Phaeton, The Lost Planet: Chapter Four, by J. Timothy Unruh
NEPTUNE: The Planet that was Discovered Before it Was Seen
Until near the end of the eighteenth century the realm of Saturn marked the frontier of interplanetary space. Perhaps no one had previously suspected the existence of planets beyond the boundary line of Saturn's orbit. Even when William Herschel (1738-1822) discovered Uranus in 1781 it was initially announced to be a comet. Several months had passed before the strange object was shown to be a new world revolving about the Sun at the enormous distance of 1,780 million miles. Sixty five years later, orbiting half again further out than Uranus, a second great planet, Neptune, was added to the list of known planets. Whereas the discovery of Uranus was accidental and represented one of the greatest achievements of observational astronomy, Neptune was "deliberately" discovered and has been regarded as one of the greatest achievements of mathematical astronomy. The chronology of events which led up to this planet's discovery make for interesting reading.
Our story begins not with Neptune itself, but with the peculiar behavior of its nearest planetary neighbor, Herschel's Uranus. On the basis of the many observations made in the years subsequent to its discovery, the path of Uranus had been well determined, enabling its past and future positions in the sky to be charted.
By coupling telescopic observations with mathematical equations astronomers are able to do this with great accuracy. In order to make these predictions, the astronomer must also consider the gravitational attraction of other planets in the vicinity of the subject planet. It was then demonstrated that Uranus had been seen and recorded as a star on several occasions during the preceding century and that no less than four astronomers had allowed this great prize to slip through their hands. For about 20 years after its discovery Uranus behaved as it should and arrived at a given point in its orbit on schedule. An unexpected difficulty had, although, arisen; if these early positions were indeed correct, Uranus was considerably off of its charted course, and neither could its path be modified in order to accommodate the old and new observations. Moreover, as time went on, Uranus continued to move still further from its predicted place. By 1840 the planet was again not where it should be, although, to be sure, not far away. However, even the slightest difference between the actual position and the predicted position is not permissible; there must be an explanation for the discrepancy. Astronomers knew that the motion of a planet is changed or perturbed by the influence of other planets in its vicinity. In the case of Uranus, Jupiter and Saturn were "close" by but when the aggregate effects of these planets were considered Uranus still did not behave as it should.
The problem of Uranus caught the interest of many. There were those who attributed the apparent discrepancies in the planet's movements to observational and mathematical error, a well known source of trouble to astronomers. Some thought the variation of Uranus indicated that the laws of gravitation do not apply at great distances. Still Others suggested that Uranus was being drawn off course by the gravitational influence of another planet, yet unknown, orbiting beyond Uranus. Among the latter were two brilliant young mathematicians who, quite independently and in fact unknown to each other at the time, set to work upon the problem of determining, from the observations of Uranus, the location of the disturbing ultra-Uranian planet. It was a problem beset with great difficulties and one whose solution required mathematical skill of the highest degree. Yet, each of these two succeeded in obtaining the probable path of the hypothetical planet and from this the point in the sky which it occupied at the time of discovery. The first of the two investigators to obtain the result appears to have been a young Englishman by the name of Adams.
In 1843, John Couch Adams (1819-1892), who had just graduated from Cambridge University began his mathematical "search" for the unknown planet. Adams spent several years working out mathematical problems to determine that there was another planet, and, once this was established, to determine where it should be located. By October 1845 he had a solution, and went to the Astronomer Royal, Sir George B. Airy (1801-1892), and asked him to search a certain section of the sky for the unknown planet. Because Airy was not convinced that there was another planet and because he believed that the erratic motions of Uranus were due to other causes, and furthermore because the portion of the sky of which Adams wanted him to search was uncharted, Airy laid the problem aside and nothing further became of the matter for almost eight months. Besides being incredulous Airy possibly felt that discovering a planet was a task for men with considerable experience. Adams was just an upstart, a young student. Meanwhile, Urbain J. Leverrier (1811-1877), a French mathematician, independently attacked the same problem. In June 1846 he published a paper which indicated the position where the new planet should be found. Among those who read the paper was Airy who noticed that the position was nearly the same as the position Adams had suggested many months earlier. Now Airy was convinced that there indeed was a new planet. He then finally asked Challis, the astronomer at Cambridge Observatory, to search for it. Even though he looked for it the Cambridge astronomer did not map out his observations and did not recognize the planet. Meanwhile, in France, Leverrier had written to Galle, a German astronomer at the Berlin Observatory, requesting him to look for the unknown planet. Leverrier had written "Direct your telescope to a point on the ecliptic in the constellation Aquarius in longitude 326 degrees, and you will find within a degree of that place a new planet, looking like a star of about ninth magnitude and having a perceptible disk." To his fortune the astronomer at Berlin possessed a new star chart of the region so that the search lasted only half an hour. On September 23, 1846, the same day that he received the letter, Galle and his assistant found the new planet located within just 52 minutes of arc from the predicted position (a distance of less than twice the apparent diameter of the Moon). Airy was a great astronomer in his own right yet it is ironic that he is probably best remembered for his failure to initiate a prompt search for the planet when receiving Adams' calculations. Subsequently a controversy raged over who deserved credit for the discovery. Even though the two later knew each other, neither took much part in the controversy and they remained cordial. A conspicuous mystery, although, remains, and that is, why Adams did not search for the planet personally. He was not only confident of the rough position of the planet but also would have been quite capable of identifying it himself with a modest telescope. Today Adams and Leverrier are both usually credited for the discovery because both men proved themselves as able mathematical astronomers and both of them "discovered" a planet before it was seen.
As for a name for the new planet, the first suggestion came from Galle, the German astronomer who was the first to actually see it. He proposed the name "Janus." In England, Challis put forth the name "Oceanus," particularly appropriate for a seafaring people. In France Arago suggested that the new planet be called Leverrier, a suggestion which was met with stiff resistance outside France. French almanacs promptly reintroduced the name Herschel for Uranus and Leverrier for the new planet. Meanwhile, on separate and independent occasions, Adams suggested altering the name "Georgian" to "Uranus" while Leverrier suggested Neptune for the new planet. Soon Uranus and Neptune became internationally accepted nomenclature. In Roman mythology Neptune was the god of the sea, identified with the Greek Poseidon. The demand for a mythological name seemed to be in keeping with the nomenclature of the other planets, all of which, except Uranus, were named in antiquity. Of interest is the fact that, as in the case of Uranus, astronomers had seen Neptune as a star on several occasions before it was discovered as a planet.
