Starship Asterisk*

Posted: **Tue May 18, 2021 4:09 am**

Jets from the Necklace Nebula

Explanation: What celestial body wears the Necklace Nebula? First, analyses indicate that the Necklace is a planetary nebula, a gas cloud emitted by a star toward the end of its life. Also, what appears to be diamonds in the Necklace are actually bright knots of glowing gas. In the center of the Necklace Nebula are likely two stars orbiting so close together that they share a common atmosphere and appear as one in the featured image by the Hubble Space Telescope. The red-glowing gas clouds on the upper left and lower right are the results of jets from the center. Exactly when and how the bright jets formed remains a topic of research. The Necklace Nebula is only about 5,000 years old, spans about 5 light years, and can best be found with a large telescope toward the direction of the constellation of the Arrow (Sagitta).

<< Previous APOD

This Day in APOD

Next APOD >>

Posted: **Tue May 18, 2021 9:20 am**

Delightful image!

Posted: **Tue May 18, 2021 9:21 am**

I'd not heard of the Necklace Nebula before - what a stunning image!

Posted: **Tue May 18, 2021 11:46 am**

One of a kind Necklace; beautiful planetary nebula!

Aww; you knew I would! Two stars orbiting so close together!

Posted: **Tue May 18, 2021 12:24 pm**

Image interesting ( APOD )

Posted: **Tue May 18, 2021 12:55 pm**

Puddock wrote: ↑Tue May 18, 2021 9:21 am
I'd not heard of the Necklace Nebula before - what a stunning image!

https://en.wikipedia.org/wiki/Necklace_Nebula wrote:
<<The Necklace Nebula (PN G054.2-03.4) is a 2.0 light-year-wide planetary nebula located about 15,000 light-years away in the northern constellation Sagitta. It was discovered in 2005 from the Isaac Newton Telescope Photometric H-alpha Survey (IPHAS), a ground-based H-alpha planetary nebula study of the North Galactic Plane.

The Necklace Nebula is the exploded aftermath of a giant star that came too close to its Sun-like binary companion. The two stars that produced the Necklace Nebula are in a relatively small orbit about each other. They have a period of 1.2 days and a separation on the order of 5 times the radius of the Sun.

About 10,000 years ago one of the aging stars ballooned to the point where it engulfed its companion star. The smaller star continued orbiting inside its larger companion, increasing the giant's rotation rate. The bloated companion star spun so fast that a large part of its gaseous envelope expanded into space. Due to centrifugal force, most of the gas escaped along the star's equator, producing a ring. The embedded bright knots are dense gas clumps in the ring.>>

Posted: **Tue May 18, 2021 2:00 pm**

Location in Sagita?

Posted: **Tue May 18, 2021 3:11 pm**

Looks like an asteroid belt and long shadows cast by the asteroid belt objects

: Click to view full size image

: Click to view full size image

Posted: **Tue May 18, 2021 3:56 pm**

There is an object in the central star of the necklace that is at the 2 o:clock position just inside the outer edge of the star.
All of the perimeter flares of the necklace are stars that look like their outer edges are being swept away by the central stars emissions.

Posted: **Tue May 18, 2021 4:16 pm**

calahnst wrote: ↑Tue May 18, 2021 3:56 pm There is an object in the central star of the necklace that is at the 2 o:clock position just inside the outer edge of the star.

It shares its alignment with the diffraction spikes seen on the bright stars. I think there's a good chance that's all it is.

Posted: **Tue May 18, 2021 4:57 pm**

orin stepanek wrote: ↑Tue May 18, 2021 11:46 am Necklace_Hubble_960.jpg
One of a kind Necklace; beautiful planetary nebula!

Click to view full size image

Aww; you knew I would! Two stars orbiting so close together!

Orin, I knew you would! Find and post this lovely kitty picture for me!

