第十组,Unit 5,The universe Galaxies The Milky Way Solar system The human new exploration of the universe,The universe,The universe is a huge wide-open space that holds everything from the smallest particle to the biggest galaxy. No one knows just how big the Universe is.,Astronomers try to measure it all the time. They use a special instrument called a spectroscope to tell whether an object is moving away from Earth or toward Earth.,光谱仪,原子吸收光谱仪,火花直读光谱仪,纤维光学光谱仪,叶变换红光光谱仪,Based on the information from this instrument, scientists have learned that the universe is still growing outward in every direction,Scientists believe that about 13.7 billion years ago, a powerful explosion called the Big Bang happened.,Scientists are not yet sure if the motion will stop, change direction, or keep going forever.,Galaxy,A galaxy contains stars, gas, and dust which are held together as a group by gravity.,There may be millions, or even billions, of stars in one galaxy. There are billions of galaxies in the universe.,Classify by shape,they look like giant pinwheels in the sky. The galaxy we live in, The Milky Way, is a spiral galaxy.,“spiral“,they look like flat balls.,“elliptical“,Sombrero Galaxy,it doesnt really have a shape.,“irregular“,Mice Galaxies,Hourglass galaxies,In this type of galaxy, new stars just seem to burst out very quickly.,“starburst“,A new type of galaxy,The Milky Way,The Milky Way is over 100,000 light years wide. It is called a spiral galaxy because it has long arms whichspin around like a giant pinwheel. OurSun is a star in one of the arms.,A myth by the ancient Greeks said this white streak was a “river of milk“. The ancient Romans called it the Via Galactica, or “road made of milk“.,Solar system,The Sun,The Greeks calledit Helios.The Suns name comes from the Romans who called it Sol.,The Sun is personified in many mythologies .,The Suns surface, called the photosphere, is at a temperature of about 5800 K. There are some regions that are much “cooler.“ These cool regions are called “sunspots.“ Sunspots are only about 3800 K in temperature , this is why they look darker than the rest of the Sun.,Sunspots can be as large as 50,000km across! Scientists are still trying to explain what causes sunspots.,The Moon passes directly between the Earth and Sun. When this happens, light from the Sun is blocked off for a short time. A solar eclipse can cause complete darkness during the daytime!,solar eclipse,Notes about sun,The Sun is a star , it is not a planet.,The Sun is so big that you could fit more than 1 million earths inside of it!,The Sun is about 75% hydrogen and 25% helium. This is the symbol for the Sun:,The Suns center is about 15 million Celsius.,The Suns energy is produced by nuclear fusion reactions.,IAU assembly vote (International Astronomical Union ),Pluto,In our solar system, eight planets circle around our Sun. The Sun sits in the middle while the planets travel in circular paths (called orbits) around it.,These eight planetstravel in the samedirection (counterclockwiselooking down fromthe Suns northpole).,Mercury Venus Earth Mars,Jupiter Saturn Uranus Neptune,The origin of the eight planets name,Mercury,In Roman mythology mercury is the god of commerce, travel and thievery, the Roman counterpart of the Greek god Hermes, the messenger of the Gods. The planet probably received this name because it moves so quickly across the sky.,Venus,Venus (Greek: Aphrodite; Babylonian: Ishtar) is the goddess of love and beauty. The planet is named probably because it is the brightest of the planets known to the ancients. (With a few exceptions, the surface features on Venus are named for female figures.),Mars,Mars (Greek: Ares) is the god of War. The planet probably got this name due to its red color; Mars is sometimes referred to as the Red Planet. (An interesting side note: the Roman god Mars was a god of agriculture before becoming associated with the Greek Ares; those in favor of colonizing and terraforming Mars may prefer this symbolism.) The name of the month march derives from Mars.,Jupiter (Jove; Greek Zeus) was the King of the Gods, the ruler of Olympus and the patron of the Roman state. Zeus was the son of Cronus (Saturn).,Jupiter,In Roman mythology, Saturn is the god of agriculture. The associated Greek god, Cronus, was the son of Uranus and Gaia and the father of Zeus (Jupiter). Saturn is the root of the English word “Saturday“,Saturn,Uranus,Uranus is the ancient Greek deity of the Heavens, the earliest supreme god. Uranus was the son and mate of Gaia the father of Cronus (Saturn) and of the Cyclopes and Titans (predecessors of the Olympian gods).,In Roman mythology Neptune (Greek: Poseidon) was the god of the Sea.,Neptune,Earth,Earth is the only planet whose English name does not derive from Greek/Roman mythology. The name derives from old English and Germanic. There are, of course, hundreds of other names for the planet in other languages. In Roman mythology, the goddess of the Earth was Tellus - the fertile soil (Greek: Gaia, terra mater - Mother Earth).,