The Sun The sun is the star at

The Sun The sun is the star at the center of our solar system. It contains nearly 99. 9% of all the matter in the entire solar system. It is a giant spinning ball of plasma whose energy is produced deep in the core by nuclear fusion reactions. Mass – 330, 000 times Earth’s mass Diameter – 110 times Earth’s diameter Rotational Period (“day”) – 25. 4 Earth days On the scale of this exhibit, the sun would be approximately this size (. 55 inch):

Mercury is a small, dense planet a little bigger than Earth’s Moon. Even though Mercury is the planet closest to the Sun, it is not the hottest. Diameter – 38% of Earth’s diameter (3, 030 miles) Period of orbit (“year”) – 88 Earth days Average distance from sun – 39% of Earth’s distance (36 million miles) Light travel time from Sun – 3. 2 minutes On this scale, Mercury would be the size of this period (. 002 inch): .

Venus is very similar in size and composition to the Earth. Its dense atmosphere and proximity to the Sun make its surface the hottest in the Solar System. Diameter – 95% of Earth’s diameter (7, 520 miles) Period of orbit (“year”) – 225 Earth days Average distance from sun – 72% of Earth’s distance (67 million miles) Light travel time from Sun – 6. 0 minutes On this scale, Venus would be the size of this period (. 005 inch): .

Earth is our home planet. For many centuries it was assumed to be the center of the universe, but it is now known to be just one planet orbiting the sun. The first images of Earth from space were taken in 1946. This famous photo called The Blue Marble was taken by the crew of Apollo 17 in 1972. Diameter – 7, 930 miles Period of orbit – 1. 0 year (365. 2425 days) Average distance from sun – 93 million miles (1 astronomical unit) Light travel time from Sun – 8. 3 minutes On this scale, Earth would be the size of this period: .

Mars, the red planet, has familiar features including ice caps, volcanos, canyons, and seasons. Plans are being made by NASA and others to visit Mars in the next few decades. Diameter – 53% of Earth’s diameter (4, 220 miles) Period of orbit (“year”) – 1. 88 Earth years Average distance from sun – 1. 52 times Earth’s distance (142 million miles) Light travel time from Sun – 12. 7 minutes On this scale, Mars would be the size of this period (. 003 inch): .

The Asteroid Belt and Ceres, a dwarf planet, is the largest member of the Asteroid Belt, which contains hundreds of thousands of smaller, irregularly shaped objects. Some of these occasionally reach Earth as meteorites. Ceres has large quantities of salty ice and water on its surface. It is probably a protoplanet whose growth halted early in the history of our solar system. Diameter – 7. 5% of Earth’s diameter (610 miles) Period of orbit (“year”) – 4. 6 Earth years Average distance from sun – 2. 77 times Earth’s distance (260 million miles) Light travel time from Sun – 23. 3 minutes On this scale, Ceres would be the size of this period (. 0004 inch): .

Jupiter is more than twice as massive as all the other planets combined and made mostly of hydrogen and helium, like the Sun. Its system of moons includes a fascinating variety of volcanic and watery worlds, some of which are large enough to be considered planets if they orbited the Sun. Diameter – 11. 2 times Earth’s diameter (88, 840 miles) Period of orbit (“year”) – 11. 9 Earth years Average distance from sun – 5. 2 times Earth’s distance (484 million miles) Light travel time from Sun – 43. 2 minutes On this scale, Jupiter would be the size of this dot (. 06 inch): ᴏ

Saturn, a “gas giant” like Jupiter, is most famous for its rings, which are more than 155, 000 miles in diameter but only about ½ mile thick. It has a large collection of interesting moons, including Titan, which has oceans and clouds of methane circling in a weather system with similarities to Earth’s. Diameter – 9. 5% of Earth’s diameter (74, 900 miles) Period of orbit (“year”) – 29. 5 Earth years Average distance from sun – 9. 6 times Earth’s distance (887 million miles) Light travel time from Sun – 1 hours 19 minutes On this scale, Saturn would be the size of this dot (. 05 inch): ᴏ

Uranus Like Saturn, Uranus has rings, but the whole Uranus system – its rings, its moons, and even the spin of the planet itself – is tipped more than 90 degrees from the horizontal. Diameter – 4 times Earth’s diameter (31, 770 miles) Period of orbit (“year”) – 84 Earth years Average distance from sun – 19. 2 times Earth’s distance (1, 780 million miles) Light travel time from Sun – 1 hour 40 minutes On this scale, Uranus would be the size of this period (. 02 inch): .

Neptune and Uranus are “ice giant” planets because water, ammonia, and methane ices make up much of their mass. Neptune has the solar system’s fastest winds, as high as 1, 250 mph. Diameter – 3. 9 times Earth’s diameter (30, 780 miles) Period of orbit (“year”) – 165 Earth years Average distance from sun – 30. 1 times Earth’s distance (2, 790 million miles) Light travel time from Sun – 3 hours 10 minutes On this scale, Neptune would be the size of this period (. 02 inch): .

The Kuiper Belt and Pluto is one of many objects in the Kuiper Belt, which lies beyond the orbit of Neptune and is still largely unexplored. Since 1930 when Pluto was discovered and designated the 9 th planet, even larger objects have been discovered in the Kuiper Belt, and in 2006 Pluto was downgraded to a “dwarf planet”. Diameter – 19% of Earth’s diameter (1, 430 miles) Period of orbit (“year”) – 248 Earth years Average distance from sun – 39. 2 times Earth’s distance (3, 680 million miles) Light travel time from Sun – 6 hours 50 minutes On this scale, Mercury would be the size of this period (001 inch): .

More about Pluto’s orbit is very unusual. It is tilted out of the plane of the orbits of all the planets and it is more elliptical. In fact, at its nearest to the sun (perihelion), Pluto’s orbit brings it inside Neptune’s orbit, and at its farthest (aphelion) it is 4½ billion miles from the sun, more than 50% farther away than Neptune. Look through the telescope to locate the dot on the side of the parking garage that represents Pluto’s distance from the sun at aphelion.

Distances and Diameters The first number is the number of miles. The second is the number of feet or inches in this exhibit. Distances from the center Sun – 0 Mercury – 36 million miles – 1. 9’ Venus – 67 million miles – 3. 5’ Earth – 93 million miles – 4. 8’ Mars – 142 million miles – 7. 4’ Ceres – 260 million miles – 13. 5’ Jupiter – 484 million miles – 25. 2’ Saturn – 887 million miles – 46. 2’ Uranus – 1, 784 million miles – 93’ Neptune – 2, 794 million miles – 145. 6’ Pluto – 4, 586 million miles – 239’ Diameters Sun – 864, 949 miles -. 55” Mercury – 3, 031 miles -. 002” Venus – 7, 521 miles -. 005” Earth – 7, 926 miles -. 005” Mars – 4, 217 miles -. 003” Ceres – 609 miles -. 0004” Jupiter – 88, 844 miles -. 06” Saturn – 74, 900 miles -. 05” Uranus – 31, 765 miles -. 02” Neptune – 30, 777 miles -. 02” Pluto – 1, 429 miles -. 001”

The Solar System This representation of the solar system, at a scale of approximately 20 million miles to 1 foot, shows the relative distances of the planets and other major objects. The sizes of the objects are also calculated but -- aside from the sun, Jupiter and Saturn -- at this scale they would all be smaller than a grain of sand.