The solar system and beyound
- 1. T h e S o l a r S y s t e m a n d B e y o u n d * B y B e l l e a n d N a n g f a r *
- 2. T h e S o l a r S y s t e m * O ur solar system consists of an average star we call the Sun , the planets Mercury , Venus , Earth , Mars , Jupiter , Saturn , Uranus , Neptune , and Pluto . It includes : the satellites of the planets; numerous comets , asteroids , and meteoroids; and the interplanetary medium . The Sun is the richest source of electromagnetic energy ( mostly in the form of heat and light ) in the solar system . The Sun's nearest known stellar neighbor is a red dwarf star called Proxima Centauri, at a distance of 4.3 light years away . The whole solar system, together with the local stars visible on a clear night, orbits the center of our home galaxy, a spiral disk of 200 billion stars we call the Milky Way . The Milky Way has two small galaxies orbiting it nearby, which are visible from the southern hemisphere . They are called the Large Magellanic Cloud and the Small Magellanic Cloud . The nearest large galaxy is the Andromeda Galaxy . It is a spiral galaxy like the Milky Way but is 4 times as massive and is 2 million light years away . Our galaxy, one of billions of galaxies known, is traveling through intergalactic space .
- 3. T h e S u n * T he Sun is the most prominent feature in our solar system . It is the largest object and contains approximately 98% of the total solar system mass . One hundred and nine Earths would be required to fit across the Sun's disk, and its interior could hold over 1.3 million Earths . The Sun's outer visible layer is called the photosphere and has a temperature of 6,000°C ( 11,000°F ). This layer has a mottled appearance due to the turbulent eruptions of energy at the surface .
- 4. M e r c u r y * M ercury was named by the Romans after the fleet-footed messenger of the gods because it seemed to move more quickly than any other planet. It is the closest planet to the Sun , and second smallest planet in the solar system . Its diameter is 40% smaller than Earth and 40% larger than the Moon . It is even smaller than Jupiter's moon Ganymede and Saturn's moon Titan .
- 5. V e n u s * V enus, the jewel of the sky , was once know by ancient astronomers as the morning star and evening star . Early astronomers once thought Venus to be two separate bodies. Venus, which is named after the Roman goddess of love and beauty, is veiled by thick swirling cloud cover. Astronomers refer to Venus as Earth's sister planet . Both are similar in size, mass, density and volume . Both formed about the same time and condensed out of the same nebula . However, during the last few years scientists have found that the kinship ends here . Venus is very different from the Earth . It has no oceans and is surrounded by a heavy atmosphere composed mainly of carbon dioxide with virtually no water vapor . Its clouds are composed of sulfuric acid droplets . At the surface, the atmospheric pressure is 92 times that of the Earth's at sea - level .
- 6. E a r t h * E arth is the 3rd planet from the Sun at a distance of about 150 million kilometers ( 93.2 million miles ). It takes 365.256 days for the Earth to travel around the Sun and 23.9345 hours for the Earth rotate a complete revolution . It has a diameter of 12,756 kilometers ( 7,973 miles ) , only a few hundred kilometers larger than that of Venus . Our atmosphere is composed of 78 percent nitrogen, 21 percent oxygen and 1 percent other constituents .
- 7. M a r s * M ars is the fourth planet from the Sun and is commonly referred to as the Red Planet . The rocks, soil and sky have a red or pink hue . The distinct red color was observed by stargazers throughout history . It was given its name by the Romans in honor of their god of war . Other civilizations have had similar names . The ancient Egyptians named the planet Her Descher meaning the red one .
- 8. J u p i t e r * J upiter is the fifth planet from the Sun and is the largest planet in the solar system . If Jupiter were hollow, more than one thousand Earths could fit inside . It also contains two and a half times the mass of all the other planets combined . It has a mass of 1.9 x 10 27 kg and is 142,800 kilometers ( 88,736 miles ) across the equator . Jupiter possesses 62 known satellites . The four largest are Callisto , Europa , Ganymede and Io , and were named after Galileo Galilei who observed them as long ago as 1610 . The German astronomer Simon Marius claimed to have seen the moons around the same time, but he did not publish his observations and so Galileo is given the credit for their discovery .
