Thursday, June 16, 2016
The Dryden Universe and M24
With all the galaxy to choose from, I wanted a section that was distant from Planet Earth and its solar system, and I wanted an area which was small enough, with suns close enough together, to form a cohesive empire. So I did some homework on star clusters. Globular clusters, it seemed, were not the best fit. The stars are very old first generation, and gravitationally bound to each other. Current knowledge suggested that mitigates against planetary systems, both because of the forces, and also because the material from which planets (and we humans) are formed comes from supernova debris, and these clusters are poor in such material.
However, a recent article in the Harvard-Smithsonian Center for Astrophysics website argues against that premise. It's a wonderful time to be an astrophysicist. The Hubble and Kepler telescopes between them have blown apart so much that had been taken for granted. The universe is a strange and beautiful place, and we're not as smart as we thought we were.
Anyway, I picked M24 as my sandbox because it's an open cluster. The stars are younger, without being too young for planetary systems to have formed. And although the suns are fairly close together, it's believed eventually they drift off to do their own thing. A bit like our own families where kids eventually leave home. According to the article in the Messier objects website M24 is in the constellation Sagittarius and it's pretty big - ten to sixteen thousand light years across. There are thousands and thousands and thousands of stars in there, relatively close together, so it seems to be an ideal place for an author to set up a civilization. Yay me.
But then I found this site.
I was absolutely fascinated. If the author is right, M24 isn't any sort of cluster. It's a window. Bear in mind that the galactic center is in the direction of Sagittarius, so the argument makes a lot of sense. There's so much out there we can't see. The Parkes telescope in Australia recently cataloged hundreds of galaxies which had been obscured by the stars and dust of the Milky Way.
This doesn't mean I've given up on M24. My criteria haven't changed: close together, second generation stars. But it puts another spin on what we do and don't know about this place where we live.
I love astronomy.
have a look here. There are already two Dryden books - the third will be coming soon.