In the Beginning The solar system consists of the sun, the eight official planets, at least three "dwarf planets", more than 130 moons of the planets, satellites, comets, and asteroids. The inner solar system contains the sun, Mercury, Venus, Earth and Mars. Mercury, Venus, Earth and Mars are terrestrial planets. A terrestrial planet or rocky planet is a planet that is primarily composed of silicate rocks and/or metals. The main asteroid belt lies between the orbits of Mars and Jupiter. The asteroid belt between Mars and Jupiter forms the boundary between the inner solar system and the outer solar system. The planets of the outer solar system are Jupiter, Saturn, Uranus, and Neptune. These are known as the gas giants. A gas giant is a large planet that is not primarily composed of rock or other solid matter.
The Sun The sun is by far the largest object in the solar system. It contains more than 99.8% of the total mass of the solar system. It is often said that the sun is an "ordinary" star. About half the stars in our galaxy are probably less than half the mass of the sun. The surface of the sun is called the photosphere.
Mercury Mercury is the closest planet to the sun and the eighth largest planet. Mercury is named after the Roman god of commerce, travel and thievery. Mercury has been visited by two spacecrafts, Mariner 10 and MESSENGER. Mariner 10 flew by three times in 1974 and 1975, and was able to map 45% of the surface of Mercury. MESSENGER was launched by NASA in 2004 and will orbit Mercury starting in 2011 after several flybys. It is now known that Mercury rotates three times in two of its years.
Venus Venus is the second planet from the sun and the sixth largest planet. Venus' orbit is the most nearly circular of that of any planet. Venus is named after the Greek goddess of love and beauty. The planet is so named probably because it is the brightest of the planets known to the ancients. The first spacecraft to visit Venus was Mariner 2 in 1962. It may be the least hospitable place for life in the solar system. It is composed mostly of carbon dioxide. There are several layers of clouds many kilometers thick composed of sulfuric acid. Venus' surface is actually hotter than Mercury's despite being nearly twice as far from the Sun. Venus has no magnetic field, perhaps because of its slow rotation. On June 8 2004, Venus passed directly between the Earth and the Sun, appearing as a large black dot travelling across the sun's disk. This event is known as a "transit of Venus" and is very rare. The last one was in 1882; the next one will be in 2012.
Earth Earth is the third planet from the Sun and the fifth largest planet. Earth is the only planet whose English name does not derive from Greek/Roman mythology. The name derives from Old English and Germanic. It was not until the time of Copernicus (the sixteenth century) that it was understood that the Earth is just another planet. Early scientists thought that the Earth was the center of the universe. The crust varies considerably in thickness. It is thinner under the oceans, thicker under the continents. The inner core and crust are solid; the outer core and mantle layers are plastic or semi-fluid. The Earth is the densest major body in the solar system. Earth is currently the only astronomical body in the universe where life is known to exist. The moon is the Earth's only known natural satellite.
Mars Mars is the fourth planet from the Sun and the seventh largest. Mars is named after Ares the Greek god of War. The planet probably got this name due to its red color. Mars is sometimes referred to as the Red Planet. The of the month March gets its name from Mars. The first spacecraft to visit Mars was Mariner 4 in 1965. Several others followed including Mars 2, the first spacecraft to land on Mars and the two Viking landers in 1976. Though Mars is much smaller than Earth, its surface area is about the same as the land surface area of Earth. Mars has some of the most highly varied and interesting terrain of any of the terrestrial planets, some of it quite spectacular. Olympus Mons, rising 24 km, is the largest mountain in the solar system. Like Mercury and the Moon, Mars appears to lack active plate tectonics. At present; there is no evidence of recent horizontal motion of the surface such as the folded mountains so common on Earth. A small number of meteorites are believed to have originated on Mars.
Asteroid Belt The asteroid belt is the region of the solar system located roughly between the orbits of the planets Mars and Jupiter The asteroid belt in simpler terms is what separates Mercury, Venus, Earth, and Mars from Jupiter, Saturn, Uranus, and Neptune. The asteroid belt is filled with many rocky structures.
Jupiter Jupiter is the fifth planet from the sun and the largest planet within the solar system. Jupiter was named after the Roman god, Jupiter, who was the leader of all gods. In Roman mythology, Jupiter was the biggest and most powerful god. Because of these characteristics and Jupiter’s size, the planet was given the same name. Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium. It may also have a rocky core of heavier elements. Jupiter has a faint planetary ring system composed of three main segments, an inner group of particles known as the halo, a relatively bright main ring, and an outer gossamer ring. Jupiter possesses 62 known satellites. The four largest are Callisto, Europa, Ganymede, and were named after Galileo Galilei who observed them as long ago as 1610.
Saturn Saturn is the sixth planet from the sun and the second largest planet in the solar system. Saturn is named after the Roman god, Saturn. Because of Saturn's large mass and resulting gravitation, the conditions produced on Saturn are extreme when compared to Earth. The interior of Saturn is probably composed of a core of iron, nickel, silicon and oxygen compounds, surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium and finally, an outer gaseous layer. Saturn has nine rings which consist mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-twoknown moons orbit the planet. Fifty-three of the moons are officially named. Titan, Saturn's largest and the solar system's second largest moon is larger than the planet Mercury and is the only moon in the Solar System to possess a significant atmosphere.
