Using the world’s largest optical telescope, the 400-inch KECK, three American astronomers recently discovered two Saturn-sized planets outside our solar system. Both orbit “main sequence” stars (stable, hydrogen-burning stars) like our sun.1 Discovery of these two planets, smaller than any extra-solar planets previously discovered, has led to excited speculation that Earth-sized planets may be plentiful.2 The speculation continues, of course, that an abundance of Earth-sized planets means an abundance of life sites in the universe.
Geoffrey Marcy, Paul Butler, and Steven Vogt did not actually “see” the planets. Rather, they established the planets’ existence by carefully measuring tiny wobbles in the positions of the stars they orbit. When a planet is between us and its star, the planet’s gravity tugs the star slightly toward us. When the planet is on the opposite side of its star, it pulls the star slightly away from us. The more massive the planet, the bigger the wobble it causes and, thus, the easier it is to detect.
Until now, all the planets discovered (the list includes over 40 to date) outside our solar system have been huge, half the mass of Jupiter or larger (Jupiter = 317 Earth masses). According to Butler, new instruments now give us the capacity to detect planets as small as five percent the mass of Jupiter (about 17 Earth masses).2 So, we can expect to find many more in the months ahead. Detection of Earth-sized or Mars-sized planets will require new technology, however.
One of the two newly discovered planets has about 75% the mass of Saturn (22% the mass of Jupiter); the other is a little larger, about 84% the mass of Saturn (25% the mass of Jupiter). Neither is a candidate for life support. Like other planets discovered thus far, both reside too near their stars and have orbital paths too eccentric (too elongated, non-circular) to permit life. These and other characteristics rule out the possibility of life anywhere within the planetary systems to which these two planets belong.
Whether or not Earth-sized planets prove plentiful, scientists have no rational basis for assuming that such planets will have the capacity to support life. Size is only one of over 100 different planetary characteristics that must be fine-tuned for advanced life support.3 The estimated probability that a non-designed, Earth-sized planet will have the capacity to support life is less than one in 10150 (the number 1 with 150 zeros following it).3 And that is not to mention the larger problem of life’s “spontaneous” origin.4 Christians, however, have a rational basis for excitement. As these discoveries advance our understanding of solar system formation, they underline the uniqueness, the divine and purposeful design, of our own solar system and planetary home.
- Ron Cowen, “Less Massive than Saturn?,” Science News, 157 (2000), pp. 220-222.
- Cowen, p. 220.
- Hugh Ross, “Design Evidences for Life Support,” (Pasadena, CA: Reasons To Believe, 2000).
- Robert Shapiro, Origins: A Skeptic’s Guide to the Creation of Life on Earth (New York: Summit Books, 1986), p. 128.