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What is a protostar?

  • Stars A star is a huge ball of gas and dust that gives out both heat and light. When the gases in the star burn out, it dies. A star can live for millions, even billions, of years depending on its size. Each galaxy in the universe is made up of several billion stars.

    Stars are born in clouds of dust and gases, mainly hydrogen. More and more gas is pulled together by gravity to form a cloud. After a while the cloud begins to spin. This makes the gas atoms bump into each other at high speeds, creating a great deal of heat. As the cloud becomes hotter a nuclear reaction takes place inside, and the cloud begins to glow. This glowing cloud is called a protostar. The protostar continues to contract until it becomes a star. Q How long does a star live? A A star glows for millions of years until the gases in its outer layer begin to cool, and the hydrogen in the inner core is slowly used up. The cool outer layer starts to glow red. When this happens the star is called a red giant. The red giant continues to lose its brightness until it fades away. Depending on its size, a red giant may die in an explosion, get compressed to form a black hole or become a white dwarf. Q What is a white dwarf? A A small star usually shrinks to form a dense white dwarf. The size of a white dwarf is similar to the size of Earth. There are many white dwarfs in our galaxy but they are too dim to be seen. Sirius B is one of them. 8 Q What is a supernova? A A supernova is a vast explosion in which an entire star is destroyed. After the explosion, extremely bright light is emitted for several days. Supernovas appear a billion times brighter than the Sun. Sometimes, a supernova explosion can go on for weeks or even months. Supernovas mostly occur in distant galaxies. The last supernova to take place in the Milky Way occurred in 1604. It was observed by the famous astronomer Johannes Kepler. The brightest supernova to be recorded so far is 1993J in the galaxy M81. It was seen on 26 March 1993. But because the stars are so far away, we may see a supernova explosion long after it takes place. Protostar An artist’s impression of the original ball of dust and gases that combine to form a protostar. White dwarf An enhanced image of white dwarf stars, which have already shrunk to a size comparable to that of the Earth. These stars are too dim to be detected without modern telescopes.

     

     

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