Is our solar system weird? Most others are different (Introduction)

by David Turell , Wednesday, October 17, 2018, 21:32 (2018 days ago) @ David Turell

Another article which shows that our solar system is not like the others we have discovered:

https://blogs.scientificamerican.com/observations/our-solar-system-is-even-stranger-tha...

"In addition to our solar system, we now know of over 400 multi-planet systems, thanks largely to the Kepler Mission. Kepler is a NASA spacecraft (named after the 17th century German astronomer) that was launched in 2009 for the sole purpose of discovering exoplanets—worlds orbiting other stars. It finds those exoplanets by continuously measuring the brightnesses of about 100,000 stars and waiting for the starlight from any of them dim ever so slightly due to the shadow of a planet in transit. The transit of each planet is unique, allowing the discovery of multiple planets orbiting the same star.

***

"The pattern I found on that sunny afternoon: planets in the same system tend to be the same size. For example, if one planet is 1.5 times the radius of Earth, the other planets in the system are very likely to be 1.5 times the radius of Earth, plus or minus a little bit.

"This is not at all what my colleagues and I expected. In our solar system, planets range from the size of Mercury (less than half the radius of Earth) to Jupiter (more than ten times the radius of Earth). The whole population of exoplanets discovered by Kepler ranges from one quarter the size of Earth to about twenty times the size of Earth. Yet, despite this wide range of possible sizes, planets tend to be about the same sizes as their neighbors.

***

"A widely accepted (but unconfirmed) theory about planet formation involves the rise of so-called “oligarchs,” young precursors of planets that each influence a swath of fixed width within the disk around the star. (Pluto is no longer considered a planet because Pluto was never big enough to be an oligarch.)

"Oligarchic theory predicts roughly equal-mass oligarchs spaced at regular intervals, with the size of the oligarch dependent on the width of its influence. However, because our solar system is not a system of equal-mass planets at regular spacing, the rise of oligarchs is considered a mere chapter in our solar system’s history, an early pattern that was later overwritten by violent impacts that formed our very dissimilar terrestrial planets."

Comment: Another article which shows we live in a very special and unusual solar system. We can add this to the fine tuning theories.