- 9. S a t u r n * S aturn is the sixth planet from the Sun and is the second largest in the solar system with an equatorial diameter of 119,300 kilometers ( 74,130 miles ). Much of what is known about the planet is due to the Voyager explorations in 1980-81 . Saturn is visibly flattened at the poles, a result of the very fast rotation of the planet on its axis . Its day is 10 hours, 39 minutes long, and it takes 29.5 Earth years to revolve about the Sun . The atmosphere is primarily composed of hydrogen with small amounts of helium and methane . Saturn is the only planet less dense than water ( about 30 percent less ). In the unlikely event that a large enough ocean could be found, Saturn would float in it . Saturn's hazy yellow hue is marked by broad atmospheric banding similar to, but fainter than, that found on Jupiter .
- 10. U r a n u s * U ranus is the seventh planet from the Sun and is the third largest in the solar system . It was discovered by William Herschel in 1781 . It has an equatorial diameter of 51,800 kilometers ( 32,190 miles ) and orbits the Sun once every 84.01 Earth years . It has a mean distance from the Sun of 2.87 billion kilometers ( 1.78 billion miles ). It rotates about its axis once every 17 hours 14 minutes . Uranus has at least 22 moons . The two largest moons, Titania and Oberon , were discovered by William Herschel in 1787 .
- 11. N e p t u n e * N eptune is the outermost planet of the gas giants . It has an equatorial diameter of 49,500 kilometers ( 30,760 miles ). If Neptune were hollow, it could contain nearly 60 Earths . Neptune orbits the Sun every 165 years . It has eight moons, six of which were found by Voyager . A day on Neptune is 16 hours and 6.7 minutes . Neptune was discovered on September 23, 1846 by Johann Gottfried Galle , of the Berlin Observatory, and Louis d'Arrest, an astronomy student, through mathematical predictions made by Urbain Jean Joseph Le Verrier .
- 12. P l u t o * A lthough Pluto was discovered in 1930, limited information on the distant object delayed a realistic understanding of its characteristics . Pluto is the second largest known dwarf planet and tenth largest orbiting the Sun . From its time of discovery in 1930 to 2006 it was considered to be the ninth planet in the solar system, but because additional objects have been discovered including Eris which is 27% more massive, the IAU reclassified Pluto and the other objects as dwarf planets . The New Horizons spacecraft was launched on January 16, 2006 and will make its closest approach to Pluto on July 14, 2015 . This mission will provide an increased amount of information about this peculiar dwarf planet . The uniqueness of Pluto's orbit, rotational relationship with its satellite, spin axis, and light variations all give it a certain appeal .
- 13. A s t e r o i d * A steroids are rocky and metallic objects that orbit the Sun but are too small to be considered planets . They are known as minor planets . Asteroids range in size from Ceres, which has a diameter of about 1000 km, down to the size of pebbles . Sixteen asteroids have a diameter of 240 km or greater . They have been found inside Earth's orbit to beyond Saturn's orbit . Most, however, are contained within a main belt that exists between the orbits of Mars and Jupiter . Some have orbits that cross Earth's path and some have even hit the Earth in times past . One of the best preserved examples is Barringer Meteor Crater near Winslow, Arizona .
- 14. C o m e t * C omets are small, fragile, irregularly shaped bodies composed of a mixture of non - volatile grains and frozen gases . They have highly elliptical orbits that bring them very close to the Sun and swing them deeply into space, often beyond the orbit of Pluto .
- 15. M e t e o r o i d s a n d M e t e o r i t e s * T he term meteor comes from the Greek meteoron , meaning phenomenon in the sky . It is used to describe the streak of light produced as matter in the solar system falls into Earth's atmosphere creating temporary incandescence resulting from atmospheric friction . This typically occurs at heights of 80 to 110 kilometers ( 50 to 68 miles ) above Earth's surface . The term is also used loosely with the word meteroid referring to the particle itself without relation to the phenomena it produces when entering the Earth's atmosphere . A meteoroid is matter revolving around the sun or any object in interplanetary space that is too small to be called an asteroid or a comet . Even smaller particles are called micrometeoroids or cosmic dust grains, which includes any interstellar material that should happen to enter our solar system . A meteorite is a meteoroid that reaches the surface of the Earth without being completely vaporized .
- 16. N I C S *