Uranus Uranus is the seventh planet from the sun and the third largest planet. Uranus is larger in diameter but smaller in mass than Neptune. Uranus is the ancient Greek deity of the Heavens, the earliest supreme god. Uranus, the first planet discovered in modern times, was discovered by William Herschel while systematically searching the sky with his telescope on March 13, 1781. Uranus has been visited by only one spacecraft, Voyager 2, on January 24, 1986. Uranus' magnetic field is odd in that it is not centered on the center of the planet and is tilted almost 60 degrees with respect to the axis of rotation. It is probably generated by motion at relatively shallow depths within Uranus.
Neptune Neptune is the eighth planet from the sun and the fourth largest planet. Neptune is smaller in diameter but larger in mass than Uranus. In Roman mythology, Neptune was the god of the sea. Neptune has been visited by only one spacecraft, Voyager 2, on August 25, 1989. Much of what we know about Neptune comes from this one encounter. But fortunately, recent ground-based and HST observations have added a great deal, too. At the time of the Voyager encounter, Neptune's most prominent feature was the Great Dark Spot in the southern hemisphere. Neptune also has rings. Earth-based observations showed only faint arcs instead of complete rings. But, Voyager 2's images showed them to be complete rings with bright clumps. One of the rings appears to have a curious twisted structure. While Neptune's rings are very dark, like the rings of Uranus and Jupiter, their composition is unknown.
The IAU The IAU is short for International Astronomical Union. In 2006, the IAU decided to create a new classification category for solar system objects called "dwarf planets" that are distinct from "planets". Pluto was reclassified as a dwarf planet. At present, there are only four other members of this category, Ceres, Eris, Makemake and Haumea. But, it is likely that there will be many more in the future as the Kuiper Belt is more fully explored. The actual definition of "dwarf planet" is kind of technical: a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, has not cleared the neighborhood around its orbit, and is not a satellite.
Pluto Pluto is the second most massive known dwarf planet in the solar system . It is the tenth most massive body observed directly orbiting the sun. Originally classified as a planet, Pluto is now considered the largest member of a distinct population known as Kuiper belt objects.
Ceres Ceres is the smallest of the dwarf planets. Ceres is the Roman goddess of the harvest and motherly love. Ceres was discovered on January 1, 1801, by Giuseppe Piazzi. Ceres has not yet been seen up close but NASA's Dawn spacecraft will visit it in 2015.
Kuiper Belt The Kuiper belt sometimes called the Edgeworth–Kuiper Belt. It is a region of the solar system beyond the planets extending from the sun. Since the belt was discovered in 1992, the number of known Kuiper belt objects (KBOs) has increased to over a thousand.
Oort Cloud The Oort cloud is a hypothesized spherical cloud of comets which may lie roughly 50,000 AU, or nearly a light-year, from the Sun. The Oort cloud is thought to comprise two separate regions: a spherical outer Oort cloud and a disc-shaped inner Oort cloud, or Hills cloud. Objects in the Oort cloud are largely composed of ices, such as water, ammonia, and methane. Astronomers believe that the matter composing the Oort cloud formed closer to the sun and was scattered far out into space by the gravitational effects of the giant planets early in the solar system's evolution.
Comparing the Sizes of the Planets Measurements are not to scale. They are about 1/100 the actual diameter of the planets.
The Space Race was a competition of space exploration between the Soviet Union and the United States. It lasted from 1957 to 1975. It had to do with the efforts to explore outer space with satellites, to send humans into space, and to land them on the Moon. The Space Race began after the Soviet launch of Sputnik 1 on October 4, 1957. The Space Race became an important part of the rivalry between the United States and the Soviet Union during the Cold War. Space technology became an extra important area in this rivalry because of possible military uses. One part of the space race was the race to put a man into space. This part was won by the Soviet Union when Yuri Gagarin orbited the earth on April 12, 1961. On May 25, 1961, in a speech, President John F. Kennedy of the United States of America set the goal of landing a man on the Moon by the end of the decade. This also was a challenge to the Russians to try to do it first. Americans won this part of the race in 1969 when Neil Armstrong and Edwin Aldrin, Jr. landed on the moon and returned safely to the earth. At the end of the Cold War, the United States and Russia agreed to build a space station. A contest that began in fear and distrust has become a partnership. See the charts below to see the history of the space race, from 1961 to 1969. Sputnik 1 First man on the moon End Of Cold War Cooperation
The Space RaceTimeline of the American and Russian Space ProgramsUSA in blueUSSR in red
The Reason Why I think that the United States should continue to travel into space. Many people are employed in the NASA space program. During the Apollo space program NASA employed 34,000 people and about 375,000 others outside of NASA. Space exploration fuels the wonderful imagination of children. Their imagination is our hope for the future. The American space program, from its earliest days through the present, has led to thousands of technological advancements that are used every day. Two such products are handheld calculators and trash bags. Space exploration is important for maintaining our national defense. Satellites provide global spying, global targeting abilities, and are vital for global communications. These new technologies have increased our national security and safety. The space program has lead to medical advancements in radiology and other areas. Soon after pictures of the earth from space were published many people became aware of our need to protect our planet. Conservation efforts increased dramatically resulting in many ways to become more energy efficient, and more responsible in how we use our resources. The space program allows us to continue learning about our universe but more importantly to learn more about ourselves. It also provides the challenges we need to become more than what we are.