Lee Smolin:

"I've learned enough astronomy to discover something that's completely changed my view of cosmology. This is that the idea that there are principles of self-organization acting on astronomical scales seems really to be true. During the last ten years or so, people who study galaxies have discovered evidence that feed-back effects and mechanisms of self-organization are indeed happening at the level of the galaxies: they are, in fact, essential for galaxies to form stars. They're also necessary to the existence of spiral galaxies. The idea that a galaxy is a self-organized system - more an ecology than a nonliving clump of stars and gas - has become common among astronomers and physicists who study galaxies. Thus, it seems to me quite likely that the concept of self-organization and complexity will more and more play a role in astronomy and cosmology.( . . . )
Lee Smolin, Professor of physics at the Center for Gravitational Physics and Geometry at Pennsylvania State University,
quoted in"THE THIRD CULTURE" by John Brockman
Look for Professor Smolin's forthcoming book, The Life of the Cosmos

"It was only in the 1980's that the idea that our entire planet could be regarded as a single living stystem, Gaia, began to be taken at all seriously, and the Gaia hypothesis is itself still the subject of intense debate. We have not yet really grasped the notion of a single planet as a living system, so it is small wonder that it needs a large leap of the imagination to regard the entire Milky Way Galaxy as a living system. And yet, the concept of Gaia, and Jim Lovelock's insight into the nature of life itself, provide just the springboard needed to make that leap. ( . . . )

"Lovelock realized that the key feature of life on Earth is that the entire ecosystem of the planet is far from chemical equilibrium, and stays far from equilibrium. Even from a distance, a visitor from outer space could analyse the composition of the Earth's atmosphere, using spectroscopy, and infer that life was at work, creating and maintaining these non-equilibrium conditions. But a galaxy like the Milky Way is also in a far from equilibrium state, and is being maintained in that state by processes going on within it! The very criterion that led Lovelock to the insight that the entire Earth could be regarded as a living system applies to the Milky Way itself. ( . . . )

"If you had a lifespan of a few billion years, so that you could sit and watch galaxies rotate, and if you had a vantage point in the far depths of space, high above the Milky Way, looking down on its spiral patten, you would see individual stars moving through the spiral pattern. Following their orbits in obedience to the simple laws of physics. But the pattern itself, flying in the face of those simple laws, would not be disrupted as a result. Instead it would persist, refusing to be destroyed by the movement of the stars. It would be as obvious to you that something odd was going on as it would be to an alien spectroscopist that there is something odd about the atmosphere of the Earth. And as you watched the spiral arms grow, and move around the Galaxy seeemingly independently of the differential rotation of the stars, it would be obvious that you were watching a living system. ( . . . )

"There seems to be a kind of ecology in the physics of spiral galaxies by means of which the structures responsible for star formation-the spiral arms and the associated clouds of dust and gas - are maintained for time scales much longer than the relevant dynamical time scales...These must involve self-organizing cycles of materials and energy of the kind that one sees in diverse non-equilibrium states as well as in biological systems. ( . . . )

"The processes of star formation in spiral galaxies today are so efficient because they have indeed evolved to make best use of the available materials. It may be stretching a point to argue that an individual star is alive; but it is also stretching a point to argue that our Galaxy is not alive, in the same sense that the Earth is alive. And within the living Galaxy a typical giant molecular cloud/supernova system seems every bit as alive as a typical caterpillar/butterfly system here on Earth. ( . . . )

"I have argued that our Galaxy is alive - literally alive, in the full biological meaning of the term. Like other galaxies it has been produced by a process of evolution and competition within the Universe, following the Big Bang. The end-product of this evolutionary process has been spiral galaxies that are very efficient supernova-nurseries."
John Gribbin, from:
In The Beginning: The Birth of the Living Universe

(NB: Re: "It may be stretching a point to argue that an individual star is alive . . ."
May be. But the Solar system viewed from beyond the Oort cloud is strangely reminiscent of other self-organized forms . . .)

Spiral Structure in Galaxies

Imagine the Universe

The Universe at UMich.
Amazon.com:
The Life of the Cosmos, Lee Smolin
The Birth of the Living Universe, John Gribben