Almost all of the planets are naked eye objects. Even planet Uranus is within the visibility of an acute human eye on a dark clear night. Neptune, although, is only about a tenth as bright as Uranus and even though it is a giant planet, it is so remote that a powerful telescope is required to see it as anything more than an eighth magnitude star. With larger instruments it shows a small greenish disk barely more than two arc seconds in diameter which is roughly equivalent to viewing a faintly lit one-inch marble from one and a half miles away. Thus because of its small apparent size in even the largest telescope Neptune's features are difficult to see in any detail. Even its rotation remained indiscernible until the planet was directly observed with a spectroscope late in the nineteenth century, a device which enabled a reasonable measurement of approaching and receding light sources on the planet's disk as its differentially zoned visible cloud systems rotated. This device thus gave the reasonably close initial value of 18 hours for the planet's rotation period. At a distance of nearly 2,793,000;000 miles, or thirty times that of the Earth from the Sun, Neptune revolves about the Sun in an approximately circular orbit in a period of 165 years. It is the only major planet to exhibit a significant departure from Bode's rule for the spacing of the planets, although it was not enough of a departure to thwart the fine calculations and predictions of Adams or Leverrier for its discovery. With a diameter of about 30,500 miles, which includes a massive atmosphere made up of hydrogen, methane, and ammonia, Neptune is rather a twin of Uranus, although not an identical twin. In particular, Neptune is appreciably denser and more massive than slightly larger Uranus, and, unlike Uranus, appears to have an internal heat source so that despite its greater distance form the Sun it has virtually the same temperature of minus 350 degrees Fahrenheit. Neptune was found to radiate 2.7 times as much energy as it receives from the Sun. The heat source could be attributable to convective activity of some kind or possibly due to tidal effects of its large moon Triton. The light and heat which Neptune receives from the Sun are 1/900th of what we receive on Earth. Since the planet actually rotates once in a little over 16 hours it makes some 90,000 rotations during one revolution about the Sun, thus a "year" on Neptune consists of that many days. Even though Neptune's enormous orbit is nearly circular the variation of the planet's distance from the Sun amounts to a range itself as great as half the distance between the Earth and Sun. If your weight on Earth is 100 pounds, your weight on Neptune would be 110 pounds at its cloud tops.
Neptune is attended by two significant natural satellites, one, Triton ("TRY-ton"), which is somewhat smaller than our own Moon at 1,700 miles in diameter, and the other Nereid ("NEER-ee-id") which is a little over 200 miles wide. Triton revolves around Neptune at a distance that is slightly less than the distance of our Moon from the Earth, and in an orbit that is not only steeply inclined to the equator of Neptune but which carries Triton in a retrograde or backward circuit, or, in other words in a direction opposite to the rotation of Neptune on its axis and its revolution about the Sun. Triton, made up of rock and ice and thought to be similar to Pluto in size and density, takes a little under six days to complete a revolution about Neptune. Nereid, on the other hand orbits Neptune in a highly eccentric prograde orbit which causes its distance from Neptune to vary from 864,000 miles to 6,050,000 miles. Nereid makes its revolution about Neptune in 360 of our days.
Up until the time of the visit of Neptune by the U. S. Voyager II space probe not much was known about this distant planet than that previously mentioned. In 1989 cameras aboard Voyager II showed Neptune to be a mesmerizing aquamarine planet with astounding atmospheric detail never seen through earthbound telescopes. From nearly four billion miles away Voyager transmitted photographic signals which, even at the speed of light, took over four hours to traverse the vast distance from Neptune to radio antennas on Earth. New information derived through Voyager's flyby include: a great dark spot in the planet's cloud cover reminiscent of Jupiter's great red spot; streamers of cirrus-like clouds in its upper atmosphere; latitudinally zonal winds with speeds of nearly 1,000 miles per hour; a thin high-altitude atmospheric haze; a highly inclined and anomalous off-centered magnetic field possibly originating in a turbulent liquid mantle; a refined estimate of 16.1 hours for its rotational period; a half dozen tiny heavily cratered irregular asteroid-like satellites, some of which are larger than Nereid, and which abide among the planet's tenuous rings; enigmatic surface features, and geyser-like plumes on its large moon Triton which contribute to that moon's tenuous atmosphere; and among other things some confirmations of facts about the planet already known from earthbound observations. Voyage II which left Earth in 1977 and spent 12 years to get there passed within barely 3,000 miles of Neptune's north pole at an accelerated speed of 60,000 miles per hour.
If we could imagine ourselves making a visit to Neptune some interesting attributes of its environment would unfold as we cruised above the great planet's atmosphere in our spaceship. We would find that Neptune is even more isolated than Uranus. From this distant planet the Sun would have an apparent diameter of only one arc minute, too small for its shape to be resolved by the human eye. Nevertheless, its star-like point would shine with a light equivalent of more than 500 times the full moon as seen from Earth. Jupiter would never appear more than ten degrees from the Sun, Saturn never more than 18 1/2 degrees, and Uranus never further than 32 1/2 degrees, with all three barely on the border of naked eye visibility. In essence, about all that a visitor would see from Neptune would be the fixed stars, the much brighter pinpoint of the Sun, and the planet's large moon Triton appearing very nearly the same size as our own moon as seen from Earth. Neptune's second moon Nereid would be a variable wandering star ranging in brightness from second magnitude (about as bright as Polaris) to the threshold of naked eye visibility at sixth magnitude. If we were to spend a night on Triton we would see Neptune itself subtending eight degrees across the sky. However, even though Neptune reflects half the light that falls on it, so little of the Sun's light actually illuminates the planet that it would appear as an enormous somewhat ghostly bluish ball with only half the light output as our own full Moon. One of the most noticeable attributes of Neptune, and in particular Triton, would be the utterly bitter cold. At several hundred degrees Fahrenheit below zero the temperature there is only a few degrees above absolute zero, which is -459.72 degrees Fahrenheit - that hypothetical point at which a substance would have no molecular motion, hence, no heat. Visitors would have to be protected from the terrific cold by an incredibly efficient insulator in order to enable them to enjoy the other unique natural characteristics of the Neptunian environment. If we sped out to tiny Nereid during its closest approach to Neptune we could look back and see the planet appearing at about the same size as the earth seen from the Moon, or, about two degrees. If we remained on Nereid we would see the globe of Neptune gradually shrink in the course of time until six months later it would appear about two-thirds the size of the Moon in our skies. Whether Nereid is spherical or irregular in shape seems uncertain, although its size and orbital characteristics would tend to indicate that it is a captured asteroid. If Nereid is, in fact, a captured asteroid one might wonder how it came to be located so far out in the neighborhood of Neptune since most of the known asteroids are found in the inner solar system. Perhaps at one time there was yet another planet beyond Neptune which suffered some catastrophic destruction while two of its former satellites, tiny enigmatic Pluto and its companion Charon, survive as "coupled" planets orbiting the Sun in an eccentric and highly inclined orbit. Or, then again, perhaps they are escaped satellites of Neptune. In recent years, other evidences that indicate just such a possible scenario regarding a former major primeval ultra-Neptunian world have come to light.
