Globular Clusters Give Astronomers Cluster Headaches

The old story is out, and nobody knows what the new story should be.

It can be amusing to watch a dogma unravel. Textbooks told students of high-school astronomy that globular clusters are among the oldest structures in the universe, made of old stars formed shortly after the big bang 10 to 13 billion years ago. “These well-studied systems were long thought to be simple and to host a single population of stars that all formed at the same time,” Nature says. Then, the Hubble Space Telescope took a look at them:

But in 2004, everything we knew about globular clusters changed radically. Using accurate Hubble Space Telescope photometry, astronomers detected not one, but multiple stellar populations in ω Centauri, one of the most massive globular clusters in the Milky Way. Subsequent studies (see ref. 4, for example) of other globular clusters confirmed that this was not an isolated finding but the discovery of a general feature that revolutionized our understanding of such objects. These stellar populations were shown to exhibit unique chemical properties that are not found in any other stellar environment. This means that these clusters are not simple at all, and have experienced more than one star-forming event during their lifetime.

The problem (Nature calls it “exciting news”) then became accounting for “young” stars in an “old” cluster. The article discusses several theories that were proposed to explain the so-called “blue stragglers” (young stars that shouldn’t be there because they burn out too fast). “However, most of these theories suffer from major issues” (10/05/03, 7/12/08, 12/19/12). So what is the status, 12 years later? “The consensus in the community is that we urgently need alternative, innovative ideas to overcome the impasse.”

A newcomer named Chengyuan Li has a new idea. He studied some relatively young globulars in the Magellanic Cloud he thinks are 1 or 2  billion years old. He suggests “a late burst of star formation that occurred a few hundred million (up to one billion, within the errors) years after the clusters’ initial formation epoch.” Li’s team published their idea in the same issue of Nature.

But is that ad hoc? Why would a cluster 13 billion years old under go a “late burst” in the last half or quarter of its existence? “It is a plausible working hypothesis, but not a consensus view,” the article says. For one thing, “The link between young and old clusters has yet to be fully established.” To try to be charitable to this newcomer, Nature ups the perhapsimaybecouldness index and hopes for futureware:

Nevertheless, the findings present an innovative approach that deserves further attention. It will certainly advance the ongoing debate, as well as trigger original thoughts, future observations and corresponding interpretations. And it could lead to a final, robust explanation in the not too distant future — an example of how scientific debate works at its best.

Meanwhile, Charles Q. Choi at Space.com is delighted at the imaginary light on the cave wall. “This finding could help shed light on how the building blocks of galaxies evolve,” he says, calling on his favorite Darwin vocabulary. He quotes Li:

“Traditionally, scientists did not expect that a young star cluster can form additional stars after its initial formation,” Li said. “Our finding indicates that the evolution of a star cluster is much more complicated than what we thought — there must be frequent interactions between star clusters and their environment.”

From there, Choi plugs Nature‘s appeal to futureware.

If you’re an evolutionary materialist, you have to get used to discovering, repeatedly, that everything you know is wrong. To many of them, that’s “exciting news.” Obviously. It keeps them employed.

To help our dumbfounded opponents, we offer a “bold, innovative idea to overcome the impasse.” In the beginning, God created the heavens and the Earth…. He made the stars also.