The Planet that Exploded the Accretion Theory
by J. Timothy Unruh, Copyright Ó 19951
Out in the deep frigid reaches of the solar system, beyond the realm of the classical planets so well known to mankind since antiquity, is a unique and curious world unknown until barely two centuries ago. That a world so large could have escaped discovery until modern times is an interesting fact in itself. Even though scarcely visible except through a telescope the faint wandering star is although within the visibility range of an acute human eye. It is even a matter of surprise that its passage through the zodiacal constellations, some of which have areas completely lacking in bright stars, should not have attracted the attention of observers long before. The discovery of Uranus was already within the bounds of possibility before the invention of the telescope. Nevertheless the planet was not recognized or discovered as a major planetary member of the solar system until well after the advent of the telescope in 1609.
The story of the discovery of Uranus is an interesting account in its own right, of which a few highlights are brought to light here. Friedrich Wilhelm Herschel, better known to us as William Herschel, was born on November 15, 1738 in Germany. He was a gifted musician who later went to England, where he spent the rest of his life, and became perhaps the greatest observational astronomer the world has ever known. On the night of March 13, 1781, while sweeping the sky with a home-made telescope containing a 6 1/2-inch concave mirror of seven foot focal length, Herschel came across an object in the constellation of Gemini which did not look like an ordinary star. Instead of being a point of light it showed a distinct disk, rather bluish or greenish in hue. He watched the curious object move against the starry background from night to night and therefore concluded that it must be much closer than the stars. Mildly excited, Herschel initially thought it to be a comet and reported it to the Royal Society. Herschel's comet was studied by other astronomers and orbital calculations were worked out. The results were, to say the least, startling. The object was not a comet; it was a new planet, moving around the Sun at a distance far greater than that of the then outermost known planet Saturn. Almost overnight the completely unexpected discovery became a world wide sensation and Herschel suddenly became famous. From 1781 onward the reputation of Herschel was as an astronomer and builder of large telescopes, not as a musician.
More than twenty sightings of Uranus by astronomers prior to Herschel's identification had been documented since 1690, although not having Herschel's instruments or genius they all had identified it as a star. Herschel was encouraged and rewarded by George III who was king of England, and to show his gratitude to the potentate Herschel called the new planet Georgium Sidus, or George's Star. For a long time, although, the new planet was popularly called Herschel. The king's name was not accepted by the astronomers and it was later changed to Uranus, after the Greek god of the heavens. Six years after his initial discovery Herschel discovered two of the planet's five major satellites. Ever since the planet received the name Uranus the pronunciation of the word by a lecturer during a discourse on planetary science would invariably be occasioned by at least some hesitation, given that there are several ways the planet is pronounced. Common variations include Your-AIN-us, YUR-in-us, You-RAN-us, and Your-RON-us, with the latter two becoming increasingly popular among discreet advocates at the lectern. Herschel is probably best remembered for his discovery of Uranus although his main work as an astronomer was the study of double stars. This new planet was a consequential fruit of his systematic diligence. Uranus was the first planet to be discovered in modern times. The original symbol assigned to the planet consisted of an upper case letter H with a planet suspended from the letter's cross-bar, the H being in honor of Herschel. This symbol was later discarded and replaced by a figure that appeared much like the symbol for Mars, which itself consisted of a circle with a short arrow extending up from it, the difference being the addition of a dot in the middle of the circle for Uranus. Taking 84 years to revolve around the Sun Uranus has returned only twice to the point in its orbit at which it was discovered, in 1865 and in 1949. The next return to that position will occur in the year 2033.
