Astronomy www soran edu iq 1 Chapter 7

Astronomy www. soran. edu. iq 1

Chapter 7 Universe Cycle - Solar System 14. 04. 2013 Exam www. soran. edu. iq Meteorology / (Chapter 6 )

Chapter 6 Universe Cycle - Solar System www. soran. edu. iq Meteorology

Gosmolgy: Gosmolgy the branch of astronomy that deals with the general structure and evolution of the universe. The Milky Way is the galaxy that contains the Earth. Galaxy: A system of millions or billions of stars, together with gas and dust, held together by gravitational attraction www. soran. edu. iq

Universe Cycle - Solar System • The universe is commonly defined as the totality of everything that exists, including all physical matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. www. soran. edu. iq Meteorology / (Chapter 6 )

Contents • • • The Solar System Stars Solar Systems, Galaxies & the Universe Comets, asteroids and meteoroids History of the Universe Future of the Universe www. soran. edu. iq Meteorology / (Chapter 6 )

The Solar System What is the Solar System? In the Universe, the Solar System is our homeland, and the Earth is our hometown. www. soran. edu. iq Meteorology / (Chapter 7 )

The Solar System consists of • the sun in its centre • nine planets, circling around the sun • moons • asteroids • and comets. www. soran. edu. iq Meteorology / (Chapter 6 )

The Solar System How did the Solar System evolve? • Scientists are quite sure, that in the beginning of our Solar System there was a huge disc of dirt, rocks, gas, ice etc. • In the middle of this disc, the Sun formed itself and began to glow. • In some distances from the centre, the planets emerged from these rings of dirt, rocks and gas. www. soran. edu. iq

The Solar System How large is our Solar System? • The orbit on which Pluto (the farthest planet) circles the sun, has an average diameter of 5. 910. 000 km (Pluto‘s orbit is rather noncircular). • The sun itself, the largest object in our Solar System has a diameter of 1. 392. 520 km. www. soran. edu. iq Meteorology / (Chapter 6 )

The Solar System www. soran. edu. iq Meteorology / (Chapter 6 )

Planets • Rocky planets �� Formed below the frost line (≈ 3 AU) �� Rich in metal and silicates. Small sizes �� Unable to retain H 2 or He. Thin atmospheres • Gaseous planets �� Formed beyond the frost line �� Condensation of volatiles. Large sizes �� Large atmospheres of H 2 and He www. soran. edu. iq Meteorology / (Chapter 6 )

The Planets Mercury is the planet that is closest to our Sun. Pluto is the farthest. Remember the order of the planets like this: My Very Educated Mother Just Showed Us Nine Planets which means Mercury Venus Earth Mars Jupiter Saturn Uranus Neptun Pluto www. soran. edu. iq Meteorology / (Chapter 6 )

Stars • Stars are burning balls of gas e. g. our Sun • Stars give out light • This light reflects off planets so we can see them • Planets are much smaller than stars … but they seem much bigger as they are much closer • The 9 planets orbit the sun, Earth orbits the Sun once a year www. soran. edu. iq Meteorology / (Chapter 6 )

Solar Systems, Galaxies & the Universe Our Sun is one of millions of stars that orbit the centre of the Universe The Milky Way is one of more than a billion galaxies in the Universe The Universe is expanding www. soran. edu. iq Meteorology / (Chapter 6 )

Solar Systems, Galaxies & the Universe www. soran. edu. iq Meteorology / (Chapter 6 )

Small Bodies There are other smaller object that orbit the Sun, including asteroids, comets, meteoroids and dwarf planets. • Asteroids (also called minor planets) are rocky or metallic objects, most of which orbit the Sun in the asteroid belt between Mars and Jupiter. • Comets are small, icy bodies that orbit the sun. They have very long tails. • Meteoroids are small bodies that travel through space. They are stony and/or metallic and are smaller than asteroids. Most are very tiny. www. soran. edu. iq Meteorology / (Chapter 6 )