Another question which has come up in recent years is the issue of whether or not Neptune rather than Pluto is actually the present official planetary sentinel of the solar system. Due to a technicality Neptune is, in fact, currently the outermost known planet because Pluto's eccentric orbit places that planet closer to the Sun during the years 1980-2000. At least until 1930, when Pluto was discovered, Neptune was the "last" planet. When Pluto was discovered its actual size was not readily discernible, owing mostly to its great distance, although not long after its discovery Pluto was recognized to be not another large planet like Neptune but a very small world indeed. Initially it was thought to have a mass several times greater than that of Barth, which would be consistent with the "mass trail" of the solar system and with the supposed orbital perturbations of the outer planets, but over the years estimates of Pluto's size have been repeatedly downgraded. according to latest measurements Pluto is a mere 1,420 miles across, which is only two-thirds the size of our own Moon and barely a fifth of its mass, and is evidently made up mostly of rock and ice. Pluto's satellite Charon, discovered in 1978, is one-half the diameter of Pluto and about one-twelfth its mass. Some astronomers have even advocated that the Pluto pair is another type of solar system object, perhaps even a large double asteroid. An asteroid like object discovered in 1977 and named Chiron (not to be confused with Pluto's moon Charon) moving in a presumably unstable solar orbit which crosses the orbits of Saturn and Uranus is also thought to be a possible escaped moonlet. Thus, the question of Pluto has triggered a debate as to whether our solar system has nine known planets or only eight. Yet, Pluto has some of the distinct characteristics of a major planet, namely a satellite, an atmosphere, and possibly ice caps. Nevertheless, the conspicuous anomalies of Pluto, its small size, eccentric orbit, and other peculiarities give it a marked contrast with its neighboring gas giants Neptune, Uranus, Saturn, and Jupiter. A current theory about Pluto's origin suggests that while the large planets formed by material "clumping" around a Pluto-like nucleus, Pluto formed without the clumping process. This as well as other ideas are accompanied by many unanswered questions, such as why Pluto has such an eccentric and inclined orbit, compared with the orbits of the other major planets.
Another anomaly that has been observed for some years now is that there seems to be a peculiar sudden "drop-off" of planetary mass at the outer extremities of the solar system, the figurative "Edgeworth Cliff" after the British astronomer who drew attention to it in 1949. It seems as if the solar system is truncated or "sawed off" beyond Neptune. In other words, after reckoning the four gas giants in sequence outward from the Sun there seems to be nothing occupying the dim distant reaches of the solar system beyond Neptune, except tiny Pluto. It would seem sensible that yet another major planetary body even though significantly smaller than Neptune, yet nothing so small as Pluto, should exist out there to "tail off" the solar system. A planetary body with the mass of a half dozen Earths would seem to make sense, as initially conjectured. Yet after intense photographic searches, which should easily have detected such a planet, no such object has ever been found. When Uranus was discovered it was soon deduced that there was another planet further out which explained the odd perturbations in Uranus' orbit. The discovery of Neptune explained these anomalies. Yet still, even Neptune's path seems to 'have some, albeit small, unaccounted for irregularities as if this were evidence for the existence of yet another planet even further out, besides just Pluto, still unknown and exerting a gravitational effect on Neptune. Since we may not have come to the final boundary of the planetary system some have referred to such a hypothetical object as "Planet X."
On September 14, 1992 astronomers of the world learned that a mysterious object was discovered beyond Pluto, along the ecliptic in southwestern Pisces. Nothing in our solar system has been seen so far from the Sun since Pluto's discovery in 1930. Shining at visual magnitude -23.5 the object is 1,000 times fainter than Pluto. It was discovered by two astronomers at a telescope on Mauna Kea in Hawaii. The object is estimated to be some 50 AU from the Sun (an AU, or astronomical unit, is the mean distance between the Earth and Sun). Initially, it wasn't certain whether the reddish colored object was a minor planet or comet. Based on the object's distance and faintness it is estimated to be around 125 miles across, far larger than a typical large comet like Halley's which is only about ten miles across. After orbital calculations were made it was evident that the object maintained a fairly circular orbit, more like a planet rather than a comet. It received a preliminary designation of a minor planet by the International Astronomical Union, 1992 QB1. During the several years since 1992 QB1 was discovered astronomers have located more than thirty additional objects of this new type, similar to QB1, and also in rather circular orbits beyond Neptune. Astronomers agree that since so many of these objects have so far shown up in deep searches of small portions of the sky, there might be perhaps 35,000 such objects, each at least 70 miles across, and circulating at an average distance of about 50 AU from the Sun. Some astronomers have touted these objects as being evidence of the long sought "Kuiper belt," a source "cloud" of short period comets (comets, like Halley's, with periods under 200 years), a cloud similar but not identical to the supposed "Oort Cloud," which is an alleged source of long period comets vastly more distant from the Sun. Whereas the hypothetical Oort cloud model represents a sphere of comets and the Kuiper Belt a disk of comets, the new ultra-Neptunian objects now being discovered are not necessarily comets but actually appear to constitute fragments of what may very likely be a second asteroid belt, not a whole lot unlike the first such belt known since the early 1800's to be circulating between Mars and Jupiter. Like the inner asteroid belt may once have had, this new outer asteroid belt could very well contain icy volatile material in abundance such as frozen gasses which would produce comets if they ventured near the Sun. Being so remote from the Sun in the frigid reaches of the solar system it would make sense, based on what we know of the solar system, that the newly discovered belt probably does contain an abundance of "cometic" material. This new belt of objects, like the intra-Martial-Jovian asteroid belt could very well be the remains of a planet which was disrupted and now exists in pieces. A concentration of these pieces found at 50 AU would be roughly consistent with the systematic spacing of the rest of the planets outward from the Sun as noted by astronomer Johann Bode in 1778, and Heinrich Olbers not much later. It leads one to wonder if perhaps our long sought so-called "Planet X" has finally been found, in pieces!
MAGNETIC FIELD COMPARISONS: A magnetic field is likened to a giant bar magnet buried deep within the interior where it is generated. The invisible "web" and its associated phenomena poses a challenge to those who seek to understand it.
