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Our Solar System

The Sun: Age of sun: 4.5 billion years, Diameter of sun: 1,112,000 miles, Surface Temperature of Sun: 10,832 degrees F

The Sun is the largest feature in our solar system. It would take 109 Earths to fit around the Sun and 1.3 million Earths to fill the Sun. The surface of the Sun is about 11,000 degrees F while the center of the Sun is 27,000,000 degrees F. The pressure is so intense at the core that nuclear reactions take place. This reaction creates light and energy that lights and warms our planet. Sunspots (dark spots) that appear on the surface of the Sun are cool (7,000 degrees F) in comparison to the surrounding temperatures. Sunspots are known to cause electronic static storms that sometimes interrupt reception to our TVs and radios.

(The picture on the opposite side of the page is of the Earth facing towards the bright Sun)


Distance from Sun: 36 million miles, Time to orbit the Sun: 88 days, Diameter of Mercury: 3,031 miles, Surface Temperature of Mercury: side towards sun - 872 degrees F

Mercury is the fastest planet in our solar system and is named for the Greek god Mercury, who was famous for his running speed. Mercury completes its solar orbit in approximately 88 days. Mercury‘s day surface is the closest to the sun so it is the hottest planet in our solar system. Its night surface is bitter cold. The USA sent a space probe, named Mariner 10, to fly past Mercury in 1974. During its fly-by, the probe measured the surface temperatures and took detailed pictures of the planet’s surface.

Mercury is a small heavily-cratered planet baked on one side from the sun, and frozen on the other side. Mercury is caught in a synchronous orbit, so that one side always faces the sun and the other side always faces away in perpetual darkness. Because of the small size of Mercury and its close proximity to the sun, it retains little or no atmosphere. With extremes of heat and cold, Mercury has a very uncomfortable climate.

(The picture on the opposite side of the page is of a reddish brown planet Mercury in the black of space with stars around it.)


Distance from Sun: 67.6 million miles, Time to orbit the sun: 225 days, Diameter of Venus: 7,562 miles, Surface Temperature: side toward sun – 900 degrees F

Venus is the closest planet to Earth, and it is very much like Earth in many respects. Venus is very close in size to the Earth and is covered in clouds of water vapor and carbon dioxide. There is even evidence that there was once liquid water on the surface. However, the surface of Venus is an inferno, with extremes of pressure and heat, under a drizzle of hydrochloric acid rain.

Scientists have long asked what went wrong on Venus. The answer, it turns out, is that Venus suffers from an excessive greenhouse effect, something that has recently been detected on Earth.

Over the past 35 years, American and Russian probes have explored Venus. Photographs show a forbidding, rock-strewn landscape. The pressure has been found to be 90 times that of Earth’s, and the sky is a brilliant orange. It is unlikely that humans will ever want to land on Venus.

(The planet Venus is depicted as orange and yellow in the dark of space with stars in the background.)


Distance from Sun: 93 million miles, Time to orbit the sun: 365.25 days, Diameter of Earth: 7,926 miles/Surface Temperature of Earth: 72 degrees F

The Earth is by far the most varied and dynamic of the planets. Our planet has a core of molten iron, which creates a magnetic field around the entire planet. There is also a mantle in which solid rocks are not quite liquid, but behave like flexible plastic. The Earth’s crust, on which we live, does not extend down very far – some 6 miles below the continents. Temperatures increase with depth, and at the bottom of the world’s deepest mines the temperature raises to over 150 degrees Fahrenheit. Earth’s atmosphere is made up chiefly of nitrogen (78%) and oxygen (21%).

There are also trace amounts of argon, carbon dioxide, krypton, and xenon, with a variable amount of water vapor.

(Earth is depicted showing the blue water and green land masses and white clouds swirling about.)


Distance from sun: 142 million miles, Time to orbit the Sun: 687 days, Diameter of Mars: 4.222 miles, Surface Temperature of Mars: -10 degrees F

Mars is considerably smaller and less dense than the Earth. It is halfway between the Earth and the Moon in size. Because of the low gravity of Mars and its cold climate, the atmosphere is very thin. Evidence suggests that millions of years ago the atmosphere may have once been warmer and denser. Seasons on Mars are similar to Earth, but longer.

Mars is a vast desert of red rocks and sand dunes, with gigantic valleys and mountains. The “Red Planet” also has ice caps, made up of frozen carbon dioxide (dry ice) and water. There are probably large amounts of water frozen below the surface. Also, red dust storms sweep across the surface, sometimes engulfing the entire planet.

