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. 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.
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.mmThecrust 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.
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. Because of its rapid rotation, Jupiter's shape is that of an oblate spheroid (oblong and not sphere shaped). Jupiter's mass is 2.5 times that of all the other planets in our solar system combined. 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.
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 is probably best known for its system of planetary rings, which makes it the most visually identified object in the solar system.
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 Kuiperbelt 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 Kuiperbelt 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 RaceTimeline of the American and Russian Space ProgramsUSA in blueUSSR in red April 12, 1961: Soviet cosmonaut YuriGagarin became the first man in space with a 1h:48m space flight. May 5, 1961: Astronaut Alan Shepard Jr. became the first American in space with a 15-minute suborbital flight. May 25, 1961: President John F. Kennedy declared a national goal of landing a man on the moon within 10 years. July 21, 1961:.Astronaut Virgil Grissom became the second American in space with a 15-minute suborbital flight. There was a sroblem with the spacecraft door opening too soon. Grissom was rescued but the spacecraft sank. August 6, 1961: Soviet cosmonaut TitoyGherman made the first flight lasting longer than 24 hours. During this flight Gherman made 17 orbits around the earth. Feb. 20, 1962: John Glenn became the first American to orbit Earth. In the almost 5 hour flight, Glenn orbitted the earth 3 times. June 3, 1965: Edward White II became the first American to walk in space while attached to a 23-foot tether. Jan. 27, 1967: Three astronauts died when a flash fire erupted in an Apollo command module during a ground test at Kennedy Space Center in Florida. Dec. 21, 1968: Apollo 8 became the first manned spacecraft to orbit the moon. July 20, 1969: Neil Armstrong and Edwin (Buzz) Aldrinbecame the first men to walk on the moon. Dec. 7-19, 1972: Eugene Cernan and Harrison Schmitt, with the Apollo 17 mission, concluded the longest (75 hours) and final stay on the moon. May 14, 1973: US launched Skylab, its first orbiting laboratory. July 17-19, 1975: US astronauts and Soviet cosmonauts conducted a joint Apollo-Soyuz test project by docking together in space for two days. April 12, 1981: Shuttle Columbia became the first winged spaceship to orbit Earth and returned to an airstrip landing. (My Grandfather Stahl was one of the civil engineers who designed this runway).
June 18, 1983: Sally Ride became the first American woman in space. This was 20 years after the first Soviet woman went into space. Feb. 7, 1984: Bruce McCandless performed man's first untethered spacewalk from the Challenger space shuttle. Jan. 28, 1986: The space shuttle Challenger broke apart 73 seconds after launch. All seven crew members, including teacher Christa McAuliffe, were killed. March 14, 1995: Norman Thagard, riding in a Russian rocket, became the first American to visit the Russian space station Mir. June 29, 1995: The space shuttle Atlantis docks with Mir in its first shuttle-station hookup. Sept. 26, 1996: Astronaut Shannon Lucid set a US record for time in space after returning from Mir. She was in space for 188 days. May 29, 1999: The space shuttle Discovery became the first shuttle to dock with the International Space Station (ISS). Nov. 2, 2000: An American and Russian crew began living aboard the ISS. Feb. 1, 2003: Shuttle Columbia broke apart over Texas 16 minutes before it was supposed to land in Florida, killing all seven crew members. April 2003: The Ansari X PRIZE Foundation was set up to encourage privately funded human spaceflight. June 21, 2004: SpaceShipOne became the first private manned spacecraft to fly to the edge of space and back. It later won the $10 million Ansari X PRIZE.
Aug. 9, 2005: Shuttle Discovery ended a 14-day mission, the first since the Columbia tragedy 2-1/2 years earlier. After a chunk of foam fell from the fuel tank after liftoff NASA grounded the fleet again. July 4, 2006 - Feb. 24, 2010: Nineteen shuttle flights taxied to and from space. Most of these flights ferried crew and parts to the ISS. May 16, 2011: The last scheduled flight of the space shuttle Endeavour launched into space. June 28, 2011: The last scheduled flight of Atlantis will end the US shuttle program.
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.