The lines of conjecture which could explain the disruption of a major ultraNeptunian planet would run along the same lines of hypothesizing that were exercised by Olbers and others early in the nineteenth century after the first intra-Martial-Jovian asteroids were discovered. They had formulated the first, and most viable, theory regarding the asteroids and that is that they represent the remains of a lost planet between Mars and Jupiter that was somehow destroyed. What ever the cause might have been, evidence strongly indicates it was an externally induced or internally generated solar system wide trauma. One of the evidences of this is in Neptune's satellite system which is strangely anomalous. Some theorists have supposed that Neptune once had at least four major original satellites but due to some unexplained force two were lost, with the remaining two effected into peculiar orbits which appear to be unstable in the long term. The two lost satellites, some believe, are Pluto and its satellite Charon. Just how the latter two would have remained, or later become, paired remains technically unanswerable.
A remarkable characteristic of our solar system in general is the great variety and diversity found within its members. The evidence is abundant enough that the balance and uniformity of their motions, however altered since their creation, could have resulted only from forces impressed upon them by some great Omnipotent hand; a few things in creation more distinctly proclaim that God made the worlds. Furthermore, God, in His uniquely Divine benevolence, has placed man on a world fixed and furnished in the center of not only His physical concerns but also in the center of His most benign concerns for the well being of His creatures. Man exists on a statistically unlikely yet most startlingly suitable world. In context of the other planets Earth is remarkably exceptional indeed. The mere thought of man trying to breathe the poisonous air of Jupiter or Neptune, instead of the life sustaining temperate oxygen and water atmosphere characteristic of our world, again affirms the magnificent grace and love of God in designing our own unique world. The contrast between our own life sustaining earthly abode and the harsh environments of the distant planets, as our space probes have only just. recently revealed, was already pointed out thousands of years ago when the prophet Isaiah wrote: "For thus saith the Lord that created the heavens; God himself that formed the earth and made it; he hath established it, he created it not in vain ( or, "a worthless waste"), he formed it to be inhabited: I am the Lord; and there is none else." (Isaiah 45:18)
PLUTO: The Planet that May Not be a "Planet" After All
If the whole solar system were to be reduced to fit inside the confines of a football field with the Sun the size of a marble placed on the fifty yard line and Earth a small grain of sand four feet away, Pluto would be an all but invisible speck of dust on the goal line at one end. Most of the planets would be "packed" fairly close together near the Sun, but as one journeys outward distances between planets would be found to increase quickly until by the time we reach Pluto it is lonely indeed. A spectator in the stands above this football field solar system model would certainly see the brilliant Sun and, if his or her eyes were acute, possibly Jupiter and Saturn, but beyond those one would not be able to tell if any of the other planets even existed, including tiny enigmatic Pluto. Paradoxically, if they were all lined up, the largest and brightest object in the solar system, the Sun, would lie at one end while the smallest and faintest "major" solar system member would lie at the opposite extremity. The difference in size (or mass) between these two represents a factor of one in 30,000,000, and the difference in brightness represents a tongue twisting factor of one in 30,000,000,000,000,000. The Sun, of course, shines by its own light, while Pluto shines by light reflected from the Sun.
The planets have been broadly classified into two basic types; terrestrial planets and Jovian planets. The terrestrial planets which include Mercury, Venus, and Mars are so named because they resemble the Earth in size and because they have detectable solid surfaces, hence the term "terrestrial" or Earth-like. The j0', planets, on the other hand, which include Jupiter, Saturn, Uranus, and Neptune, so named because they resemble the largest one, Jupiter, in size and because they, like Jupiter, appear to be made up of gasses, with no evident solid surfaces. Of interest is the fact that the planets of the solar system not only fall neatly into these two groups according to their characteristics, but that they are also naturally divided according to the distances at which they lie from the Sun. The terrestrial planets are those nearest to the Sun, while the Jovian planets are the furthest four. Tiny Pluto, although, does not appear to fit into either classification.
Pluto is so far away, and so little is known about this planet, that there has been debate as to just what Pluto actually is. Is it really a planet, or is it a large asteroid, or even a gigantic comet? Pluto was initially discovered in the context of a search for an unknown planet purported to be the cause of unexplained perturbations in the outer planets. After Uranus was discovered in 1781, astronomers calculated the orbit of that planet and made predictions about exactly where it should be located at various times in the future. Over time, although, it became apparent that there were differences between its predicted and actual locations. This was not supposed to happen, unless there was an unseen planet beyond Uranus. Astronomers knew that planets affect the motions of other objects in their vicinity due to their gravity. Yet when the effects of these other planets were considered Uranus still did not behave as it should. It was when Neptune was discovered in 1846 that the explanation was provided. Yet in time observations of Neptune as well as further observations of Uranus still showed further variations from predictions, albeit small. Thus many people believed there was yet another planet beyond Neptune that was exerting a perturbing force.
During the early years of the twentieth century many astronomers studied the problem. Even by as late as 1900 astronomers did not have much to work with in regards to orbital data about Neptune, for this planet had not completed even a third of its orbit since it was discovered. Neptune takes 165 years to make one revolution about the Sun. Some astronomers went so far as to make calculations for a hypothetical ultra-Neptunian planet. One, William Henry Pickering (1858-1938), felt that the unknown planet should be about 4.8 billion miles out, or about 50 A.U. from the Sun and orbiting with a period of about 375 years (A.U. = Astronomical Unit, the mean distance between the Sun and Earth, or 93,000,000 miles). This would have been roughly in keeping with the spatial pattern of the known planets in their positions outward from the Sun, according to Bode (1772). It was felt that the planet would be comparable, although perhaps not as large as the other outer planets. Of course it would be dimmer, being further out, but not so dim as to be missed in an organized and systematic search. In three days, even the slow motion of such a distant planet would produce a noticeable shift in position against the background stars as viewed through a telescope. Of the astronomers who applied themselves to the task, the most persistent was Percival Lowell (1855-1916), who built an observatory at Flagstaff, Arizona, in 1894, to study the planets. Lowell worked steadily on the problem without solving it before he died in 1916. After Lowell's death his estate was tied up in a long term legal dispute which delayed the search until 1929. Early that year, a 13-inch lens, bought by the observatory from the estate of Reverend Joel Metcalf, arrived at Flagstaff, as did a young amateur astronomer from Kansas named Clyde W. Tombaugh (1906- ). Tombaugh was not quite 23 years old when he arrived at Lowell Observatory as an assistant and had no formal training in astronomy. He personally continued the search initiated by Lowell for the, by now, long sought planet by using photographic techniques through the use of a 13-inch refractor. Pairs of time-exposed photographs were made and then examined with a blink comparator, which was a device for examining numerous photographic plates in rapid succession. It was a rather simple but ingenious device for seeing any moving objects against a background containing many thousands of star images. In April of that year Tombaugh unknowingly recorded the image of a tiny world circling the Sun beyond Neptune. For the third time, Pluto went unnoticed. Twice in 1915 Lowell had recorded it. During the summer rainy season Tombaugh stopped exposing plates and went to work studying all those he had accumulated. His worst problem was the hordes of asteroids which "whizzed" across the plates, which he had to distinguish from any possible planet. Tombaugh spent the summer thinking about his difficulties.
