August 17, 2012 | David F. Coppedge

Sun, Moon and Stars in the News

What’s up in astronomy?  Surprises, by heavens.

Spherical sun:  The sun is too close to a perfect sphere than expected theoretically, a finding “baffling” to astronomers.  “Definitive” measurements by the Helioseismic and Magnetic Imager (HMI) show that “if the Sun were shrunk to a ball one meter in diameter, its equatorial diameter would be only 17 millionths of a meter larger than the diameter through its North-South pole,” according to PhysOrg.  The shape is also remarkably constant over time.  Even with its slow rotation, it should flatten into an oblate shape more than is observed; besides, it is a turbulent surface filled with magnetic disturbances and flares.  “For years we’ve believed our fluctuating measurements were telling us that the sun varies, but these new results say something different,” the team leader of the observations said. “While just about everything else in the sun changes along with its 11-year sunspot cycle, the shape doesn’t.”

Another new moon theory:  How long have the textbooks said that a glancing blow from a Mars-size object hit the earth and formed the moon?  Time for another revision.  Science Now entertained a new theory that it might have been a direct hit.  The article, “Moon Formed From Head-On Collision,” came ready-made with new artwork.

Some 4.53 billion years ago, a Mars-sized impactor slammed into Earth, forming a young, molten moon. But was it a head-on collision or a glancing blow?  New computer simulations argue for the former, indicating that the impactor scored a direct hit, crashing into Earth at a steeper angle and with a higher velocity than previously thought. The resulting smashup would have ejected far more Earth debris into space than other models have indicated, with much hotter temperatures. And that would mean the moon formed from more Earthlike material than previously thought. The origin of the impactor itself remains an open question.

As usual, the phrase “than previously thought” avoids stating who thought such notions.  Note: a smashup is not like a mashup; no intelligent design is involved.

Lunar helium:  Helium, a slippery molecule that should not have long lifetimes above the moon, has been detected in the moon’s tenuous atmosphere by the Lunar Reconnaisance Orbiter, according to PhysOrg.  It’s too early to say if it comes from the interior or is added by the solar wind; observers of lunar origin theories may want to take note and follow up on the developing story.

Creation by destruction:  Theorist Alan Boss is pretty sure a supernova led to the formation of our solar system, even though the idea is highly speculative.  This is because gas clouds need a shove to form planets, explained Space.com: “In particular, the shock wave from the explosion is thought to have compressed parts of the nebula, causing these regions to collapse.”  Boss’s computer model was programmed to make sure that short-lived radionuclides got into the nebula before they decayed, because they show up in meteorites.  It’s all work in progress: “the researchers are still trying to find various combinations of supernova shock wave parameters that will line up with observations of exploding supernovas.”

Solutions:  Not to worry: two solar system puzzles have been solved at once, according to PhysOrg: the origin of comets and asteroids.  Perhaps your textbook didn’t tell you they were puzzles.  The puzzles relate to the origin of calcium-aluminum inclusions (CAIs) in meteorites.  If you are willing to accept some complexity, a solution is at hand:  “CAIs are thought to have formed at the very beginning of the Solar System,” one said.  “Our results show that they must have experienced remarkably complex histories as they were transported chaotically all over the disk.”  Whether that is a good solution, the reader can judge.

Getting the dates right:  “Dating features on the Moon and Mars is guesswork. Scott Anderson is building a tool to change that.”  So begins a Nature News feature about Anderson’s cool new tool to date meteorites that can fit on a spacecraft.  But he has his critics, who reveal some dirty laundry about radiometric dating methods:

Anderson will have to show not only that his chronometer is fast and light, but also that his dates make sense. Radiometric dates are some of the trickiest, most delicate and most disputed measurements on Earth. Anderson wants to transform what has been a laborious process of chemical extraction and analysis into a laser-based system, automate it and shrink it into a robot small and reliable enough to send to another planet. “We’re extremely sceptical of these things working,” says Lars Borg, a chemist at the Lawrence Livermore National Laboratory in Livermore, California, whose three-person lab usually produces just two dates a year. “We really struggle to get these ages ourselves.