Mars has two moons named Phobos and Deimos. Both of the moons are very small and irregular-shaped. With the close proximity of Mars to the main asteroid belt, it is probable that Phobos and Deimos are large captured asteroids.

(The picture of Mars shows the planet as brownish with some blue patches in the dark of space with stars in the background.)


Distance from the Sun: 484 million miles, Time to orbit the sun: 11.9 years, Diameter of Jupiter: 88,700 miles, Surface Temperature of Jupiter: -240 degrees F

Jupiter, the largest of the planets, lies well beyond the main asteroid zone. It is more massive than all of the other planets combined. Jupiter is composed mainly of gases, primarily hydrogen. Because of its rapid rotation, the disc of the planet is somewhat flattened. The outer clouds of Jupiter are very cold and even contain ice crystals.

According to recent theoretical models, Jupiter has a very hot core about 15 times larger than Earth’s. Around the core is a thick shell of liquid hydrogen so compressed that it takes on the characteristics of a metal. This produces a very powerful magnetic field around the entire planet.

Jupiter has an extensive satellite family and is almost like a miniature solar system. Four of the moons – Io, Europa, Ganymede, and Callisto – are large and bright enough to be seen with any small telescope.

(Jupiter is depicted as a bright mixture of golden yellow, mustard yellow and a swath of a light pink circling around the top half of the planet.)


Distance from Sun: 887 million miles, Time to orbit the Sun: 29.5 years, Diameter of Saturn: 74,500 miles, Surface temperature of Saturn: -290 degrees F

Saturn is almost twice as distant as Jupiter. It takes over 29 years for Saturn to make one revolution around the sun. It is a bright object compared to other stars, and it is second only to Jupiter in size.

Saturn may be the most beautiful object in the solar system. It has a yellowish, flattened disk. Around the planet is a system of vast rings, which can be seen well with even a small telescope. There are three main rings, two bright and one semi-transparent. Other rings have been detected by the space probes that have flown past Saturn.

The gaseous surface of Saturn is made up mostly of hydrogen, together with smaller quantities of other gases. Below the clouds is liquid hydrogen. The rocky core is slightly larger than Earth’s, but it is much denser. The temperature at the center of Saturn may be many tens of thousands of degrees Fahrenheit. Saturn’s satellite family is quite different from that of Jupiter. Saturn has one really large moon, Titan, seven medium-sized moons, and at least fourteen smaller moons. Most of these smaller moons were discovered by the Voyager spacecraft.

(Saturn is depicted as varying shades of brown with a line of red in one of its rings.)


Distance from Sun: 1.8 billion miles, Time to orbit the Sun: 84 years, Diameter of Uranus: 32,200 miles, Surface temperature of Uranus: -350 degrees F

Uranus is the furthest planet visible with the naked eye. It appears in the sky as nothing more than a very faint star. It has a diameter half that of Saturn and a mass 14 times as great as Earth’s. The atmosphere is predominately hydrogen, and it is not easy to determine just where the atmosphere ends and where the real body of the planet begins. The planets rings are very thin, not more than 100 feet thick, and are probably made up of boulders three to seven feet in diameter.

One of the oddities about Uranus is that the planet is flipped on its side. Instead of the equator facing the sun, the Uranian poles are facing the Sun. Thus, when we look at Uranus from Earth, we see the south pole of the planet and the underside of the rings. Scientists do not know for sure why this is so, although some have theorized that Uranus may have been hit by a large object and knocked over on its side.

(Uranus is depicted as bright blue partially hidden in the shadows, on its side, with black rings around it in the dark of space with stars in the background.)


Distance from Sun: 2.8 billion miles, Time to orbit the Sun: 164.8 years, Diameter of Neptune: 30,800 miles, Surface Temperature of Neptune: -360 degrees F

Neptune is too faint to see with the naked eye. In size it is almost identical with Uranus, but it is considerably denser. Neptune takes more than 165 years to make one revolution around the Sun, but it has a fast rotation of 16 hours, 7 minutes. The blue-green disk of this planet features white clouds and a dark stormy region.

Although Uranus and Neptune appear to be near-twins, they are by no means identical. Unlike Uranus, Neptune has a strong source of internal heat. Neptune is mainly composed of ice. The upper atmosphere is composed primarily of hydrogen, with a considerable amount of helium and a little methane. There are various cloud layers, above which lies the methane haze which gives Neptune its beautiful blue-green color.