From Earth the appearance of Uranus is hardly more than a small round uniformly illuminated disk without discernible rings, belts, or spots, subtending only about four arc seconds from which it hardly varies owing to the Earth's small station near the Sun compared to the enormous circuit of Uranus. The planet proved to be a very large world indeed, in league with Jupiter and Saturn, at four times the diameter of Earth or nearly 32,000 miles. It orbits at a mean distance from the Sun of 1,783,000,000 miles, which is nearly twice the distance of Saturn and almost 20 times as far away as Earth from the solar orb. From Uranus the Sun would appear too small for its disk to be discernible to the naked eye, although it would appear as an exceedingly brilliant dazzling star. It requires 84 years for Uranus to complete its journey around the Sun, in an orbit that is only very slightly inclined to the ecliptic. The eccentricity of Uranus's orbit is not particularly noteworthy in itself, although because the planet's circuit is so huge the variation of its distance from the Sun alone amounts to a sum that is nearly twice the amount of the Earth-Sun distance. Being not very Earthlike Uranus is a gas giant consisting of a massive atmosphere made up of hydrogen, methane, and helium. Like the Earth Uranus is decidedly bluish, although for a different reason. Whereas the Earth's atmosphere scatters the Sun's light to give it a blue color, the methane in the atmosphere of Uranus absorbs red light to give that planet its characteristic aquamarine color. Voyager revealed that the entire daylight face of Uranus is radiant with an ultraviolet phenomena the scientists call electroglow. An unknown mechanism somehow pumps power into the upper atmosphere which causes it molecules to glow. The diffuse molecules are hot, as high as 1,350° Fahrenheit. This heating, likely related to the electroglow, causes very tenuous reaches of the atmosphere to expand out into the rings. The temperature of the atmosphere, otherwise, is very cold indeed at -370 degrees Fahrenheit with howling winds that blow many hundreds of miles per hour. It is thought that the planet's atmosphere is some 5,000 miles deep, surrounding a liquid ocean of ammonia and methane extending another 5,000 miles deeper, under which ultimately is a solid rocky center some 12,000 miles in diameter with a hot molten metallic core. Uranus has a magnetic field that is internally off center within the planet. As the planet rotates once every 17 1/2 hours it acts, as one scientist called it, like an oblique rotator. The planet is a slightly oblate spheroid. Uranus is about 14 1/2 times as massive as the Earth, although oddly enough a 100 pound person on Earth would weigh only 92 pounds there if they could stand on the planet's cloudtops. Much of what we know about Uranus was learned by either Earthbound telescopic observations and technical analysis or via the historic encounter of the planet by Voyager II in January 1986.
The planet Uranus is attended by five significant natural moons. These are relatively small although they are all spherical, not fragmental. Their names and sizes in the order of their distance from their primary planet are as follows: 1. Miranda (293 miles in diameter) at 80,700 miles out; 2. Ariel (720 miles) at 118,600 miles; 3. Umbriel (728 miles) at 165,300 miles; 4. Titania (982 miles) at 271,100 miles; and, 5. Oberon (947 miles) the furthest out at 362,500 miles from Uranus. Each of these satellites is remarkably different from the others in its visible surface characteristics. In addition to these five satellites there are ten others, al though they are much smaller and move within the planet's ring system.
The ring system
of Uranus is similar
to the ring system
of Saturn although
not nearly as physically
The Uranian rings
are sufficiently thin
to allow starlight to
through. The ring
from about 11,500
miles to about
16,500 miles above
the Uranian cloudtops,
equator. The rings
were discovered in
1977 during a stellar
the ninth magnitude
star SAO 158687 in
watched the star
A characteristic which makes Uranus particularly unique among the planets is the orientation of its axis. Compared to Earth's 23 1/2 degree tilt, Uranus tilts 97 degrees to the plane of the ecliptic, hence it literally rolls along on it side rather than spins like a top, while it moves through interplanetary space. Thus its axial orientation is at considerable variance with that of the other planets. Uranus is essentially a retrograde world, turned upside-down. At first it seems as though it must have had an original orientation similar to that of the other planets until something forcible made it tilt. This is, of course, what scientists assume in keeping with the theory that the Sun and planets with their moons formed originally from a gradually coalescing and rotating disk shaped cloud of interstellar dust and gasses.
