Reasons to Believe

Spin-Orbit Misalignment of Extrasolar Planets

In 1995, astronomers detected, for the first time, planets outside the solar system .1 At the time, many researchers expressed great optimism that most, if not all, exoplanets would prove to be close analogues to those in our solar system. The list of known extrasolar gas giant planets now stands at 490. Yet none of these exoplanets can be identified as a twin to any of the solar system planets and none reside in a planetary system where advanced life could possibly exist on another planet.

Kevin Schlaufman, an astronomer at the University of California, Santa Cruz, has uncovered evidence that helps explain why astronomers are failing to find any twins of the solar system’s planets.2 (His discovery adds to astronomers’ previously accumulated evidence; see previous TNRTB articles on extrasolar planets.) Schlauffman examined all the extrasolar planets for which astronomers possess the maximum information about physical and orbital characteristics.

Such information consists of radial velocity, transit, and Rossiter-McLaughlin effect measurements. Astronomers possess such comprehensive measurements for 26 of the 490 known extrasolar planets. Schlauffman found that 8 of these 26 (31 percent) manifest spin-orbit misalignments greater than 30 degrees. Spin-orbit misalignment refers to the angle between the plane of the planet’s orbit and the spin equator of its host star.

Prior to Schlauffman’s discovery, detailed simulation models demonstrated that the generation of such a spin-orbit misalignment takes either multiple planets in the system undergoing significant inward migration or significant dynamical scattering between newly formed planets and planetesimals located at a few astronomical units (one astronomical unit = mean distance of Earth from the Sun) from the star. Both situations would rule out the possibility of another planet with all physical and orbital features necessary for advanced life existing in the same system. Additionally, both situations would explain why the majority of the 490 known extrasolar planets exhibit either highly eccentric (elliptical) orbits or orbits very close to their host stars.

Schlauffman’s research adds to the weight of evidence for the rare-Earth and rare-solar system doctrines. These doctrines state that while planets the size and mass of Earth may prove abundant, planets with the just-right characteristics, physical and chemical composition, and planetary partners to support advanced life will prove either rare or non-existent. Such doctrines are consistent with the Bible’s message that God supernaturally designed Earth, its planetary partners, and its life for the specific benefit of human beings.  

Subjects: Astronomy and the Bible, Extrasolar Planets, Solar System Design

Dr. Hugh Ross

Reasons to Believe emerged from my passion to research, develop, and proclaim the most powerful new reasons to believe in Christ as Creator, Lord, and Savior and to use those new reasons to reach people for Christ. Read more about Dr. Hugh Ross.

1. Michel Mayor and Didier Queloz, “A Jupiter-Mass Companion to a Solar-Type Star,” Nature 378 (November 23, 1995): 355–59.

2. Kevin C. Schlauffman, “Evidence of Possible Spin-Orbit Misalignment Along the Line of Sight in Transiting Exoplanet Systems,” Astrophysical Journal 719 (August 10, 2010): 602–11.