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Posted: **Wed Aug 18, 2021 4:05 am**

Rings Around the Ring Nebula

Explanation: The Ring Nebula (M57), is more complicated than it appears through a small telescope. The easily visible central ring is about one light-year across, but this remarkably deep exposure - a collaborative effort combining data from three different large telescopes - explores the looping filaments of glowing gas extending much farther from the nebula's central star. This composite image includes red light emitted by hydrogen as well as visible and infrared light. The Ring Nebula is an elongated planetary nebula, a type of nebula created when a Sun-like star evolves to throw off its outer atmosphere to become a white dwarf star. The Ring Nebula is about 2,500 light-years away toward the musical constellation Lyra.

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Posted: **Wed Aug 18, 2021 4:36 am**

Like we look down a well.
Which is almost perfectly round and cylinder (with ⌀=1 ly) and which we are looking down almost perfectly along the axis.
At its outskirts the well is widening, like a hole in a doughnut, to a few ly.

Is it a many years old pair of hollow and widening jets followed by new pair of more tightly collimated hollow jets and some blue filling-clogging in the center?
Can we differentiate between one wide part moving our way and the other wide part moving away from us?

Posted: **Wed Aug 18, 2021 11:40 am**

Just beautiful; happy I wasn't on a planet of this ster when the star
gave up it;s life!

It's like a flower that came into bloom! amazing.
So symmetrical!

Posted: **Wed Aug 18, 2021 12:37 pm**

Pretty amazing that the bright central clouds are barely visible in yesterday's picture

Posted: **Wed Aug 18, 2021 1:03 pm**

orin stepanek wrote: ↑Wed Aug 18, 2021 11:40 am
Just beautiful; happy I wasn't on a planet of this ster when the star
gave up it;s life! It's like a flower that came into bloom! amazing.
So symmetrical!

Where have all the graveyards gone?
Long time passing.

Where have all the graveyards gone?
Long time ago.

Where have all the graveyards gone?
They're covered with flowers every one.
- Oh, When will they ever learn?
  Oh, When will they ever learn?

Posted: **Wed Aug 18, 2021 1:14 pm**

Gather ye rosebuds while ye may
Old time is still a-flying
And this same flower that smiles today
Tomorrow will be dying.

Posted: **Wed Aug 18, 2021 1:48 pm**

Click to play embedded YouTube video.

E Fish wrote: ↑Wed Aug 18, 2021 1:14 pm

Gather ye rosebuds while ye may
Old time is still a-flying
And this same flower that smiles today
Tomorrow will be dying.

Posted: **Wed Aug 18, 2021 3:18 pm**

seems to me that the hollow jet moving towards us is narrower and faster than the counter-jet.
It makes sense if on our side there is less interstellar media to slow down the jet and to curve the magnetic field lines of the jet's tube further away from the axis, does it?

Posted: **Wed Aug 18, 2021 4:05 pm**

The "central ring" link is wrong. It is linking to the 8/15/2021 APOD instead of the intended 8/17/2021 APOD.

Posted: **Wed Aug 18, 2021 6:41 pm**

ems57fcva wrote: ↑Wed Aug 18, 2021 4:05 pm The "central ring" link is wrong. It is linking to the 8/15/2021 APOD instead of the intended 8/17/2021 APOD.

Congratulations! You've passed the "click on every link" test. I had been wondering what an APOD about the Perseids had to do with a "ring" - central or otherwise - and was also going to post about the problem, but you beat me to it.

Posted: **Wed Aug 18, 2021 6:45 pm**

So do the concentric rings represent more than one event, a few episodes of the star expelling layers of its shell?

Posted: **Wed Aug 18, 2021 7:02 pm**

Avalon wrote: ↑Wed Aug 18, 2021 6:45 pm So do the concentric rings represent more than one event, a few episodes of the star expelling layers of its shell?

Yes, at least two events are clearly visible.

There may well be more.

Ann

Posted: **Wed Aug 18, 2021 8:28 pm**

https://en.wikipedia.org/wiki/Ring_Nebula wrote:
HaRGB image of the Ring Nebula (M57) showing the faint outer shells. Data from the Liverpool Telescope on La Palma, Islas Canarias.
<<M57 is 2,570 light-years from Earth. Photographs taken over a period of 50 years show the rate of nebula expansion is roughly 1 arcsecond per century, which corresponds to spectroscopic observations as 20–30 km/s. M57 is illuminated by a central white dwarf or planetary nebula nucleus (PNN) of 15.75v visual magnitude.

All the interior parts of this nebula have a blue-green tinge that is caused by the doubly ionized oxygen emission lines at 495.7 and 500.7 nm. These observed so-called "forbidden lines" occur only in conditions of very low density containing a few atoms per cubic centimeter.

In the outer region of the ring, part of the reddish hue is caused by hydrogen emission at 656.3 nm, forming part of the Balmer series of lines. Forbidden lines of ionized nitrogen or N II contributes to the reddishness at 654.8 and 658.3 nm.>>

Posted: **Wed Aug 18, 2021 8:58 pm**

Avalon wrote: ↑Wed Aug 18, 2021 6:45 pm So do the concentric rings represent more than one event, a few episodes of the star expelling layers of its shell?

That is certainly one model of how stars in this mass range eject their outer layers. Likely, and broadly accepted as likely. But not certain.

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