Cosmologic philosophy: why this planetary arrangement? (Introduction)

by David Turell , Thursday, June 09, 2022, 20:26 (898 days ago) @ David Turell

All theories, no satisfactory theories; we just don't look like all teh others we now see:

https://www.quantamagazine.org/how-are-planets-made-new-theories-are-taking-shape-20220...

"Now look out past the sun, way beyond. Most of the stars harbor planets of their own. Astronomers have spotted thousands of these distant star-and-planet systems. But strangely, they have so far found none that remotely resemble ours. So the puzzle has grown harder: Why these, and why those?

"The swelling catalog of extrasolar planets, along with observations of distant, dusty planet nurseries and even new data from our own solar system, no longer matches classic theories about how planets are made. Planetary scientists, forced to abandon decades-old models, now realize there may not be a grand unified theory of world-making — no single story that explains every planet around every star, or even the wildly divergent orbs orbiting our sun. “The laws of physics are the same everywhere, but the process of building planets is sufficiently complicated that the system becomes chaotic,” said Alessandro Morbidelli, a leading figure in planetary formation and migration theories and an astronomer at the Côte d’Azur Observatory in Nice, France.

"Still, the findings are animating new research. Amid the chaos of world-building, patterns have emerged, leading astronomers toward powerful new ideas. Teams of researchers are working out the rules of dust and pebble assembly and how planets move once they coalesce. Fierce debate rages over the timing of each step, and over which factors determine a budding planet’s destiny. At the nexus of these debates are some of the oldest questions humans have asked ourselves: How did we get here? Is there anywhere else like here?

DAVID: there follows a hugh comopilation of a plethora of theories.

"...we come from a diffuse cloud of gas and dust. Four and a half billion years ago, probably nudged by a passing star or by the shock wave of a supernova, the cloud collapsed under its own gravity to form a new star. It’s how things went down afterward that we don’t really understand.

***

"ALMA [telescope array in Chile] disproved the classical model of planetary formation. “We have to now reject it and start thinking about completely different models,” Drążkowska said. The observations showed that, rather than being smoothly dispersed through the disk, dust collects in particular places, as dust likes to do, and that is where the earliest planet embryos are made.

***

"The exoplanet hunt took off after the Kepler space telescope opened its lens in 2009. We now know the cosmos is peppered with planets; nearly every star has at least one, and probably more. Most seem to have planets we lack, however: hot Jupiters, for instance, as well as a class of midsize worlds that are bigger than Earth but smaller than Neptune, uncreatively nicknamed “super-Earths” or “sub-Neptunes.” No star systems have been found that resemble ours, with its four little rocky planets near the sun and four gas giants orbiting far away. “That does seem to be something that is unique to our solar system that is unusual,” said Seth Jacobson, an astronomer at Michigan State University. (m y bold)

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"In other words, we might have gotten lucky in our solar system, with multiple giant planets keeping each other in check, so that none swung sunward and destroyed the rocky planets. (my bold)

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"Between condensation lines, pebbles, migrations and rebounds, a complex story is taking shape. Still, for now, some answers may be in hiding. Most of the planet-finding observatories use search methods that turn up planets that orbit close to their host stars. Lunine said he would like to see planet hunters use astrometry, or the measurement of stars’ movements through space, which could reveal distantly orbiting worlds. But he and others are most excited for the Nancy Grace Roman Space Telescope, set to launch in 2027. Roman will use microlensing, measuring how the light from a background star is warped by the gravity of a foreground star and its planets. That will let the telescope capture planets with orbital distances between Earth’s and Saturn’s — a “sweet spot,” Lunine said."

Comment: I skipped most of the new theories, interesting but totally unproven. So, clear blind lucky contingencies, or are we on the perfect planet for life by design? My bolds set the point. I await dhw's thoughts.