Monster mash: A previous announcement about stars too big for theory now has an explanation: smaller stars did the Monster Mash.  Details at Live Science.

Primitive star?  A puzzling star thought to be among the “second generation” of stars was announced in Nature News.  “The chemical content of a star that was born relatively shortly after the formation of the Milky Way calls into question conventional understanding of how stars formed in the early Universe.”  The problem is that this low-mass Milky Way star has one of the lowest metallicities (elemental abundances heavier than lithium) of any star at a time when such stars should have been massive.  This and other problems call into question star formation theories and their progress since the Big Bang; the astronomers do not yet see a pattern.

Plasma puzzle:  We’ll just reproduce the opening sentence of this entry on PhysOrg, typical of the “everything you know is wrong” genre: “The first controlled studies of extremely hot, dense matter have overthrown the widely accepted 50-year old model used to explain how ions influence each other’s behavior in a dense plasma. The results should benefit a wide range of fields, from research aimed at tapping nuclear fusion as an energy source to understanding the inner workings of stars.

The dark rulers of all:  For an entertaining story, read the book review on black holes at Nature August 16. The book is Gravity’s Engines: How Bubble-Blowing Black Holes Rule Galaxies, Stars, and Life in the Cosmos (Caleb Scharf Scientific American: 2012).  Mario Livio lavished in the speculation: “Scharf speculates that black holes rule everything in the cosmic landscape — from the large-scale structure of the Universe to life. Using rich language and a brilliant command of metaphor, he takes on some of the most intricate topics in theoretical and observational astronomical research. He weaves a wonderfully detailed tapestry of what modern astronomy is all about, from the complexities of cosmic microwave background studies to the X-ray mapping of galaxy clusters.”  But then he had some quibbles.  Scharf tends to overstate things.  “I have quibbles, too, with the passages in which Scharf attempts to support his argument that black holes are the main engines driving everything from re-ionization and cosmic star formation to galactic evolution and the emergence of life.”  Far be it from astronomers to exaggerate.

All this culminates with his intriguing statement that “the entire pathway leading to you and me would be different or even nonexistent without the coevolution of galaxies with supermassive black holes and the extraordinary regulation they perform”. Scharf admits that many steps remain uncertain and that numerous questions have yet to be answered. But he proposes that because the cosmic and galactic environments leading to the rise of complexity and life are part of black holes’ galactic evolution, it is reasonable to ask what special things link us directly to that history.

However, I feel less certain than Scharf about the answer. He explains that the tight correlation between the masses of supermassive black holes and of stellar bulges at galaxies’ centres reveals a co-evolution. It is equally certain that feedback from supermassive black holes had an important role in the ensuing star-formation history in the bulges of galaxies. But was this the key factor in determining whether life-bearing planets should exist or not? I doubt it. Still, the idea makes for a very interesting journey.

In short, read Scharf as a nice story, not as solid science.

Within much of astronomy these days, what you thought you knew is wrong, and what you think you know now is likely to be proved wrong in the future, but what scientists tell you they know at the moment is a sure thing.  Does the fable of the Blind Men and the Elephant come to mind?


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Comments

  • tjguy says:

    “New computer simulations argue for the former, indicating that the impactor scored a direct hit, crashing into Earth at a steeper angle and with a higher velocity than previously thought. ”

    I don’t know too much about this, but wouldn’t a direct hit from a Mars sized object have left an unmistakable mark on the surface and probably shape of the earth? But our planet too seems to have a beautiful spherical shape.

    “And that would mean the moon formed from more Earthlike material than previously thought.”

    This should be testable I would think. Perhaps they already know that the moon is composed of more earthlike material? If this isn’t a revision to fit the facts, then this could be tested by doing various tests on moon rocks. We might need to return to the moon to get better and more numerous samples though.

    Any bets as to the chances of this idea being accurate?

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