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Creation Astronomy
by Jason Lisle

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Planets and migrating theories

by Wayne Spencer

Image JPC, NASA and R. Hurt

Artist impression of a gas giant.

Artist impression of a gas giant.

For many years the accepted theory of planet formation has been the ‘Nebular Hypothesis’. This holds that all the planets in our solar system formed—in the regions where they are now located—from a disk of gas and dust. But, now astronomers are entertaining the possibility that the planets in our solar system formed nearer to the Sun and then ‘migrated’ to their current orbital positions in the first few million years after the planets formed. Others have claimed the opposite—that planets formed further away and migrated in. Both of these ideas show that the original Nebular Hypothesis is inadequate, but these attempts to save materialism have fatal flaws of their own.

Other solar systems

In the past 10 years astronomers have found evidence of planets orbiting other stars.1 These ‘extrasolar’ planets are often detected by measuring the ‘wobble’ of their star. Some have been detected by other methods, such as studying the changes in the star’s light as the planet passes in front of the star.

How did the planets form?

Image NASA

Artist impression of a gas giant.

This artist's concept shows the newly discovered Neptune-sized extrasolar planet circling the star Gliese 436. In this depiction, the planet appears gaseous like Jupiter, with a cloudy atmosphere.

Exoplanets, as they are sometimes called, have raised difficult questions for scientists trying to explain their origin.2 These extrasolar stellar systems sometimes have planets similar to the gas giants Jupiter, Saturn, Uranus, and Neptune. Unlike these four gas giant planets in our solar system, many of the exoplanets are located very near their star and they often follow very elongated elliptical orbits.

Evolutionary planetary scientists have had difficulty explaining how a spinning disk can form planets very close to the star. Rather, they believe gas giants could form only if it was cool enough for ice to condense, so that the planet could accumulate enough mass to suck gas in from the cloud (the ice also helps the rock to stick).2 So, some astronomers propose that in some systems planets could form at a large distance from the star and then move inward closer to the star, being pulled by the matter in the disk.

Death spiral

But this theory leads to a problem that has been called the ‘death spiral’.3 If the disk can make the planets move inward close to the star, what will prevent the planets from falling into the star?

Recent computer simulations showed what happens when several planets were migrating inward toward their star—it is highly probable that the planets would eventually collide with the star. Multiple planets would tend to ‘all go down together’ due to their mutual gravitational pulls on each other.

Evolutionary stories

We can thank the Creator that our own solar system is more stable than this. The problem of the planets spiraling into the star is a serious one for scientists who do not allow for the possibility of a Creator God. Some scientists now propose that perhaps some planets do fall into the star but then there are other planets that form. They suggest there could be multiple generations of planets and only some of the planets remain in stable orbits for long periods of time. The difficulty with multiple generations of planets is that the disk of dust and gas that provides the raw material for planet formation cannot last long enough. In ‘only’ a few million years the disk would dissipate and become too thin for planets to form—a big problem for billions-of-years belief. Today various new ideas on planet formation are being explored.

New model: outward migration

Image ESA, NASA and G. Bacon

Artist impression of a transitting extrasolar planet

Artist's view of a transitting extrasolar planet.

A new model of the origin of the planets in our solar system is generating some excitement. It is called the Nice Model, after the city of Nice, France, where the scientists met to develop the theory in 2004.4 The Nice model proposes that Uranus and Neptune originally formed much closer to our Sun than where they currently reside. Also, at one time Jupiter and Saturn supposedly had different orbits that nudged Uranus and Neptune just right to cause them to migrate outward from the Sun. The model also proposes that matter left over after planet formation would cause the newly formed planets’ orbits to change.

The enthusiasm for the Nice Model is because it explains not only why the planets are in their present orbits, but also explains some of the small objects in the solar system and why there was an intense bombardment of impacts after the planets formed. If the large gas planets in our solar system were migrating outward, then this would cause collisions and drastically affect the asteroids as well as objects in the Kuiper region, beyond Neptune’s orbit.

Computer simulations and assumptions

Models such as this are simulated in computer programs. These simulations only work when the investigators assume certain special arrangements. For example, the disk of material left over from planet formation can only be about 30 Astronomical Units (AU) in diameter (one AU is the mean distance of the earth from the sun, 150 million km (93 million miles)). Any larger, and the gaseous planets would move too far out. However, some astronomers have objected to the Nice Model on the grounds that real observed disks around stars are normally much larger, such as 100 or even 300 A.U. in diameter. Another ‘special arrangement’ is that there would have to be a significant number of objects beyond where Saturn formed for the model to work. These objects beyond Saturn would have to cause small changes in the orbits of Jupiter and Saturn. If Jupiter and Saturn were not nudged just right, Uranus and Neptune would not end up in an orbit as we see today.5

Conclusion

There are always unrealistic assumptions when scientists rely on natural processes alone without allowing for a Creator God. From a Christian perspective, God made the special arrangements of the planets to suit His purposes, so that our solar system would be a stable neighborhood for us to reside in. He also apparently created heavenly bodies in such a way as to defy naturalistic explanations.6 The biblical picture of supernatural creation in a young universe is the best explanation of the origin of planets.

Related Articles

Further Reading

References

  1. Spencer, W.R., The existence and origin of extrasolar planets, Journal of Creation 15(1):17–25, 2001. Return to text
  2. See also Planetary evolutionary core theory collapses, Creation 27(1):7, 2004, after New Scientist 183(2457):9, 24 July 2004, where a leading planetary theorist Alan Boss admits, ‘The leading theory for giant planet formation has encountered a mortal blow.’ Return to text
  3. Than, K., Death spiral: why theorists can’t make solar systems, <www.space.com/scienceastronomy/060328_gas_giant.html>, 15 January 2007. Return to text
  4. Chandler, D.L., New world order, New Scientist 192(2579):40–43, 25 November 2006. Return to text
  5. One evolutionist, recognizing problems with evolutionary ideas of the formation of these ‘Ice Giants’, said, ‘Pssst … astronomers who model the formation of the solar system have kept a dirty little secret: Uranus and Neptune don’t exist. Or at least computer simulations have never explained how planets as big as the two gas giants could form so far from the sun.’ R.N., Birth of Uranus and Neptune, Astronomy 28(4):30, 2000; Psarris, S., Neptune: monument to creation, Creation 25(1):22–24, 2002. Return to text
  6. This would be an ‘astronomic message’ by analogy with The Biotic Message by Walter ReMine, available from our store. See also review by Don Batten, Journal of Creation 11(3):292–298, 1997. Return to text
Published: 13 February 2007 (GMT+10)

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