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Posted: **Wed Jun 14, 2023 4:06 am**

The Shark Nebula

Explanation: There is no sea on Earth large enough to contain the Shark nebula. This predator apparition poses us no danger as it is composed only of interstellar gas and dust. Dark dust like that featured here is somewhat like cigarette smoke and created in the cool atmospheres of giant stars. After being expelled with gas and gravitationally recondensing, massive stars may carve intricate structures into their birth cloud using their high energy light and fast stellar winds as sculpting tools. The heat they generate evaporates the murky molecular cloud as well as causing ambient hydrogen gas to disperse and glow red. During disintegration, we humans can enjoy imagining these great clouds as common icons, like we do for water clouds on Earth. Including smaller dust nebulae such as Lynds Dark Nebula 1235 and Van den Bergh 149 & 150, the Shark nebula spans about 15 light years and lies about 650 light years away toward the constellation of the King of Aethiopia (Cepheus).

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Posted: **Wed Jun 14, 2023 12:53 pm**

Who is the goofball that named this the shark nebula?

Posted: **Wed Jun 14, 2023 3:22 pm**

Guest wrote: ↑Wed Jun 14, 2023 12:53 pm Who is the goofball that named this the shark nebula?

One person's goofball, another person's genius.

Anyway. There is a nice galaxy in the APOD, UGC 11861:

I liked the galaxy so much that I started looking for other pictures of it, but to my surprise, very few other images exist! One picture of UGC 11861 has been taken by dcrowson, and published in Astronomy Magazine. But how different it looks!!!

UGC 11861 and bright star 16 Cep.
Credit: dcrowson.

dcrowson wrote:

UGC 11861 (PGC 67671 and others) is a low surface brightness galaxy located approximately 58 million light-years away in Cepheus.

A low surface brightness galaxy, yes, I'd say! Today's APOD shows that UGC 11861 is a nice spiral galaxy that contains star formation, but judging from dcrowson's image, its overall color seems to be light brown from cosmic dust! The stars don't seem to add very much color to this galaxy, because there are relatively few of them.

Here is a picture of the Shark Nebula and UGC 11861 by Jim Thommes:

: The Shark Nebula and UGC 11861 by Jim Thommes. Several of the stars look very blue, but the galaxy (at right) looks beige.

So we have a foreground gas cloud that glows softly blue in places because it contains dust, which reflects the blue color primarily of stars hotter than the Sun. And then there is a background "gas and dark matter structure" that is light brown from dust!

: An old woman sweeping cobwebs from the sky! Yikes!

Well, if the old woman can only reach seventeen times as high as the Moon, then the nebulas of the sky should be safe from her broom! Even though they are dusty, so that they, possibly, need cleaning!

Finally, let me recommend this page where you can see color pictures of all van den Bergh objects! How about this one, vdB 33?

: van den Bergh 33. Credit: Laubing.

Ann

Okay, one more. Am I the only one who thinks that today's APOD looks like a weird sky over a landscape?

Posted: **Wed Jun 14, 2023 7:29 pm**

Ann wrote: ↑Wed Jun 14, 2023 3:22 pm
Guest wrote: ↑Wed Jun 14, 2023 12:53 pm Who is the goofball that named this the shark nebula?
One person's goofball, another person's genius.

Anyway. There is a nice galaxy in the APOD, UGC 11861:

APOD 14 June 2023 detail annotated.png

I liked the galaxy so much that I started looking for other pictures of it, but to my surprise, very few other images exist! One picture of UGC 11861 has been taken by dcrowson, and published in Astronomy Magazine. But how different it looks!!!

UGC 11861 and 16 Cep dcrowson cropped.png
UGC 11861 and bright star 16 Cep.
Credit: dcrowson.

dcrowson wrote:

UGC 11861 (PGC 67671 and others) is a low surface brightness galaxy located approximately 58 million light-years away in Cepheus.

A low surface brightness galaxy, yes, I'd say! Today's APOD shows that UGC 11861 is a nice spiral galaxy that contains star formation, but judging from dcrowson's image, its overall color seems to be light brown from cosmic dust! The stars don't seem to add very much color to this galaxy, because there are relatively few of them.

Here is a picture of the Shark Nebula and UGC 11861 by Jim Thommes:

The Shark Nebula and UGC 11861 by Jim Thommes. Several of the stars look very blue, but the galaxy (at right) looks beige.

So we have a foreground gas cloud that glows softly blue in places because it contains dust, which reflects the blue color primarily of stars hotter than the Sun. And then there is a background "gas and dark matter structure" that is light brown from dust!

An old woman sweeping cobwebs from the sky! Yikes!

Well, if the old woman can only reach seventeen times as high as the Moon, then the nebulas of the sky should be safe from her broom! Even though they are dusty, so that they, possibly, need cleaning!

Finally, let me recommend this page where you can see color pictures of all van den Bergh objects! How about this one, vdB 33?

van den Bergh 33. Credit: Laubing.

Ann

Okay, one more. Am I the only one who thinks that today's APOD looks like a weird sky over a landscape?

APOD 14 June annotated .png

Actually for me, this is one of the times I really felt that this is a really appropriate name for this nebula. It truly looks like a big fish or a shark! And I love sea creatures!

Posted: **Wed Jun 14, 2023 8:09 pm**

At last we have an aptly named nebula. Looks a LOT like a shark indeed in this particular image - open mouth, eye, fins and all!

Posted: **Wed Jun 14, 2023 8:14 pm**

I don't know; but I think it sorta looks like a
Shark!

Posted: **Wed Jun 14, 2023 8:47 pm**

This raises a curious question. Why is the shark Nebula blue here when in the APOD 6 years ago

https://apod.nasa.gov/apod/ap150907.html

the Shark was brown and the PGC 67671 galaxy was also brown?

Posted: **Wed Jun 14, 2023 9:01 pm**

De58te wrote: ↑Wed Jun 14, 2023 8:47 pm This raises a curious question. Why is the shark Nebula blue here when in the APOD 6 years ago

https://apod.nasa.gov/apod/ap150907.html

the Shark was brown and the PGC 67671 galaxy was also brown?

Color processing is partly black magic. I'd wager that the older image is closer to what we might call "true color". Most of the nebula is not well enough lit to be scattering blue. You can see the bits that are as blue reflection nebula regions, but most should probably be the typical brown of interstellar dust when it's just reflecting the light of many stars.

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APOD: The Shark Nebula (2023 Jun 14)

APOD: The Shark Nebula (2023 Jun 14)

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Re: APOD: The Shark Nebula (2023 Jun 14)

Re: APOD: The Shark Nebula (2023 Jun 14)