Red Square Nebula

Not to be confused with Red Rectangle Nebula.

Red Square Nebula

Reflection nebula
Protoplanetary nebula
Observation data: J2000 epoch
Subtype	bipolar nebula
Right ascension	18h 21m 16.060s
Declination	−13° 01′ 25.69″
Distance	5000 ly   (1500 pc)
Constellation	Serpens
Designations	MWC 922

The Red Square Nebula is a celestial object located in the area of the sky occupied by star MWC 922 in the constellation Serpens. The first images of this bipolar nebula, taken using the Mt. Palomar Hale telescope in California, were released in April 2007. It is notable for its square shape, which according to Sydney University astrophysicist Peter Tuthill, makes it one of the most symmetrical celestial objects ever discovered.

The explanation proposed by Tuthill and his collaborator James Lloyd of Cornell University claims that the square shape arises from two cone shapes placed tip-to-tip, as seen from the side. This also explains the "double-ring" structure seen in SN 1987A.

There is no clear explanation of how the central star could produce the nebula's shape:

Towards the end of their lives, many low-mass stars, like the Sun, slough off their outer layers to produce striking 'planetary' nebulae. But the hot star at the heart of the Red Square nebula, called MWC 922, appears to be relatively massive, suggesting another process formed its signature shape. "How did all this beautiful, crisp structure form?" asks Peter Tuthill of the University of Sydney in Australia. "This is the million dollar question."

One possible explanation is that these two outer faint radial spokes are shadows cast by periodic ripples or waves on the surface of an inner disk close to the central star.

External links

• 
• APOD – MWC 922: The Red Square Nebula (2007-04-16)
• APOD – MWC 922: The Red Square Nebula (2011-03-23)