Ann

Posted: **Tue May 18, 2021 5:04 pm**

neufer wrote: ↑Tue May 18, 2021 12:55 pm About 10,000 years ago one of the aging stars ballooned to the point where it engulfed its companion star. The smaller star continued orbiting inside its larger companion, increasing the giant's rotation rate. The bloated companion star spun so fast that a large part of its gaseous envelope expanded into space. Due to centrifugal force, most of the gas escaped along the star's equator, producing a ring. The embedded bright knots are dense gas clumps in the ring.>>

[/quote]

Sadly not a word about harsh shadows radially cast by the "necklace diamonds" equator-gone-ring gas clumps

Posted: **Tue May 18, 2021 5:11 pm**

VictorBorun wrote: ↑Tue May 18, 2021 5:04 pm
neufer wrote: ↑Tue May 18, 2021 12:55 pm About 10,000 years ago one of the aging stars ballooned to the point where it engulfed its companion star. The smaller star continued orbiting inside its larger companion, increasing the giant's rotation rate. The bloated companion star spun so fast that a large part of its gaseous envelope expanded into space. Due to centrifugal force, most of the gas escaped along the star's equator, producing a ring. The embedded bright knots are dense gas clumps in the ring.>>

Sadly not a word about harsh shadows radially cast by the "necklace diamonds" equator-gone-ring gas clumps
[/quote]

I don't see anything I'd describe unambiguously as shadows, and certainly not "harsh" ones.

Posted: **Tue May 18, 2021 5:36 pm**

Chris Peterson wrote: ↑Tue May 18, 2021 5:11 pm I don't see anything I'd describe unambiguously as shadows, and certainly not "harsh" ones.

They must be radial wind shadows, glowing rather than glooming

: Click to view full size image

Posted: **Tue May 18, 2021 5:43 pm**

VictorBorun wrote: ↑Tue May 18, 2021 5:36 pm
Chris Peterson wrote: ↑Tue May 18, 2021 5:11 pm I don't see anything I'd describe unambiguously as shadows, and certainly not "harsh" ones.
They must be radial wind shadows, glowing rather than glooming
Click to view full size image

I see a fairly typical, radially dispersing planetary nebula with some knots of gas that are being blow outwards. Nothing I'd describe as "shadows".

Posted: **Tue May 18, 2021 6:14 pm**

Trying to understand the source of a planetary nebula's jet's energy, I found this other source.

A 3D version would be cool as in this investigation of another energy.

It got me wondering, while dark energy leads to expansion, if dark matter has an affinity for itself?

Posted: **Tue May 18, 2021 6:17 pm**

Fred the Cat wrote: ↑Tue May 18, 2021 6:14 pm Trying to understand the source of a planetary nebula's jet's energy, I found this other source.

A 3D version would be cool as in this investigation of another energy. 8-) It got me wondering, while dark energy leads to expansion, if dark matter has an affinity for itself? :?

The evidence suggests that dark matter has an "affinity for itself" in precisely the same way that all matter that has the property of mass does.

Posted: **Tue May 18, 2021 8:21 pm**

SubhanaLloh, very beautiful.
I believe that the featured image is not artificially colored but color enhanced.
A star millions of light year away orbiting another in just a day, means that the speed is extremely high. If only we know the estimated distance between the two stars....

Posted: **Tue May 18, 2021 8:25 pm**

neufer wrote: ↑Tue May 18, 2021 12:55 pm
Puddock wrote: ↑Tue May 18, 2021 9:21 am
I'd not heard of the Necklace Nebula before - what a stunning image!
https://en.wikipedia.org/wiki/Necklace_Nebula wrote:
<<The Necklace Nebula (PN G054.2-03.4) is a 2.0 light-year-wide planetary nebula located about 15,000 light-years away in the northern constellation Sagitta. It was discovered in 2005 from the Isaac Newton Telescope Photometric H-alpha Survey (IPHAS), a ground-based H-alpha planetary nebula study of the North Galactic Plane.

The Necklace Nebula is the exploded aftermath of a giant star that came too close to its Sun-like binary companion. The two stars that produced the Necklace Nebula are in a relatively small orbit about each other. They have a period of 1.2 days and a separation on the order of 5 times the radius of the Sun.

