APOD: MWC 922: The Red Square Nebula (2016 Jan 31)

[APOD Robot]

MWC 922: The Red Square Nebula

Explanation: What could cause a nebula to appear square? No one is quite sure. The hot star system known as MWC 922, however, appears to be embedded in a nebula with just such a shape. The featured image combines infrared exposures from the Hale Telescope on Mt. Palomar in California, and the Keck-2 Telescope on Mauna Kea in Hawaii. A leading progenitor hypothesis for the square nebula is that the central star or stars somehow expelled cones of gas during a late developmental stage. For MWC 922, these cones happen to incorporate nearly right angles and be visible from the sides. Supporting evidence for the cone hypothesis includes radial spokes in the image that might run along the cone walls. Researchers speculate that the cones viewed from another angle would appear similar to the gigantic rings of supernova 1987A, possibly indicating that a star in MWC 922 might one day itself explode in a similar supernova.

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[geckzilla]

Almost fooled myself into thinking there were two more linear, symmetrical structures emanating from the star. Just diffraction spikes.

[Chris Peterson]

Almost fooled myself into thinking there were two more linear, symmetrical structures emanating from the star. Just diffraction spikes.

I see the characteristic hexagonal Keck diffraction spikes on some of the outlying stars, but I don't see any obvious diffraction spikes around the central star of the nebula. What are you seeing?

[geckzilla]

Almost fooled myself into thinking there were two more linear, symmetrical structures emanating from the star. Just diffraction spikes.

I see the characteristic hexagonal Keck diffraction spikes on some of the outlying stars, but I don't see any obvious diffraction spikes around the central star of the nebula. What are you seeing?

Presumably the last pair is also there but lined up with one of the lines forming the cross of the Red Square.

square_spikes.jpg

[Chris Peterson]

Almost fooled myself into thinking there were two more linear, symmetrical structures emanating from the star. Just diffraction spikes.

I see the characteristic hexagonal Keck diffraction spikes on some of the outlying stars, but I don't see any obvious diffraction spikes around the central star of the nebula. What are you seeing?

Presumably the last pair is also there but lined up with one of the lines forming the cross of the Red Square.

square_spikes.jpg

Ah, nice catch. I agree (and also that there is another pair lost in the actual structure).

[Boomer12k]

Arrrgh, matey...X marks the spot....

:---[===] *

[mollwollfumble]

> A leading progenitor hypothesis for the square nebula ...

The red square nebula is not at all well understood. The reason for this is the physical and spectroscopic similarity to the red rectangle nebula, which is not understood at all. The spectrum of light arriving at Earth absorbed by the interstellar medium contains absorption lines from "diffuse interstellar bands". Continual research into the spectrum of diffuse interstellar bands has not reached anything like a consensus, with umpteen possibilities including modified buckyballs, unusual anthracenes and metal-organic dust grains. Searches for similar spectra elsewhere found only one match - the red rectangle. That makes the red rectangle unique, definitely not similar to other planetary nebulae. The red square also shares spectral details with the red rectangle, which makes it the second closest match to the "diffuse interstellar bands".

As a result, the red square should not be considered to be closely related to other planetary nebulae, it's too weird.

[Dennis Moore]

I've seen a square cooling tower that had a water sprayer that emitted a square pattern. I'd start there.

[JohnD]

Could this be a 'visible pulsar"?

As a pulsar is thought to be a stellar remnant with a fast spin and precession, so that its jets rotate like a lighthouse beam, what if those jets were not only radio emissions, but gas ionised to glow or illuminated by the star? The jets would form a cone on either side of the star, and if the angle of precession were 45 degrees would appear as a square when seen in side view.
The same argument would serve to explain supernova 1987A, if the jets there were intermittent. And must have been in place before the supernova, if that occurred in 1987, and the Hubble picture from 1994 showed rings so far from an object 150MLY away.

John

[lisawoody]

Why isn't light distortion due to coming from behind a black hole considered as part of the symmetry of what we are seeing?

[Chris Peterson]

Why isn't light distortion due to coming from behind a black hole considered as part of the symmetry of what we are seeing?

A black hole is too small to appreciably distort light, except when seen from very close. At the scale of this image, a black hole would be smaller than a pixel. When we see gravitational lensing, it is caused by the combined mass of entire galaxies or galaxy clusters, consisting mostly of dark matter, which bend much, much more distant light. This is a nearby nebula.

[JohnD]

Somehow, I got to this object, ppreviously featired on APOD: http://apod.nasa.gov/apod/ap020618.html and http://apod.nasa.gov/apod/ap000416.html
A cylinder of glowing gas at Nebula IC 4066, with maybe an originator star visible at its centre.

Could the mechanism I susggest above make this too, if the star with jets were in orbit around another object? This video https://www.youtube.com/watch?v=jT_T0xxRqKQ demonstrates how this would sculpt a cylinder around the two stars, as the jets describe smaller circles around them. I see that the video suggest that with time the orbiting pulsar would move towards its partner, and tilt its axis of rotation, which would tend to make the cylinder radius smaller at one end and larger at the other. I've no reply to that as a criticism of the theory, ecedpt to suggest that the system hasn't been in existence long enough?

John

[ta152h0]

and I thought this was a better image of Proxima Centauri. A faint attempt at guessing prior to reading the APOD

[Jim S]

This reminds me of the shape that Tom Noddy develops when he blows a "square bubble."

See https://www.youtube.com/watch?v=np4n5PPIa38 at about the 4 minute mark.

///Jim\\\