Comets • Comets appear every few years • Comets have highly elliptical orbits around the Sun Tail is pushed away from sun by solar pressure Tail is made of ice and rock • Comets are visible when they are close to the Sun • A comet’s orbit is fastest near the Sun due to the Sun’s gravity. It slows as it moves further away from the Sun www. soran. edu. iq Meteorology / (Chapter 6 )

History of the Universe Big Bang Theory • Universe was compressed and exploded – Big Bang • Occurred 15 billion years ago • Estimated by current rate of expansion • Expansion is slowing due to gravity www. soran. edu. iq Meteorology / (Chapter 6 )

Summary • Solar system – 9 planets & 1 star • Stars emit light, planets reflect this light • Solar systems are in galaxies which are in the Universe • Comets (rock and ice) have long elliptical orbits around Sun • Life cycle of stars – differs for massive & small stars • History of the Universe – Big Bang www. soran. edu. iq Meteorology / (Chapter 6 )

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Planets • Rocky planets �� Formed below the frost line (≈ 3 AU) �� Rich in metal and silicates. Small sizes �� Unable to retain H 2 or He. Thin atmospheres • Gaseous planets �� Formed beyond the frost line �� Condensation of volatiles. Large sizes �� Large atmospheres of H 2 and He www. soran. edu. iq Meteorology / (Chapter 6 )

The Planets Mercury is the planet that is closest to our Sun. Pluto is the farthest. Remember the order of the planets like this: www. soran. edu. iq

Mercury What are Mercury‘s features? second smallest planet nearest to the sun one Mercury-year is a quarter Earth-year Mercury is very difficult to be spotted with the naked eye • Mercury has no moons • • www. soran. edu. iq Meteorology / (Chapter 6 )

Venus What are Venus‘ features? • it is a medium sized planet, 2. 5 times as large as Mercury • second nearest to the sun • Venus is very well visible to the naked eye, always close to the sun before sunrise or after sunset • Venus has no moons www. soran. edu. iq Meteorology / (Chapter 6 )

Earth What are Earth‘s features? • it is a medium sized planet, a bit larger than Venus • (probably) the only planet with liquid water in our Solar System • the Earth has one moon • (probably) the only planet with intelligent life in our Solar System www. soran. edu. iq Meteorology / (Chapter 6 )

Mars What are Mars‘ features? it is a small sized planet, half as large as Earth Mars is well visible to the naked eye Mars has two moons: Phobos and Deimos Mars has been visited by robotic vehicles: Pathfinder, Spirit and Opportunity • the question for (former) life on Mars is still unsolved • • www. soran. edu. iq Meteorology / (Chapter 6 )

Jupiter What are Jupiter‘s features? • it is the largest planet of the Solar System, more than 1. 300 Earths could fit inside • Jupiter is well visible to the naked eye • The Great Red Spot on its surface is a giant storm as wide as three Earths • Jupiter has 63 moons! (the largest are Io, Callisto, Ganymede and Europa) www. soran. edu. iq Meteorology / (Chapter 6 )

Saturn What are Saturn‘s features? • it is the second-largest planet of the Solar System, only a bit smaller than Jupiter • Saturn is well visible to the naked eye • the famous rings can be seen with small telescopes • Saturn has at least 34 moons! (recently a probe landed on Jupiter‘s moon Titan) www. soran. edu. iq Meteorology / (Chapter 6 )

Uranus What are Uranus‘ features? • it is medium sized planet of the Solar System • it is quite far away but still can be spotted with small telescopes • like Saturn, Uranus has a system of rings • Saturn has at least 27 moons www. soran. edu. iq Meteorology / (Chapter 6 )

Neptune What are Neptune‘s features? • it is medium sized planet of the Solar System, only a little bit smaller than Uranus • it is quite far away but still can be spotted with small telescopes • Neptune has four rings and at least 13 moons www. soran. edu. iq Meteorology / (Chapter 6 )

