APOD: A Giant Squid in the Flying Bat (2016 Oct 27)

[APOD Robot]

A Giant Squid in the Flying Bat

Explanation: Very faint but also very large on planet Earth's sky, a giant Squid Nebula cataloged as Ou4, and Sh2-129 also known as the Flying Bat Nebula, are both caught in this cosmic scene toward the royal constellation Cepheus. Composed with almost 17 hours of narrowband image data, the telescopic field of view is 4 degrees or 8 Full Moons across. Discovered in 2011 by French astro-imager Nicolas Outters, the Squid Nebula's alluring bipolar shape is distinguished here by the telltale blue-green emission from doubly ionized oxygen atoms. Though apparently completely surrounded by the reddish hydrogen emission region Sh2-129, the true distance and nature of the Squid Nebula have been difficult to determine. Still, a recent investigation suggests Ou4 really does lie within Sh2-129 some 2,300 light-years away. Consistent with that scenario, Ou4 would represent a spectacular outflow driven by HR8119, a triple system of hot, massive stars seen near the center of the nebula. The truly giant Squid Nebula would physically be nearly 50 light-years across.

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[Ann]

My personal belief, ever since I first saw the Squid Nebula, has always been that it must lie inside the large red Ha nebula Sh2-129. Not only that, but the hot star HR 8119 must be responsible for ionizing both nebulas. I just thought that it was far too much of a coincidence that both nebulas would be centered on HR 8119 and still be at different distances.

The fact that HR 8119 is a multiple star makes it more likely that it might have giant outbursts, or so I believe anyway. Eta Carina anyone? And type Ia supernovas are thought to always originate in binary stars.

Ann

[JohnD]

Bit of a thread diversion,but "the telltale blue-green emission from doubly ionized oxygen atoms" raises a long held Q, about aurorae.
How is it that one element becomes ionised, or doubly ionised, in a mixture of several other gases>

The aurora shows distinct green or red displays, said to be oxygen and nitrogen respectively, when the mixture of gases at that height is the same as at ground level, with no layering, certainly not in the apparently vertical "curtains" that the aurora shows.
In this APOD, a highly discrete area glows with an oxygen discharge - it seems unlikely that a cosmic gas cloud should have a bubble of oxygen in it, conveniently close to a solurce of radiation.
So how is a specific element energised, in the aurora or the Squid?

JOhn

[heehaw]

How is it that one element becomes ionised, or doubly ionised, in a mixture of several other gases>
JOhn

Just different ionization energies! https://en.wikipedia.org/wiki/Ionization_energy

[Chris Peterson]

How is it that one element becomes ionised, or doubly ionised, in a mixture of several other gases>
JOhn

Just different ionization energies! https://en.wikipedia.org/wiki/Ionization_energy

Other things to consider: Just because the light of one species dominates doesn't mean that other isn't also present (this often shows up in the individual channels of narrowband images). And often we're not seeing a homogeneous mixture of gases- different elements can be separated physically by the sequential nature of their ejection and by separating processes after they're ejected.

[JohnD]

Thank you, heehaw!
Ah! Ionisation!

And Chris, I suppose as the elements that were in Primordial Earth were separated, so that mining is worthwhile, so different processes can separate gas elements.
John

[Fred the Cat]

That squid looks like a ghost just in time for Halloween. The Bat is in time for Trick or Treat too though I can't really make it out as one - flying or hanging.

[MarkBour]

A squid should be in water. Is there reason to believe that we are looking at a process that can create water? I mean, at least the elements are there, the O in a larger cloud of H, and then the energy from the star to ionize the parts ...

[Boomer12k]

How does one make out the "flying bat"?? My pareidolia seems to miss it...thanks.

Incredibly nice image...
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