glowing spiral structure

None of the world’s experts know what exactly the strange spiral structure on the left is. Why the spiral glows is a mystery, with a leading hypothesis being illumination by light reflected from nearby stars.

NASA astronomers think it is related to a star in a binary star system entering the planetary nebula phase, when its outer atmosphere is ejected. The huge spiral spans about a third of a light year across and winding four or five complete turns, has a regularity that has never been observed before.

Given the expansion rate of the spiral gas, a new layer must appear about every 800 years, a close match to the time it takes for the two stars to orbit each other. The star system that created it is known as LL Pegasi. The image was taken in near-infrared light by the Hubble Space Telescope.

Image credit: ESA, Hubble, R. Sahai (JPL), NASA