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Using the word list at the bottom of the page, fill in the blanks in the paragraphs below.
The Universe is believed to have been formed from a very dense fireball _____________ of years ago. As the fireball expanded and cooled stars and galaxies formed. The fireball explosion is often called the ___ ________. The explosion threw all the material outwards; that is why scientists believe the universe is getting bigger or ____________. Scientists have confirmed that the Universe is expanding by examining the light given off by stars. Astronomers now know that the distance to the furthest galaxies is becoming greater as these galaxies are moving away the __________. Stars are produced from gas clouds or ___________, which contain mainly the element ____________. The _________ Nebula is a typical example. The type of star produced depends on the mass of the star. Red _________ are stars formed which have a mass _________ than that of our ____________ The most common star system to form is a ___________ star system. These star systems contain only _______ stars. Sometimes the mass of a star is not ________ enough for the star to undergo _________ _____________ The planet __________ could be such a star, which are called brown ________________
Hydrogen is the __________ of all stars. During nuclear fusion the hydrogen molecules combine producing ____________, releasing lots of ____________ in the process. How quickly the hydrogen is used up depends on the size of the star. Massive stars burn hydrogen very quickly. Additional nuclear fusion reactions can convert helium into elements with larger atoms, for example lithium. However the elements with the largest atoms only form when a star explodes as a _______________
Nuclear fusion is the opposite of nuclear fission. During nuclear fusion elements with a small mass combine to make bigger mass elements. Nuclear fission works by splitting up the elements with a large mass to make smaller elements. __________________ is the fuel normally used in nuclear fission reactions. Nuclear power stations are used to produce __________________.
The amount of energy given out by a star, its luminosity, varies considerably. ____________ dwarfs are stars that have a very low luminosity, about one hundredth of the Sun. Super giant stars which are very large red giant stars, can give out as much energy as 1,000,000 Suns. Some scientists believe that our Solar System was once a binary star system. The Sun was the __________ of the two stars and burnt its fuel slowly, lasting millions of years. The larger star used up all its fuel and destroyed itself in a supernova explosion, leaving the Sun behind.
The Sun is a very stable star. In a few billion years from now the Sun will use up its fuel supply and start to change. It will probably expand and form a red giant. Finally, it may form a white dwarf or a ____________ star. When this happens there will no longer be life on the Earth, but by then we should have found new _________ around other stars.
WORD LIST
Big, Jupiter, billions, fusion, dwarfs, fuel, binary,
large, Orion, nuclear, nebula, expanding, two, less, Bang,
Sun, hydrogen, smaller, energy, electricity, helium, uranium,
quickest, supernova, homes, white, neutron, giants, brown,
dwarfs.
