Tuesday, January 23, 2018

Space-y matters

And my fascination with matters astronomical continues. If you share my interest, you will want to read on.

Whistling in the dark (matter)?
To date, not a single experiment has shed any light (bon mot intended) on the nature of dark matter or dark energy. The former is invoked to explain certain otherwise inexplicable, and presumably gravitationally caused, behaviors (e.g., the orbital periods of stars in galaxies, and galaxies within clusters). The latter is invoked to explain the otherwise inexplicable increasing-with-time rate of the Universe's overall expansion. The rate of expansion is inferred from the observed red shifts of distant, hence seen in their distant pasts, "standard candle" supernovae.

This lack of success in understanding dark matter and/or dark energy is what makes the following -- very sketchy, so far -- article so provocative: "Radical dark matter theory prompts robust rebuttals: The idea that dark energy and dark matter aren’t needed to explain the properties of the universe is meeting fierce opposition." Stay tuned.

And speaking of galaxies, what begins and ends their formation of stars? Again, there are lots of theories. Evidence? That's another matter. So I was delighted to read this: "We Just Got The First Direct Evidence That Supermassive Black Holes Control Star Formation." (How massive is super massive? Oh, about a million times the mass of the Sun.)

Among astrophysicists, a popular exercise is explaining, as best they can, the relative abundances and distributions of various elements and isotopes. (You don't wonder about the abundance of aluminum-26 in the early Solar System? What's wrong with you?) And why is that? Because it is believed the explanation(s) is to be found in a deep understanding of the mechanisms of the early Universe and, since then, such violent stellar processes as supernovae. (Useful buggers, those supernovae. As long as they don't happen in your neighborhood.)

Image by ESA/Hubble
In our Sun's beginning? (Image by ESA/Hubble)

Where the above/dark-whatever item speculated about possible changes in cosmic attributes over time, this item deals with a non-homogeneity in space. To wit: "Our solar system may have formed inside a giant space bubble: This new theory explains the proportions of certain elements in the early solar system."

Experience teaches that any explanation at odds with the Copernican principle merits skepticism. Still, nothing in astronomy precludes local anomalies. In this case, the local "quirk" would be our Solar System having formed from, and within, the exploded remains of a onetime Wolf-Rayet star (like the image immediately above). Bottom line: there's nothing definitive in this speculation, either ... just an intriguing idea.

Can you say Kardashev Type II?
You've probably encountered musings about the weird, aperiodic, short-term dimmings -- by up to 22% -- of Tabby's Star. The most provocative proposed explanation is a Dyson Sphere under construction. Another way-out-there (heh!) idea is huge clouds of comets. Every past effort at making sense of these bizarre observations has had a serious shortcoming(s). The latest crack at the puzzle -- despite the headline, not yet a fully satisfying explanation -- is: dust clouds. See: "The strangest star in the sky finally has an explanation for its flicker."

Speaking of stars, there is much we have yet to suss out about our own. Such as how particles of the solar wind can move as fast as they do. And why the photosphere (the Sun's outer shell) is way hotter than the outer reaches of the dense ball of plasma within. The good news: we should know a lot more soon about these and other solar mysteries -- courtesy of the Parker Solar Probe. Imagine: a spacecraft that will swoop to within 4 million miles of the Sun's "surface." Read all about it: "This NASA spacecraft will get closer to the sun than anything ever before."

I'll end this post with an article that's not news, but rather a recently encountered excellent non-mathematical overview of gravity. After all, gravity is (it is currently understood, anyway) the dominant factor in the life cycle of stars, the creation of galaxies, and even the ultimate fate of the Universe. Important! If you have (as Cosmos estimates it) four minutes to spare, I recommend this to you: "Explainer: What is gravity?"

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