Considered by many scientists as the best theory on the origin of the solar system, is the solar nebula hypothesis. Certainly it is the most widely published theory today. This theory and its variations can be traced ultimately back to an eighteenth century German philosopher by the name of Immanuel Kant. This theory's popularity can be attributed primarily to the fact that it accounts very nicely for the direction of rotation and revolution of the planets and their moons (for the most part) and their orbital inclinations. Yet, this seemingly most promising of theories on planetary origins is plagued by some very serious problems. One of these problems involves the process of accretion itself, namely that high (or low) velocity colliding particles or grains would not stick together. This has been demonstrated in laboratory experiments. The density and integrity of coalescing masses of materials and their gravitational interaction with more tenuous masses within the cloud would more likely inhibit the process especially in consideration of the time frame and the formation of nebular eddies. In fact, dissipation of the nebular cloud would be more likely than accretion in keeping with known physical laws. Other problems, to name a few, include; the question of why the Sun is tilted in relation to the plane of the ecliptic, why the planets do not all rotate in the same direction after all, why the calculated angular momentum of the solar system does not fit within the framework of the nebular model, why the decay rates of the Earth's magnetic field yields too young of an age for the earth, why cometary orbits are so eccentric, why the chemical compositions of the individual planets are so different, and so on.
Even more impressive in all of this is the planet Uranus. Its orientation is entirely incompatible with an evolving solar system. Had Kant known about Uranus, and other solar system anomalies discovered after his time, he might well have had second thoughts about his theory. In order to remedy this inconsistency today it is imagined that Uranus underwent some calamitous experience in the past. It has been suggested that if Uranus had been struck by an object with five percent of its mass the anomalous axial tilt would be accounted for. A mass of this proportion would be equal to one third of the Earth's mass or nearly four times that of planet Mars. Undoubtedly Uranus has undergone some degree of internal trauma and external impaction by cosmic debris as is evident in the other planetary members although the intensity may have been comparative minor in contrast to Mars, for instance, which appears to have sustained intense devastation. There is, although, no object in the solar system other than the planets themselves that is so massive as to inflict a planet toppling result. Furthermore, an object of this size would undoubtedly disrupt the Uranian satellite system if not the planet itself. Yet the orbital elements of these satellites are closer to being perfect than those of any other planetary satellites in the solar system, a fact which seems to strongly negate the possibility of this type of disaster. To consider such a scenario as a collision so large as to disrupt Uranus' axial tilt would be akin to reintroducing catastrophism into the cosmology of the solar system as the dynamic mechanism driving the course of its evolution. Then to be consistent, the only sensible conclusion must be that the the solar system is not as old as it is touted to be by cosmic evolutionists and that it was indeed created ex-nihilo after all. Furthermore, if Uranian satellites formed in accordance with the nebular hypothesis they and their primary should have a prograde orientation which they do not. Then there is, of course, again that perennial question of just where did the primeval material of the solar system itself come from in the first place?
It is much more sensible to assume that the Uranian system was created essentially in the state that it now exists, instantaneously by the same creator, owner, and sustainer of the universe who changed water to wine, healed the infirm, and brought newness of life to countless individuals during and as a result of His earthly ministry. The unique properties of the planet Uranus and the stability of its satellite system indicate, with little exception, a relatively quiet history, and that its orientation in space has always been essentially the same as it is now. The planet stands like a sentinel at the outer reaches of the solar system, a signpost as if to say I am proof that the universe did not evolve by random fate but is singularly the creative work of an eternal, almighty, omniscient and benevolent living God. For as it is written: The fear of the Lord is the beginning of knowledge: but fools despise wisdom and instruction. Through faith we understand that the worlds were framed by the word of God, so that things which are seen were not made of things which do appear. So then faith cometh by hearing, and hearing by the word of God. - Proverbs 1:7; Hebrews 11:3; Romans 10:17
On Tuesday, January 28, 1986, as Voyager scientists were preparing to sum up the Uranus portion of the probe's long mission for the press the space shuttle Challenger exploded. Those clustered in JPL's press center shared a horrible irony. One monitor displayed replay after replay of seven lives evaporating over the Atlantic, while an adjacent TV screen exhibited the latest triumphant photographs from Uranus. As the nation mourned Voyager's present glory was eclipsed.
