Is the Red Square Nebula MWC 922 Really a Hypercube?

[starkind]

http://apod.nasa.gov/apod/ap070416.html
http://apod.nasa.gov/apod/ap070416.html

Found this yesterday on dailygalaxy.com. explanation given is that this is ejecta of two cones from a central star, seen edgewise. I am not convinced by that explanation for several reasons. My first thought was that this looks remarkably like a hypercube or tesseract. I would be interested in hearing what other members of this forum think.

http://apod.nasa.gov/apod/ap070416.html
http://apod.nasa.gov/apod/ap070416.html

 

[starkind]

further web search, there is a similar object, The Red Rectangle nebula, HD 44179, very close, I think, to the directly opposite side of the sky. Simbad shows HD 44179 at right ascension 18:21:15.94 declination -10:39, and MWC 922 at right ascension 06:20.0 declination -13:01:27.1

 

[Drakkith]

The edge on view sounds like a logical explanation to me.

 

[starkind]

You have to look at the pictures. If this is two ejecta cones, there are some unanswered questions. Notice that the ejecta cones are spreading out at an internal angle of 90 degrees. I have seen no other ejecta spread like that. What kind of ejection can result in such a wide spread? Also, notice that the end of the cone is flat...so, either the cone is hollow (just try to explain that one) or else the outer edges of the cone are moving faster than the central material. If this really is an ejecta cone, the ends should be curved.

 

[DaveC426913]

Well, I note that, while most articles do not mention it, the central system seems to be a close binary.
http://en.wikipedia.org/wiki/Red_Rectangle_Nebula#Characteristics
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002A&A...393..867M

That could explain why this looks different from most other nebulae.

The bright component of the spectroscopic binary HD 44179 is a post-AGB star with mass M\star ~ 0.57 Msun, luminosity L\star ~ 6000 Lsun, and effective temperature T\star ~ 7750 K. Based on the orbital elements of the binary, we identify its invisible component with a helium white dwarf with MWD ~ 0.35 Msun, LWD ~ 100 Lsun, and TWD ~ 6 x 104 K. The hot white dwarf ionizes the low-density bipolar outflow cavities inside the dense torus, producing a small H II region observed at radio wavelengths. We propose an evolutionary scenario for the formation of the Red Rectangle nebula, in which the binary initially had 2.3 and 1.9 Msun components at a separation of ~ 130 Rsun. The nebula was formed in the ejection of a common envelope after Roche lobe overflow by the present post-AGB star.

 

[starkind]

yes, that is an excellent article, and thanks for the lead. I was interested in the torus explanation, which seems to me to attempt to answer the flat-ended cone question. However, if the structure were a torus on edge, would not the evacuated cones sides appear curved?

 

[DaveC426913]

Your idea that the outer edges must be curved assumes that the inner volume between the spikes must be filled .i.e. a volumetric cone. If the cone instead is empty, then there is no surface to be curved; we are seeing simply the surface of a hollow cone.

An empty cone would occur formed if the structure is formed by two opposite jets, off the centre of rotation, sweeping out a circle.