Lessons From Other Worlds
In the past 25 years mankind has been able to use technology to examine areas of the cosmos far removed from our own solar system. New optical systems, new sensing systems, and a variety of telescopes in orbit around Earth using X rays, infrared, ultraviolet as well as visible light have greatly influenced our ability to detect other objects in the cosmos. One of the things that has been studied in considerable depth is the presence of other solar systems--planets orbiting other stars. As of August 2004, science has identified 107 solar systems and 120 planets. Robert Zimmerman writing in Astronomy (August 2004, pages 43-47) says "Of the 107 known solar systems, not one resembles our own, even approximately."
The very fact that these other systems are so much different than ours has some things to tell us, and in fact the more we study these other systems the more we learn about our own system and why things are the way they are. One of the interesting facts about other systems is that even though some planets are very large and obviously gaseous, they can exist very close to their stars. It used to be that astronomers explained the inner planets of our own solar system being rocky and hard by saying that the Sun burned off the gases and left the rocky material. That may in fact be partially true, but recently an object named OGLE-TR-56b was discovered that is about the same mass as Jupiter but is over 30 percent larger. It would have to be a gaseous object to have such a low density, but it is orbiting its star at an average distance of only 2 million miles--much closer than Mercury is to the Sun (Mercury is 36 million miles away from the Sun). The outer atmosphere of this planet must be around 3000°F. We do not know what the chemical composition of this planet is, but it is obvious that gaseous planets can exist very close to their stars, and our old explanation of the inner planets in our own solar system is vastly oversimplified.
Most of the planets we see around other stars are very large. That is not too surprising as it is obviously easier to see a big planet than it is a small one. One planet has been seen which is 17 times as massive as Jupiter. The strange thing is that a large number of these planets are closer to the Sun than Venus. Old theories of planet formation suggested that due to the large gravity values of stars, it was impossible for planets to form close to the stars. We now know that is not true.
Science programs on television have delighted in proposing that the cosmos is full of planets and that every galaxy has literally millions of planets. The hope is that if you have enough planets the chance of having another Earth is improved. We now know that many galactic systems do not have planets at all. In 1999 the Hubble Space Telescope surveyed globular cluster 47 Tucanae looking for planets; 34,000 stars were examined and no planets were found. The composition and age of galactic systems obviously have a major impact on whether planets can exist or not, but claims of billions and billions of planets in the cosmos are obviously an exaggeration.
The type of star that we are considering also has an impact on whether planetary systems can form or not. Planets have been found orbiting pulsars, binary stars, and spectral classes of stars like our Sun. Most stars in the cosmos are binary systems containing more than one star. A planet can orbit the stars at a great distance, but shifting gravity fields make planets unlikely if the stars are close together as most are. We now know that how much metal there is in a star system has an effect on planet formation. Metal content varies within galaxies as well as between stars, so a part of space dominated by gases like hydrogen and helium are not as likely to produce planets as areas where there are large amounts of iron, manganese, cobalt, and the like.
Perhaps one of the most interesting lessons we have learned from other solar systems has been that the shape of the orbits of the objects in our solar system is very unusual. Most planets in our solar system have a very circular orbit. What that means is that their distance from the Sun does not vary a great deal. Venus has an orbit that is .007 with 0 being a perfect circle and a straight line being 1. Pluto has the most elliptical orbit, but even Pluto is less than .3 on the scale above. Circular orbits like ours have been almost nonexistent in other solar systems. In other solar systems .7 is a very common orbital value and virtually all orbits exceed .3. If a planet swings way out away from its star and then comes within 2 million miles after having been many million miles away, it should be obvious that temperature conditions are going to be extreme. Not only will such a planet have extreme conditions itself, but it will have a very negative effect on any planets that do have a circular orbit in the system. If Jupiter came closer to the Sun than Earth every time it orbited, imagine what the conditions would be on Earth as Jupiter went by us.
We now know that our giant planets (Jupiter, Saturn, Uranus, and Neptune) are important to us because their gravitational fields sweep up any debris floating in space. Without these objects, comets and asteroids would pound Earth and life here would be difficult if not impossible. The fact that they are outside Earth's orbit at a considerable distance and in a circular orbit allows us to exist in a stable condition for extensive lengths of time. The comets that do come into our system do not come in along the plane of the solar system called the ecliptic, because the giant planets swallow them up. The ones that come in from other directions have no chance of hitting Earth since they are not in the plane of the Earth's orbit around the Sun. The Hale-Bopp comet was beautiful, but it posed no danger to us here on Earth.
Like everything in science, the study of the cosmos and of other solar systems speaks eloquently to us about the design and planning that has been a part of everything in the creation. As more data is discovered other lessons will come that will tell us how special and how well designed our home is. It also should impress upon us the importance of following God's instructions to take care of the Garden--dress it and keep it (Genesis 2:15). In the twenty-first century we have more of a reason than any humans have ever had to repeat the old Psalmist message "The heavens declare the glory of God, and the firmament showeth His handiwork" (Psalm 19:1)
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