Ouroboros from A. Eleazar, Donum Dei, Erfurt, 1735— in Alexander Roob, Alchemy & Mysticism, Taschen, Köln, 1997, p. 403. Original B&W drawing colored with yellow-cyan radial glow in Photoshop 7.0

Ouroboros: This symbol appears principally among the Gnostics and is depicted as a dragon, snake or serpent biting its own tail. It is symbolic of time and of the continuity of life. In some versions of the Ouroboros, the body is half light & half dark, alluding to the successive counterbalancing of opposing principles in the Chinese Yang-Yin symbol. Evola says that it represents the dissolution of the body, or the universal serpent which "passes through all things." The ouroboros biting its own tail is symbolic of self-fecundation, or the primitive idea of a self-sufficient Nature— a Nature, that is, its own beginning. There is a Venetian manuscript on alchemy which depicts the Ouroboros with its body half-black (symbolizing earth & night) and half-white (denoting heaven & light). — J. E. Cirlot, A Dictionary of Symbols (1962), p. 235

Ouroboros: Depicted as a serpent or dragon biting its own tail. "My end is my beginning." It symbolizes the undifferentiated; the Totality; primordial unity; self-sufficiency. It begets, weds, impregnates, and slays itself. It is the cycle of disintegration and reintegration, power that eternally consumes and renews itself; the eternal cycle; cyclic time; spatial infinity; truth and cognition in one; the united primordial parents; the Androgyne; the primeval waters; darkness before creation; the restriction of the universe in the chaos of the waters before the coming of light; the potential before actualization. In funerary art, Ouroboros represents immortality, eternity and wisdom. In Orphic cosmology it encircles the Cosmic Egg. The Alpha and Omega are often depicted with the Ouroboros. Alchemy: The latent power of nature; unformed materia; the opus circulare of chemical substances in the hermetic vessel. Buddhist: Wheel of samsara. Egyptian: The circle of the universe; the path of the sun god. Greek: "All is one". "The All was from the beginning like an egg, with the serpent as the tight band or circle round it" (Epicurus). Hindu: Wheel of samsara. As latent energy Ouroboros shares the symbolism of kundalini. Sumero-Semitic: The All One. — J. C. Cooper, Encyclopaedia of Traditional Symbols (1978), pp. 123-124

More Sources on Ouroboros:
What is the Ouroboros?
Ouroboros in Alchemy
Ouroboros Around the World
Ouroboros— "the tail-devourer"
The Androgyne: Serpent Ouroboros
Spira Solaris and the Universal Ouroboros
The Eureka Phenomenon: Kekule's Dream

The NASA Hubble Space Telescope photo of V838 Monocerotis (above) was breathtaking to behold in the New York Times (March 9, 2004). This photo reminded me of the Ouroboros— the serpent or dragon swallowing its own tail. I've scanned a drawing of the Ouroboros from an alchemical text (right) so these two images may be compared and studied side by side. In Coptic, Ouro means king, and in Hebrew ob means a snake. My first encounter with the Ouroboros was reading about Kekule's discovery of benzene after he had dreamt of a snake biting its own tail. Here are two references on V838 Moncerotis (below) and two sources on Ouroboros from my library (right) as well as web links.

The Variable star V838 Monocerotis lies near the edge of our Milky Way Galaxy, about 20,000 light-years from the Sun. Still, ever since a sudden outburst was detected in January 2002, this enigmatic star has taken the centre of an astronomical stage while researchers try to understand where it fits into the picture of stellar evolution. As light from the stellar flash echoes across pre-existing dust shells around V838 Mon, its appearance changes dramatically. Revealed in a sharp snapshot recorded in February by the Hubble's Advanced Camera for Surveys, this portion of the dust shell is about six light-years in diameter. But because light reflected from the dust follows only a slightly indirect path compared to the direct line-of-sight to the star, the light echoes visible now are only lagging about two years behind the outburst itself. Astronomers expect the expanding echoes to continue to light up the dusty environs of V838 Mon for at least the rest of the current decade. (Astronomy Picture of the Day)

Images courtesy of:   http://www.alchemylab.com/ouroboros.htm