July 12, 2008 | David F. Coppedge

What Mean These Stars?

There are more things in heaven and earth than are dreamt of in current astronomical models.  Two articles recently underscored the fact that astronomers still have a lot to learn.

  1. Cluster generation conundrum:  The members of globular star clusters were long thought to be old stars of the same age, like seniors at a care facility.  Then the discovery of “blue stragglers” caused consternation; they were too massive to be billions of years old.  In the first episode of a new DVD series produced by Astronomy magazine, “The Life and Death of Stars,” an astronomer proposed that the blue stragglers are stars born from collisions among the older stars.  Now, a third population is further upsetting cluster age models, according to a press release from the Space Telescope Science InstituteScience Daily stated that the dilemma of three out-of-sync stellar populations in globular cluster NGC 6791 “may fundamentally challenge the way astronomers estimate cluster ages.”
        The article says that astronomers have found three populations of stars with different estimated ages: 4 billion, 6 billion and 8 billion years.  Two of the populations consist of white dwarf stars.  “The age discrepancy is a problem because stars in an open cluster should be the same age,” said one astronomer.  “They form at the same time within a large cloud of interstellar dust and gas.  So we were really puzzled about what was going on.”  Another added, “This finding means that there is something about white dwarf evolution that we don’t understand.”
        The article proposed a simple and “elegant” reconciliation of the two discrepant ages of white dwarf populations.  They might be binary systems.  The brightness of the binaries makes them look younger, the team of astronomers suggested.  They did not explain why this was never discovered before, or what it means to other estimates of cluster ages and distances.  White dwarfs are commonly-used age indicators, because according to leading models of stellar evolution, they are the end products of main sequence stars of a certain range of masses after the red giant phase.  For more on problems with globular cluster dating, see 01/05/2003, 01/01/2004, 08/28/2006 and 05/03/2007National Geographic News published the stunning Hubble image that shows the interior of the cluster.  A couple of distant spiral galaxies can be seen in the background.
  2. Cosmic baby boom:  Another conundrum “baffles astronomers,” according to Space.com.  The article subtitle explains the problem: “Our galaxy cranks out about 10 new stars per year.  Now astronomers have found one near the beginning of time that’s generating a whopping 4,000 a year.  At that rate, the galaxy needs only 50 million years to grow into one equivalent to the most massive ever observed.  Such rapid-fire starbirth and growth confounds theory.”  Sure enough, the leading “Hierarchical Model” of galaxy evolution expects that galaxies should grow slowly, not explosively “in one big burst” of star formation.  Peter Cepak of Caltech used a human analogy to explain the problem: “If our human population was produced in a similar boom, then almost all of the people alive today would be the same age.”  He continued, “If the universe was a human reaching retirement age, it would have been about 6 years old at the time we are seeing this galaxy.”
        The new finding further exacerbates the problem of instant maturity in the early universe (see 06/04/2001, 01/03/2004, 09/21/2005, 03/31/2006).  Why would stellar evolution occur at a much more rapid pace in the early universe?  What was exceptional about that epoch?  The idea contradicts uniformitarianism.  Astronomers announced the results based in images of a galaxy taken by the Hubble Space Telescope and the James Clerk Maxwell Telescope in Hawaii.  Now, the team is trying to see if this “Baby Boom galaxy” is an exceptional case.  If not, and most early galaxies were bursting into growth in their cosmic infancy, the Hierarchical Model of galaxy formation may be falsified.

How scientists treat anomalies in their models is instructive.  Many scientists are reluctant to jettison a working model just because of a few anomalies.  More often they employ rescuing devices to save the model.  Sometimes, however, the anomalies are just too stubborn to fit.  It is up to observers outside the paradigm to decide when the rescuing devices have become less plausible than other models.

We’ll let our readers chew on these stories and ponder their implications.  Some will feel comfortable with the explanations offered by the pros.  Others will wonder if a scientific revolution is in the offing.  For a diversion, try this riddle on someone today:
Q: I am the end of time and the beginning of eternity.  I am the last of space, and the beginning of every end.  What am I?
A: The letter ”e.”
Have a stellar day.

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Categories: Astronomy, Cosmology

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