Toward the end of summer Tombaugh implemented a new plan. The young astronomer found that if he restricted his photographic exposures to the region of the sky directly opposite the Sun, or the "opposition" position which is in the sky night, such strategy would afford a much more accurate distinction between relatively nearby asteroids and any distant ultra-Neptunian planet, knowing that the real and apparent motion of a planetary body, hence the length of the trailing it would leave on a photograph, is inversely proportional to the object's distance from the Sun. There was, although, another precaution that was of paramount importance. Owing to the Earth-Sun positional geometry during their opposition to each exterior planet appears to reverse and move backward across the sky for a time. The length and duration of this retrograde arc or loop depends on the distance of each respective planet from the Earth and Sun, being greater for nearby planets such as Mars and the asteroids and very small for objects as far away as Neptune and beyond. The change in direction of a planet from the usual eastward to a temporary westward motion occurs at a stationary point, reached some time before opposition to the Sun, and then again at a second stationary point after opposition where it resumes its normal eastward progress against the backdrop of the stars. While passing through its stationary points, even an asteroid will seem to move so slowly that for about a week it may imitate the apparent motion of a very distant planet. However near the opposition point, which is the point in the middle between the two stationary points, a typical asteroid is in rapid westward apparent motion, and thus can be readily distinguished from any trans-Neptunian object. These considerations limited the strip of sky to be searched each dark-moon period to a 30-degree extent in celestial longitude roughly straddling the ecliptic where any planets should be found. By adhering closely to the actual opposition point, the night to night shift of each planetary suspect served as a quick index of its distance, since most of the apparent retrograde motion was a reflex of the constantly changing positional relationship between the Sun and the Earth. It was an ingenious method of providing an almost fool-proof sky search. Hence Tombaugh started in the constellation Aquarius and worked his way into Pisces and Aries. By November he was making photographs of Taurus, moving closer and closer to the constellation Gemini. Thus the asteroid problem had been eliminated entirely. Nevertheless the effort still represented a tedious process necessitating the examination of typically 50,000 stars per plate.
During that past summer one of several astronomers who had passed through Flagstaff, and had been shown the project during a visit at the observatory, bluntly commented that the program of looking for trans-Neptunian planets was a waste of time and effort. In January though, Tombaugh pointed his telescope at the star Delta Geminorum and exposed three plates of the region, one on January 21st, another on the 23rd, and the third on the 29th. It was not until February 18th that Tombaugh actually studied these plates. Late in the afternoon that winter day he noticed the shift of a small puzzling object. With increasing excitement he compared the three plates and found the object in the right place on all three. After he estimated the faint object to be many millions of miles beyond Neptune, that same afternoon he informed his superiors of the discovery. Two days later with the benefit of a clear night the main telescope of the observatory was turned to Delta Geminorum and with the aid of a finder chart the faint star-like object, which had moved perceptibly from its plate position, was visually observed. After tracking the object for several weeks the astronomers at Lowell Observatory sent a telegram to Harvard College Observatory late on March 12. Then on the 13th of March, 1930, the discovery was announced to the world. The announcement came on the 75th anniversary of the birth of Percival Lowell, founder of the observatory which bears his name, and the 149th anniversary of the discovery of Uranus by William Herschel in 1781. The public besieged Lowell Observatory for news about the object. Newspaper headlines read "Ninth planet discovered on edge of solar system; first found in 84 years." Immediately a great debate ensued over a name for the "new planet." Subsequent observations showed that the object was changing position among the stars thus proving it to be a member of the Sun's family. Neptune was bright in comparison and after the mathematics were complete it had taken only a few minutes to find that planet in 1846, whereas Pluto required many years. Even after all of the mathematical preparations, coupled with the advance of the best equipment and search techniques, it still took more than a year Tombaugh, who himself had arrived at the scene on the eve of fruition of enterprise, to find this elusive little world. Whereas the discovery of Uranus one of the greatest achievements in observational astronomy, and the discovery Neptune was one of the greatest achievements in mathematical astronomy, the discovery of Pluto is considered to be one of the greatest scientific achievements in photographic astronomy!
The names of the planets are drawn from mythological traditions. Mercury, Venus, Mars, Jupiter, and Saturn received their names in antiquity. Since early on, the problem of naming a planet did not reoccur until the discovery of Uranus in 1781. Uranus was Saturn's father, and, after a period of hesitation, this name for William Herschel's planet became universal. Following this precedent there was less argument when Neptune, named after the brother to Jupiter - one of the senior Olympians, made its entry 65 years later. Satellite designations have been accompanied with a greater degree of controversy. Today the International Astronomical Union "officially" names all such objects. In the matter of Pluto the discretion of naming the new object belonged to Lowell Observatory and its director, V. M. Slipher, who, in the words of Clyde Tombaugh, was "urged to suggest a name for the new planet before someone else did." Soon suggestions began to pour in from all over the world. Constance Lowell, Percival's widow who had delayed the search through her lawsuit, proposed "Zeus," then "Lowell," and finally her own first name, none of which met with any enthusiasm. One young couple even wrote to ask that the planet be named after their newborn child. Mythological names were much to the fore. Cronus and Minerva were high on the list. Also there were Odin, Persephone, Atlas, Prometheus, Cosmos, Athene, Hercules, Hera, Pax, Icarus, and many more. One complication was that many of the mythological names had already been allotted to the numerous asteroids. Virtually all the female names had been used up, and male names were usually reserved for objects with unusual orbits. Among the many letters which came forth was one bearing a suggestion inspired by an 11-year old English girl named Venetia Burney. The suggestion was "Pluto," king of the dim and mysterious nether kingdom. After favorable consideration which was almost unanimous, the name Pluto was officially adopted as of an announcement made by Slipher on May 1, 1930. It was fully supported by its discoverer, Tombaugh, and subsequently was never questioned. Interesting enough the first two letters of the name were the initials of Percival Lowell and the last two letters are the first two letters of the discoverer's surname. Perhaps the middle letter "u" stood for the "underworld"! It all seems so fitting; pure coincidence?
After Tombaugh discovered Pluto Slipher encouraged him to continue with his systematic techniques in the search for other distant planets. With the 13-inch telescope the hunt was continued entirely around the sky, and to a considerable distance from the ecliptic. The program of photographing and blinking the images was a long and difficult task. By 1943 a major part of the sky had been combed for planetary bodies as faint as 17th magnitude, but no new planet suspects were found. The pressure of World War II ended the search. Nevertheless some 1,600 new asteroids were marked on plates and over 1,800 variable stars were noted. As well, one new globular star cluster, six galactic star clusters, and 30,000 additional galaxies were counted as by products of the search. Yet, after all this, only one comet was found. Based on the Lowell surveys it seems safe to conclude that no further unknown planets of any consequence exists beyond Neptune that are brighter than magnitude 16. If there were, someone would likely have discovered them long before 1930. As it turns out, the discovery of Pluto is, more than anything, a testimony to the quality of the search rather than the validity of calculations. The thoroughness of the hunt coupled with coincidence compensated for the elusiveness of the object itself.