The most interesting of Neptune’s eight or so moons is Triton, which is slightly smaller than Earth’s moon. The surface temperature of Triton is hundreds of degrees below zero, making it the coldest world ever encountered by a space probe.

(The graphic of Neptune depicts it as a light blue with white streaks in it in the black of space with stars in the background.)


Distance from Sun: 3.6 billion miles, Time to orbit the Sun: 247.7 days, Diameter of Pluto: 1420 miles, Surface temperature of Pluto: -380 degrees F

Named after the god of the underworld, this perpetually frozen world is presumably a gloomy place. Pluto has a curiously eccentric orbit, and when closest to the sun it moves well within the orbit of Neptune. However, since Pluto’s path is inclined by as much as 17 degrees to the plane of the other planets in the solar system, there is little chance of collision.

It was found that Pluto is not a solitary traveler in space. It is associated with a secondary body, which has been named Charon in honor of the boatman who ferries souls across the River Styx on their way to the underworld in Greek mythology. Both Pluto and Charon are locked in synchronus rotations around one another.

Pluto lost its status of planet in August of 2006. It is now regarded as a dwarf planet as is Charon.

(Pluto is depicted as part reddish and brown mottling and the other side is white, on the left side of Pluto is its companion dwarf planet Charon which is all white. Both are in the dark of space with stars in the background.)


Distance from Sun: 267 million miles/Time to orbit the Sun: 4.84 years, Average distance around Asteroids: 587 miles max, Average Surface Temperature: Unknown

Beyond the orbit of Mars lies the main belt of asteroids, or minor planets. Only one, Ceres, is as much as 587 miles in diameter. Most of the members of this swarm of planetary debris are very small, and there are fewer than twenty main-belt asteroids which are as much as 150 miles across. Ceres is the largest member of the swarm.

The current total of asteroids whose paths have been properly worked out is more than 5,000. These small bodies will often wander, venturing in and out of the inner solar system, and sometimes passing close to or even colliding with planets. Two asteroids, 951 Gaspra and 243 Ida, have been surveyed from close range by the Galileo spacecraft, which passed through the main zone on its way to Jupiter. Both are elongated and irregular in shape. Gaspra measures twelve by seven by six miles, and has a dark pitted surface. Ida is larger, with craters which are more degraded.

(Asteroids are depicted as three large black and white rocks in the black of space with stars in the background.)


Distance from Sun: 55 million to 320 billion miles, Time to orbit the Sun:35 to 500 years, Average diameter of Comets: 9 miles max, Average surface temperature of Comets: Unknown

A comet is a ghost-like object. The only substantial part is the nucleus, which has been aptly described as a dirty snowball. When the comet is heated, as it nears the sun, the ices in the nucleus start to evaporate, so that the comet develops a head or coma which may be very large. There may also be one or more tails, although some small comets never produce tails of any sort.

A cometary’s nucleus is composed of rock fragments and dust, held together with ices of frozen ammonia, methane and water. Tails are of two kinds. A gas or ion tail is produced by the pressure of sunlight which drives very small particles out of the head, while a dust tail is due to the pressure of the solar wind. In general, an ion tail is straight, while a dust tail is curved. Tails always point more or less away from the sun.

(The comet is depicted as bright white light in the front with a tail of blue and turquoise going through the black of space with stars in the background.)

Our Moon

Distance from Earth: 618,884 miles, Diameter of Moon: 5,596.36 miles, Time to orbit Earth: 29.5 days

The Moon is the Earth’s natural satellite. It has no atmosphere and no magnetic field like that of Earth. The core is no longer active and thought to be solid. The surface is covered by craters, rocks, and fine dust. With no magnetic field, the surface of the moon is exposed to solar wind and radiation.

It is believed that the moon was formed out of a collision between the Earth and a large wandering body, so that the cores of Earth and the wandering body merged and ejected debris from the Earth’s mantle. This debris formed a temporary ring around the Earth from which the moon eventually built up. This is supported by analysis of lunar rocks, which suggest that the Earth and the Moon are of the same age.

The Moon is the only planetary body to have been visited and have samples returned by humans. The first visit took place July 20, 1969.

(The Moon is depicted as bright white with dark splotches in the dark of space with stars in the background.)

Other sites you can visit:

National Aeronautics and Space Administration (NASA)

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