Square Nebula

[Sociotard]

Yes, people see things in nebulae just as they do in clouds, and it doesn't mean a thing. Still, a square shaped nebula? That's odd.

[Silverhawk]

Re: Square Nebula

 

Whether it is just how you look at it or some fancy scientific theory. It really does the diversity that exists across the cosmos.

 

[Merovign]

Re: Square Nebula

 

Since we're talking Sci-fi a lot here, what could that be, in a sci-fi world?

 

A beacon? Navigational marker? Maybe it's a magnetic lens and we're seeing it slightly off-angle, like it's aimed as a trade gate at a system near us?

 

Maybe it's a distress call, some massive machine-mind stellar engineering vessel is trapped near there and can't move, so they've modified the nebula to signal for help?

 

Maybe it's art?

[Sociotard]

Re: Square Nebula

 

It's a remenant from very early in the universe, when God was working with a low-quality machine and everything came out really pixelated.

[McCoy]

Re: Square Nebula

 

Gravity lensing was my first thought too. Be interesting to see if it looks the same in ten years or so.

 

Alternately, this could actually be an hourglass nebula who's long axis is exactly ninty degrees from us.

 

But whatever it is, it looks cool!

[austenandrews]

Re: Square Nebula

 

It's Mothra!

[Cancer]

Re: Square Nebula

 

There's a lot of evidence accumulated that planetary nebulae (the result of non-violent stellar death, the red giant --> white dwarf transition) are generally closer to cylindrically symmetric rather than spherically symmetric. You can do this if most of the "action" in the nebular ejection is coming out of the rotational poles of the forming white dwarf in "jets". Those "jets" may have a rather large opening angle, with the faster the rotation the narrower the "jet". Most of the emission of light (that is, the bright parts) happens at the edges of the "jet", where expelled material is colliding with more or less stationary material in the surrounding interstellar gas. More complicated features can be modeled in the same way, with multiple episodes of gas ejection, not always with the same expulsion rate (that is, solar masses per year) or expulsion velocity.

 

If that picture is correct, then an apparently square thing like this can result from something that (1) is seen from dead on its equatorial plane and (2) has a 45-degree opening angle. If seen from "above", that is, looking down the axis, the same object would look like a ring.

 

This idea is versatile enough to account for just about any nebula that looks symmetric. Versatility is nice, but it makes it harder to find features that can test the idea. The Astronomy Picture of the Day site (linked in the leadoff post in the thread) has lots of nice planetary nebulae images, some of which were generated with the help of one of the posters on these boards (not me).

 

(There are polar jets also seen in both black hole systems, like quasars, and in forming stars (the FU Ori stars). The idea there is that the thing doing the expelling is embedded in a disk whose thickness is rather greater than the size of the expeller. Whether or not the thing expelling material is doing it with spherical symmetry or not, the material escapes the disk first at the thinnest part of the disk, i.e., along the poles. The jets are seen only after they've escaped the disk. With young stars, the jets slowly widen as the accretion disk of the forming star is cleared away; with black holes, the disk is always far larger than the black hole itself so the jet is always tightly collimated.)

[Jaxom]

Re: Square Nebula

 

The central star is a Be star... (I know Cancer is familiar with them, but that's a B star with hydrogen emission lines for those not familiar...) The image is land-based IR composites. That would suggest a lower temperature than I would expect in most B systems. Without optical images, it is hard to tell whether or not this thing is still covered in its accretion disk (which might explain the temperatures in the IR)...

 

My specialty was (10 years gone now) planetary nebulae and they're the ones that are good for all the symmetrical tricks... B stars are not candidates for planetaries though because they are too massive... Unless something wonky happens, this thing is a supernova in the end (too much mass to support with electron or even neutron pressure as a cooling dwarf). That combined with the short life expectancies of B stars would lead me at least to think that this is the remnant of an accretion disk that is being burned off. If that's the case, you'd have to appeal to edge-on and opening angle, as Cancer suggests.

 

I'm seeing some people claim that this is bipolar ejection, but without spectroscopy results you couldn't claim that with any certainty. It's just as likely that this is gas in place being illuminated by the star... I say that based on my own personal bias of course (some of the most interesting planetaries were the ones with clumps of dense material moving at the the wrong velocity for the rest of the nebula)... And of course, if this thing really is edge-on as is suggested, spectroscopy can't give you any information about velocity of possible ejecta anyway.

 

Regardless, a cool image and one which implies all sorts of interesting dynamics which is why I got sucked into nebulae when I was a grad student. (Arguably, spectroscopy can give you a picture of an equally interesting set of Dynamics which Cancer could probably expound upon at length but I never found atmospheric dynamics as interesting as the massive gas flow dynamics of nebulae.)

[Vestnik]

Re: Square Nebula

 

It's A Giant Space Gelatinous Cube!

[NuSoardGraphite]

Re: Square Nebula

 

perhaps an alien race from another galaxy has built a stargate out of the remants of the original star, utilizing the nebulae gas as fuel for inter-galactic teleportation of its entire war-machine.

Its the gravitational fluctuations that occur during transport that has caused the nebulae to form that shape over time...

[Narratio]

Re: Square Nebula

 

Hey, who smeared strawberry jam on the the end of the telescope? I spent days polishing that!