Arien van der Wel, an astronomer at Johns Hopkins University, has made a discovery about galaxy structure and morphology that implies that there may be more to the design of a galaxy for the possible support of life than what had previously been recognized.1 He noted that astronomers face a serious limitation in accurately determining a galaxy’s morphology if that galaxy is not nearby. For distant galaxies astronomers have used galaxy structure as a proxy for galaxy morphology. Van der Wel determined to test whether or not this proxy assumption had any validity. He performed this test thanks to the recent release of the deepest-ever survey of galaxies, namely the fifth data release of the Sloan Digital Sky Survey.
Van der Wel extracted detailed features of 4,594 galaxies from the Sloan Digital Sky Survey between redshifts of 0.2 and 0.3 (corresponding to distances between about two and a half and four billion light-years). This sample was complete down to a galaxy mass of ten billion solar masses. (By way of comparison, the total mass of the Milky Way Galaxy is sixty times greater). The features of these galaxies unambiguously established that galaxy morphology does not depend on galaxy structure. Thus, galaxy structure cannot be used as a proxy for galaxy morphology.
The analysis also revealed the causes for both a galaxy’s morphology and its structure. Van der Wel showed that galactic structure depends mainly on the galaxy’s mass, whereas a galaxy’s morphology depends primarily on the galaxy’s environment. (A galaxy’s environment refers to the quantity, types, sizes, and proximities of neighboring galaxies.)
Van der Wel offered an explanation for the dependencies he had observed. A galaxy’s environment will determine the timing and the quantity of the amount of gas and dust it will either ingest or lose from its interactions with neighboring galaxies. This gain or loss of gas and dust will affect the star formation rates and histories of the galaxy. For obvious reasons, these star formation rates and histories influence a galaxy’s luminosity and color, but, evidently, they have little effect on the distribution of mass within the galaxy.
This research means that astronomers now face a much more challenging task in determining the detailed characteristics of distant galaxies. Van der Wel’s work also has significant implications for the list of requirements for life-supporting galaxies.
For advanced life to be possible within a galaxy, the planet on which that life exists must orbit about a star that orbits around the center of the galaxy at just inside the co-rotation distance where that orbit remains undisturbed for billions of years. Advanced life also requires that both the measure of a galaxy’s co-rotation distance and the timing of the life-friendly planet’s birth relative to the birth date of the galaxy must be fine-tuned. If not, the planet will either possess the wrong mix of heavy elements, be subjected to deadly radiation, or experience gravitational disturbances.
(The co-rotation distance is that distance from the center of a galaxy where a star orbits about the galactic center at the same rate as the spiral arm structure rotates. A star too distant from the co-rotation distance will cross spiral arms too frequently for advanced life. However, if it is exactly at the co-rotation distance, it will suffer a mean motion resonance, which will destabilize its orbit. Just inside is necessary because outside the co-rotation distance the quantity of heavy elements is too low.)
In order to meet all of the above-listed requirements for the existence of advanced life, both the structure and the morphology of a galaxy must be carefully fine-tuned. That a galaxy’s morphology exerts very little or no dependence on a galaxy’s structure implies that both of these two features, rather than just one, need to be fine-tuned. Van der Wel’s study provides yet another demonstration that the more astronomers learn about the science of the universe and the population of galaxies, stars, planets, etc., the more reasons they uncover for the supernatural, super-intelligent design of the universe and its constituent components for the specific benefit of human life.2