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Moab’s Model Solar System Now in Place

by Jeff Richards

Moab’s own scale model of the solar system was recently installed, allowing residents and visitors to take a stroll from one planet to the other. Although each of the four inner planets (Mercury, Venus, Earth, and Mars) can be walked to with relative ease, getting to Pluto would involve a one-way hike of 9.5 miles! According to project designer Sam Allen, the display is meant to continue the theme started on East Center Street with Star Hall, Sun Court and Moon Stone Gallery. “I got the idea from the scale model solar system that was on display in the stores along Main Street a few years ago. The concept was fascinating to me.” said Allen. The Moab City Council approved the project and planning and community development director David Olsen was instrumental in getting it done, Allen said, adding that special thanks are also due to Rob Morris of the Clark Planetarium for help with the scale calculations and NASA for the images used on the plaques. The distance between the planets of our solar system is hard to comprehend,” said Allen. “By human standards the distances are enormous and yet, when compared to distances between stars in our galaxy the distance between planets seems small.” “This scale model solar system is designed to help convey the enormous distances between the planets compared to their relatively small proportional sizes,” added Allen.

The Sun is represented by a 142-inch diameter yellow disc at the center of the Sun Court, an outdoor basketball court just east of the historic Star Hall building. All of the distances and planet sizes are scaled accordingly (1 inch equals approximately 10,000 kilometers). The locations of the inner planets are marked with plaques around town and along the Mill Creek Parkway. A map showing the location of each plaque is reprinted here, and copies are also available at the Grand County Public Library, where the plaque for Mercury also is located. “Even at this small scale, the solar system is too big to fit inside Moab City limits,” Allen said.

The final plaque on the Mill Creek Parkway represents Mars. The outer five planets are not represented by plaques, but are denoted by their approximate locations along Highway 191 south of town. They are as follows: Jupiter would be at mile marker 124 (near the Farm & City feed store), Saturn at mile marker 123 (by Grand Rental Center and Moab 4x4 Outpost), Uranus at mile marker 121 near the KOA Kampground and Spanish Trail Arena), Neptune at mile marker 118 (by LeGrand Johnson’s) and Pluto at mile marker 116, about two miles south of Old Airport Road. Allen said that at this same scale, the nearest star in our galaxy, Alpha Centauri, would be 65,044 miles away, too far to represent on any earthly scale (this distance is more than two and a half times around the equator of the Earth). The relative sizes of the planets seem miniscule in light of the sizable distances between them, Allen said, adding that the Earth is only the size of a large marble or jawbreaker 1.3 inches in diameter. Saturn is about the size of a basketball, and Jupiter slightly larger than that. Uranus and Neptune are each about the size of a softball or a large grapefruit. Tiny Pluto – demoted to “dwarf planet” status last year ¬¬– is nothing more than a pebble less than a quarter of an inch across. Allen’s son John, 15, is currently working on a web page and Power Point presentation detailing the project, and plans to make the materials available to local school teachers.

The Sun

Start the tour at the Sun Court. The Yellow disc in the center of the basketball court represents the Sun. The Sun is the closest star to Earth, at a mean distance from our planet of 149.60 million kilometers (92.96 million miles). This distance is known as an astronomical unit (abbreviated AU), and sets the scale for measuring distances all across the solar system. The Sun, a huge sphere of mostly ionized gas, supports life on Earth.
The Sun is a huge, glowing ball at the center of our solar system. The Sun provides light, heat, and other energy to Earth. The Sun is made up entirely of gas. Most of it is a type of gas that is sensitive to magnetism. This sensitivity makes this type of gas so special that scientists sometimes give it a special name: plasma. Nine planets and their moons, tens of thousands of asteroids, and trillions of comets revolve around the Sun. The Sun and all these objects are in the solar system. Earth travels around the Sun at an average distance of about 92,960,000 miles (149,600,000 kilometers) from it.


Walk to the Library. The scale size of the planet Mercury is represented by a small marble. The small and rocky planet Mercury is the closest planet to the Sun; it speeds around the Sun in a wildly elliptical (non-circular) orbit that takes it as close as 47 million km and as far as 70 million km from the Sun. Mercury completes a trip around the Sun every 88 days, speeding through space at nearly 50 km per second, faster than any other planet. Because it is so close to the Sun, temperatures on its surface can reach a scorching 467 degrees Celsius. But because the planet has hardly any atmosphere to keep it warm, nighttime temperatures can drop to a frigid -170 degrees Celsius.

Mercury is the planet nearest the Sun. It has a diameter of 3,032 miles (4,879 kilometers), about two-fifths of Earth's diameter. Mercury orbits the Sun at an average distance of about 36 million miles (58 million kilometers), compared with about 93 million miles (150 million kilometers) for Earth.


Next walk to the location of Venus. It is at the southeast corner of the ball park, 300 E. 100 S. The scale size of Venus is about the size of a quarter. Venus and Earth are similar in size, mass, composition, and distance from the Sun, but Venus has no ocean. Venus is covered by thick, rapidly spinning clouds that trap surface heat, creating a scorched greenhouse-like world with temperatures hot enough to melt lead and pressure so intense that standing on Venus would feel like the pressure felt 900 meters deep in Earth's oceans. These clouds reflect sunlight in addition to trapping heat. Because Venus reflects so much sunlight, it is usually the brightest planet in the sky.

