a resemblance to Michelangelo’s “Creation of Adam”…



And for Orin …



Eric

If we hah an 'I like button"; I'd push it! Thanks Eric!

[Cat Gabrel]

I am very appreciative of these wonderful pictures, explanations and the added kittens and cats give me joy. Thank you all.

[Curious Cat]

Lower left, what is the black upside down "V" shaped thing coming out of the clouds?

[Ann]

Lower left, what is the black upside down "V" shaped thing coming out of the clouds?

You mean this thing, don't you?

Well, it is obviously a dust lane of some kind. Maybe one dust lane that is bent in the middle at a sharp angle. Or, more likely, it is two dust lanes.

If you look closely - and please click on the image to see the full size of it - you can see, faintly, that the edges of these dust lanes seem to glow. They glow faintly, but they do glow.

They remind me of dust bunnies - sorry, Bok globules - with glowing edges that are found in the Carina Nebula:

Bok globules in the Carina Nebula. Copyright: NASA, ESA, N. Smith (University of California, Berkeley), and The Hubble Heritage Team (STScI/AURA)

---

ESA wrote:

One globule nicknamed the caterpillar is shown in the central image. Its glowing edge indicates that it is being photoionized by the hottest stars in the cluster. It has been hypothesized that stars may form inside such dusty cocoons.

I think that the same thing might be going on in the dusty "V" in the Eagle Nebula. The dust is being photoionized by the hottest stars in the Eagle Nebula, making the gas in the "V" slowly evaporate and glow from ionization.

What about the strange shape of the "V"? (I think of it as a pair of pants.)

I have no idea what causes the two-legged shape. But please note that other "pant shapes" turn up at other places in the dust below the brightest part of the nebula.

Ann

[MoonRockMan]

Edit: Disregard, already answered

[johnnydeep]

Looking at the middle of the nebula…



I can’t help but think of a resemblance to Michelangelo’s “Creation of Adam”…



And for Orin …



Eric

If we hah an 'I like button"; I'd push it! Thanks Eric!

Me too - admins: we need a "Like" or "Rec" button pronto!

[johnnydeep]

What's going on to cause the almost circular "crown" or halo at the top? Anything special?

[heehaw]

The universe without stars! Suppress the diffuse radiation too, and the image will be the three degree background!

[Ann]

What's going on to cause the almost circular "crown" or halo at the top? Anything special?

Click to view full size image

Click to view full size image

It looks like half a donut. It's amazing.

Some time ago I tried to figure out what it might be or what might have caused it, and I came up empty. But we may note a few things.

There are some - mind you, some - similarities between the "half a donut" of the Eagle Nebula and M43 of M42 - and M42 is, of course, the Orion Nebula.

The Eagle Nebula. The 'half a donut' is seen, faintly, at upper right. Photo: ESO.

---

The Orion Nebula, M42, with small nebula M43 at upper left. Image: Opo Terser.

---

Consider some similarities between the Eagle Nebula and the Orion Nebula. In both cases, the main ionizing star cluster is seen "in the upper part of the nebula" - let's talk about up and down here for simplicity's sake - and a dark dust structure is "hanging down" in front of, or near, the bright stars.

This dark dust structure near the stars is connected to more dust, which separates the Orion Nebula proper, and the Eagle Nebula proper, from a smaller, quite round, nebula "above" the two large bright nebulas.

The main difference - and that's a huge difference - is that M43 is lit up by a star of its own making, whereas the donut of the Eagle Nebula is "empty". For the same reason, M43 is much, much brighter than the Eagle donut.

The strangest thing about the donut of the Eagle is the perfect hole in the middle. I'm wondering if by any chance it could actually be a hole.

Let's take a look at a nebula with a real hole inside it:

Orion Nebula with M43 at top and NGC 1999 at lower left.
Image: Giuseppe Donatiello

NGC 1999 is a nebula with a hole in it. Image: NASA and The Hubble Heritage Team (STScI).

---

Wikipedia wrote about NGC 1999:

NGC 1999 is a dust-filled bright nebula with a vast hole of empty space represented by a black patch of sky, as can be seen in the photograph.
...
The exact cause of this phenomenon is still being investigated, although it has been hypothesized that narrow jets of gas from some of the young stars in the region punctured the sheet of dust and gas, as well as, powerful radiation from a nearby mature star may have helped to create the hole.

So if there is a hole in NGC 1999, could the hole lookalike of the donut of the Eagle Nebula be a hole for real? If so, it would be much, much larger than the hole of 1999. It seems doubtful.

However, the donut of the Eagle Nebula is located not all that far from the raging powers of massive star formation. Bear in mind that the Eagle Nebula is larger than the Orion Nebula and contains more, and more massive, stars. Maybe possibly maybe just the right kind of outburst from the hotbed of stars and star formation in the Eagle Nebula sent exactly the right shock wave through the dust curtains to blow out a hole in the dust and push the remaining dust "upward" to form a graceful arc.

It still seems less than plausible. But it is the best I can come up with.

Ann

[johnnydeep]

Thanks, Ann. It's remarkable to me just how much your first image makes the "donut" look like there's "nothing there there" compared to the same donut structure in this APOD. A side-by-side - shown below - makes it very striking. The lesson for me is that the particular image source and subsequent processing is CRUCIAL in order to be able to discover something real (or not!) going on, or to, instead, miss the (possibly extremely important) thing entirely!

[AstroLux]

Very interesting to see the expansion of the dust, awesome job on the image , very much a 3D effect with all the contrast from narrowband.