With the discovery of Pluto there were surprises. The orbit of the new planet was found to be most unusual. Pluto's orbit is highly inclined and remarkably eccentric, or off-centered in its relationship to the Sun. The 17.2 degree inclination of Pluto's orbit from the plane of the ecliptic is far greater than that of any other planet. Mercury held the previous record of a mere seven degrees. Furthermore, the eccentricity of Pluto's orbit, at .250, is also a record, exceeding Mercury's .2056 by a considerable margin. Because of this the total range in Pluto's distance, 2,700,000,000 miles from the Sun at perihelion to 4,600,000,000 miles at aphelion, is 1,900,000,000 miles. This range is equivalent to twenty times the distance between the Earth and the Sun, or the distance between the Sun and a point well past Uranus! At perihelion, Pluto actually crosses the orbit of Neptune, as viewed from above the solar system. This does not mean, however, that a collision is imminent when the two planets approach the intersection point at the same time. The inclination of Pluto's orbit is such that where the two orbits seem to cross Pluto's orbit carries it far below the orbit of Neptune, which separates these planets by a distance of 870,000,000 miles. Furthermore, it has been calculated that the actual motions of Neptune and Pluto are such that they (presently) never meet at the "intersection" point or even near it at the same time, at least under their present orbital economies. Thus, the actual closest distance between the two planets at the "near" approach is not less than 1,550,000,000 miles, which is equivalent to more than sixteen times the distance between the Earth and the Sun. Viewed from Pluto, Neptune at its brightest, might be barely visible, perhaps no brighter than something like a sixth magnitude star. In fact, due to the peculiar geometry of its orbit, Pluto actually passes considerably closer to Uranus than Neptune. For a period of some twenty years during its perihelion approach Pluto remains closer to the Sun the Neptune. The current perihelion of Pluto, in progress from 1979 through the year 1999, thereby makes Neptune the furthest planet in the solar system at the present Neptune is the furthest planet from the Sun for about ten percent of the time. Pluto was certainly not the planet that either Lowell or Pickering had searched for, since its orbit was considerably different from the orbit either had calculated. That Pluto happened to be in the general area where calculations had shown it would be appears to be a coincidence more than anything else. One notable mathematician, after reviewing Lowell's analysis, believed Pluto's discovery was an accident. Controversy over the validity of the predictions continued, fueled by ignorance of Pluto's mass.
If Pluto was actually the heretofore unknown planet astronomers had been looking for, it should have been at least several times the mass of the Earth. In fact initial estimates gave Pluto such a mass, but a disturbing suspicion to the contrary arose very shortly after its discovery. Its magnitude was found to be only 14.90, which was much to low. Lowell had predicted a disk one arc second in diameter with a stellar magnitude of 12. When the astronomers at Lowell Observatory first looked at Pluto visually with the 24-inch refractor no disk could be made out even though the seeing was good. A debate ensued over whether Pluto's faintness was due to its low reflectivity or its small size. If Neptune were at the position of even Pluto's aphelion, its magnitude would be about 10. For Pluto to be so dim must mean that it was a very dark object, or that it was considerably smaller than Neptune. Initially, it was thought to be at least the size of Earth, but through the years since its discovery it size has been continually down graded. In 1950 astronomer Gerard P. Kuiper obtained a view of Pluto as a tiny disk, and after measuring its apparent size calculated its diameter at 3,600 miles which is less than the planet Mars. Astronomers were reluctant to believe this figure and thought Kuiper was mistaken. However, on April 26, 1965, Pluto passed in front of a faint star, and if its diameter had indeed been greater than that of Mars the light from the star would have been totally blocked out during the "eclipse." Since the star was not altogether blocked, all doubts that Pluto was smaller than Mars were eliminated. According to latest measurements Pluto is a mere 1,420 miles across, which is only two-thirds the size of our own Moon and barely a fifth of its mass, being evidently made up mostly of rock and ice. With Pluto many times fainter and less than 1/3,000th as massive than the hypothetical planet originally calculated by Pickering or Lowell, it has, for all practical purposes, no effect on either Uranus or Neptune. In fact, the Earth exerts a greater gravitational force on these two than Pluto ever does. Clearly an object as small as Pluto, which never approaches closer than a billion miles to Uranus or Neptune cannot account for the small discrepancies that remain in the orbits of these latter two. Whatever Pluto is, it is not the planet whose presence was calculated by either Lowell or Pickering. The discovery of Pluto's moon, Charon, and the subsequent determination of Pluto's mass eliminated Pluto as the culprit responsible for any' deviation in Neptune's orbit. It does not, however, remove those deviations, they do still exist.
The assumption that the solar system has always functioned as a dynamic system that runs flawlessly like clockwork is, after all, possibly an erroneous assumption. That the planets are basically well spaced, following nearly circular, nearly coplanar orbits without deviation, is perhaps too often taken for granted. In recent years some astronomers appear to have uncovered certain kinds of unexplained instabilities of a different sort taking place throughout the solar system. Irregularities in the motions of planetary satellites, certain gaps in the asteroid belt between Mars and Jupiter, and even "pseudo-perturbations" in the orbits of the system's planets themselves are leading researchers to argue that these instabilities are the result of inherently chaotic elements in these complex dynamic Systems. There are other peculiarities in the solar system as well, whether or not these are related is not known. Interesting enough, Pluto revolves about the Sun almost precisely twice for every three revolutions of Neptune. In another instance Venus, having a retrograde rotation about its axis, mysteriously shows the same face toward Earth at successive inferior conjunctions. Thus there appears to be in more than one case some remarkable evidence of a resonance function going on between members of the solar system. Otherwise, given a cosmos afflicted by decay rates of various sorts, perhaps in this new science there is an explanation for the heretofore unresolved perturbations of Uranus and Neptune of which astronomers, up to this time, have not considered in their continued search for "Planet X." The present state of the outer planets and their manifest effects could, after all, be "down wind" consequences of initial factors no longer operating. Thus we see Uranus "toppled" on its axis, Neptune "bereaved" of satellites, Pluto a "maverick," and finally the trans-Neptunian asteroid belt just now being discovered. All of this might all very well represent the signature of a solar system wide catastrophe in which the very outer member met a cataclysmic end.
