In several of my speaking events, I remind my audiences that stars are like human beings: they are all unstable to some degree. Also, like humans, the most stable stars are those that are middle-aged.

A multidecade set of observations of the Sun and the most Sun-like stars now shows that the Sun may be the most stable of all stars.1 It is certainly the most stable of all stars for which astronomers have performed stability observations. That stability attests to a design and purpose for the Sun and human beings living near it.

All stars exhibit both activity and variability. By “stellar activity,” astronomers mean the flares that arise from the generation, evolution, and annihilation of magnetic fields in local regions of a star’s atmosphere and layers just below its surface. By variability,” astronomers mean changes in the total luminosity or brightness output of a star.

A team of five astronomers headed up by Richard Radick of the National Solar Observatory—located in the appropriately named town of Sunspot, New Mexico—reported on a study comparing the Sun’s activity and variability with that of 72 Sun-like stars over the time period spanning from 1992 to 2017. While such comparisons had been done before 1992, the new observations have been achieved with unprecedented precision. Much of the credit for this greatly enhanced precision is due to the Solar Radiation and Climate Experiment (SORCE) satellite (see figure below). This satellite was able to measure the total solar irradiance (TSI) to 0.001 percent precision.

blog__inline--our-uniquely-smooth-stable-sun

Figure: The SORCE satellite for monitoring the Sun’s activity and variability.

Data from SORCE shows that solar flares manifest at least two orders of magnitude (at least a factor of 100) higher levels of variability than does the Sun’s TSI. The amplitude of TSI variability is only 0.1 percent, and this variation is in lockstep with the sunspot number and the corresponding 11-year sunspot cycle. The reason why the TSI varies so little is that it reflects the slight imbalance between the luminosity deficit produced by dark sunspots and the luminosity enhancement produced by bright faculae (solar faculae are short-lived convection cells that form bright spots on the Sun’s surface).

Radick’s team determined four conclusions from their comparative study:

  1. The variability of Sun-like stars younger than the Sun is dominated by dark starspots, which is unlike the Sun, where the facular spots dominate the variability.
  2. Sun-like stars older than the Sun show a direct correlation between total luminosity variation and chromospheric emission variations. (The chromosphere is the region beyond a star’s atmosphere where flaring activity is especially prominent.)
  3. The Sun is unique in that, unlike the Sun-like stars, it exhibits a smooth, regular activity cycle.
  4. The Sun is unique in that it manifests a low TSI variation relative to its chromospheric activity level and variation.

Radick and his team deduced that the two unique features they had found for the Sun perhaps show “that facular emission and sunspot darkening are especially well-balanced on the Sun.”2 What they did not comment on is that the Sun’s two unique features that they discovered especially benefit human civilization on Earth. The extreme climate stability that we have been enjoying for the past nine thousand years is due, in large part, to the Sun’s low TSI variation by its smooth, regular activity cycle.3 Without our current and recent past extreme climate stability, billions of humans could not live on Earth at one time, nor could billions of humans achieve the technology for billions to hear and respond to Jesus Christ’s offer of salvation and eternal life. Thank God for the Sun!

Featured image: The bright spots are faculae, and the dark spots are sunspots. Image credit: NASA

Endnotes
  1. Richard R. Radick et al., Patterns of Variation for the Sun and Sun-like Stars, Astrophysical Journal 855 (March 2018): id. 75, doi:10.3847/1538-4357/aaaae3.
  2. Radick et al., Patterns of Variation, 27.
  3. Hugh Ross, Ready for Occupancy, chap. 15 in Improbable Planet: How Earth Became Humanity’s Home (Grand Rapids: Baker Books, 2016).

Check out more from Dr. Hugh Ross @Reasons.org

About The Author

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. I also am eager to equip Christians to engage, rather than withdraw from or attack, educated non-Christians. One of the approaches I’ve developed, with the help of my RTB colleagues, is a biblical creation model that is testable, falsifiable, and predictive. I enjoy constructively integrating all 66 books of the Bible with all the science disciplines as a way to discover and apply deeper truths. 1 Peter 3:15–16 sets my ministry goal, "Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect, keeping a clear conscience." Hugh Ross launched his career at age seven when he went to the library to find out why stars are hot. Physics and astronomy captured his curiosity and never let go. At age seventeen he became the youngest person ever to serve as director of observations for Vancouver's Royal Astronomical Society. With the help of a provincial scholarship and a National Research Council (NRC) of Canada fellowship, he completed his undergraduate degree in physics (University of British Columbia) and graduate degrees in astronomy (University of Toronto). The NRC also sent him to the United States for postdoctoral studies. At Caltech he researched quasi-stellar objects, or "quasars," some of the most distant and ancient objects in the universe. Not all of Hugh's discoveries involved astrophysics. Prompted by curiosity, he studied the world’s religions and "holy books" and found only one book that proved scientifically and historically accurate: the Bible. Hugh started at religious "ground zero" and through scientific and historical reality-testing became convinced that the Bible is truly the Word of God! When he went on to describe for others his journey to faith in Jesus Christ, he was surprised to discover how many people believed or disbelieved without checking the evidence. Hugh's unshakable confidence that God's revelations in Scripture and nature do not, will not, and cannot contradict became his unique message. Wholeheartedly encouraged by family and friends, communicating that message as broadly and clearly as possible became his mission. Thus, in 1986, he founded science-faith think tank Reasons to Believe (RTB). He and his colleagues at RTB keep tabs on the frontiers of research to share with scientists and nonscientists alike the thrilling news of what's being discovered and how it connects with biblical theology. In this realm, he has written many books, including: The Fingerprint of God, The Creator and the Cosmos, Beyond the Cosmos, A Matter of Days, Creation as Science, Why the Universe Is the Way It Is, and More Than a Theory. Between writing books and articles, recording podcasts, and taking interviews, Hugh travels the world challenging students and faculty, churches and professional groups, to consider what they believe and why. He presents a persuasive case for Christianity without applying pressure. Because he treats people's questions and comments with respect, he is in great demand as a speaker and as a talk-radio and television guest. Having grown up amid the splendor of Canada's mountains, wildlife, and waterways, Hugh loves the outdoors. Hiking, trail running, and photography are among his favorite recreational pursuits - in addition to stargazing. Hugh lives in Southern California with his wife, Kathy, and two sons.



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