In some final notes, thanks to a handful of photographs returned by Voyager II we know Uranus' moon Miranda to be one of the most intriguing bodies in the solar system. Miranda is a moon who's features show evidence that it sustained titanic collisions at one time in its past which disrupted its small body and scrambled its innards. At just under 300 miles in diameter Miranda is three times closer to Uranus than the Moon is to our own Earth. With Uranus four times wider than Earth, even at half phase, the planet dominates the Mirandan sky as a turquoise ball of vapor, some six degrees across, whose dayside and nightside are bisected by rings so thin they give the impression of a spider's web strand in space. Auroral streamers are undoubtedly visible on the dark hemisphere. On Miranda a man, or woman, would weigh about 1/100th of what they would weigh on Earth. Thus a 150 pound man on Earth would weigh a measly one pound and eight ounces on Miranda. Such a person could perform superman-like feats. For example, you could heft an automobile sized boulder of ice over your head and toss it 100 feet up into the airless sky. Even though it weighs only 20 pounds you would not, although, want to be under it when it comes back down. If you tried to catch it you would be in for a very hard lesson in the difference between weight and mass. Returning at a mere five miles per hour, the chunk of ice would crunch down with the bone splitting force of a 2,000 pound mass. The physics might be comparable to getting your foot caught between a dock and a powerboat moving at five miles per hour. Your foot might be crushed, yet if that boat were sitting in still water, you could easily shove it away with a kick. Hence the same laws apply to tossing boulders on Miranda, or any other low gravity world in the solar system for that matter. You could jump 30 feet into the sky and remain sky bound for nearly half a minute. In a single bound, you may drift 200 feet from where you leapt. Though you barely weigh two pounds fully dressed in a space suit, you still carry the same mass that goes along with 200 Earth pounds; your forward momentum is one hundred times as sluggish as it would be on Earth. This means you simply cannot just sprint off in some direction and immediately accelerate to ten feet per second. Even slow running speeds must be built up gradually, which means you would need a runway ahead of you! The same goes for when you decide to stop, your mass will tend to continue forward, and if you don't take 25 steps to wind down to a halt you may, after a bumpy quarter-mile long skid on the ice, fall headlong making a three-point landing - two knees and a nose - and end up with your face covered with frozen Mirandan dust! The low gravity there does not provide the surface friction or traction that we normally encounter on Earth.
If you like to skydive you would have the greatest opportunity of
anywhere in creation on Miranda. This little moon happens to be the
location of the tallest known cliff in our solar system. The cliff at
Miranda Canyon, as photographed by Voyager II, is a sheer drop
straight down, well more than 25 times the distance down the sheer face
of Half Dome in Yosemite National Park, or ten times the depth of the
Grand Canyon in Arizona. As one stood at the brink of the precipice his
view would undoubtedly be astounding. Equally astounding might be the
challenge of generating the nerve to jump over the edge at this point.
Once you did, during the first three seconds of your jump off this cliff at
Miranda Canyon, you would fly 30 feet out from the cliff's edge but
barely two feet downward. You count to ten and you are still almost
level with the top of the cliff, now 100 feet behind you. As you would
discover, most of your motion is horizontal. Meanwhile you have plenty
of time for sightseeing, if you are not so distracted by the adrenalin flowing
through your body in a free fall that makes any skydive or bungie
jump back on Earth pale by comparison. After thirty seconds you are 300
feet out from the face of the cliff and 140 down. Finally your downward
velocity catches up with your outbound speed as you are traveling at the
end of a long arc. If you had driven off the cliff at 120 miles per hour in
your Miranda Rover you could actually have gone into orbit around this
moon returning to the cliff top for a relatively uneventful re-entry and a
four wheeled landing some eight hours later.
To an Earthbound observer Uranus appears as a star of magnitude 5.7. The eye can see stars as faint as magnitude 6.2, thus Uranus is well within the limits of human eye visibility. When the planet is favorably placed in a clear dark sky a keen-eyed backyard astronomer equipped with accurate information on its position and a good star map may be able to locate the planet visually and observe the four arc-second object through a modest sized portable telescope. In a telescope Uranus may be seen as a yet tiny although distinct greenish disk.
Asimov, Isaac, Saturn and Beyond, Lothrop, Lee & Shepard Company,
New York, 1979.
NOTES AND REFERENCES
1Back Yard Astronomers, Box 1034, Rocklin, California 95677-1034