It was earlier observed that Pluto's brightness fluctuates over a period of a little over six days which presumably corresponds to its rate of rotation and co-revolution with its large satellite. By noting the entwined objects' motion around their common center of gravity it has been deduced that Pluto's satellite, Charon, is one-half the diameter of Pluto and about one-tenth its mass. Thus Pluto has set another record, its moon is the most massive satellite relative to its primary in the solar system. The two are essentially a "double planet." As a comparison, it would be like Earth having Mars for its moon. Charon was discovered in 1978 as the result of close examinations of consistently appearing "bulges" in Pluto's image on previously made photographic plates. Accurate diameters of Pluto and Charon at 1,420 and 745 miles respectively have now been derived from the known distance of Pluto, the orbital distance of Charon which is around 12,000 miles from Pluto, and the duration of eclipses between the two. By a fortuitous circumstance a once in 124 years "eclipse season" occurred over a several year period starting in February of 1985 which brought Pluto's moon directly in front of and behind Pluto from our line of sight on Earth. During this rare opportunity to observe a number of inter-Plutonian transits as such, individual spectral analysis of both bodies were possible as well as an indication of the variation in their surface albedos. Apart from a spacecraft mission the eclipse season was about the best thing to being there, for through it much speculation about Pluto and Charon was replaced with solid knowledge. Images of Pluto and Charon obtained recently with the improved Hubble Space Telescope reveal the disks of the two more clearly than any previous views, and show the tiny planet cleanly separated from its even tinier companion. Because of suspected compositional differences between Pluto and Charon, the latter appearing to be more similar to the water ice moons of Saturn it seems evident that the two little worlds did not form together.
The great variation in Pluto's distance from the Sun provides for some interesting peculiarities. From 1979 through the year 1999 while Pluto makes its perihelion passage, it "sees" the Sun shining just as brightly as Neptune does, 1/900th as bright as the solar orb is seen from Earth, or 500 times brighter than our full Moon. In fact, in 1989, at its closest approach, the Sun is actually brighter at Pluto than at Neptune because at this time Pluto is 60,000,000 miles closer to the Sun than Neptune (a distance nearly equivalent to that between Venus and the Sun). When Pluto swings out to its aphelion position in the year 2113, the Sun will appear only about 1/2500th as bright as it is to us on Earth. Even then, the distant Plutonian Sun will shine with the light of nearly 200 full Moons. Famous Halley's comet reaches aphelion at 3,250,000,000 miles which is beyond Neptune, and Pluto at its perihelion. However the comet's distance at this point is only seven tenths as far as Pluto is at aphelion. For one to journey out far enough from the Sun to see the solar "star" only as bright as the full Moon he would have to catch a ride on a comet that went out as far as sixty two billion miles from the Sun, or thirteen and a half times as far as Pluto ever gets! This is only slightly more than a hundredth of a light year away. To see the Sun drop below the threshold of visibility (sixth magnitude) one would have to travel outward to a point about 50 light years from the solar orb.
The origin of Pluto has long been a favorite topic of speculation. Because of its many irregular characteristics this object simply does not seem to fit into any category of a typical planet. Among things the inner extent of Pluto's highly eccentric orbit touches the realm of its neighboring planet, Neptune, on one hand while the outer extent of its orbit touches the realm of a possible former planet, at nearly 50 A.U., on the other hand. Of interest is the fact that numerous very faint 23rd magnitude objects have been discovered out in that far reaching realm since late August of 1992. These objects were, of course, well beyond the magnitude limit of Tombaugh's searches in the 1930's and early 40's. These apparently sizable chunks of debris orbiting in a rather circular stream around the Sun at about 50 A.U. are the objects of the newly discovered "Kuiper belt," which is, in reality, not so likely to be a "comet cloud" but the solar system's second asteroid belt, comprised of planetesimal pieces which are the residue of a disrupted major outer planetary member of the solar system. It seems possible that Pluto is a casualty, or survivor, of some mishap which once must have affected this region, and the solar system as a whole. For many years now astronomers have recognized some rather startling similarities between Pluto and Neptune 5 moon Triton. Both objects have peculiar orbits, both bodies are about the same size, and both appear to be made up of the same substance. Considering Triton's highly anomalous retrograde motion about Neptune some astronomers have surmised that Pluto is an escaped satellite of Neptune, especially given the evidence of the possibility that some past calamitous event disturbed the satellite system of Neptune and ejected Pluto along with Charon. Pluto seems to fit within a subclass of solar system objects which also includes the intra-Saturnian-Uranian "asteroid," Chiron, which was discovered in 1977, as well as Nereid which is the small eccentric secondary satellite of Neptune discovered' in 1949, and Phoebe which is an eccentric retrograde outer satellite of Saturn discovered in 1898. These five objects, including the Pluto pair, could possibly be surviving satellites of disturbed or disrupted major solar system members. These factors along with others previously touched upon, continue to raise the question of Pluto's planetary status.
If we could imagine ourselves traveling in a space ship to that most distant planetary destination at a typical cosmic velocity of 20 times the speed of a high powered rifle bullet, or 36,000 miles per hour, our journey to Pluto would take us well over ten years to get there. For a visitor arriving in the vicinity of Pluto, one of the conditions he would notice first is undoubtedly the exceeding cold. At temperatures near absolute zero, almost all substances are frozen in a granite-hard solid state. Only a residue of gas would probably exist in Pluto's tenuous atmosphere. If we were to land our spacecraft on Pluto we would find that its gravity is so low that a crew member who weighed 120 pounds on Earth would weigh less than five pounds on this alien world. As we viewed the sky we would see the familiar stars and constellations that we know on Earth although in different positions relative to the ground owing to Pluto's anomalous 50 degree axial tilt to its orbital plane. The stars would shine continually during Pluto's nearly week long "day" although the Sun would still illuminate the ground with the brightness of perhaps the turf of a typical outdoor ball park at night. The disk of the Sun would be unresolvable to the eye being merely a point of light, although a very brilliant light source indeed, of magnitude -20, which is still a million times brighter than Venus appears in the twilight sky on Earth. Objects would cast razor sharp shadows on Pluto's surface. An eclipse of the Sun by Pluto's moon Charon would not be a gradually darkening process, as solar eclipses advance on Earth, but an almost sudden and instantaneous plunge into darkness, a darkness which would last for hours rather than just a few minutes as during the totality of terrestrial eclipses.
