May 10, 2018 | David F. Coppedge

Star Formation Theories Fail to Shine

Big things are wrong in astrophysics, say several news articles.

The laws of star formation challenged (Phys.org). Once we learn a couple of terms, we’ll see how bad the news is about star formation. IMF1 stands for the mass distribution of stars at birth. CMF2 stands for the mass distribution of cores from which they formed. Those numbers should agree, but new work “could challenge the widespread assumption that the mass distribution of a population of star-forming cores is identical to that of the stars they spawn.” Salpeter’s Law, stated by Edwin Salpeter in 1955 based on molecular clouds near our solar system, says those distributions should agree. The bad news: when astronomers look at more distant stars, they don’t. The ALMA Telescope allowed them to check the relationship for more distant stars. The implications could reverberate through astrophysics:

It turned out that, in the W43-MM1 cloud, there was an overabundance of massive cores, while less massive cores were under-represented. These findings call into question not only the relationship between the CMF and the IMF, but even the supposedly universal nature of the IMF. The mass distribution of young stars may not be the same everywhere in our Galaxy, contrary to what is currently assumed. If this turns out to be the case, the scientific community will be forced to re-examine its calculations about star formation and, eventually, any estimates that depend on the number of massive stars, such as the chemical enrichment of the interstellar medium, the numbers of black holes and supernovae, etc.

Burst of newborn stars in young star cluster puzzles astronomers (Phys.org). Another term to learn is “blue stragglers.” These are hot blue stars that shouldn’t be where they are: they “‘straggle’ behind the natural evolution of most stars in a cluster.” Blue stars are assumed to burn up very fast. They shouldn’t exist in globular clusters, therefore, which are assumed to be very old. Those clusters are also depleted of the gas needed to form new stars. To get around this conundrum, astronomers hoped that blue stars might have formed more recently by collisions. The Chinese Academy of Sciences, using the Hubble Space Telescope, now says that explanation does not appear probable. They found an unexpected population of blue stars in a “young” globular cluster (two billion years). What does that imply? “This is surprising, because blue straggler stars in this cluster seem to have formed in a well-defined burst,” not from random collisions. It’s like they all ‘burst’ on the scene together, so to speak. A collapsing globular cluster might bring about this situation, but it shouldn’t be happening in a young cluster.

“When the very cores of clusters collapse under the gravity of all the stars in that small volume of space, we witness one of the most extreme astronomical events. When this happens, the cluster becomes extremely dense and you can imagine that many stellar collisions could happen in the core region. As a result, lots of blue straggler stars could be produced. For this reason, the double sequence of blue stragglers can be expected in clusters only when they get old, older than 10 billion years,” said Dr. DENG.

However, we did not find any evidence that supports the presence of a collapsed core in this cluster. In addition, the conditions in this cluster even disfavor the occurrence of many stellar collisions,” said Dr. LI.

An anonymous reviewer solicited by the editors of The Astrophysical Journal wrote, “This work certainly presents unexpected, and therefore interesting observational results… It challenges the generality of explanations put forward for other such blue straggler sequences.

 

Stars and Habitability

Small Stars are Awesome — But Can They Support Life? (Space.com). In this article, Paul Sutter (astrophysicist at Ohio State) explains why red dwarf stars (the most numerous in the universe) are unlikely candidates for hosting habitable planets. For one thing, the habitable zone is close to the star. And then, red stars tend to erupt with killer flares. If that isn’t bad enough for life, a planet in the zone would most likely become tidally locked to the star. One side would be exposed to the killer flares; the other side would face away into the freezing cold of space.

Sutter takes the gamble anyway. There are so many of these stars, he says, and they last so long, a few might beat the odds. “So, even if life has trouble getting started or sticking around, there are a ridiculously high number of chances available for life to get a crack,” he says. “Your odds may not be that great at a penny slot machine in Vegas, but if you’ve got a lot of pennies you might just come out ahead.” Since the only star we know of that hosts a habitable planet is not a red dwarf, good science would like to see evidence before trying Sutter’s odds. Probability theory itself warns against reckless drafts on the bank of time. Sutter has a finite number of pennies, but he should calculate the odds of getting even one protein by chance. Watch the animation, “The Amoeba’s Journey” from the Illustra Film Origin. There isn’t enough time in the universe to try the number of rolls required to get a small protein, let alone life.

Elements from the stars—the unexpected discovery that upended astrophysics 66 years ago (Phys.org). In this article, Spyrou and Schatz review the 1952 discovery of technetium in a stellar spectrum and what that meant for the future of astronomy. Technetium, having no stable forms, must have formed recently, concluded Paul Merrill working at the Mt. Wilson Observatory. This “completely unexpected” discovery led to the common secular statement, popularized by Carl Sagan, that ‘we are all made of starstuff.’

On May 2, 1952, Merrill reported his discovery in the journal Science. Among the three interpretations offered by Merrill was the answer: Stars create heavy elements! Not only had Merrill explained a puzzling observation, he had also opened the door to understand our cosmic origins. Not many discoveries in science completely change our view of the world – but this one did. The newly revealed picture of the universe was simply mind-blowing, and the repercussions of this discovery are still driving nuclear science research today.

The field of stellar nucleosynthesis was born, but the article reveals some incidents for historians of science to consider. Prior to 1952, astronomers assumed that all the elements were formed in the big bang. Alternative scenarios were considered, “But no one really had come up with a convincing theory for the origin of the elements – until Paul Merrill’s observation.” A convincing theory, however, should be distinguished from a true theory.

Spyrou and Schatz show how the new paradigm led to the 1957 B2FH paper (Burbidge, Burbidge, Fowler and Hoyle) that seemed to convince everyone that stars make heavy elements. But while theories can work on paper, fusion is difficult to study in the lab: “for more than six decades, nuclear physicists have continued to work to get a handle on the nuclear reactions that drive the stars.” I.e., they’re not there yet. Computer models crank out solutions, “trying to recreate the parts of the universe we see, while reaching out toward the ones that are still hiding until the next major discovery.

Could the next major discovery “upend” the last major discovery? The current theory of stellar nucleosynthesis is not without problems. The reactions up to the element iron are exothermic, therefore give off energy. The elements heavier than iron are endothermic, requiring the input of energy. Astronomers assume that supernovae will be powerful enough to supply the energy, but nobody has quite figured out how to create a supernova in the lab. The situation described in this article reminds one of Thomas Kuhn’s portrayal of scientific paradigms. Everyone in the ‘guild’ is occupied with working on the paradigm, not questioning it. The next scientific revolution could replace this paradigm of nucleosynthesis with a different one.

Chalk this entry up under the Psarris title, “What you’re not being told about astronomy.” How many books, TV shows or movies have you seen that assume habitable planets are as common as dirt? How many that assume science has figured out star formation? How many that blissfully stated that globular clusters are old, with only old stars? How many that you are just starstuff? Dig a little deeper with a skeptical eye, and you often find a house of cards sitting on a foundation of sand.

 

 

 

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