Bad Astronomy and Universe Today Forum - View Single Post - Milky Way Halo Globular Clusters May Not Have Originated The

ljbrs · #1 (**permalink**) 31-July-2002, 03:24 AM

Oh, dear, oh dear, oh dear!

It looks as if Halo globular clusters are captured objects from other nearby galaxies and did not necessarily originate in the Milky Way, after all.

In *Of Clusters and Galaxies,* by Christine M. Clement (SCIENCE, 26 July 2002, Perspectives - Astronomy, pp. 532 to 533), this subject is discussed in depth. A bottom-up theory, rather than a top-down theory in galactic formation (as is now thought to be the case) might explain the varying ages of the various globular clusters if they had actually originated separately in different nearby galaxies (such as the Sagittarius Dwarf Galaxy or the Large and Small Magellanic Clouds), and were separately captured by the Milky Way. It is difficult to adequately measure the horizontal distances to celestial objects; at present, only radial distances seem to be accurately possible.

Anyway, I always like a new slant on an old scientific idea. It cleans up the brain and throws out musty, dusty, rusty ideas.

Astronomers have made Hertzsprung-Russell (H-R) diagrams of the various globular clusters in the galactic halo and have studied the halo stars on the horizontal branch (HB) and have found that the ages in different clusters seem to vary quite a bit -- at least in those where there is a radial measurement.

So, the halo globular clusters may not be the oldest objects in our galaxy (having originated elsewhere), but may, instead, have been captured by the Milky Way as it (a/k/a The Galaxy) was developing. This will be something to keep track of and to think about when you are viewing one of these jewels in the sky.

I just love science. It always is throwing a bejeweled monkey wrench into a theory and forcing me to rethink everything! The idea of galaxies being built up through merging (bottom up) rather than having come from a primordial cloud (top down) makes sense.

Changing ideas because of new, carefully measured data, is so much fun. It is great for the brain!

ljbrs [img]/phpBB/images/smiles/icon_biggrin.gif[/img] [img]/phpBB/images/smiles/icon_smile.gif[/img] [img]/phpBB/images/smiles/icon_rolleyes.gif[/img] [img]/phpBB/images/smiles/icon_confused.gif[/img]