Question: when will the world end

Colin Johnston answered on 17 Nov 2014:

Just adding to what Triona has already said…

Our Sun now is a main sequence star. This means the Sun is in its prime of life, steadily converting hydrogen into helium in its core and producing heat and light as a by-product. There are huge stars called red giants. These are stars which are running out of hydrogen in their cores and are instead generating energy using other fuels such as helium. Producing energy this way makes them swell enormously into bloated stars with reddish surfaces, cool by stellar standards.

In the distant future, 6.4 billion years or so from now our Sun is doomed to become one of these red giants. The Sun will redden, it’s surface cooling, and it will expand enormously. Planet Mercury will be absorbed by the expanding Sun, Venus will probably meet the same fate and the icy moons of Jupiter will be vaporised. But theory suggests Earth as a planet will survive but as an airless ball of rock.

Red giant stars like the Sun will become blast off great clouds of gas until eventually all the star’s outer layers have been blown away into space. Eventually only the tiny shrunken core, about the size of the Earth, remains as what is called a white dwarf. White dwarf stars no longer produce light by nuclear fusion, merely continuing to glow like dying embers until they have slowly cooled to cold black balls of dense matter not much bigger than a planet.

This will be the ultimate fate of our Sun. A cold, dead earth will still be orbiting it.

Thankfully this sad fate lies far in the future!