Over one hemisphere of this strange world we would see Charon perpetually hanging in the sky owing to the fact that the two bodies are locked in a synchronous configuration, in other words Pluto and Charon continually face each other as they revolve about a common center of gravity like the two lobes of a dumbbell held together by a connecting shaft. We would see Charon going through complete phase cycles without ever departing from the sky. As a large stationary moon, Charon would appear quite impressive in size, at almost ten times wider than our Moon appears from Earth, although dimly lit by the distant Sun. In light of Pluto's weak gravity it is amazing enough that this planet has a satellite. If the orbit of Earth's Moon were the same distance from Earth as Charon's orbit is from Pluto the Moon would race around the Earth once in a matter of a few hours. As previously mentioned, Pluto and Charon are so close in size that the two are sometimes referred to as a double planet. In fact Pluto should no longer be referred to as an "it" but a "they"! Both appear to be of the same essential characteristic, large icy rocks. If we were to stand on Pluto's surface and look back toward Earth it would appear as a faint star of about fourth magnitude and never more than two degrees to one side of the Sun, and usually lost in its glare. A powerful telescope would be required to resolve the Earth's one half arc second disk. It would be like looking at something with the thickness of a human hair from 20 feet away.
Prior to 1978 Pluto was characterized as a dense, dark, terrestrial planet that somehow had ended up in the outer reaches of the solar system. Then it became pictured as a relatively small, low-density methane snowball, containing possibly ammonia and other impurities and a highly reflective but irregular surface with dark spots thought by some to be depressions, or possibly even explosion burns. The surface composition and atmosphere of Pluto has even more recently been spectroscopically refined to include an overwhelming amount of nitrogen rather than methane, with traces of frozen carbon monoxide, both existing as either marble-sized gravel or heavily fractured sheets. No water ice or frozen carbon dioxide has yet been confirmed on Pluto's frosty surface. Sublimation of these ices may produce Pluto's tenuous atmosphere which is thought to become thicker during Pluto's "warm" season when the planet is closest to the Sun, although it is likely a mere "wisp" with a surface pressure of only 150 millionths of that on Earth. Pluto's stellar magnitude range has been calculated to be 14.8 as an average, 15.9 at minimum, and 13.7 at brightest, based on a function of its distance. There has been, although, an anomalous dimming of the planet since its discovery which is contrary to what should be expected since it is now closer to us than ever. One suggestion is that as Pluto approaches the warmth of the Sun some of its bright ice is "melting" or sublimating, exposing darker rock underneath.
As we end our "tour" of the outer solar system it is realized that after more than 60 years since its discovery Pluto has remained a mystery on the frontier of the planetary system. Its size, mass, density, surface composition, and albedo, which have been subject to speculation and debate for so long, have only recently been determined with any degree of accuracy. Even if this tiny little world is nothing more than a large trans-Neptunian asteroid, the fascination this object has held for astronomers, or the mysteries it still hides, makes elusive Pluto even more paradoxical and interesting. Then again, even though Pluto is the only planet not yet visited by a man made space probe, our view of Neptune's moon Triton by Voyager II may have already given us a preview of what Pluto is like. Pluto's legacy truly may be one that is far more precious to science in general and astronomy in particular than we realize, as we investigate the unexplored outer reaches of the solar system and examine the traumatic modifications that it has apparently sustained since creation. Pluto's aphelion point at nearly 50 AU, is in the same realm as the early sensibly predicted orbit of hypothetical planet ''X, based on Bode's formula for the systematic spacing of the planets. This rule held very consistent out to Uranus, and to a somewhat lesser degree at Neptune. Perhaps, and just perhaps, those enigmatic ultra-Neptunian fragments lying in the belt now being discovered at 50 AU are the actual remains of that once sentinel planet which marked the outer boundary of the solar system. If such a planet still existed today, it, rather than Pluto would have been our "ninth" planet. Pluto has probably encountered some of these fragments, at one time or another, and is likely a battered world. It must be a wonder that Charon has not already been knocked clear out of her orbit from Pluto. Then again, the volume of space at that far realm is so vast compared to that space occupied by the asteroids in the inner solar system that the likelihood of Pluto or its moon actually being struck by a very large chunk of debris may be comparable to the likelihood of a collision between two randomly placed row boats in the Pacific Ocean.
The planets are the roving stars of heaven which the Almighty made among the lesser lights to illuminate and comfort our world. The ancients had named them after their gods, the same probably were those fallen beings who committed the atrocity recorded in Genesis 6:1-4, and those who inspired the mythological traditions of old which have survived to this day. That He made a few planets that cannot be seen may at first seem useless. Yet there appears to be a higher purpose for these celestial orbs of the planetary realm. In the Scriptures there seems to be an implicit relationship between the angelic host of heaven and the celestial luminaries of which these beings must have their comings, and goings. That these places would be inhabited by angels from the realm of glory seems not only sensible but probable, especially when the Scripture declares "Thus the heavens and the earth were finished, and all the host of them" (Genesis 2:1). We are clearly told that the Earth was furnished to be a suitable habitation for man (Isaiah 45:18), while it is apparent that the heavenly host dwelleth among the starry heavens and amidst the invisible realms of God. Certainly, if we must be like a child to enter the kingdom of God, we may also, with childlike faith, believe that which God has said about His creation and the starry realm above our heads. As the reader of Scripture will see, the Word of God has much to say about astronomy, and after careful study it will be found to be, in all respects, of strategic importance to the believing scientist in his understanding of the cosmos. Certainty, the trans-Neptunian realm confirms the unique Divine creation of not only the Earth, but the planets and the whole of the cosmos. As God's revelation touches upon astronomy it is possible to develop sensible models and predictions in this most wonderful of sciences.
Pluto is the only planet that presents a real challenge to the backyard astronomer with his moderate sized telescope. Even at its brightest, at magnitude 13.7, Pluto is still a hundred times fainter than Neptune and requires a telescope with an aperture of at least 10 inches in order to see it as a tiny speck of light, then only after the difficult effort of finding it. Since its discovery in the constellation of Gemini in 1930, and after taking years to move through each subsequent constellation, Pluto is presently moving slowly eastward through Virgo. Finder maps showing its location among the stars are usually published in the major astronomical journals. Because Pluto's closest approach to Earth for anyone now living occurred on the night of May 4-5, 1989 it has been about the brightest it will ever get, hence the most accessible to amateur telescopes. Whereas now an observer with a 10-inch aperture telescope can see it, in the year 2113 when Pluto will be furthest away at its aphelion point in the constellation Cetus, a 20-inch instrument will be needed to reveal it. This elusive yet highly attractive and challenging telescopic target is a spectacular sight given the knowledge and history of what the backyard observer is actually seeing when he or she peers at it through the magnifying glass of and astronomical telescope.
Copyright © 1995, 1996. All Rights Reserved. Published by RUHE COMPANY, P.O. Box 1034, Rocklin, California 95677-1034. No portion of this book may be reproduced in any form whatsoever without written permission from the publisher. Internet edition, January 17, .1997
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