Reasons to Believe

Enhanced Activity in Solar-Type Stars

Many stars share certain characteristics with the Sun, such as age, metallicity (abundance of elements heavier than helium), luminosity, and effective temperature. Yet, these stars exhibit much higher chromospheric activity than the Sun’s, which rules out the possibility of a planet sustaining advanced life for long periods of time while orbiting such stars. For more than three decades astronomers have worked to discover the source of the higher chromospheric activity and to explain why the Sun exhibits such low levels by comparison. Now, two astronomers, Ansgar Reiners and Mark Giampapa, have solved the puzzle.

Reiners and Giampapa studied fifteen solar-type stars in the solar-age star cluster M67.1 They analyzed high-resolution spectra of these stars obtained using the Very Large Telescope. Operated by the European Southern Observatory, this telescope is an array of four optical telescopes, each 8.2 meters in diameter, located at a high altitude desert site in Chile.

The spectra showed that solar-type stars with high chromospheric activity all exhibited rotation speeds that were at least twice as rapid as the Sun’s rather slow spin rate of 24.5 days as measured at the equator. Reiners and Giampapa thus conclude that the fundamental cause of high chromospheric activity, at least for solar-type stars, is a much higher rotation rate. They further deduced that the most likely cause of the faster rotation rates is a reduced braking efficiency in the stars’ interior layers, which in turn must arise from an elemental composition distinctly different from the Sun’s.

These results add to the already mounting evidence for the supernatural design of the Sun for the benefit of advanced life. Reiners and Giampapa’s work studied solar analogues—stars that approximate the mass, age, and spectral type of the Sun, what astronomers would identify as a main sequence dwarfs between spectral type G0 and G5 (the Sun spectral type is G2). A solar twin is a star whose characteristics are “almost identical to the Sun’s.” Solar twins are more likely to exhibit high chromospheric activity. A previous study of the 21 known solar twins and solar analogues that come the closest to matching the Sun’s characteristics showed that compared to the best solar twins the Sun has a 20 percent depletion of refractory elements (such as aluminum, calcium, magnesium, and silicon) relative to volatile elements (such as carbon, nitrogen, and oxygen).2 The research team that demonstrated the Sun’s unique elemental abundance attributed it to the Sun’s peculiar suite of planets consisting of a few relatively small gas giant planets (volatile-rich planets) at large distances from the Sun and some relatively medium-sized rocky planets (refractory-rich planets) at close-in distances from the Sun.

Evidently, the Sun’s distinct elemental abundance explains its low level of chromospheric activity, its slow rotation rate, and its unique set of planets. These three features are all essential for making advanced life possible on Earth. That the Sun and its system of planets are proving to possess characteristics that are rare and unique strengthens the conclusion that our solar system was supernaturally designed for the specific benefit of the human species.

Endnotes:

1. A. Reiners and M. S. Giampapa, “The Origin of Enhanced Activity in the Suns of M67,” Astrophysical Journal 707 (December 10, 2009): 852–57.

2. J. Meléndez et al., “The Peculiar Solar Composition and Its Possible Relation to Planet Formation,” Astrophysical Journal Letters 704 (October 10, 2009): L66–L70.

Subjects: 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.