Venus is known as the Earth's "twin" because the two planets are so similar in size. The diameter of Venus is about 7,520 miles (12,100 kilometers), approximately 400 miles (644 kilometers) smaller than that of the Earth. No other planet comes nearer to the Earth than Venus. At its closest approach, it is about 23.7 million miles (38.2 million kilometers) away.


Now walk by the bridge in the Cross Trails Park. This is the location of Earth. It is a little larger than Venus, but the scale size is still pretty close to the size of a quarter. Earth, our home planet, is the only planet in our solar system known to harbor life. All of the things we need to survive are provided under a thin layer of atmosphere that separates us from the uninhabitable void of space. Earth is the third planet from the Sun and the fifth largest in the solar system. Earth's diameter is just a few hundred kilometers larger than that of Venus. The four seasons are a result of Earth's axis of rotation being tilted more than 23 degrees.


Follow the path and go through the tunnel under 300 South Street. When you get out of the tunnel on the south side you are about to the orbit of Mars. At this scale Mars is about the size of a dime. Mars is a small rocky body. Its surface has been changed by volcanism, impacts from other bodies, movements of its crust, and atmospheric effects such as dust storms. It has polar ice caps that grow and recede with the change of seasons; areas of layered soils near the Martian poles suggest that the planet's climate has changed more than once, perhaps caused by a regular change in the planet's orbit.

Mars is the fourth planet from the Sun. The planet is one of Earth's "next-door neighbors" in space. Earth is the third planet from the Sun, and Jupiter is the fifth. Like Earth, Jupiter, the Sun, and the remainder of the solar system, Mars is about 4.6 billion years old.


Jupiter is the most massive planet in our solar system. Its scale dimension is about the size of a 14” beach ball. Jupiter resembles a star in composition. In fact, if it had been about eighty times more massive, it would have become a star rather than a planet.

Jupiter is the largest planet in the solar system. Its diameter is 88,846 miles (142,984 kilometers), more than 11 times that of Earth, and about one-tenth that of the Sun. It would take more than 1,000 Earths to fill up the volume of the giant planet. When viewed from Earth, Jupiter appears brighter than most stars. It is usually the second brightest planet -- after Venus.


Saturn is surrounded by thin, flat rings. Saturn is made mostly of hydrogen and helium. Its volume is 755 times greater than that of Earth. At this scale it is a little larger than a basketball. Winds in the upper atmosphere reach 500 meters per second in the equatorial region. These super-fast winds, combined with heat rising from within the planet's interior, cause the yellow and gold bands visible in the atmosphere.

Saturn is the second largest planet. Only Jupiter is larger. Saturn has seven thin, flat rings around it. The rings consist of numerous narrow ringlets, which are made up of ice particles that travel around the planet. The gleaming rings make Saturn one of the most beautiful objects in the solar system. Jupiter, Neptune, and Uranus are the only other planets known to have rings. Their rings are much fainter than those around Saturn.


Uranus is a gas giant with no solid surface. It has some of the brightest clouds in the outer solar system and 11 rings. Its scale size is comparable to a large grapefruit. The first planet found with the aid of a telescope, Uranus was discovered in 1781 by astronomer William Herschel. The seventh planet from the Sun is so distant that it takes 84 years to complete one orbit.
Uranus, (YUR uh nuhs or yu RAY nuhs), is the seventh planet from the Sun. Only Neptune and Pluto are farther away. Uranus is the farthest planet that can be seen without a telescope. Its average distance from the Sun is about 1,784,860,000 miles (2,872,460,000 kilometers), a distance that takes light about 2 hours 40 minutes to travel.


Neptune was the first planet located through mathematical predictions rather than through regular observations of the sky. Nearly 4.5 billion kilometers from the Sun, Neptune orbits the Sun once every 165 years. It is invisible to the naked eye because of its extreme distance from Earth. It is a little smaller than Uranus, so its scale size also about the size of a large grapefruit.
Neptune is one of the two planets that cannot be seen without a telescope. The other is Pluto. Neptune is about 30 times as far from the Sun as is Earth. Pluto is the only planet farther from the Sun than Neptune. But every 248 years Pluto moves inside Neptune's orbit for about a 20-year period, during which it is closer to the Sun than Neptune. Pluto last crossed Neptune's orbit on Jan. 23, 1979, and remained within it until Feb. 11, 1999.


Pluto was discovered in 1930. It was known as the most distant planet from the Sun until August 24, 2006 when the International Astronomical Union (IAU) formally downgraded Pluto to a dwarf planet. Pluto takes 248 years to orbit the Sun. At this scale it is about the size of a pea.
Pluto, (PLOO toh), is a dwarf planet that orbits far from the Sun. It shares the region of its orbit, known as the Kuiper belt, with a collection of similar icy bodies called Kuiper belt objects (KBO’s). From its discovery in 1930, people widely considered Pluto to be the ninth planet of our solar system. However, because of its small size and irregular orbit, many astronomers questioned whether Pluto should be grouped with worlds like Earth and Jupiter. Pluto seemed to share more similarities with KBO’s. In 2006, this debate led the International Astronomical Union, the recognized authority in naming heavenly objects, to formally classify Pluto as a dwarf planet. Pluto cannot be seen without a telescope

Special thanks to for the images.

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