Researchers think complex carbon-rich molecules called polycyclic aromatic hydrocarbons (PAHs) are responsible for the ERE. The odd glow is always associated with dust bathed in ultraviolet light, as well as with a kind of photoluminescence or afterglow. It has been a mystery for more than 30 years. It was first discovered in 1975 right here in the Red Rectangle, and has since been observed elsewhere, even in other galaxies. Physicists are only recently homing in on its composition, and it’s not what they expected.Īstronomers call this nebula’s alien illumination Extended Red Emission, or ERE. Dust fluorescing? The dust in our homes thankfully doesn’t glow, and neither does the celestial variety. But here it’s diluted and dominated by a different shade of orange-red given off by glowing dust. Spectrographs detect glowing hydrogen - the normal hum-drum white-bread emissions of nebulae everywhere. However you see it, the question remains: Why should gem-like symmetry materialize in an enormous gaseous nebula? Or perhaps it’s more like a squared-off bow tie or a woven “God’s eye.” Or maybe it’s a giant X with interconnected ladder-like steps. In a universe of vast swirling curves, where celestial straight lines are almost nonexistent and geometric shapes the stuff of dreams, we stare at a giant rectangle. The first head-twister is immediately obvious. It took years, and better instrumentation, including studies performed by the Hubble Space Telescope, to fully reveal how odd and intriguing is this dusty gas cloud 2,300 light-years away. Things changed in 1973 when a rocket-borne infrared sky survey discovered the ruddy nebula surrounding the binary, soon labeled HD 44179 after the star’s catalog designation. Located in the constellation Monoceros the Unicorn, its central 9th-magnitude binary star was discovered in 1915 by the famous double-star hunter Robert Grant Aitken. Its very light is strange, its composition is food for philosophy, and it remains a hot venue of current research. Size (arcmin): 5×3.The Red Rectangle Nebula doesn’t merely look modern-art cubist bizarre. Location: New Mexico Skies, Mayhill, NM, USA This image was taken at the suggestion of Don Goldman. A large dithering was used in order to try to grab as much detail as possible of the “ladder-like” features. Halpha images did not add any valuable information, just like the Luminance images. Several trials about the right exposure time ended up in taking 200 second RGB images. The capture of this object was not a straight forward process. The image below shows the explanation of the unusual “rectangular looking” features of this nebula. This produces the effect of “ladder rungs” that, being circles seen edge on, creates the illusion of seeing a straight “rung”. The flow of mass is not constant and happens in irregular periods of about a few hundred years. The mechanism for this formation involves the creation of a torus (doughnut-shaped) of gas around the star, that is seen edge on as well as a pair of “wine glass-shaped” cups, along which matter is flowing from the parent star. Actually, being this the precursor stage for a planetary nebula, it is called a “proto-planetary” nebula. This star will end up the same way, but meanwhile, the combined effect of expanding its shells and the presence of the companion star, is forming this weird structure. This is a stage, that the solitary stars undergo by slowly producing a planetary nebula. The binary star system conforming HD 44179 involves a Sun-like star that is running out of its primary fuel and expanding its outer shells enough for the second star (orbiting the primary one every 319 days) to start to gravitationally pull some of its mass. Initially, when this nebula was discovered in 1973, its structure was much of a mystery. At least another such nebula is known, the Red Square Nebula, around the star MWC 922, in the constellation Serpens. The Red Rectangle Nebula is a very peculiar (but not unique) structure around a binary system catalogued as HD 44179 in the constellation Monoceros. Click on the image for a full resolution version
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