Pluto What are Pluto‘s features? • it is the smallest planet of our Solar System • Since Pluto is far away and so small, you need a medium-sized professional telescope or a good amateur telescope to spot it. • Noone knows what Pluto looks like – it‘s too far away and too small. The picture in the background is an artist‘s rendition. • Pluto has one moon: Charon www. soran. edu. iq Meteorology / (Chapter 6 )

Moons What are moons? • Moons are like little planets that encircle the real planets. • Usually, they are much smaller than planets. • Planets can have no moons (like Mercury and Venus), one moon (like Earth) or up to a very large number of moons (e. g. 63 for Jupiter). www. soran. edu. iq Meteorology / (Chapter 6 )

Moons Phobos and Deimos • Phobos and Deimos are Mars‘ companions. Phobos means “fear“, Deimos means “panic“. Mars itself has been named for the Roman God of War. • They are quite small (<15 km) and look rather like potatoes than like moons. www. soran. edu. iq Meteorology / (Chapter 6 )

Moons Io, Callisto, Ganymed and Europa • These four moons are the biggest moons of Jupiter. They can be seen with small telescopes or even with binoculars. Io Europa www. soran. edu. iq Meteorology / (Chapter 6 )

Planets of other stars Are there more planets in the Universe (except for the ones in the Solar System)? • Yes, there are other planets, so-called extra-solar planets. But it is very difficult to spot them, since they are far away. www. soran. edu. iq Meteorology / (Chapter 6 )

Planets of other stars How can planets of other stars be spotted? There are two main ways that astronomers search for these planets: • If you observe a star very accurately with special instruments, you may be able to measure a slight “wobble“. This can indicate a planet. • If you can observe many stars after night, you may sometimes see one get slightly fainter for a little while. This happens if a planet passes between us and the star – like a mini-eclipse. www. soran. edu. iq Meteorology / (Chapter 6 )

More Information Sky. Watch links: • Views of the Solar System • The Nine Planets • Star. Child Celestia Exploration Activity: http: //learn. arc. nasa. gov/planets/ Solar System Exploration: http: //solarsystem. nasa. gov/planets/ Welcome to the Planets: http: //pds. jpl. nasa. gov/planets/ www. soran. edu. iq Meteorology / (Chapter 6 )

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Discovering the atmosphere on different planets An atmosphere is the layer of gases that envelop a planet. On the Earth, it is this envelope that allows organisms to live. Atmospheric ozone protects us from ultraviolet radiation. CO 2 and other gases trap heat and keep the surface warm enough for life to thrive. Oxygen has allowed life to evolve. Each of the planets has a different atmosphere, although there are clear similarities between the atmospheres of the four terrestrial planets and the four gas giant planets. The terrestrial planets are rich in heavier gases and gaseous compounds, such as carbon dioxide, nitrogen, oxygen, ozone, and argon. In contrast, the gas giant atmospheres are composed mostly of hydrogen and helium. The atmospheres of at least the inner planets have evolved since they formed. This is clearest for the Earth. The Earth’s original atmosphere was probably similar to Venus in composition, consisting of carbon dioxide and nitrogen. The evolution of photosynthesis converted carbon dioxide in the Earth’s atmosphere to oxygen, increasing the amount of O 2 in it from an initial 0. 01% to its current 22% level. www. soran. edu. iq

Astronomical unit 1 AU = 149, 597, 870. 691 kilometers Definition: An Astronomical Unit is approximately the mean distance between the Earth and the Sun. It is a derived constant and used to indicate distances within the solar system www. soran. edu. iq Meteorology / (Chapter 6 )

NASA • The (National Aeronautics and Space Administration) is an Executive Branch agency of the United States government, responsible for the nation's civilian space program and aeronautics and aerospace research. Since February 2006, NASA's self-described mission statement is to "pioneer the future in space exploration, scientific discovery and aeronautics research. " www. soran. edu. iq Meteorology / (Chapter 6 )

Atmospheres of the rocky planets www. soran. edu. iq Meteorology / (Chapter 6 )

Atmospheres of Uranus and Neptune www. soran. edu. iq Meteorology / (Chapter 6 )

Homework www. soran. edu. iq