Adolfo

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Adolfo

  1. 1. TEMA 2 Adolfo Marquina Rubio 1ºB
  2. 2. The stars • The stars are huge spheres of hydrogen and helium gas. According to their colour and temperature, they are classified in different types: STAR TEMPERA TURE Blue 30.000ºC White 9.000ºC Yellow 5.500ºC Orange 4.000ºC Red 3.000- 1000ºC
  3. 3. Energy of a star • The life of a star depends on the amount of energy that is capable of generating at all times. They emit energy due to nuclear reactions/fusions. • Nuclear fusion is a reaction in which two simple atoms come together and combine their nuclei to form a new atom much more complex. • In the stars the union of two atoms of hydrogen atoms forms helium. The stars are in a continuous state of nuclear fusion.
  4. 4. Vital cycle of a star • Stars are born in galactic nebulae which are composed by hydrogen and helium. In our galaxy there are many great nebulae as the Orion nebula and the Trifid nebula. • Protostar: The contraction of the nebula due to gravitational attraction produces the formation of thousands of stellar-mass fragments. The protostars are formed mainly by hydrogen.
  5. 5. Young star • The hydrogen will become into helium. Then the protostar will become a star. Nuclear reactions take place in the center of the star. The energy is released to the surface keeping the whole star hot. The Sun is currently at this stage. The Sun is composed by hydrogen (71%), helium (29%) and other heavier elements (2%).
  6. 6. Red Giant Star • It is the final stage of the life of a star. The structure of the star has changed. The core is now formed by helium and nuclear reactions don’t occur in it anymore. • Nuclear reactions take place in the layer of production of energy. The increase of density makes the core begin to shrink and the temperature increases too. The layer of production of energy becomes denser and the temperature increases. An acceleration of the nuclear reactions is produced. • The production of energy increases the thermal pressure and radiation pressure increase , both will be greater than the force of gravity. The star becomes bigger, outer layers cool down and the star gets red. When the sun becomes a red giant star it will engulf both Mercury and Venus, the Earth will be melted.
  7. 7. Red Supergiant Star • Not all the stars end their life as a red giant star. Massive stars have a more complicated final. During the contraction of the helium nucleus, temperatures of 100.000.000 degrees are reached. New chains of nuclear reactions begin. The nuclear fusion of helium is going to produce carbon and oxygen. The star has two areas of energy production: the core and the outer layer. The percentage of energy production is very large, the pressure increases and the star becomes a red supergiant star.
  8. 8. Cumulus and Galaxies • Galaxies are huge groups of stars, gas and dust. They differ by their shapes and sizes and the number of stars they contain. There are 3 types of galaxy: • Spiral galaxies: Contain a core and a variable number of arms • Elliptical galaxies: They don’t have arms. They consist of old stars and are the largest galaxies known • Irregular galaxies: They don’t have definite form and they are the most abundant. Some of them given their size, are classified as dwarf galaxies • The galaxies are grouped to form even larger structures, called cumulus. • The Milky Way is part of a cumulus called the “Local Group”.
  9. 9. Nebulae, Quasars and Black Holes • Nebulae are giant clouds of gas and dust with different shapes. They are result of big explosions that occur at the end of the life of massive stars. A massive star is a star with a mass ten times the mass of the Sun (2x1030 kg). • Quasars are stellar objects that emit a large amount of energy as radio waves. • Black holes are objects in which the light can’t escape because of their enourmous gravitational attraction.
  10. 10. La formación de los Planetas • Casi toda la materia de la nube que se contrae para convertirse en una estrella acabará dentro de la propia. Sin embargo, una pequeña fracción escapará y quedará girando alrededor de la estrella, se denomina disco protoplanetario. El material que lo compone es principalmente hidrógeno molecular y helio. Si el proceso esta teniendo lugar en una galaxia algo evolucionada como la nuestra hay también carbono, oxígeno, vapor de agua, CO2, silicio, hierro, níquel y más elementos en cantidades menores. • Las moléculas y los granos de polvo giran alrededor de la estrella central, se producen interacciones y choques. Los choques se producen a muy baja velocidad y al chocar los granos se van uniendo y se forman aglomerados cada vez más grandes. Todo el material que contenía el disco protoplanetario pasa a formar los planetas.
  11. 11. La formación de los planetas II • Si el vapor de agua se encuentra lejos de la estrella central, el agua puede formar cristalitos de hielo que pueden unirse entre si formando planetas más grandes. Cerca de la estrella el agua no forma hielo y solo el polvo y los silicatos participan en los procesos de agregación formando planetas pqeuqños y rocosos.
  12. 12. Los Planetas • Para medir la distancia de los planetas al Sol se utiliza la unidad astronómica (para que sobrevivan los cristales de hielo se necesitan 5) que es la distancia media entre la tierra y el Sol, unos 150.000.000 de kilómetros. • A menos de esta distancia se encuentran cuatro planetas pequeños y rocosos: Mercurio, Venus, la Tierra y Marte. • Más alejados se encuentran los otros cuatro planetas, que son gaseosos. Estos planetas son: Júpiter, Saturno, Urano y Neptuno.
  13. 13. Otros astros celestes • Satélite: Son astros que orbitan alrededor de los planetas • Asteroides: Objetos de menor tamaño que los planetas y los satélites. Destacan el cinturón de asteroides entre Marte y Júpiter. • Cometas: Objetos con un núcleo sólido formado principalmente por agua y amoníaco. Cuando se acercan al Sol desprenden partículas de gas que forman la cola del cometa. • Meteoritos: Fragmentos de planetas, cometas y asteroides que van a la deriva por el espacio. Pueden caer sobre la superficie de los planetas y su tamaño varía de unos gramos a toneladas.

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