About 10,000 years ago one of the aging stars ballooned to the point where it engulfed its companion star. The smaller star continued orbiting inside its larger companion, increasing the giant's rotation rate. The bloated companion star spun so fast that a large part of its gaseous envelope expanded into space. Due to centrifugal force, most of the gas escaped along the star's equator, producing a ring. The embedded bright knots are dense gas clumps in the ring.>>

I'm frankly surprised they can deduce all that, especially that "The smaller star continued orbiting inside its larger companion, increasing the giant's rotation rate." How could they possible know that? Or is this just a case of this is the ONLY way this ever happens? That is, that when the one star expands at the end of it's life, it will ALWAYS envelop its binary companion, and it will ALWAYS increase the bloated star's rotation rate? Seems unlikely to always be true to me though.

Posted: **Tue May 18, 2021 8:57 pm**

johnnydeep wrote: ↑Tue May 18, 2021 8:25 pm
neufer wrote: ↑Tue May 18, 2021 12:55 pm
Puddock wrote: ↑Tue May 18, 2021 9:21 am
I'd not heard of the Necklace Nebula before - what a stunning image!
https://en.wikipedia.org/wiki/Necklace_Nebula wrote:
<<The Necklace Nebula (PN G054.2-03.4) is a 2.0 light-year-wide planetary nebula located about 15,000 light-years away in the northern constellation Sagitta. It was discovered in 2005 from the Isaac Newton Telescope Photometric H-alpha Survey (IPHAS), a ground-based H-alpha planetary nebula study of the North Galactic Plane.

The Necklace Nebula is the exploded aftermath of a giant star that came too close to its Sun-like binary companion. The two stars that produced the Necklace Nebula are in a relatively small orbit about each other. They have a period of 1.2 days and a separation on the order of 5 times the radius of the Sun.

About 10,000 years ago one of the aging stars ballooned to the point where it engulfed its companion star. The smaller star continued orbiting inside its larger companion, increasing the giant's rotation rate. The bloated companion star spun so fast that a large part of its gaseous envelope expanded into space. Due to centrifugal force, most of the gas escaped along the star's equator, producing a ring. The embedded bright knots are dense gas clumps in the ring.>>

I'm frankly surprised they can deduce all that, especially that "The smaller star continued orbiting inside its larger companion, increasing the giant's rotation rate." How could they possible know that? Or is this just a case of this is the ONLY way this ever happens? That is, that when the one star expands at the end of it's life, it will ALWAYS envelop its binary companion, and it will ALWAYS increase the bloated star's rotation rate? Seems unlikely to always be true to me though.

That the system is binary is determined by looking at the periodicity of the light curve, and also at the spectrum, which is consistent with a pair of blackbodies with different temperatures. The conclusion that the stars shared a common envelope before the nebula was ejected (as a circular ring) comes from the very short orbital period (just over a day) and the equatorial ejection pattern.

Posted: **Tue May 18, 2021 9:27 pm**

Ann wrote: ↑Tue May 18, 2021 4:57 pm
orin stepanek wrote: ↑Tue May 18, 2021 11:46 am Necklace_Hubble_960.jpg
One of a kind Necklace; beautiful planetary nebula!

Click to view full size image

Aww; you knew I would! Two stars orbiting so close together!

Orin, I knew you would! Find and post this lovely kitty picture for me!

Ann

Anytime!

Posted: **Wed May 19, 2021 3:37 am**

Deathfleer wrote: ↑Tue May 18, 2021 8:21 pm I believe that the featured image is not artificially colored but color enhanced.

the order of RGB colors correctly maps the order of wavelenghts of the narrow-band filters:
B 438 nm
OIII 502 nm
V 555 nm
I 814 nm
H-alpha 656 nm
NII 658 nm

Posted: **Wed May 19, 2021 12:55 pm**

Fred the Cat wrote: ↑Tue May 18, 2021 6:14 pm Trying to understand the source of a planetary nebula's jet's energy, I found this other source.

