APOD: IC 4628: The Prawn Nebula (2023 Jul 26)

[APOD Robot]

IC 4628: The Prawn Nebula

Explanation: South of Antares, in the tail of the nebula-rich constellation Scorpius, lies emission nebula IC 4628. Nearby hot, massive stars, millions of years young, irradiate the nebula with invisible ultraviolet light, stripping electrons from atoms. The electrons eventually recombine with the atoms to produce the visible nebular glow, dominated by the red emission of hydrogen. At an estimated distance of 6,000 light-years, the [url=https://www.eso.org/public/videos/eso1535a/"</a>region shown</a> is about 250 <a href="https://spaceplace.nasa.gov/light-year/en/]light-year[/url]s across, spanning over three full moons on the sky. The nebula is also cataloged as Gum 56 for Australian astronomer Colin Stanley Gum, but seafood-loving deep sky-enthusiasts might know this cosmic cloud as the Prawn Nebula. The graceful color image is a new astronomical composition taken over several nights in April from Rio Hurtado, Chile.

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[Ann]

There is such a thing as getting too close to an object. You know what this is?

Credit: ESA/Hubble & NASA. Acknowledgement: Judy Schmidt

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Oh, c'mon. Don't tell me you couldn't see it's the Tarantula Nebula?

Credit: ESO

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Yeah, well. The ESA/Hubble Tarantula Nebula picture shows the outskirts of the Tarantula Nebula, which is why it is basically impossible to recognize it. As for today's APOD, I also don't think it tells us the whole story:

IC 4628: The Prawn Nebula Image Credit & Copyright: Daniel Stern

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And I don't know about you, but I have some problems spotting the uncanny resemblance of IC 4628 to a prawn...

Wikipedia has an interesting picture of IC 4628 which I think shows us more than the APOD:

IC 4628. Credit: ESO.

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At lower center right in the ESO image, you can see a blue-white star which I believe is HD 152723, which according to Simbad is a blisteringly hot star of spectral class O6.5III. I believe it is this star that is responsible for ionizing the nebula, blowing away gas and dust in the region and creating a ridge somewhat similar to the one in NGC 3324:

Dusty ridge in NGC 3324. Credit: NASA, ESA, and The Hubble Heritage Team.

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If you look at the ESO image of IC 4628 again, you can see a bright "clump" at upper left that is clearly connected to IC 4628 through a dark dusty "sling". This is an obvious case of triggered star formation.


Anyway. This is my point. IC 4628 is part of a large region of fascinating objects, and showing just the nebula - let alone without any information about technical details and filters - is not wrong, but I strongly feel that this picture is just a part of a larger story that needs to be told!

First of all, IC 4628 is one end of a structure that Messier would have spotted if it had been a bit farther north, because comet-hunters without optical aid really need to look out! They could really mistake nebula IC 4628 and brilliant star cluster NGC 6231 for a comet. Appropriately, the nebula and cluster are known as the False Comet in the sky:

The False Comet, with IC 4628 above center, brilliant cluster NGC 6231 below center, and a string of stars connecting them. Credit: Jose Carlos Diniz

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Yes, IC 4628 and NGC 6231 are almost certainly connected, or at least they are part of the same starforming area in Scorpius. Here is a great annotated overview of the larger region in Scorpius by Sergio Eguivar:

Another and more easily accessible version of the image is here. Note that the image is almost 700 KB.

At top center in Sergio Eguivar's image you can see the Dark Tower, a cometary globule (or a "pillar"), blown by the strong winds of the the stars of NGC 6231. Gerald Rhemann has taken a brilliant picture of it:

The Dark Tower is a top right, and NGC 6231
is at bottom left. Credit: Gerald Rhemann.

The False Comet is part of constellation Scorpius:

Constellation Scorpius. Credit:
Jerry Lodriguss.

Bright orange Antares is above center in this image. Can you spot the False Comet below center?


And one final tidbit here. Many globular clusters of the Milky Way orbit the center of the galaxy in such a way that they periodically plunge right through our galaxy's disk. I once read that globular cluster NGC 6397 was thought to have plunged through the disk in the region of constellation Scorpius and caused the kind of local disarrangement and "choppy seas" that led to the formation of NGC 6231!

NGC 6397... (Credit: NASA, ESA, and T. Brown and S. Casertano (STScI), Acknowledgement: NASA, ESA, and J. Anderson (STScI)

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...caused the formation of NGC 6231? Crdit: roberto Mura

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I've never seen the claim that NGC 6397 caused the formation of NGC 6231 confirmed anywhere, and I don't think astronomers believe in it. Still, I like the idea, and I think it's fun to imagine.

Ann

[orin stepanek]

Nice!

[johnnydeep]

Ah, yes, the Prawn and Moth nebulas!

[Avalon]

In regards to nebulae representing their namesakes, I have observed that ever since Hubble came on the scene with sharper, clearer, more expressive images, the distant objects no longer as easily resemble prawns, eagles, or hearts as they once did in our former fuzzier, less detailed visions of objects in space. The Webb telescope is now recording even more spectacular, finely tuned pictures that hardly resemble the common shapes once seen in older, murkier observations of days past.

[Chris Peterson]

In regards to nebulae representing their namesakes, I have observed that ever since Hubble came on the scene with sharper, clearer, more expressive images, the distant objects no longer as easily resemble prawns, eagles, or hearts as they once did in our former fuzzier, less detailed visions of objects in space. The Webb telescope is now recording even more spectacular, finely tuned pictures that hardly resemble the common shapes once seen in older, murkier observations of days past.

That is true for classic objects mostly named based on visual telescopic views. But many new ones (like this) are getting names now based on how they look to somebody in high resolution imagery.

[johnnydeep]

In regards to nebulae representing their namesakes, I have observed that ever since Hubble came on the scene with sharper, clearer, more expressive images, the distant objects no longer as easily resemble prawns, eagles, or hearts as they once did in our former fuzzier, less detailed visions of objects in space. The Webb telescope is now recording even more spectacular, finely tuned pictures that hardly resemble the common shapes once seen in older, murkier observations of days past.

That is true for classic objects mostly named based on visual telescopic views. But many new ones (like this) are getting names now based on how they look to somebody in high resolution imagery.

While that may be true, the pareidolia effect is still highly dependent on the part of the spectra and the filters used.

[rstevenson]

That's not a prawn. This is a prawn...

"Prawn" alien from District 9 film

Rob (not a prawn)