{"id":16993,"date":"2022-08-21T19:00:24","date_gmt":"2022-08-21T17:00:24","guid":{"rendered":"https:\/\/www.sciencefocus.com\/?p=123894"},"modified":"2022-08-21T19:20:13","modified_gmt":"2022-08-21T17:20:13","slug":"the-life-cycle-of-a-star-how-will-our-solar-system-end","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/rss_feed\/the-life-cycle-of-a-star-how-will-our-solar-system-end\/","title":{"rendered":"The life cycle of a star: How will our Solar System end?"},"content":{"rendered":"

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By Iain Todd\n \t\t<\/p>

Published: Sunday, 21 August 2022 at 12:00 am<\/p>

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The Sun formed about 4.6 billion years ago and is set to survive in its current state, roughly speaking, for another 4.5 \u2013 5.5 billion years. And while we can\u2019t predict what will happen in billions of years to come, knowledge of how stars evolve has enabled astronomers to broadly infer how the Sun\u2019s life is likely to play out. More massive stars may end their lives in an explosion known as a supernova, but that is not the likely scenario that awaits our own.<\/p>\n

1. Hydrogen-burning phase<\/h2>\n
Every second the Sun<\/a> converts 600 million tonnes of hydrogen into four million tonnes of energy: the rest is converted into helium \u2018ash\u2019. Throughout its life the Sun\u2019s energy output has continued to increase, and it is thought to have grown 30 per cent brighter in the 4.6 billion years since it formed. Over the next billion years, as more hydrogen is converted to helium, the Sun is set to get about 10 per cent brighter, leading to an increase in heat energy. If we consider the effect that human-made climate change<\/a> is already having on the weather patterns of our planet, imagine the effect of an increase such as that.<\/p>\n
The rising heat will cause the polar ice caps to start to melt and the oceans to warm, sending water vapour into our atmosphere. That water vapour will trap more heat, creating a \u2018moist greenhouse\u2019 effect that will raise global temperatures even higher. About 3.5 billion years from now, the Sun will be 40 per cent brighter than it is today, causing our oceans to boil, the ice caps to melt completely and our atmosphere to be stripped away. Earth will become like Venus<\/a>: scorched, arid and lifeless.<\/p>\n
Read more:<\/strong><\/p>\n
What colour is the Sun really? Hint: it\u2019s not yellow<\/a><\/li>\n
Will increased Sun activity make climate change worse?<\/a><\/li>\n
What would happen if the Earth became tidally locked to the Sun?<\/a><\/li>\n
Does the Sun make a sound?<\/a><\/li>\n<\/ul>
2. Subgiant phase<\/h2>\n
As horrific as this scenario is, it is only the beginning of the Sun\u2019s demise. About five billion years from now, the Sun will have reached the end of the main sequence of its lifespan, and will have used up all the hydrogen in its core.<\/p>\n
With no fusion process<\/a> to counter the force of gravity<\/a>, the core will begin to contract and become denser over time. As it does so, its temperature will rise and eventually ignite the remaining hydrogen lying outside the core.<\/p>\n
This new source of fuel will generate enormous amounts of energy that will push the outer layers outwards, causing the Sun to expand two to three times its current diameter, turning it into a subgiant star.<\/p>\n
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2. Subgiant phase<\/h2>\nAs horrific as this scenario is, it is only the beginning of the Sun\u2019s demise. About five billion years from now, the Sun will have reached the end of the main sequence of its lifespan, and will have used up all the hydrogen in its core.<\/p>\n