26. Do they really think that in billions of years the Sun is going to expand and burn? (A K2S Question)
From The Space Library
The power of the Sun does not come from any burning process but is created as a result of nuclear fusion. This power to convert the mass of four hydrogen atoms into helium releases a huge amount of energy and has kept the Sun powered and stable for over 4.6 billion years. Scientists have been studying the Sun and gathering enough data from distant stars to better understand the average life span of a star like our Sun. They now know it is a middle-aged star that formed about 4.6 billion years ago and will remain active for another 4.6 billion years. Somewhere in the distant future, in three billion to five billion years, all the hydrogen in the core will be depleted. Once this happens, the core will begin to cool. This event will throw off the delicate balance between pressure in the core and gravity and result in a sudden collapse of the Sun's outer atmosphere on the core. The collapse will initiate a rise in temperature which will then force additional hydrogen surrounding the Sun's spent core to begin fusing into helium which will rapidly elevate the temperature, causing it to expand into a Red Giant star. Our Sun has now entered the Red Giant phase as new-found internal energy reserves drive its outer atmosphere to eventually engulf the orbits of Mercury and Venus. This phase may last a billion years until the helium in the core rises to over 100 million degrees K and begins to fuse. Helium fusion will only sustain our once stable Sun for a mere 100 million years, until it turns the core into carbon ash and the same process of contraction and expansion happens again, but only briefly, for a few million years. The Sun will now rapidly expand to almost within reach of Earth's orbit, and then, at some distant future moment, will hurl off its outer atmosphere, creating a magnificent planetary nebula and leaving only a very cool carbon core as a white dwarf remnant that will continue to slowly cool over billions and billions of years until it eventually flickers out of existence. It will be a magnificent end to our solar system that might be witnessed by survivors of the human race looking back from a safe distance at their former home world.
Answer provided by Jim Zebrowski
Question and Answer extracted from the book Kids to Space - by Lonnie Schorer
 Buy This Book Click here |
