Transcript stars_space
Galaxies Galaxies consist of billions of stars bound together by the force of gravity. There are thought to be at least 200 billion galaxies in our Universe each containing on average 2 billion stars. The Andromeda Galaxy The Sun’s position in the Milky Way Types of galaxy Barred-Spiral – NGC 1300 Our galaxy is this type Spiral – The Whirlpool Galaxy Elliptical – M32 Irregular – The Small Magellanic Cloud Choose appropriate words to fill in the gaps below: Universe The ___________ is made up of billions of galaxies which billions consist of __________ of stars bound to each other by the force of ___________. gravity galaxy Sun is The name of our _________ is The Milky Way. The ______ located towards the outer edge of our galaxy. spiral The are different types of galaxy; ________, barred-spiral, barred-spiral elliptical and irregular. The Milky Way is a ____________ Andromeda galaxy. The _____________ Galaxy is the nearest spiral galaxy to the Milky Way. WORD SELECTION: Andromeda galaxy spiral Sun Universe gravity barred-spiral billions Stars A star is a massive, luminous ball of gas that is held together by gravity. The Sun is a typical star that consists of about 75% Hydrogen, 24% Helium and 1% other elements such as carbon and oxygen. There are about 2 billion stars in our galaxy. The Pleiades Star Cluster The birth of the Sun Nebula Stars usually form inside a nebula. This is a cloud of mostly hydrogen along with smaller amounts of other elements ‘dust’. Many young stars are found inside the Orion nebula The life history of a star Notes questions from pages 268 & 269 1. 2. 3. 4. 5. 6. 7. Copy Figure 2 on page 269. Outline the life history of a star like our Sun. Your account should include what is meant by (a) protostar, (b) red-giant, and (c) white dwarf. Explain the additional stages undergone by the most massive stars. Your account should include what is meant by (a) supernova, (b) neutron star, and (c) black hole. (a) How does a star produce energy? (b) Explain why the Sun is neither expanding or contracting at the present time. Copy and answer questions (a), (b), (c) and (d) on pages 268 and 269. Copy the ‘Key points’ table on page 269. Answer the summary questions on page 269. The life history of a star ANSWERS In text questions: (a) The potential energy of gas and dust decreases when it gathers and is transformed into heat energy. (b) The outward pressure of radiation from its core stops it collapsing. (c) Gravity. (d) Gravity. Summary questions: 1. (a) B, A, C, D. (b) (i) A (ii) It will fade out and go cold. 2. (a) (i) Expand, collapse. (i) Explode, collapse. (b) (i) The neutron star must have sufficient mass. (ii) The gravitational field is so strong that nothing can escape from it. The formation of elements Hydrogen and helium Hydrogen and some helium was formed at the time of the Big Bang. Helium is also formed by nuclear fusion in main sequence stars like the Sun. Lighter elements Elements such as carbon, oxygen and silicon are formed by nuclear fusion in red-giant stars. The heaviest element formed in red-giants is iron. The internal ‘onion’ structure of a red supergiant star Heavier elements All elements heavier than iron are thought to have been formed during supernovae explosions. The fact that such elements exist on Earth is evidence that our Sun and the entire solar system has been formed out of the supernova explosion of an earlier star. Elements such as copper, gold and uranium were formed in supernovae explosions Choose appropriate words to fill in the gaps below: The lightest and most common element in the Universe is hydrogen helium ___________. Hydrogen and some __________ were formed from the Big Bang. fusion Most elements have been formed by nuclear _________ in the lighter cores of stars. Helium and the __________ elements such as carbon _________ are formed by stars like the Sun. iron Elements up to ______ are formed in the core of red supergiant stars. The heaviest elements are formed in supernovae explosions. ___________ WORD SELECTION: carbon hydrogen fusion helium lighter iron supernovae The light year A light year is the distance travelled by light in one year. Light travels at 300 000 000 metres per second = 300 000 kilometres per second = 18 million kilometres per minute = 1.08 billion km per hour = 26 billion km per day = 9.5 trillion km per year!