This animation presents two faraway red smears in the axis of a pair of invisible jets as arcs of cooling spiral jets generated with precession.
Sadly the phase of red glowing does not last as long as one period of precession so we can't very well see spiral coils.

Posted: **Wed May 19, 2021 1:20 pm**

VictorBorun wrote: ↑Wed May 19, 2021 3:37 am
Deathfleer wrote: ↑Tue May 18, 2021 8:21 pm I believe that the featured image is not artificially colored but color enhanced.
the order of RGB colors correctly maps the order of wavelenghts of the narrow-band filters:
B 438 nm
OIII 502 nm
V 555 nm
I 814 nm
H-alpha 656 nm
NII 658 nm

Note that the B, V, and I filters are all broadband. An image made with just these three would approximate "true" colors, with some distortion due to the red channel being pushed to longer wavelengths than we can see, and having poor overlap with the green channel. The addition of the narrowband filters adds more color distortion, although probably not too severe since, as you point out, these narrow bands are mapped into the output color channels where we would expect to find them.

Technically, the use of the IR filter means that this image is described as "false-color". But probably not so far from "true color" to make Ann too unhappy!

Posted: **Wed May 19, 2021 2:16 pm**

Chris Peterson wrote: ↑Wed May 19, 2021 1:20 pm
VictorBorun wrote: ↑Wed May 19, 2021 3:37 am
Deathfleer wrote: ↑Tue May 18, 2021 8:21 pm I believe that the featured image is not artificially colored but color enhanced.
the order of RGB colors correctly maps the order of wavelenghts of the narrow-band filters:
B 438 nm
OIII 502 nm
V 555 nm
I 814 nm
H-alpha 656 nm
NII 658 nm
Note that the B, V, and I filters are all broadband. An image made with just these three would approximate "true" colors, with some distortion due to the red channel being pushed to longer wavelengths than we can see, and having poor overlap with the green channel. The addition of the narrowband filters adds more color distortion, although probably not too severe since, as you point out, these narrow bands are mapped into the output color channels where we would expect to find them.

Technically, the use of the IR filter means that this image is described as "false-color". But probably not so far from "true color" to make Ann too unhappy!

Hmm. I haven't commented on this APOD, except to express my delight over the cute kitties that were hidden in one of the links, and that Orin "unearthed" for me!

The reason why I haven't commented on the Necklace Nebula is precisely because I don't trust the colors. Yes, I can imagine that the green stuff in the center of the nebula is green OIII, and the pink "flares" emerging from the "necklace" itself might be Hα, possibly mixed with something to make it look diluted.

But what is all the blue stuff? And why is it blue? The way I understand it, planetary nebulas are not typically blue at all. And I hate it when non-blue objects are shown as blue, because it makes me so disappointed to find out that they are really non-blue. For example, I once read about a certain kind of white dwarfs (helium-rich white dwarfs, I think), that turned blue when they grew colder. I thought that was really neat.

Yes, but then I read about what really happened to these white dwarfs! At a certain temperature, when the white dwarfs had grown so cold that they emitted most of their light in the infrared part of the spectrum, their emission shifted from invisible infrared to visible red! So these stars grew bluer by growing redder!!!

(Yes, I know, I know - the wavelengths of visible red light are shorter than the wavelengths of infrared light. So instead of emitting photons of increasingly large wavelengths, these cooling helium-rich dwarfs suddenly "jumped backwards" and emitted light of a shorter wavelength, namely red! Therefore these optically redder white dwarfs could be described as growing bluer! I understand the reasoning, but I hated it!)

So, in short, Chris, does the Necklace Nebula really emit a lot of truly blue light, or should I ignore this nebula the way I ignore those "blue but red" helium white dwarfs?

Ann

Starship Asterisk*

APOD: Jets from the Necklace Nebula (2021 May 18)

APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)

Re: APOD: Jets from the Necklace Nebula (2021 May 18)